This PDF file contains the front matter associated with SPIE Proceedings Volume 9899 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

We probe the dynamics of objective laser speckles as the axial distance between the object and the observation plane changes. With the purpose of measuring out-of-plane motion in real time, we apply optical spatial filtering velocimetry to the speckle dynamics. To achieve this, a rotationally symmetric spatial filter is designed. The spatial filter converts the speckle dynamics into a photocurrent with a quasi-sinusoidal response to the out-of-plane motion. The selectivity of the sensor relates directly to the uncertainty on sensor measurements. The selectivity most be derived from a temporal power spectrum of the photocurrent produced by this filter. This main contribution of this paper is a model, which describe the selectivity of the sensor, applied to speckle dynamics generated by an object moving out-of-plane. To motivate our interest in these filters we also present an all optical element which implements the spatial filter and experimentally demonstrate the ability of the technology to obtain displacement measurements of a vibrating object in real-time.

The inspection of functional elements is a crucial part of modern production cycles. However, with higher integration of production machinery and products, the accessibility for measurement systems is more and more limited. A solution for this problem can be found in endoscopy techniques, which are able to transport the image information for optical measurement methods. In this paper, an optical inspection system based on the fringe projection profilometry technique is presented. The fiber-optic fringe projection system uses two high-resolution image fibers to connect a compact sensor head to the pattern generation and camera unit. In order to keep inspection times low, the system is developed with particular focus on fast projection times. This can be achieved by using a digital micro-mirror device, which is capable of projecting grey-scale patterns at a rate of more than 10 images per second. However, due to the low numerical aperture of the optical fibers, a limiting factor for the pattern rate is the illumination path of the pattern generator. Two different designs of the illumination path are presented, which are based on a LASER light source as well as a LED light source. Due to low beam divergence and high intensities LASERs are well suited for fiber coupling. Unfortunately, the coherent property of the light has negative effects in certain measurement applications, as interference patterns, the so called speckle, appear on rough surfaces. Although speckle reducing methods are employed in the LASER beam path, the emergence of interference cannot be prevented completely. As an alternative, an illumination path based on a LED light source is demonstrated. To compare the effects of the speckle, based on measurements on a planar calibration standard both designs are compared in terms of phase noise, which is directly related to the noise in the reconstructed 3-D point data. Additionally, optical power measurements of both methods are compared to give an estimation of coupling efficiency. Finally, the capabilities of the system are shown based on measurements of a micro-contour standard.

Optical interferometry enables highly accurate non-contact displacement measurement. The optical phase ambiguity needs to be resolved for absolute distance ranging. In controlled laboratory conditions and for short distances it is possible to track a non-interrupted displacement from a reference position to a remote target. With large distances covered in field applications this may not be feasible, e.g. in structure monitoring, large scale industrial manufacturing or aerospace navigation and attitude control. We use an optical frequency comb source to explore absolute distance measurement by means of a combined spectral and multi-wavelength homodyne interferometry. This relaxes the absolute distance ambiguity to a few tens of centimeters, covered by simpler electronic distance meters, while maintaining highly accurate optical phase measuring capability. A virtually imaged phased array spectrometer records a spatially dispersed interferogram in a single exposure and allows for resolving the modes of our near infrared comb source with 1 GHz mode separation. This enables measurements with direct traceability of the atomic clock referenced comb source. We observed agreement within 500 nm in comparison with a commercial displacement interferometer for target distances up to 50 m. Furthermore, we report on current work toward applicability in less controlled conditions. A filter cavity decimates the comb source to an increased mode separation larger than 20 GHz. A simple grating spectrometer then allows to record mode-resolved interferograms.

We proposed a system composed of a frequency comb interferometer and an optical interferometer of an optical frequency comb mode-locked femtosecond laser to measure the profile of an object. The profile of the object was fast measured by the frequency comb interferometer by means of a single pixel camera. Because of the larger size of the sampling point of the masks integrated in the single pixel camera and the long wavelength of the radio frequency, the profile of the object obtained in this step has low spatial resolution. Since then the measurement was carried out by the optical interferometer using Michelson’s setup. The very accurate and high lateral and axial resolution object’s profile can be partly observed by using low-coherence interference chromatic phase shifting technique. Resultantly, the combination of the frequency comb interferometer and the optical interferometer by matching the relative phases allowed measuring the object’s profile with meter order depth and nano-scale resolution. Employing the proposed system, the whole object or parts of the object with very high resolution can be determined and the measurement time was reduced, dramatically.

Colloidal Quantum Dots (CQD), due to their extremely large optical absorption coefficient and tunability of the absorption bands, are very promising for the realization of photodetectors. PbS quantum dots, in particular, can be effectively employed as a material for near infrared photodetectors with sensitivity peaks ranging from 1 to 2μm. CQD photodetectors, nevertheless, present still many unsolved issues when it comes to fast detection and noise performance. Thanks to the recent advances in CQD material synthesis and treatment, photodetectors achieved unprecedented performance but the aforementioned issues could still not be fully addressed. Concerning photodetectors, however, material quality is only the starting point for the realization of performing devices: CQD technology came to the point where an engineering approach is needed in order to fully comprehend the behavior of the photodetectors, to define proper strategies for the enhancement of their performance and introduce them in practical applications. In this work we analyze the optical and electrical characteristics of PbS CQD near infrared photodetectors fabricated on SiO₂ substrate and demonstrate how even a simple, fully passive readout circuit topology could be employed in order to obtain a dramatic enhancement of the characteristics of the devices.

optically biased by ultra-violet illumination of the front or back surfaces. The front surface is also used for several pulsed single wavelength signals within the visible range. Experimental results show that the ultra-violet bias illumination at the front surface of the device enhances wavelengths longer than 500 nm while quenching the wavelengths shorter than 500 nm. The opposite happens when the bias is set at the back surface of the device; wavelengths shorter than 500 nm are enhanced while the ones above are quenched. Several digital applications have been built using the p’inpin device. This paper focuses on the use of the pi’npin device for seven channel Wavelength Division Multiplexing (WDM) digital communication using Manchester coded signals, with a single wavelength for each channel. The seven channels form a frame with 7*256 bits with a preamble for signal intensity and synchronization purposes. Results show that the clustering of the received signal enables the successful recovery of the seven channel data using the front and back illumination of the surfaces of the pi’npin photo device.

High dynamic range pixels are required in a number of automotive and scientific applications. CMOS pixels provide different approaches to achieve this. However, these suffer from poor performance under low light conditions due to inherently high leakage current that is present in CMOS processes, also known as dark current. The typical approach to reduce this dark current involves process modifications. Nevertheless, energy considerations suggest that the leakage current will be close to zero at a close to zero voltage on the photodiode. Hence, the reduction in dark current can be achieved by forcing a zero voltage across the photodiode. In this paper, a novel logarithmic CMOS pixel design capable of reducing dark current without any process modifications is proposed. This pixel is also able to produce a wide dynamic range response. This circuit utilizes two current mirrors to force the in-pixel photodiode at a close to zero voltage. Additionally, a bias voltage is used to reduce a higher order effect known as Drain Induced Barrier Lowering (DIBL). In fact, the contribution of this effect can be compensated by increasing the body effect. In this paper, we studied the consequences of a negative bias voltage applied to the body of the current mirror pair to compensate for the DIBL effect thereby achieving a very small voltage drop on the photodiode and consequently, a higher sensitivity in low light conditions.

LinoSPAD is a reconfigurable camera sensor with a 256×1 CMOS SPAD (single-photon avalanche diode) pixel array connected to a low cost Xilinx Spartan 6 FPGA. The LinoSPAD sensor’s line of pixels has a pitch of 24 μm and 40% fill factor. The FPGA implements an array of 64 TDCs and histogram engines capable of processing up to 8.5 giga-photons per second. The LinoSPAD sensor measures 1.68 mm×6.8 mm and each pixel has a direct digital output to connect to the FPGA. The chip is bonded on a carrier PCB to connect to the FPGA motherboard. 64 carry chain based TDCs sampled at 400 MHz can generate a timestamp every 7.5 ns with a mean time resolution below 25 ps per code. The 64 histogram engines provide time-of-arrival histograms covering up to 50 ns. An alternative mode allows the readout of 28 bit timestamps which have a range of up to 4.5 ms. Since the FPGA TDCs have considerable non-linearity we implemented a correction module capable of increasing histogram linearity at real-time. The TDC array is interfaced to a computer using a super-speed USB3 link to transfer over 150k histograms per second for the 12.5 ns reference period used in our characterization. After characterization and subsequent programming of the post-processing we measure an instrument response histogram shorter than 100 ps FWHM using a strong laser pulse with 50 ps FWHM. A timing resolution that when combined with the high fill factor makes the sensor well suited for a wide variety of applications from fluorescence lifetime microscopy over Raman spectroscopy to 3D time-of-flight.

A readout channel based on continuous-time incremental sigma-delta analog-to-digital converter for FET-based terahertz (THz) imaging applications was implemented in a 0.15 μm standard CMOS technology. The designed readout circuit is suitable for implementation in pixel arrays due to its compact size and power consumption. The system-level analysis used to define the modulator parameters and to specify its analog building blocks is presented. The loop filter has been realized by using a Gm-C integrator. Circuit linearization techniques have been implemented to improve the linearity of the transconductor cell and reduce the impact of parasitic capacitances. Moreover, chopper stabilization technique is adopted in the loop filter, significantly reducing the low-frequency flicker noise thereby preserving the Noise Equivalent Power (NEP) of the FET detector within the required specifications of minimum detectable signal. The resulting input referred noise voltage is 87.5 nV/√Hz . The incremental ADC achieves 68-dB peak signal-to-noise-and-distortion-ratio (SNDR), equivalent to 11 bits effective resolution over 1 kHz signal bandwidth at 1 MHz sampling frequency. In order to meet the requirements of large sensor arrays, a first order architecture is realized. This leads to lower area occupancy and power consumption. The readout circuit draws 80 μW of power from a supply voltage of 1.8 V. The channel occupies an area of 90 x 273μm².

