This PDF file contains the front matter associated with SPIE Proceedings Volume 10209, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

The utilization of metamaterials as spatial light modulators (SLMs) offers a new route to achieve reconfigurable single pixel imaging systems. Here we demonstrate a metamaterial SLM hat permits high speed imaging at terahertz frequencies using communications engineering techniques. Specifically we implement quadrature amplitude modulation (QAM) with our all-electronic metamaterial SLM, which enables a doubling of the imaging frame rate. A second independent technique of frequency diverse imaging uses a number of sub-carriers to permit parallelization of the imaging process, which results in an increase in imaging speed only limited by signal to noise. Our results are not limited to the terahertz band, but may be scaled to nearly any sub-optical range of the electromagnetic spectrum, and verify the potential of metamaterials to operate as reconfigurable multifunctional devices which will enable next generation imaging systems.

Conventional optical lenses focus electromagnetic waves by imparting position-dependent phase delay through shaping their geometry. This poses difficulties in eliminating the geometric aberrations in high numerical aperture lenses, in addition to the fabrication challenges when operating at short wavelengths (e.g. visible light), and bulky devices operating at long wavelengths (e.g. microwaves). In contrast, metasurfaces realize full control of phase through tailoring the subwavelength resonant structures, allowing for the demonstration ultrathin flat lens, although the efficiency is still rather low using single-layer metasurfaces. Here we report the demonstration of high-performance flat lens in the terahertz frequency range using few-layer metasurfaces. The three-layer metasurface structure is capable of rotating the incident linear polarization by 90° with a very high efficiency over a bandwidth of two octaves. More importantly, the phase of the output light can be tuned over the entire 2π range with subwavelength resolution through simply tailoring the structure geometry of the basic building blocks. Based on this success, we design, fabricate, and characterize a metasurface lens operating at 0.4 THz. With a lens diameter and focal length both 5 cm, we realize a high numerical aperture of 0.5 and diffraction-limited terahertz beam focusing. Terahertz time-domain spectroscopy measurements show that the metasurface lens is capable of achieving the same signal intensity as compared to a bulk TPX lens of the same size and focal length.

We review here our efforts to make high power THz sources. We have developed different plasmonic structural designs for the confinement of incident excitation infra-red (800nm, 10fs) laser pulse on SI-GaAs surface. The SI-GaAs surface is modified so that incident radiation is less reflected and more absorbed in the substrate. Fabricating THz antenna structures on it increases the efficiency of the THz source. We have demonstrated this idea in its simplest form by increasing the overall surface area by fabricating trenches on the GaAs surface in the past. The new designs are expected to increase the THz source emission by at least a factor 2 to 4. We have also fabricated quasi-crystal pattern on SI-GaAs substrate to enhance the incident light confinement and checked THz emission from it. The simulated plasmonic structures will be fabricated on the SI-GaAs substrates as well as C-irradiated GaAs substrates. We have shown that our in-house fabricated THz Sources from C-irradiated SI-GaAs showed ~2 orders power increase. The detectors fabricated from these materials showed replica of the incident THz wave compared to the one detected using ZnTe. We will also present use of the C-irradiated substrates in the generation of Continuous Wave (CW) THz sources. All the aforementioned sources have been compared with the commercially available sources made of LT-GaAs.

Although the quantum cascade laser (QCL) is a promising compact semiconductor terahertz (THz) source, its success in creating ultra-short pulses is limited. THz short pulses have many applications, including in time domain spectroscopy. There have been demonstrations of short pulse (few picosecond duration) generation from THz QCLs based on active modelocking, although the stability of the pulses is limited. We show that THz QCLs can be modelocked passively using a two-section cavity, where the sections are in- dependently controlled by bias voltages. While one of the sections produces gain, the other produces quantum coherent saturable absorption and helps to create ultra-short pulses.

We propose new approach for THz image quality enhancing using correlation function (convolution function) between Fourier transform of the image under consideration and Fourier transform of a standard image which can be enough complex. It is very important to stress that a standard image choosing allows us to remove essentially spurious parts of the image.

We discuss one more possibility to remove noise from background of the image as well as possibility of the image decomposition and its reconstruction.