In this paper an integrated wavelength optical filter and photodetector working as a DEMUX device is used to detect modulated optical signals of visible wavelengths for Visible Light Communication (VLC). The proposed application demonstrates the viability of indoors positioning using VLC technology established by the modulation of indoor warm light lamps lighting with ultra-bright white tri-cromatic LEDs. The signals were transmitted into free space and the generated photocurrent was measured by a pin-pin photodetector based on a-SiC:H/a-Si:H. This device operates in the visible spectrum, allowing thus the detection of the pulsed light emitted by the modulated chips of the white RGB LEDs. However, as the device works also as a visible optical filter with controlled wavelength sensitivity through the use of adequate optical biasing light, it is able to detect different wavelengths, turning it into a DEMUX device. This feature allows the detection of the individual components of the tri-chromatic white LED and is the basis for the indoors location algorithm. We demonstrate the possibility of decoding four transmission optical channels supplied by two different wavelength LEDs modulated under different bit sequences, which allows the location identification and indoor navigation.

This paper presents an 8 channel ASIC for SiPM anode readout based on a novel low input impedance current conveyor (under patent¹). This Multiple Use SiPM Integrated Circuit (MUSIC) has been designed to serve several purposes, including, for instance, the readout of SiPM arrays for some of the Cherenkov Telescope Array (CTA) cameras. The current division scheme at the very front end part of the circuit splits the input current into differently scaled copies which are connected to independent current mirrors. The circuit contains a tunable pole zero cancellation of the SiPM recovery time constant to deal with sensors from different manufacturers. Decay times up to 100 ns are supported covering most of the available SiPM devices in the market. MUSIC offers three main features: (1) differential output of the sum of the individual input channels; (2) 8 individual single ended analog outputs and; (3) 8 individual binary outputs. The digital outputs encode the amount of collected charge in the duration of the digital signal using a time over threshold technique. For each individual channel, the user must select the analog or digital output. Each functionality, the signal sum and the 8 A/D outputs, include a selectable dual-gain configuration. Moreover, the signal sum implements dual-gain output providing a 15 bit dynamic range. Full die simulation results of the MUSIC designed using AMS 0.35 µm SiGe technology are presented: total die size of 9 mm², 500 MHz bandwidth for channel sum and 150 MHz bandwidth for A/D channels, low input impedance (≈32 Ω), single photon output pulse width at half maximum (FWHM) between 5 and 10 ns and with a power consumption of ≈ 30 mW/ch plus ≈ 200 mW for the 8 ch sum. Encapsulated prototype samples of the MUSIC are expected by March 2016.

A Fast and Low-noise Optical Receiver using a Silicon Avalanche Photodiode with an internal gain of 100 connected to a Broadband Preamplifier Circuit was developed. The optical receiver and the receiving optics form the detection channel of a Cloud-Aerosol Lidar Remote Sensing System used to measure profiles of aerosol and cloud backscatter at the near-infrared wavelength of 1064 nm. While a 10 Hz repetition rate solid state pulsed Nd:YAG laser emitting at 1.06 μm and the emission optics form the transmission channel. The preamplifier circuit with a 300 MHz bandwidth and a gain of 10 is capable of accommodating laser pulses of 10 ns full width at half maximum. The preamplifier matches 50 Ω impedances at the input and the output sides. The input matching is used to reduce the Johnson noise and hence a much better sensitivity was achieved. The output matching was useful when this preamplifier is to be connected to other instrumentation requiring 50 Ω impedance matching or to be interfaced in cascade to increase the overall gain of the detection chain. These 50 Ω impedances at the input and output sides, also allows using the preamplifier coupled with a photodiode at the input in the detection of fast signals without distortion or integration. A low noise level at the preamplifier circuit input of only 1.6 nV/Hz^1/2 and a very good linearity from 1 KHz to 280 MHz were achieved, allowing the transmission of the backscattered signal to the acquisition system without distortion. In addition, the experimental characterization of the optical receiver coupled with the receiving optics showed good detection performance of the lidar detection channel: A low Noise Equivalent Power of 50 pW/Hz^1/2 and a high Signal-to- Noise Ratio of 2 were achieved. Furthermore, the maximal range of the lidar remote sensing system was estimated.

In developing sensitive optical sensors, issues associated with optical crosstalk, dark count, and dark current persist. While designs have been created to mitigate the effects of these optical noises on the performance of the sensors, they are never fully addressed. This is mainly due to the highly probabilistic nature of the interaction of light and matter. This paper theoretically explores possible solutions that could lead to the significant reduction of these optical noises by presenting the problem in both the Markovian and Bayesian quantum feedback schemes and identifying the parameters that can be controlled and/or regulated. This paper then attempts to translate the quantum processes into realizable materials and/or systems suitable for fabrication or integration to existing system.

The emergence of new laser-based mid-infrared (MIR) sources, such as quantum cascade lasers (QCL), led to substantial developments in the field of MIR spectroscopy in the last decade. Recently, also MIR supercontinuum (SC) sources became available. They combine broadband spectral emission known from thermal sources emission with coherent properties known from laser sources like QCLs. Nevertheless, while the latter already find practical application in the field of optical sensing, SC sources have yet to prove their applicability. In this contribution we present the development, characterization and application of a measurement concept consisting of a fiber-coupled broadband MIR SC source (1.75 μm-4.2 μm, 75 mW optical power) and a fully-integrated MOEMS-based Fabry-Pérot microspectrometer (FPMS) for MIR spectroscopy. The main hindrance for the use of SC sources in spectroscopy so far, are the significant pulse-to-pulse fluctuations arising from the non-linear nature of the SC generation process. We show to what extent spectral averaging makes sense and evaluate the noise performance. By combining a SC source and a FPMS it was possible to significantly reduce noise in spectral, time and polarization domain, resulting in a set-up suitable for MIR spectroscopy. The performance of the set-up was characterized both in transmission and reflection geometry. Low-noise absorption spectra of oils, polymers and aqueous solutions of acetic acid were acquired . Furthermore, time-resolved measurements of the curing process of ethyl-2-cyanoacrylate and results of the chemical mapping of a painted metal surface are reported. The obtained results prove the concept of SC-FPMS promising for MIR spectroscopy, characterized by its simplicity and versatility.

Recent studies led in the field of infrared spectroscopy focused on the use of nanoantennas to enhance electromagnetic field on the bonds of molecules, in order to improve detection. We propose to take benefit from dipolar optical resonances in dielectric free-standing nanorod arrays as an innovative component to achieve spectroscopy in the mid-infrared wavelength range. The particularity of this component is not only to allow electromagnetic field enhancement, but also its ability to shift spectrally the resonance according to incidence angle. Spectroscopy is thus possible on a wide wavelength range for a given geometry of the nanorods. We present here numerical studies of the impact of the size of nanorods on the reflection spectra. We use the permittivity of a test molecule determined by transmission spectra. In addition, we introduce the fabrication process, transmission and reflection measurements of nanorods.

Detection of methane at 3.3μm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective path length of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm path length single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration.

In this paper, we report the results concerning electron beam irradiation of mid-IR windows and mid-IR detectors for possible use in trace gas detection systems, in the 1 μm to 5 μm spectral range under ionizing radiation conditions. Four windows materials (CaF₂, BaF₂, ZnSe, and sapphire) for the mid-IR were tested as they were exposed to electron beam irradiation at a dose rate of 4 kGy/min, for doses from 0.5 kGy to 2.2 kGy. Two IR detectors (photoconductive – PbSe, photovoltaic – InAs) were subjected to the same type of irradiation at dose rate of 4 kGy/min, in three subsequent exposures, for a total dose up to 6.8 kGy. Before the irradiation and after each irradiation step the windows were measured as it concerns the spectral optical transmittance, spectral optical diffuse reflectance, and, in the THz range (0.06 THz – 3 THz), the dielectric constant and the refractive index were evaluated. THz imaging analysis of the irradiated samples was done. For the IR detectors we measured at different irradiation stages the spectral responsivity and the dark current. The most affected by electron beam irradiation was the CaF₂ window, in the spectral interval 250 nm – 800 nm. The spectral transmittance of the four windows remained unchanged after their exposure to ionizing radiation in the near-IR and mid-IR. Noticeable variations of the spectral responsivity appeared upon electron beam irradiation in the case of the InAs detector.

Hyperspectral imaging (HSI) is an emerging technique that combines the imaging properties of a digital camera with the spectroscopic properties of a spectrometer able to detect the spectral attributes of each pixel in an image. For these characteristics, HSI allows to qualitatively and quantitatively evaluate the effects of the interactions of light with organic and/or inorganic materials. The results of this interaction are usually displayed as a spectral signature characterized by a sequence of energy values, in a pre-defined wavelength interval, for each of the investigated/collected wavelength. Following this approach, it is thus possible to collect, in a fast and reliable way, spectral information that are strictly linked to chemical-physical characteristics of the investigated materials and/or products. Considering that in an hyperspectral image the spectrum of each pixel can be analyzed, HSI can be considered as one of the best nondestructive technology allowing to perform the most accurate and detailed information extraction. HSI can be applied in different wavelength fields, the most common are the visible (VIS: 400-700 nm), the near infrared (NIR: 1000-1700 nm) and the short wave infrared (SWIR: 1000-2500 nm). It can be applied for inspections from micro- to macro-scale, up to remote sensing. HSI produces a large amount of information due to the great number of continuous collected spectral bands. Such an approach, when successful, is quite challenging being usually reliable, robust and characterized by lower costs, if compared with those usually associated to commonly applied analytical off-line and/or on-line analytical approaches. More and more applications have been thus developed and tested, in these last years, especially in food inspection, with a large range of investigated products, such as fruits and vegetables, meat, fish, eggs and cereals, but also in medicine and pharmaceutical sector, in cultural heritage, in material characterization and in waste recycling. Examples of some application, based on HSI, originally developed by the authors, are presented, critically analyzed and discussed, with reference to the different hardware configuration and logics utilized to perform the analysis, according to the characterization, inspection and quality control actions to apply.

In this work we present a laser-based system for standoff/remote, sensitive detection of gases based on a tunable diode laser source and Wavelength Modulation Spectroscopy method (WMS). System performance was experimentally characterized. The constructed device has proven its capacity of efficient detection of methane in air at the single ppm levels and distances from 10 to 50 m (distance to a scattering object). The minimum detection limit of the system was estimated at the level of 10 ppm-m for the standoff arrangement and the measurement path of approximately 20 m (round trip). Potential application of the device to hydrogen sulfide detection and current limitations in this area are discussed.

We report the results of the application of Laser-Induced Breakdown Spectroscopy (LIBS) for the detection of some common military explosives and theirs precursors deposited on white varnished car’s external and black car’s internal or external plastic. The residues were deposited by an artificial silicon finger, to simulate material manipulation by terrorists when preparing a car bomb, leaving traces of explosives on the parts of a car. LIBS spectra were acquired by using a first prototype laboratory stand-off device, developed in the framework of the EU FP7 313077 project EDEN (End-user driven DEmo for CBRNe). The system operates at working distances 8-30 m and collects the LIBS in the spectral range 240-840 nm. In this configuration, the target was moved precisely in X-Y direction to simulate the scanning system, to be implemented successively. The system is equipped with two colour cameras, one for wide scene view and another for imaging with a very high magnification, capable to discern fingerprints on a target. The spectral features of each examined substance were identified and compared to those belonging to the substrate and the surrounding air, and those belonging to possible common interferents. These spectral differences are discussed and interpreted. The obtained results show that the detection and discrimination of nitro-based compounds like RDX, PETN, ammonium nitrate (AN), and urea nitrate (UN) from organic interfering substances like diesel, greasy lubricants, greasy adhesives or oils in fingerprint concentration, at stand-off distance of some meters or tenths of meters is feasible.

A detailed analysis of the quality factor, the resonance frequency and the electrical resistance of custom quartz tuning forks (QTFs) having different geometrical parameters is reported. We implemented custom QTFs in a quartz enhanced photoacoustic sensor targeting water vapor detection and compared the fundamental and first overtone flexural modes gas sensor performances.

In this work we have proposed a new configuration based on a tilted charged coupled device (CCD) camera and bandpass sampling theorem which not only decreases the spectrometer size but also operates in the traditional spectrometers wavelength range of 400 nm – 1100 nm. The static Michelson interferometer is built by attaching a quartz cube and a prism together, and a CCD camera is attached to the quartz cube in 45 degree to record path length differences (PLD). An algorithm is developed to process the signal and calculate the Fourier transform of the recorded interferograms on the CCD camera.

In this work, microRaman spectroscopy is used to investigate the stratigraphic mapping in paintings. The objective of mapping imaging is to segment the dataset, here spectra, into clusters each of which consisting spectra that have similar characteristics; hence, similar chemical composition. The spatial distribution of such clusters can be illustrated in pseudocolor images, in which each pixel of image is colored according to its cluster membership. Such mapping images convey information about the spatial distribution of the chemical substances in an object. Moreover, the laser light source that is used has excitation in 1064 nm, i.e., near infrared (NIR), allowing the penetration of the radiation in deeper layers. Thus, the mapping images that are produced by clustering the acquired spectra (specifying specific bands of Raman shifts) can provide stratigraphic information in the mapping images, i.e., images that convey information of the distribution of substances from deeper, as well. To cluster the spectra, unsupervised machine learning algorithms are applied, e.g., hierarchical clustering. Furthermore, the optical microscopy camera (×50), where the Raman probe (B and WTek iRaman EX) is plugged in, is attached to a computerized numerical control (CNC) system which is driven by a software that is specially developed for Raman mapping. This software except for the conventional CNC operation allows the user to parameterize the spectrometer and check each and every measurement to ensure proper acquisition. This facility is important in painting investigation because some materials are vulnerable to such specific parameterization that other materials demand. The technique is tested on a portable experimental overpainted icon of a known stratigraphy. Specifically, the under icon, i.e., the wavy hair of “Saint James”, can be separated from upper icon, i.e., the halo of Mother of God in the “Descent of the Cross”.

Development of novel methods for non-destructive evaluation of composite materials (CMs) at manufacturing and operational stages remains challenging problem of applied physics, optics and material science. In this paper, we have considered the ability to use the terahertz (THz) time-domain spectroscopy (TDS) for non-destructive evaluation of CMs. By combining the TDS technique with appropriate methods of solving the inverse ill-posed problems, we have shown that TDS could be applied for CM testing. At first, we have demonstrated that TDS could be used to control the polymerization process and, as a consequence, the CM binder curing. Secondary, we have shown the ability to detect the internal defects (non-impregnated voids) inside the CMs via the TDS-based THz time-of-flight tomography. Thereby, the results of our study allow highlighting the prospective of non-destructive evaluation of CMs using the TDS.

The presence of carcinogenic aflatoxins in food and feed products is a major worldwide problem. To date, the aflatoxin contamination can only be detected by the use of destructive sample-based chemical analyses. Therefore, we developed an optical setup able to detect the localized aflatoxin contamination in individual maize kernels, on the basis of one- and two- photon induced fluorescence spectroscopy. Our developed optical configuration comprises a tunable titanium-sapphire laser (710nm-830nm) in combination with second harmonic wavelength generation (355nm-415nm), enabling the measurement of both one- and two-photon induced fluorescence spectra. Moreover, an accurate scanning of the kernel’s surface was induced by the use of automated translation stages, allowing to study the localized maize contamination. First, the operation of the setup is validated by the characterization of pure aflatoxin B1 powder. Second, the fluorescence spectra of healthy (< 1ppb aflatoxin B1) and contaminated maize kernels (>70ppb aflatoxin B1) were measured, after excitation with 365nm, 730nm, 750nm and 780nm. For both the one- and two- photon induced fluorescence processes, the presence of the aflatoxin inside the contaminated maize kernels influenced the intrinsic fluorescence signals. Based on the fluorescence spectrum between 400nm and 550nm, we defined a detection criterion to identify the contaminated maize kernels. Furthermore, we demonstrate the sensing of the localized contamination level, indicating both contaminated maize kernels with a high contamination level in a limited surface area (as small as 1mm²) as with a lower contamination spread over a large surface area (up to 20mm²). As a result, our developed measurement methodology allows the identification of the localized aflatoxin contamination, paving the way to the non-destructive, real-time and high-sensitive industrial scanning-based detection of aflatoxins in food products.

The major issues concerning to food products are related to its authenticity. Honey is one of the common food products that suffer from adulteration, mainly due to its constant high market demand and price. Several studies on the authenticity detection have been done mainly on honey from genus Apis (GA), but less research has been conducted on Stingless Bee Honey (SBH) even the market demand for this food product is increasing, particularly in Malaysia due to its possible health benefits. Thus, identification of unadulterated and authenticity of honey is a very key issue for products processors, retailers, consumers and regulatory authorities. There is an increasing demand for appropriate instruments and methods to shield consumers against fraud and to guarantee a fair competition between honey producers. The study presented in this paper shows the effect of diluting pure honey from both genus Apis and Stingless Bee towards its physicochemical attributes (i.e. soluble solids content and pH) and VIS-NIR spectral absorbance features.

In order for fiber optic sensors to compete with electrical sensors, several critical parameters need to be addressed such as performance, cost, size, reliability, etc. Relying on technologies developed in different industrial sectors helps to achieve this goal in a more efficient and cost effective way. FAZ Technology has developed a tunable laser based optical interrogator based on technologies developed in the telecommunication sector and optical transducer/sensors based on components sourced from the automotive market. Combining Fiber Bragg Grating (FBG) sensing technology with the above, high speed, high precision, reliable quasi distributed optical sensing systems for temperature, pressure, acoustics, acceleration, etc. has been developed. Careful design needs to be considered to filter out any sources of measurement drifts/errors due to different effects e.g. polarization and birefringence, coating imperfections, sensor packaging etc. Also to achieve high speed and high performance optical sensing systems, combining and synchronizing multiple optical interrogators similar to what has been used with computer/processors to deliver super computing power is an attractive solution. This path can be achieved by using photonic integrated circuit (PIC) technology which opens the doors to scaling up and delivering powerful optical sensing systems in an efficient and cost effective way.

In this work, the potential of fiber Bragg gratings (FBGs) in low-loss perfluorinated polymer optical fibers (PF-POFs) is explored. The FBG is femtosecond-inscribed in a commercial multi-mode (MM) PF-POF based on Cytop polymer. Femtosecond inscription leads to creation of a highly saturated grating with a number of higher order reflection peaks visible throughout the visible and near-infrared spectral region. For 2 mm long FBG having a pitch of 2.2895 μm, a total of nine higher-order MM reflection bands are visible spanning from 1548 nm (4th order) to 520 nm (12th order). Strain sensitivity was measured for 6 peak bands in 500-900 nm region, where relatively low cost CCD based spectrometers and broadband LEDs are available. Strain sensitivity increases almost linearly with increasing initial peak wavelength, growing from 4.82 ± 0.02 nm/% measured for 12th order peak at 517 nm to 8.12 ± 0.04 nm/% measured for 7th order peak at 883 nm. These values correspond to roughly 20 % higher sensitivity than silica FBGs exhibit in this spectral range. The gratings in PF-POFs combine the higher strain sensitivity and low-loss operation while maintaining the mechanical advantages of polymer optical fibers. Therefore, they hold a high potential for considerable broadening of polymer optical fiber Bragg gratings application range.