Superconducting niobium nitride (NbN) hot electron bolometers (HEBs) have been used widely in the astronomical observations with its low noise temperature [1] (a few times of the quantum noise limit) as heterodyne detectors. On the other hand, with high temperature coefficient of resistance (TCR) and low noise characteristics, NbN HEB can be considered as direct detectors. Combined with NbN material’s quick response property (response time:~ps), NbN HEB direct detector can be used in quick terahertz (THz) imaging and weak THz ultrashort pulse signal detection. A direct detector system similar to the microwave stability system[2] in our lab has been constructed. The injected microwave is used to suppress the superconducting current and bias the HEB to an optimum bias point combined with the constant DC voltage source. The bias current changes corresponding to the incident THz signal power is read out by the dynamic signal analyzer. Compared to the thermal bias method which used the heating methods to heat the HEB to its critical temperature, the proposed method can enhance the direct detector’s stability and decrease the consumption of the liquid helium, which is key for the long time observations in the astronomical field and so on. More importantly, we found that our method can enhance the TCR of the NbN HEB from 8.45/K with the thermal bias method to 961/K. We obtained the noise equivalent power (NEP) of 1.4×10-12 W/Hz1/2 at 4.2 K and 0.65 THz. This value is mainly limited by the read out circuit at this moment. The response time of 86 ps is obtained in the separate measurement. Further improvement of NEP can be realized with optimizing the read out circuit.

Terahertz (THz)-band communication is envisioned as a key wireless technology to satisfy the need for much higher wireless data rates. To date, major progress in electronic, photonic and plasmonic technologies is finally closing the so-called THz gap. However, the exceedingly large available bandwidth at THz frequencies comes at the cost of a very high propagation loss. Combined with the power limitations of THz transceivers, this results in very short communication distances. Moreover, the absorption by water vapor molecules further splits the THz band in multiple transmission windows, which shrink as the transmission distance increases. To overcome these limitations, the concept of Ultra-Massive Multi-Carrier Multiple Input Multiple Output (UMMC MIMO) communication, which relies on the use of ultra-dense frequency-tunable plasmonic nano-antenna arrays, has been recently proposed. In this paper, the end-to-end performance of a UMMC MIMO link is analytically and numerically investigated. More specifically, an optimization framework is developed to determine the information capacity of UMMC MIMO communication by taking into account both the capabilities of THz plasmonic nanoantenna arrays and the peculiarities of the THz channel. In relation to the arrays, the frequency tunability of each individual element in the transmitter’s and receiver’s plasmonic arrays is taken into account. In terms of the channel, the impact of the spreading loss and the molecular absorption loss is considered. Extensive numerical results are provided to illustrate the performance of the proposed communication scheme.

Digital holography and coherent imaging are explored in the terahertz frequency region at 0.480 Terahertz with highly coherent, frequency-tunable continuous wave sources. The long coherence length of microwave sources suggests that interferometric imaging techniques such as Fresnel off-axis holography can achieve sub-micrometer depth resolution of surfaces and through materials and structures that are transmissive in the terahertz spectral region. Research in this area will provide an important non-destructive imaging tool for the rapidly expanding field of additive manufacturing and composite fabrication. Unfortunately, imaging optics as they are used in confocal imaging and optics in general adversely affect the performance of terahertz imagers as their aperture size if comparable to the wavelength, which artificially limits image resolution according to the diffraction limit and can cause undesirable coherence effects in the image. We report on imaging methods that minimize the use of optics but use signal processing techniques that form images digitally from recorded holograms. This approach is directly applicable to focal plane arrays in contrast to confocal imaging modalities. Furthermore, the performance of image reconstruction at multiple aspect angles compiled into videos as user friendly inspection tool is investigated.

Image sensing technologies and systems operating from the ultraviolet (UV) to long-wave infrared (LWIR) spectral range are being developed for a variety of defense and commercial systems applications. Reflection loss of a significant portion of the incident signal limits the performance of image sensing systems. One of the critical technologies that will overcome this limitation and enhance image sensor performance is the development of advanced antireflection (AR) coatings. In this paper, we review our latest work on high-quality nanostructure-based AR structures, including recent efforts to deposit nanostructured AR coatings on substrates transparent to infrared (IR) radiation. Nanostructured AR coatings fabricated via a scalable self-assembly process are shown to enhance the optical transmission through transparent optical components by minimizing reflection losses in the spectral band of interest to less than one percent, a substantial improvement over conventional thin-film AR coating technologies. Step-graded AR structures also exhibit excellent omnidirectional performance, and have recently been demonstrated in medium wavelength and long wavelength IR spectral bands.