Different methods have already been developed to measure the magnetic field with fiber Bragg gratings (FBGs). They are based on the use of a magnetic fluid or magnetostrictive materials. In addition to these methods, a direct measurement of the magnetic field is also possible by determining the circular birefringence created by the magnetic field inside the fiber. In standard optical fiber, this circular birefringence is of the same order as the intrinsic fiber birefringence or even below. The polarization properties of FBGs are therefore used to perform such measurement since they allow to determine weak birefringence with higher accuracy than standard read-out techniques. However, the obtained accuracy is usually low due to the influence of the intrinsic fiber birefringence. To mitigate this issue, we study in this work the use of the diattenuation vector. This parameter is obtained from the Mueller matrix and we show that it evolves in response to a magnetic field. In practice, we analyze its response by both simulation and experiment. In our simulations, we solve numerically the coupled mode equations of the FBG. For the experiments, the Mueller matrix is measured by an optical vector analyzer for the gratings connected in transmission. We apply an increasing magnetic field on different Bragg gratings photo-written in SMF28 fibers. The rotation of the diattenuation vector is then used to retrieve the magnetic field induced circular birefringence. A linear increase of the reconstructed circular birefringence is reported for increasing magnetic field values in the range 0-1T.

A new concept for the self-diagnosis of embedded fiber Bragg grating (FBG) strain sensors was developed, simulated and experimentally tested. This concept is based on a magnetostrictive metallic layer directly coated on the fibre cladding over the grating segment of the FBG sensor, so that an on-demand external magnetic field in a millitesla scale can produce a controllable artificial strain as an indication signal for the remote optical interrogator. The relationship between the pre-defined magnetic field and its induced Bragg wavelength shift characterizes this validation concept. Any deviation of the local bonding state of the interfaces from the initial or/and any change of shear strain transferring mechanism from composite matrix to the optical fibre core will result in alterations in this sensitive relationship, and thus triggers an immediate alert for a further inspection. The finite element method is used to simulate the strain of this configuration as result of different values of the magnetic field in order to optimize the geometrical sensor parameters. The simulations are verified by experiments results.

Due to their high mechanical and corrosion resistance, low signal attenuation, optical fiber sensors and more particularly fiber Bragg gratings (FBGs) have demonstrated their high potential in various sensors applications such as health monitoring of structural pieces when their are placed under constrain, vibration or temperature variation. In this paper, we evaluate the capability of a low cost optical fiber Bragg gratings interrogator, based on the edge filter demodulation technique, combined with a cepstral-based signal processing to address three cascaded FBGs along a railway track. We show in real-life conditions that, thanks to this method, it is possible from a noisy measurement to retrieve the speed of the trains.

This paper presents a highly sensitive ambient refractive index (RI) sensor based on 81° tilted fiber grating (81°-TFG) structure UV-inscribed in standard telecom fiber (62.5μm cladding radius) with carbon nanotube (CNT) overlay deposition. The sensing mechanism is based on the ability of CNT to induce change in transmitted optical power and the high sensitivity of 81°-TFG to ambient refractive index. The thin CNT film with high refractive index enhances the cladding modes of the TFG, resulting in the significant interaction between the propagating light and the surrounding medium. Consequently, the surrounding RI change will induce not only the resonant wavelength shift but also the power intensity change of the attenuation band in the transmission spectrum. Result shows that the change in transmitted optical power produces a corresponding linear reduction in intensity with increment in RI values. The sample shows high sensitivities of ~207.38nm/RIU, ~241.79nm/RIU at RI range 1.344–1.374 and ~113.09nm/RIU, ~144.40nm/RIU at RI range 1.374–1.392 (for X-pol and Y-pol respectively). It also shows power intensity sensitivity of ~ 65.728dBm/RIU and ~ 45.898 (for X-pol and Y-pol respectively). The low thermal sensitivity property of the 81°-TFG offers reduction in thermal cross-sensitivity and enhances specificity of the sensor.

A tilted fiber Bragg grating is photo-inscribed in the core of a single-mode optical fiber, leading to the coupling of cladding mode resonances all along a wide region of the near-infrared spectrum. The grating is then coated with a thin film of gold in order to create a metal-dielectric interface. This way, light propagating through the cladding of the optical fiber is able to excite a surface plasmon wave on the outer interface. As sensitive element, a molecularly imprinted polymer is deposited by electropolymerization as a thin film around the previous gold coating. The thickness of the polymer is controlled by means of the surface plasmon resonance signature in order to preserve a correct surrounding refractive index sensitivity when used in a gaseous environment. The chosen polymer has an affinity to formaldehyde, which is a volatile organic compound worth to detect, especially because of its toxicity for the human being. We report a global wavelength shift of the grating cladding mode resonances in the presence of formaldehyde in gaseous state. This shift is due to a change in the refractive index of the polymer when it bounds to the target molecules. The sensor exhibits a linear response, together with a low limit of detection.

The detection of volatile organic compounds is accomplished with a sensing device based on a long period fiber grating (LPFG) coated with a zinc oxide (ZnO) thin layer with self-temperature compensation. The ZnO coating structure was produced onto the cladding of the fiber by thermal oxidation of a metallic Zn thin film. The morphological characterization of ZnO thin films, grown at the same time on silicon substrates, was performed using X-ray diffraction, X-ray Photoelectron Spectroscopy and Scanning Electron Microscope which shows very good agreement. LPFGs with 290 nm thick ZnO coating were fabricated and characterized for the detection of ethanol and hexane in vapor phase. For ethanol a sensitivity of 0.99 nm / g.m^-3 was achieved when using the wavelength shift interrogation mode, while for hexane a much lower sensitivity of 0.003 nm / g.m^-3 was measured, indicating a semi-selectivity of the sensor with a spectral resolution better than 3.2 g.m^-3.

The present article reports a hydrogel coated Fiber Bragg Grating (FBG) based sensor for chromium metal ion detection. The presence of chromium metal ion in environmental water causes many toxic effects both on humans and animals. The inability of sensing traces of chromium ions is still remains a challenging problem for decades, as the Chromium exists in the environment in different oxidation states. This Paper discusses a chemo-mechanical-optical sensing approach for sensing harmful Chromium ions in environmental water. Fiber Bragg Grating is functionalized with a stimulus responsive hydrogel which swells or deswells depending on ambient chromium ion concentrations. This volume change of the hydrogels causes a bragg shift of the FBG peak. Different peak shifting’s, corresponding to different concentrations of the Cr ion concentrations, can be considered as a measure for quantifying traces of chromium ions. Hydrogel network cross-linked with (3-Acrylamidopropyl)-trimethylammonium chloride (ATAC) was synthesized and coated on FBG by dip coating method. Chromium ion concentrations up to ppm (parts per million) can be sensed by this technique.

Optical fiber temperature sensors using Raman effect are a promising technology for temperature mapping of nuclear power plant pipes. These pipes are exposed to high temperature (350 °C) and gamma radiations, which is a harsh environment for standard telecom fibers. Therefore metal coated fibers are to be used to perform measurement over 300 °C. Temperature variations can affect the attenuation of the metallic coated fiber before irradiation. The latter induces an extra attenuation, due to light absorption along the fiber by radiation-induced defects. The recombination of these defects can be strongly accelerated by the high temperature value. As backscattered Raman signal is weak it is important to test optical fibers under irradiation to observe how it gets attenuated. Different experiments are described in this conference paper: two in situ irradiation campaigns with different dose rates at, both ambient and high temperature. We observe that the tested off-the-shelf metallic coated fibers have a high attenuation under irradiation. We also noticed the fact that thermal annealing plays a massive role in the +300 °C temperature range.

An investigation into a novel in-vivo PMMA (polymethyl methacrylate) fiber-optic dosimeter to monitor the dose of ionizing radiation, both for instantaneous and integrating measurements, for radiotherapy applications is proposed. This fiber sensor is designed as an intracorporal X-ray ionizing sensor to enhance the curative effect of radiotherapy. The fiber-optic dosimeter is made in a PMMA fiber, whose core is micromachined to create a small diameter (0.25 to 0.5 mm) hole at one fiber end. An inorganic scintillating material, terbium-doped gadolinium oxysulfide (Gd₂O₂S:Tb) is chosen as the sensing material, because it can fluoresce on immediately under exposure of ionizing radiation (X-Rays or electron beam). This sensing material is filled and packaged in the small hole by epoxy resin adhesive. This kind of novel structure dosimeter shows high light coupling efficiency compared with other kind of inorganic scintillation dosimeter. This fiber-optic dosimeter shows good repeatability with a maximum deviation of 0.16%. The testing results of the fiber-optic dosimeter are perfectly proportional to the data of IC with R² as 0.9999. In addition, the fiber sensor shows excellent isotropic in its radial angular dependence. All the experiments indicate that the fiber-optic dosimeter is properly used for patient in-vivo dosimeter such as brachytherapy applications or intraoperative radiation therapy.

In this manuscript we present the fabrication and characterization of a novel, polymer whispering gallery modes (WGMs) spherical micro-resonator, formed around the waist of an optical fiber taper. Fiber taper with well attached spheroid works as a cord, fixed on two ends enabling strain application to the resonator body. Controllable elastic elongation of the encapsulated fiber taper causes a change in the shape of the spheroid, which modifies the diameter and directional refractive index of the cavity. These changes influence the wavelength position of the WGMs resonances with a linear blue shift up to 0.6 nm, with corresponding strains up to 700Μɛ. The strain induced WGMs shift with respect to resonator diameter and annealing process is presented and analyzed.

Optical fiber sensors has become one of the most promising sensing technologies. Within all the optical fiber sensing technologies, the Fabry-Perot interferometer (FPI) micro-cavities are one of the most attractive, due to the size, linearity and higher sensitivity. In this work we present the recent results, achieved by our group, regarding the production of optical sensors, by recycling optical fibers destroyed through the catastrophic fuse effect. This enabled the production of FPI sensors, in a cost effective way, tailored for the monitoring of several physical parameters, such as relative humidity (RH), refractive index (RI) and hydrostatic pressure.

Optical fibers are promising tools for performing biological and biomedical sensing due to their small cross section and potential for multiplexing. In particular, fabricating ultra-small sensing devices is of increasing interest for measuring biological material such as cells. A promising direction is the use of interferometric techniques combined with optical fiber post-processing. In this work we present recent progress in the development of Fabry-Perot micro-cavities written into optical fiber tapers using focused ion beam (FIB) milling. We first demonstrate that FIB milled optical fiber microcavities are sensitive enough to measure polyelectrolyte layer deposition. We then present new results on the fabrication and optical characterization of serially-multiplexed dual cavity micro-sensors. Two cavities were written serially along the fiber with two different cavity lengths, producing a total of four reflecting surfaces and thus six possible interferometric pairs/cavities. By using fast Fourier transform it is possible to obtain de-multiplexed measurements for each cavity. This will be particularly important for bioassays where positive and negative controls are required to be measured within close spatial proximity.

We report a high temperature fiber sensor based on the multimode interference effect within a suspended core microstructured optical fiber (SCF). By splicing a short section of SCF with a lead-in single-mode fiber (SMF), the sensor head was formed. A complex interference pattern was obtained in the reflection spectrum as the result of the multiple excited modes in the SCF. The complexity of the interference indicates that there are more than two dominantly excited modes in the SCF, as resolved by Fast Fourier Transform (FFT) analysis of the interference. The proposed sensor was subjected to temperature variation from 20°C to 1100°C. The fringe of the filtered spectrum red-shifted linearly with respect to temperature varying between 20°C and 1100°C, with similar temperature sensitivity for increasing and decreasing temperature. Phase monitoring was used for an extended temperature experiment (80 hours) in which the sensor was subjected to several different temperature variation conditions namely (i) step-wise increase/decrease with 100°C steps between 20°C and 1100°C, (ii) dwelling overnight at 400°C, (iii) free fall from 1100°C to 132°C, and (iv) continuous increase of temperature from 132°C to 1100°C. Our approach serves as a simple and cost-effective alternative to the better-known high temperature fiber sensors such as the fiber Bragg grating (FBG) in sapphire fibers or regenerated FBG in photosensitive optical fibers.

Resonant profile shift resulting from a change of resonant conditions is classically used for sensing, either liquid refractive index or immobilized biological layer effective thickness. Resonant waveguide gratings (RWG) allow sensing over a large spectral domain, depending on the materials and geometrical parameters of the grating. Profiles measurements usually involve scanning instrumentation. We recently demonstrated that direct imaging multi-assay RWGs sensing may be rendered more robust using spatial Fano profiles from “chirped” RWG chips. The scheme circumvents the classical but demanding scans: instead of varying angle or wavelength through fragile moving parts or special optics, a RWG structure parameter is varied. Our findings are illustrated with resonance profiles from nanostructured silicon nitride waveguide on glass. A sensitivity down to Δn=2x10^-5 or biomolecules mass density of 10 pg/mm² is demonstrated through theory and experiments. To assess different sensing wavelength, the period might also vary within the same chip support. We discuss guiding properties and sensing sensitivities of RWG sensing over the whole visible spectral range. Resonant profiles are analyzed using a correlation approach, correlating the sensed signal to a zero-shifted reference signal. This analysis was demonstrated to be more accurate than usual fitting, for analyzing signals including noise contribution. The current success of surface plasmon imaging suggests that our work could leverage an untapped potential to extend such techniques in a convenient and sturdy optical configuration. Moreover, extended spectral range sensing can be addressed by dielectric waveguide structures. This allows sensitive sensing of small volumes of analyte, which can be circulated close from the resonant waveguide. Together with the demonstration of highly accurate fits through correlation analysis, our scheme based on a “Peak-tracking chip” demonstrates a new technique for multispectral sensitive sensing through nanostructured chip imaging.

Sensors based on functionalized optical resonators provide high specificity, high sensitivity, very high detection limit and fast response. The sensing principle of such sensors is based on the detection of a change of environment at the vicinity of the optical resonator surface. This change induces an effective index variation of the guided mode circulating in the resonator, resulting in a resonance spectral shift in the optical resonator response. The detection limit (i.e. the smallest amount of analyte that can be detected by sensors) depends on the resolution of the sensor and of its background noise. Improving the detection limits of sensors requires then to minimize their background noise by exploring various real-time configurations. In this report, we present direct measurements methods at different points of the resonance transmittance response (at minimum point and at inflexion points where the slope of transmittance is maximum) and indirect methods (resonance transmittance fit with Lorentzian and microresonator transmission models) to determine the resonance wavelength. Using an optofluidic label-free sensor based on a polymeric vertically coupled optical microracetrack, we demonstrated that measuring a spectral shift at the minimum of the sensor spectral transmittance at resonance is not the best solution to reduce the measurement background noise of sensors. For different analyte concentrations, the background noise obtained with the inflexion point method is reduced 3 times as compared to the minimum point method. On another hand, the sensor response time is 1000 times less than that obtained with the method using transmission model fitting or Lorentzian fitting. This method of measurement can be extended for any sensors based on optical resonators.

This paper considers possible ways of application of whispering gallery modes and resonators for rotation sensing.

We demonstrate that Fourier-domain transmission OCT is a versatile tool to measure optical material properties of turbid media. We develop an analytical expression for the transmission OCT signal. Based on this analysis we determine the group refractive index, group velocity dispersion, absorption coefficient, and scattering coefficient. The optical dispersion is accurately measured for glasses, liquids, and water/glucose mixtures. The optical attenuation is measured in the spatial domain and compared to Mie calculations combined with concentration dependent scattering effects. In the wave vector domain the spectral dependence of the optical attenuation is measured and compared to literature values. The developed technique can be used for optical sensing of attenuation and dispersion.

Under mechanical stress, the optical transmission coefficient of a translucent composite material changes. In this study, the optical response, defined as transmitted luminous flux function of the stress, is used to characterize the optomechanical behavior. Tensile tests were carried out on composite specimens made of glass fibers and epoxy resin. A visible imaging instrument has been developed to characterize this opto-mechanical response. The used camera has permitted to map the two-dimensional behavior, resulting from the heterogeneous stress field. Monotonic tests have been conducted as well as fatigue tests, to analyze de damage state along the material cycle life. In this study, both the principle and the experimental setup of this contactless method are described.

We analyze the effect of contaminants on the quadrupolar magnetic, dipolar electric and dipolar magnetic resonances of silicon nanoparticles (NPs) by considering the spectral evolution of the linear polarization degree at right angle scattering configuration, P_L(90°). From an optical point of view, a decrease in the purity of silicon nanoparticles due to the presence of contaminants impacts the NP effective refractive index. We study this effect for a silicon nanosphere of radius 200 nm embedded in different media. The weakness of the resonances induced on the P_L(90°) spectrum because of the lack of purity can be used to quantify the contamination of the material. In addition, it is shown that Kerker conditions also suffer from a spectral shift, which is quantified as a function of material purity.

This study introduces the application of small ceria nanoparticles (NPs) as optical sensor for peroxide using fluorescence quenching technique. Our synthesized ceria nanoparticles have the ability to adsorb peroxides via its oxygen vacancies. Ceria nanoparticles (NPs) solution with added variable concentrations of hydrogen peroxides is exposed through near UV excitation and the detected visible fluorescent emission is found to be at ~520nm, with reduced peak intensity peaks with increasing the peroxide concentrations due to static fluorescence quenching technique. The relative intensity change of the visible fluorescent emission has been reduced to more than 50% at added peroxide concentrations up to 10 wt.%. This research work could be applied further in optical sensors of radicals in biomedical engineering and environmental monitoring.

One of the most significant challenges facing physical and biological scientists is the accurate detection and identification of single molecules in free-solution environments. The ability to perform such sensitive and selective measurements opens new avenues for a large number of applications in biological, medical and chemical analysis, where small sample volumes and low analyte concentrations are the norm. Access to information at the single or few molecules scale is rendered possible by a fine combination of recent advances in technologies. We propose a novel detection method that combines highly sensitive label-free resonant sensing obtained with high-Q microcavities and position control in nanoscale pores (nanopores). In addition to be label-free and highly sensitive, our technique is immobilization free and does not rely on surface biochemistry to bind probes on a chip. This is a significant advantage, both in term of biology uncertainties and fewer biological preparation steps. Through combination of high-Q photonic structures with translocation through nanopore at the end of a pipette, or through a solid-state membrane, we believe significant advances can be achieved in the field of biosensing. Silicon microrings are highly advantageous in term of sensitivity, multiplexing, and microfabrication and are chosen for this study. In term of nanopores, we both consider nanopore at the end of a nanopipette, with the pore being approach from the pipette with nanoprecise mechanical control. Alternatively, solid state nanopores can be fabricated through a membrane, supporting the ring. Both configuration are discussed in this paper, in term of implementation and sensitivity.