There are enormous optical advantages to use a curved image sensor in place of conventional flat focal plane arrays (FPA) because optical systems intrinsically want to focus to a curved focal surface. For this reason, biological imagers such as the human eye have evolved a curved image sensor (i.e. the retina) that enables use of a simple lens to achieve nearly diffraction-limited imaging over a wide FOV – all in a compact package. Today’s digital imagers sample the curved focal surface using a flat FPA resulting in field-curvature aberrations that impose stringent limitations on the imager’s FOV, F/#, resolution and image quality. Here, we introduce techniques to fabricate hemispherical focal plane arrays to enable the development of compact, wide FOV imaging systems. We have developed monolithically integratable flexible interconnects that can be integrated onto the backside of a planar, silicon FPA designed for hemispherical deformation. These interconnects provide: (1) backside signal routing between small regions of the FPA that were designed to be electrically isolated and (2) a flexible handle for the FPA before a through-wafer etch is performed to mechanically separate the electrically isolated regions of the FPA wafer. This process provides a fully interconnected, flexible FPA that can conform to a hemispherical surface for use in visible (all silicon) or infrared (hybrid) imagers.

After the development of the OCAM2 EMCCD fast visible camera [1] dedicated to advanced adaptive optics wavefront sensing, First Light Imaging moved to the SWIR fast cameras with the C-RED One and the C-RED 2 cameras. These cameras and their performances are described extensively in this paper.

First Light Imaging C-RED One infrared camera is capable of capturing up to 3500 full frames per second with subelectron readout noise and very low background. C-RED One is based on the last version of the SAPHIRA detector developed by Leonardo UK. This breakthrough has been made possible thanks to the use of an e-APD infrared focal plane array which is a real disruptive technology in imagery. C-RED One is an autonomous system with an integrated cooling system and a vacuum regeneration system. It operates its sensor with a wide variety of read out techniques and processes video on-board thanks to a Xlinks embedded FPGA.

In addition to this project, First Light Imaging developed an InGaAs 640x512 fast camera with unprecedented performances in terms of noise, dark and readout speed for equivalent products. This camera is based on the SNAKE SWIR detector from Sofradir and was called C-RED 2. The C-RED 2 characteristics and performances are also fully described in this paper.

The C-RED One project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement N° 673944. C-RED2 development is supported by the "Investments for the future" program and the Provence Alpes Côte d'Azur Region, in the frame of the CPER.

This work presents the deposition and characterization of Al_xN_y thin films for using them as pyroelectric detector material. To test the pyroelectric effect, capacitors with Au electrodes were fabricated. The diameter of the electrodes for capacitor used was 1100 μm while the distances between these two electrodes was 2200 μm. On a 3- inch diameter cleaned silicon wafer a 100-nm thick Al_xN_y films were deposited using an Al target and Ar:N₂ = 1:1 flow and 5 mTorr chamber pressure. Finally, a 100-nm thick Au layer was deposited and lifted off by using conventional photo lithography to form the electrodes of capacitors. All the layers were deposited by radio frequency sputtering at room temperature. The Al_xN_y thin films were annealed at 700 ⁰C in N₂ environment for 10 minutes. X-ray diffraction showed that the films are poly-crystalline with peaks in (100), (002) and (101) directions. The pyroelectric current increased from 3.38 × 10^-14 A at 303 K to 1.75 × 10^-13 at 353 K. When the temperature varied between 303 K to 353 K the pyroelectric coefficient was increased from 8.60 × 10^-9 C/m²K to 3.76 × 10^-8 C/m²K while the loss tangent remains almost constant to ~1.5 × 10^-5 when the temperature was varied in the same range.

We design lattice matched InP/In_0.53Ga_0.47As mesa structured heterojunction p-n photodiodes with a novel passivation methodology based on a fully depleted thin p-InP layer. Mesa-structured detectors are targeted due to their competitive advantages for applications such as multicolor/hyperspectral imaging. Test detector pixels with different perimeter/area ratios are fabricated with and without etching thin InP passivation layer between pixels in order to comparatively examine passivating behavior. I-V characteristics of the test detectors are measured at room temperature. Based on the results from different sized pixel groups, bulk and surface dark current components are separated. Results show that thin InP layer decreases dark current by a factor of 3 while increasing photo current due to a higher carrier collection efficiency.