In this work, we present a study on photonic biosensors based on Si₃N₄ asymmetric Mach-Zehnder Interferometers (aMZI) for Aflatoxin M1 (AFM1) detection. AFM1 is an hepatotoxic and a carcinogenic toxin present in milk. The biosensor is based on an array of four Si₃N₄ aMZI that are optimized for 850nm wavelength. We measure the bulk Sensitivity (S) and the Limit of Detection (LOD) of our devices. In the array, three devices are exposed and have very similar sensitivities. The fourth aMZI, which is covered by SiO₂, is used as an internal reference for laser (a VCSEL) and temperature fluctuations. We measured a phase sensitivity of 14300±400 rad/RIU. To characterize the LOD of the sensors, we measure the uncertainty of the experimental readout system. From the measurements on three aMZI, we observe the same value of LOD, which is ≈ 4.5×10⁻⁷ RIU. After the sensor characterization on homogeneous sensing, we test the surface sensing performances by flowing specific Aflatoxin M1 and non-specific Ochratoxin in 50 mM MES pH 6.6 buffer on the top of the sensors functionalized with Antigen-Recognising Fragments (Fab’). The difference between specific and non-specific signals shows the specificity of our sensors. A moderate regeneration of the sensors is obtained by using glycine solution.

Here, we report on the enhancement of molecular vibrational transitions overtones due to the excitation of surface plasmon polariton waves. We show that, assuming a modified Kretschmann-Reather configuration with ultra-thin dielectric over-layer, the effective absorption cross section of higher harmonics of molecular vibrations is boosted by at least two orders of magnitude. Based on the experimental observations reported by Karabchevsky and Kavokin [1] on photonic waveguides, we calculate the differential absorption which appears to exhibit a Fano-like line shape. This manifests the interaction between a narrow molecular resonance and a broad plasmonic mode. In fact, the interaction occurs due to the highest enhancement of the vibrational transitions overtones when the vibration mode and plasmonic mode are detuned. The enhancement factor reported in this study points on feasibility of vibrational overtones detection using conventional spectrometers. In addition, having high signal-to-noise ratio opens a new route for molecular detection and sensing.

This paper presents a novel infrared and visual image registration method based on phase grouping and mutual information of gradient orientation. The method is specially designed for infrared image navigation, which is different from familiar multi-sensor image registration methods in the field of remote sensing. The central idea is to firstly extract common salient structural features from visual and infrared images through phase grouping, then registering infrared image to visual image and estimating the exterior parameters of the infrared camera. Two subjects are involved in this reports: (1) In order to estimate image gradient orientation accurately, a new method based on Leguerre-Gauss filter is presented. Then the image are segmented by grouping of pixels based on their gradient orientations and ling support regions are extracted as common salient structural features from infrared and visual images of the same ground scene. (2)In order for registering infrared and visual image, coordinate systems are constructed, coordinate transformations are formularized, and the new similarity measures based on orientation mutual information is presented. Quantitative evaluations on real and simulated image data reviews that the proposed method can provide registration results with improved robustness and accuracy.

The foundation of measurement systems for environmental and structural health monitoring based on molecular condensation nuclei (MCN) detector is the measurement of the intensity of light scattered by aerosol particles. Aerosol particles are formed in the condensation chamber around single molecules of detected impurities (harmful and dangerous substances in the case of environmental monitoring and biomarkers in the case of structural health monitoring). The size of an aerosol particle is about 10⁶ times larger than the size of the original impurity molecule. The ability of the aerosol particle to scatter incident light also increases ~10¹⁴÷10¹⁶ times compared with the original molecule. By measuring the light scattering intensity the concentration of chemical impurities in the air is determined. The paper investigates many aspects of the detection process - the optical scattering by aerosol particles inside the photometer of MCN detector; signal conditioning, processing of light scattering measurements results, determination of the criteria for making a decision about the presence of detected impurities in the environment; multi-component sensing of detected impurities and graphical user interface design. Experimental results of the detection of toxic substances in micro-concentrations in the environment are presented.

The article is based on some researching considering the three-axis angle measuring autocollimation sensor. Such a sensor allows measuring the deformation of large constructed objects while receiving the information about all three angular freedom degrees. The feasibility of a special tetrahedral prism reflector, with two modes of operation is described and proved. The ability to synthesize such a reflector is proved mathematically; including the description of it’s both modes functioning. All algorithms were taken from the mathematical model of such a reflector functioning, which was created while the researching. First mode allows measuring the roll angle with high accuracy, and the second mode allows measuring the collimation angles, using different types of light reflected beams. So there are two ways to measure collimation angles: rough and precise. The algorithm for rough way of collimation angles measuring is quite similar to the roll algorithm measuring and used for the adjustment and for the initial setting the autocollimation sensor. The precise algorithm is used for the prime measuring in a complex with roll angle measuring to get full information of three-dimensional deformation of the object. The experimental stand was researched to confirm the correctness of all algorithms of the reflector and the sensor functionality in the whole. The technical characteristics of the experimental setup are presented.

The efficient application of electro-optic effect in lithium niobate based Mach-Zehnder interferometer (MZI) to construct the temperature sensor is used. An experimental set up for liquid temperature sensor is proposed. Temperature dependence of the bending loss light energy in multimode micro-plastic optical fiber (m-POF) and electro-optic effect of MZI are used. The performance of sensor at different temperatures is measured. It is seen that the light output of MZI switches from one port to the other port as temperature of liquid changes from 0°C to 100°C.

In this paper, an interferometric fiber optic vibration sensor based on a four-core optical fiber is described. When the light is coupled into the four cores, each core acts as a mutually coherent waveguide with the other ones, which allows obtaining an interference fringe pattern at the far field. Vibrating a section of the four-core optical fiber causes a path difference between the light beams guiding in the separate cores, which results in a shift in the fringe pattern. Such a mechanism allows one to relate the fringe shift to the vibration amplitude and frequency. In this study, a source, which is capable to generate 100 Hz frequency sound waves is attached to the optical fiber to maintain vibration of the section of the fiber. A single slit and a photodetector are used to detect the shifting of the fringe pattern that causes a change in the phase of the guiding light. When a He-Ne laser beam is coupled into the optical fiber, the structured fringe pattern is projected onto the slit behind the photodetector, then a small part of the fringe pattern is analysed. Thus, an interferometric fiber optic vibration sensor based on a four-core optical fiber, which has a simple structure and high sensitivity, is accomplished.

An intensity modulated Fiber optic prism based liquid concentration sensor is proposed. The sensing principle is based on total internal reflection (TIR) inside the prism which gets modulated in the vicinity of liquid as a function of refractive index. The precise movement of sensor head in liquids, gives rise to a hysteresis curve which is considered as a measure of liquid concentration. Different liquid concentrations of Sucrose, Saline solution (NaCl) and Glycerin are taken for the study. The sensor exhibits sensitivity of 371.16, 2133.25 and 1501.89 Sucrose, Saline water and Glycerin solutions respectively.

Laser Doppler Velocimeter (LDV) with a laser diode and Self-mixing effect is a new type of downsized and low cost LDV with high precision measurement. We propose a new LDV using a 3-beam fiber irradiation scheme. The sensor head consists of 3-fibers which are intersected perpendicularly each other. This new LDV enables three-dimensional velocity measurement. That is, the magnitude and direction of the velocity vector of the moving object can be measured independent on the relative position between the moving object and the 3-beam sensor head. We also study the case that these 3 beams are not right-angled each other. Operation principle and experimental results for both cases are reported.

In this paper, a novel design of highly sensitive biosensor based on photonic crystal fiber is presented and analyzed using full vectorial finite element method. The suggested design depends on using silver layer as a plasmonic active material coated by a gold layer to protect silver oxidation. The reported sensor is based on the detection using the quasi transverse electric (TE) and quasi transverse magnetic (TM) modes which offers the possibility of multi-channel/multi-analyte sensing. The sensor geometrical parameters are optimized to achieve high sensitivity for the two polarized modes. High refractive index sensitivity of about 4750 nm/RIU (refractive index unit) and 4300 nm/RIU with corresponding resolutions of 2.1×10^-5 RIU, and 2.33×10^-5 RIU can be obtained for the quasi TM and quasi TE modes, respectively.

As the progress of optical technologies, different commercial 3D surface contour scanners are on the market nowadays. Most of them are used for reconstructing the surface profile of mold or mechanical objects which are larger than 50 mm×50 mm× 50 mm, and the scanning system size is about 300 mm×300 mm×100 mm. There are seldom optical systems commercialized for surface profile fast scanning for small object size less than 10 mm×10 mm×10 mm. Therefore, a miniature optical system has been designed and developed in this research work for this purpose. Since the most used scanning method of such system is line scan technology, we have developed pseudo-phase shifting digital projection technology by adopting projecting fringes and phase reconstruction method. A projector was used to project a digital fringe patterns on the object, and the fringes intensity images of the reference plane and of the sample object were recorded by a CMOS camera. The phase difference between the plane and object can be calculated from the fringes images, and the surface profile of the object was reconstructed by using the phase differences. The traditional phase shifting method was accomplished by using PZT actuator or precisely controlled motor to adjust the light source or grating and this is one of the limitations for high speed scanning. Compared with the traditional optical setup, we utilized a micro projector to project the digital fringe patterns on the sample. This diminished the phase shifting processing time and the controlled phase differences between the shifted phases become more precise. Besides, the optical path design based on a portable device scanning system was used to minimize the size and reduce the number of the system components. A screwdriver section about 7mm×5mm×5mm has been scanned and its surface profile was successfully restored. The experimental results showed that the measurement area of our system can be smaller than 10mm×10mm, the precision reached to ±10μm, and the scanning time for each surface of an object was less than 15 seconds. This has proved that our system own the potential to be a fast scanning scanner for small object surface profile scanning.

This article proposes an optical method for monitoring the growth of Escherichia coli in Luria Bertani medium and Saccharomyces cereviciae in YPD. Suitable light is selected which on interaction with the analyte under consideration, gets adsorption / scattered. Required electronic circuitry is designed to drive the laser source and to detect the intensity of light using Photo-detector. All these components are embedded and arranged in a proper way and monitored the growth of the microbs in real time. The sensors results are compared with standard techniques such as colorimeter, Nephelometer and hemocytometer. The experimental results are in good agreement with the existed techniques and well suitable for real time monitoring applications of the growth of the microbs.

In this paper, the simulation and design of a waveguide for water turbidity sensing are presented. The structure of the proposed sensor uses a 2x2 array of multimode interference (MMI) coupler based on micro graphene waveguide for high sensitivity. The beam propagation method (BPM) are used to efficiently design the sensor structure. The structure is consist of an array of two by two elements of sensors. Each element has three sections of single mode for field input tapered to MMI as the main core sensor without cladding which is graphene based material, and then a single mode fiber as an output. In this configuration MMI responses to any change in the environment. We validate and present the results by implementing the design on a set of sucrose solution and showing how these samples lead to a sensitivity change in the sensor based on the MMI structures. Overall results, the 3D design has a feasible and effective sensing by drawing topographical distribution of suspended particles in the water.

Often, in practice, there is a problem of large areas of space viewing in order to fix certain parameters of moving objects. A multichannel optical-electronic monitoring system with a discrete angular field (or, as they say, artificial compound eye system) is an interesting variant to solve this problem. Such systems can be used for the analysis of various parameters of the objects, as an example for positioning of the object in wide annular zone. Using these systems we can get a wide angular field up to the full sphere due to a combination of a large number of elementary light detecting channels (like compound eyes of insects) and have a gain in the useful signal due to overlapping angular fields of channels. Currently, multichannel optoelectronic systems with discrete angular field are described and studied less than other up-to-date monitoring devices. But existing analogues are presented by experimental samples, which demonstrate the relevance of the research and design of such devices. This work presents a brief review of monitoring system with discrete angular field and theoretical description of proposed prototype. Results of experimental studies of mentioned prototype are presented as well.

A novel gas sensing system based on a tunable fiber Bragg grating (FBG) and a Super luminescent light emitting diode (SLED) source is proposed for trace gas sensing. Such a system has been demonstrated for precise detection of acetylene (C₂H₂) using wavelength modulation spectroscopy technique (WMS) based on modulating the Bragg wavelength of FBG within the width of an absorption line of a target gas. The sensing system has been calibrated against specific gas concentrations (ppm) through controlled experiments and the minimum detectable acetylene (C₂H₂) gas concentration is experimentally found to be ~ 80 ppm (0.008% by volume). Furthermore, the detection limit of the system is estimated to be limited by the noise floor of our system at ~ 7 ppm (0.0007% by volume). The proposed system provides a relatively inexpensive alternative for trace gas sensing based on a well-established FBG technology. Moreover, the proposed system has tremendous potential for simultaneous detection of multiple species through the use of a cascaded set of carefully chosen FBGs.

We compare two algorithms to determine the radial profile of the photoelastic coefficient C in glass optical fibers. We first measure the retardance profile of a transversally illuminated fiber as a function of tensile load. The radial profile C(r) is obtained from the inverse Abel transform of this retardance profile. Our first algorithm expands the measured retardance in its Fourier coefficients before computing the inverse Abel transform. With the second algorithm the expected result of the inverse Abel transform is expanded and the forward Abel transform of that expansion is compared to the measured retardance. We apply both approaches on the retardance measurement of commercially available single mode and multi-mode fibers.

The paper deals with influence of orientation of matrix detector relative to incident light on its sensitivity area from the viewpoint of polarization. The calculation algorithm based on Jones matrix formalism is presented. The results obtained with calculations and experiment with Stokes polarimeter are shown.

Remote optoelectronic probing is one of the most actual aspects of overhead electric line maintenances. By installing such systems on a helicopter (for example) it becomes possible to monitor overhead transmission line status and to search damaged parts of the lines. Thermal and UV-cameras are used for more effective diagnostic. UV-systems are fitted with filters, that attenuate visible spectrum, which is an undesired type of signal. Also these systems have a wide view angle for better view and proper diagnostics. For even more effectiveness, it is better to use several spectral channels: like UV and IR. Such spectral selection provides good noise reduction. Experimental results of spectral parameters of the wide view angle multispectral objective for such systems are provided in this report. There is also data on point spread function, UV and IR scattering index data and technical requirements for detectors.

In this paper, the fiber Bragg gratings are investigated in the context of sensing of deformation inside a sample of a glued laminated timber. For this purpose, a fiber with acrylate recoated Bragg grating is placed and glued between the timber laminates. Since there are still some open questions leading now, one of the goals is to specify, if the sensor that is embedded inside the timber can operate as the sensor that is not. Therefore, the strain of the not embedded sensor is numerically investigated in the first step as the change in the grating period. In order to calculate the Bragg wavelength associated to the grating period, the light propagation through the fiber has been modeled by rigorous and versatile eigen mode expansion method. Based on the simulation result, the authors are able to determine the sample strain under the mechanical load by measuring the reflected Bragg wavelength. Moreover, the measured strain is compared with the strain analytically obtained from the known force applied on the sample. The both strains are in good agreement.

In this publication we investigate distributed mode-mode fiber interferometer (MFI) with ability of external impact localization. It is based on bidirectional continuous selective excitation of multimode fiber (MMF) with increasing of launched modes quantity along the MMF from excitation point to the opposite end of fiber. Two photo detection systems register output signals from both directions. MFI output signal characteristics such as amplitude and spectrum width depend on excited modes quantity at the point of perturbation. Thus, every fiber point is characterized by two opposite direction signal parameters. Calculating these parameters’ values makes it possible to localize the segment subjected by external impact. Experimental MFI setup include 3 MMF segments with 2 mode controllers among them which increase excited modes number from segment to segment. During the experiment, every MMF segment was subjected by arbitrary external perturbations and output signals were analyzed. Obtained results confirmed the ability of localization.

Robust classification of pharmaceuticals in an industrial process is an important step for validation of the final product. Especially for pharmaceuticals with similar visual appearance a quality control is only possible if a reliable algorithm based on easily obtainable spectroscopic data is available. We used Principal Component Analysis (PCA) and Support Vector Machines (SVM) on Raman spectroscopy data from a compact Raman system to classify several look-alike pharmaceuticals. This paper describes the data gathering and analysis process to robustly discriminate 19 different pharmaceuticals with similar visual appearance. With the described process we successfully identified all given pharmaceuticals which had a significant amount of active ingredients. Thus automatic validation of these pharmaceuticals in a process can be used to prevent wrong administration of look-alike drugs in an industrial setting, e.g. patient individual blistering.

We present a reference-less and time-multiplexing phase retrieval method by making use of the digital micromirror device (DMD). In this method, the DMD functions not only as a flexible binary mask which modulates the optical field, but also as a sampling mask for measuring corresponding phases, which makes the whole setup simple and robust. The DMD reflection forms a sparse intensity mask in the pupil which produces speckle pattern after propagation. With the recorded intensity on the camera and the binary pattern on the DMD, the phase in all the ‘on’ pixels can be reconstructed at once by solving inverse problems with iterative methods, for instance using Gerchberg-Saxton algorithm. Then the phase of the whole pupil can be reconstructed from a series of binary patterns and speckle patterns. Numerical experiments show the feasibility of this phase retrieval method and the importance of sparse binary masks in the improving of convergence speed.

Because of high surface-to-volume ratio, few layers MoS₂ material as a kind of 2D materials has been attracted more attention nowadays to be used for photonics devices. We investigated the performance of few-layer MoS₂ when it is covered on a side polished fiber (SPF) to sense relative humidity (RH) of environments. The SPF was made by wheel side polishing method. The few layers MoS₂ was deposited on the side polished surface to be a sensing material. As the environmental humidity changes, the output optical power of the all fiber sensor will change due to the interaction between evanescent field of fiber and MoS₂ material. The change of output power of fiber sensor can reach 16.67dB in the relative humidity range of 40-85%. Experiments using the fiber sensor on human breathing have been made and the respondence has achieved. The experiments showed that the fiber sensor can be used in medical instruments. Key words: fiber sensor, side-polished fiber, humidity sensing, 2D material, MoS₂.

The aim of this paper is to develop and investigate MOEMS displacement-pressure sensor for biological information monitoring. Developing computational periodical microstructure models using COMSOL Multiphysics modeling software for modal and shape analysis and implementation of these results for design MOEMS displacement-pressure sensor for biological information monitoring was performed. The micro manufacturing technology of periodical microstructure having good diffraction efficiency was proposed. Experimental setup for characterisation of optical properties of periodical microstructure used for design of displacement-pressure sensor was created. Pulsating human artery dynamic characteristics in this paper were analysed.

Advanced metrology equipment, in particular an average power meter for laser radiation, is necessary for effective using of laser technology. In the paper we propose a measurement scheme with periodic scanning of a laser beam. The scheme is implemented in a pass-through average power meter that can perform continuous monitoring during the laser operation in pulse mode or in continuous wave mode and at the same time not to interrupt the operation. The detector used in the device is based on the thermoelastic effect in crystalline quartz as it has fast response, long-time stability of sensitivity, and almost uniform sensitivity dependence on the wavelength.

A novel type of coreless side-polished fiber (CSPF) was investigated numerically and experimentally for sensing refractive index (RI). Numerical simulations and experiments found that multi-mode interference can be excited at the transitional section of coreless side-polished fiber, leading to resonant dips in transmission spectrum through such a CSPF. A red shift of such dips was observed due to increase in surrounding RI, whereby the CSPF can be used as RI sensor. Interestingly, by such a simple CSPF structure, ultra-high sensitivity of 7225nm/RIU for RI range of 1.432 to 1.434 was achieved in our experiment. As the CSPF can act as a versatile platform, the high sensitivity of the CSPF will open new opportunities for other high sensitive sensors and fiber devices.

The industry of the agave-derived bacanora, in the northern Mexican state of Sonora, has been growing substantially in recent years. However, this higher demand still lies under the influences of a variety of social, legal, cultural, ecological and economic elements. The governmental institutions of the state have tried to encourage a sustainable development and certain levels of standardization in the production of bacanora by applying different economical and legal strategies. However, a large portion of this alcoholic beverage is still produced in a traditional and rudimentary fashion. Beyond the quality of the beverage, the lack of proper control, by using adequate instrumental methods, might represent a health risk, as in several cases traditional-distilled beverages can contain elevated levels of harmful materials. The present article describes the qualitative spectral analysis of samples of the traditional-produced distilled beverage bacanora in the range from 0 cm⁻¹ to 3500 cm⁻¹ by using a Fourier Transform Raman spectrometer. This particular technique has not been previously explored for the analysis of bacanora, as in the case of other beverages, including tequila. The proposed instrumental arrangement for the spectral analysis has been built by combining conventional hardware parts (Michelson interferometer, photo-diodes, visible laser, etc.) and a set of self-developed evaluation algorithms. The resulting spectral information has been compared to those of pure samples of ethanol and to the spectra from different samples of the alcoholic beverage tequila. The proposed instrumental arrangement can be used the analysis of bacanora.

Identifying methane anomalies responsible for the temperature increase, by hiking trails in the Arctic requires great human labor. It is necessary to use lidar methods for search and identification of methane from permafrost. Necessary to create a Raman lidar for monitoring of emissions of methane hydrate from the permafrost. Hyperspectral resolution would resolve the isotope shifts in the Stokes spectra, thereby to determine the isotopic composition of methane ratio C¹⁴/C¹² CH₄ carbon emissions and identify the source for study (permafrost or oil deposits)

To provide operating supervision of the process there is a need of means of control with high temporal stability and resistance to radiation excess. Receivers based on the thermoelastic effect in crystalline quartz are designed for energy measurement of lasers in single impulse mode or for average power measurement in operation monitoring of industrial lasers. In the research we analyze work of the receiver at single impulse exposure. The heat storage time of the receiver is defined. Specifics of signal generation in receivers on thermoelastic effect at multiple impulse exposure are also analyzed. An algorithm for voltage calculation of the receiver with given parameters is developed. The modelling shows that generated signal growth in the detector exposed to an impulse consequence can influence the power measurement result and thus the ways to reduce the effect are proposed.

As a part of the work carried out a project supported by the Danish council for technology and innovation, we have investigated the option of smoothening standard CNC machined surfaces. In the process of constructing optical prototypes, involving custom-designed optics, the development price and time can become a prohibitively large part of a research budget. Machining the optical surfaces of a molding tool may be done directly using diamond turning, but it is expensive and time consuming. Alternatively, a more standardized and cheaper machining method can be used, however, calling for manual polishing afterwards. Particularly, this last process is expensive as well, and will introduce an uncertainty in precisely how much material the polishing process will remove, introducing roughness on a larger lateral scale, such as waviness. Therefore, we have investigated the possibilities of smoothening surfaces of various shapes succeeding a standard CNC machining process. Different coatings have been tested for their abilities to fill and smoothen out structures of larger scales, while removing the small-scale roughness, which is critical for optical uses. In this work we will present an optical element, designed for optical spatial filtering velocimetry. The spatial filter is the key component in an optical sensor for non-contact measurement of surface vibrations, based on speckle dynamics. The optical element is casted in silicon. The results of smoothing an optical element will be demonstrated, and the sensor will be demonstrated for real-time measurements.

The article is devoted to assessing the impact of various external factors on the characteristics of microoptical gyroscope sensing elements. The rating is based on the results of a m ultiphysical modeling using software OOFELIE: Multiphysics.

The report presents the results of analysis of the angle measurement system intended for measuring angles between some directions set in the space by reflectors. Dynamic mode of system operation is defined by continuous rotation of platform with the autocollimating null-indicator. The angle measurements are provided by the ring laser or the holographic optical encoder.

Hollow gold nanostructures (HGNS) have been used in variety of optical biosensors due to their inherent advantage of operating at near infra red (NIR) wavelength, large extinction coefficient and high dielectric sensitivity. The absorption wavelength of these nanostructures can be modulated by changing the ratio of hollow region to the core shell thickness. The aim of the present study is to incorporate the properties of HGNS, to develop LSPR based U-bent fiber optic sensor for detection of pathogens. The detection was carried out using an experimental set up consisting of a white light source, 200 μm diameter optical fiber having bend diameter of 1.6 mm ± 0. 2 mm and a spectrometer. The HGNS were immobilized on the decladded portion of the fiber optic probe by chemisorptions. The effective plasmon penetration depth of the HGNS immobilized fiber optic sensor was approximated by using alternating layers of positively and negatively charged polyelectrolytes. The HGNS immobilized U-bent fiber optic sensor was used for detection of E.coli B40 strain using bacteriophage T4. The preliminary experiments were carried out with 10⁴ cfu/ml of E.coli B40 and the change in absorbance obtained was approx. 0.042 ± 0.0045 abs. units (n = 3). The response of this sensor was found to be better than spherical gold nanoparticle immobilized sensing platforms.

Interferometric sensors can be categorized as highly sensitive and precise devices with series inconsiderable benefits from the possibility of using standard telecommunication fibers. They can be measured even small changes in the deformation of shapes in time, changes in temperature, pressure, voltage, vibration, electric field, etc. The basic idea, which is described in this article is the usage of the interferometer as a security and monitoring component, which offers a solution for securing of closed spaces, especially before unwanted entries. Its primary task is to detect intrusions - disrupting the integrity of the transparent window area due to vibration response. The base of the solution is a Mach-Zehnder interferometer, which consists of two arms in the power distribution ratio of 1:1, consisting of the SM optical fiber excited by a DFB laser. The interferometer is working on the wavelength of 1550 nm. The resulting signal is registered as a result of interference of optical beams from the reference and sensor arm. Realized measuring scheme was terminated optical receiver comprising PbSe detector. Below described experimental measurements have shown that implemented interferometer has a sufficient value of the signal to noise ratio (SNR) and is able to detect very weak signals in a wide frequency range from tens of Hz to kHz units. The signal was processed by applications developed for the amplitude-frequency spectrum. Evaluated was the maximum amplitude of the signal and compared to the noise. The results were verified by retesting the assembled prototype.

We report results from a wide range of laser operating conditions, typical for laser induced breakdown spectroscopy (LIBS) and laser ablation (LA) experiments on copper metallic target, which form the basis of further systematically investigation of the effect of laser irradiance, pulse duration and wavelength, on the target, plume and plasma behavior, during and after laser-solid interaction. In the LA experiment, the laser beam was focused through a 25 cm focal length convergent lens on a plane copper target in air, at atmospheric pressure. The target was rotated in order to have fresh areas under laser irradiance. In the LIBS experiment, the Applied Photonics LIBS-6 instrument allowed modifying the laser irradiance at the sample surface by changing the pulse energy or the laser focusing distance. For the duration of the laser pulse, the power density at the surface of the target material exceeds 10⁹ W/cm² using only a compact laser device and simple focusing lenses. The plasma parameters were experimentally estimated from spectroscopic data generated by the plasma itself, namely by the line intensities and their ratio which reflect the relative population of neutral or ionic excited species in the plasma. The fitting of the Saha-Boltzmann plot to a straight line provides an apparent ionization temperature, whose value depends on the lines used in the plots. For the typical conditions of LA and LIBS, the temperature can be so high that Cu+ ions are formed. The first-order ionization of Cu (i.e., the ratio of Cu⁺/Cu⁰ ) is calculated.

A promising area of modern astronomy is the study of the field of millimeter waves. The use of this band is due to a large extent the spectrum characteristics of the propagation of waves in the atmosphere, short wavelength. Currently, Russia jointly with Uzbekistan is implementing a project to build a radio astronomy observatory on the Suffa plateau (Uzbekistan). The main instrument of the observatory is fully steerable radio telescope RT-70 type. Main mirror telescope is a fragment of an axisymmetric parabolic with a focal length of 21 m, consisting of 1200 reflecting panels; main mirror diameter - 70 m; diameter of counter reflector - 3 m. A feature of the radio telescope as a means of research in the millimeter wavelength range are high for the quality requirements parabolic surface of the primary mirror (standard deviation of points on the surface of the theoretical parabolic is not more than 0.05 mm), to the stability of the mutual arrangement of the primary mirror and the counter reflector (not more than 0, 07 mm) for precision guidance in the corners of the mirror system azimuth and elevation (margin of error 1.5-2"). Weight of structure, temperature changes and air shock result in significant deformation elements radio telescope construction (progressive linear displacements of points of the surface of the main mirror), reaching in the marginal zone of 30 mm; counter reflector shift of up to 60 mm; Unlike the angular position of the axis of the beam pattern of the radio telescope of the measured angle transducers can reach 10 ". Therefore, to ensure the required quality of the reflective elements RT-70 systems, as well as the implementation of precision-guided munitions needs complex measuring deformation elements telescope design. This article deals with the construction of opto-electronic system of remote optoelectronic displacement sensor control elements mirror telescope system.