Microbolometer arrays are the most used technology in thermal infrared imaging. Recent progress in materials and fabrication techniques for these devices have sparked much competition. Vanadium oxide (VO_x) has been and is currently the most used material for commercial use of bolometers, followed by amorphous silicon (a-Si). However, other silicon derivatives, such as silicon-germanium (a-SiGe, poly-SiGe, and a-Ge_xSi_1-xO_y) have shown promise in the recent years. Extensive research is performed to search for different bolometer materials that combine performance, lowcost, and convenience for uncooled thermal infrared imaging applications. In this review article, we discuss materials derived from VO_x and Si and their fabrication process used in microbolometers, as well as important figures of merit such as temperature coefficient of resistance, responsivity, detectivity and resistivity.

Pyroelectric detectors are the class of thermal detectors which change their spontaneous polarization when there is a change in temperature. The change in the spontaneous polarization occurs due to the absorption of infrared radiation which eventually produces a voltage. This work demonstrates the deposition and characterization of calcium modified lead titatante (Pb_1-xCa_xTiO₃, PCT) thin films for using them as materials of pyroelectric thermal detectors. The PCT thin films were sputtered using an RF sputter system in Ar:O₂ environment at room temperature. The thin films were grown on Au electrode. The capacitance was formed by using Au electrodes on top of PCT thin films which were fabricated by sputtering and liftoff. The PCT films were annealed at 450, 500, 550 and 600 °C in O₂ environment for 15 minutes. Energy dispersive spectroscopy was done to determine the atomic composition of PCT films. Variations of capacitance, pyroelectric voltage, loss tangent and pyroelectric current between the temperature range 303 K to 353 K were determined. The PCT films were annealed at 550 °C showed the highest value of pyroelectric current and pyroelectric coefficient of 2.45 × 10^-12 A and 1.99 μC/m²K respectively at room temperature. The loss tangent did not change much with temperature for all the PCT samples.

In this work, we show that the direct integration of ultraviolet metal-dielectric filters with Si sensors can improve throughput over external filter approaches, and yield devices with UV quantum efficiencies greater than 50%, with rejection ratios of visible light greater than 10³. In order to achieve these efficiencies, two-dimensional doping methods are used to increase the UV sensitivity of back-illuminated Si sensors. Integrated filters are then deposited by a combination of Al evaporation and atomic layer deposition of dielectric spacer layers. At far UV wavelengths these filters require the use of non-absorbing dielectrics, and we have pursued the development of new atomic layer deposition processes for metal fluorides materials of MgF₂, AlF₃ and LiF. The performance of the complete multilayer filters on Si photodiodes and CCD imaging sensors, and the design and fabrication challenges associated with this development are demonstrated. This includes the continued development of deep diffused silicon avalanche photodiodes designed to detect the fast 220 nm emission component of barium fluoride scintillation crystals, while optically rejecting a slower component at 300 nm.

NMOS and PMOS CMOS imager design comparisons and performance differences are reviewed for night vision and scientific applications. Parameters include pixel read noise, charge transfer efficiency, charge collection efficiency, pixel readout speed, dark current and radiation damage tolerance. Focus of the paper is given to pixel read noise and dark current since these are the only parameters that require further development for our CMOS imagers. Discussions reveal that PMOS read noise is limited to ~ 1 h+ rms by flicker noise and why PMOS can fundamentally achieve lower noise than NMOS. We will examine where flicker noise is apparently generated and discuss various experiments that have been tried to lower it. New design and fabrication remedies are explored to reduce read noise below 1 h+ rms floor without reducing 1/f noise. Data is presented showing that PMOS and NMOS imagers are generating the same amount of dark current that is limited by silicon wafer contamination sources introduced in the fabrication process. Test data from a new stitched PMOS/NMOS Mk x Nk x 10 um pixel CMOS sensor suited for space borne NASA scientific applications is presented.

Two types of resonant antennas were integrated with uni-traveling-carrier photodiodes (UTC-PDs) to increase THz-wave output powers. Slot-antenna integrated UTC-PDs exhibited two to three times larger output powers at their peak frequencies than those of a non-resonant bowtie-antenna-integrated device. Output power was enhanced at frequencies from 900 GHz to 1.6 THz for a narrow-slot UTC-PD and from 350 to 850 GHz for a wide-slot UTC-PD. The detected output power was 3.5 μW at 1.25 THz and 28 μW at 700 GHz for a photocurrent of 10 mA with a bias voltage of -0.4 V. A resonant bowtie-antenna, which can be designed by simple analytical calculation, was also integrated with a UTC-PD. The fabricated device exhibited about three times larger output powers at its peak frequency than those of a non-resonant bowtie-antenna-integrated device with an output-power-enhanced frequency range from 400 to 700 GHz.

The earth sensors on the satellites measure the attitude by observing the discontinuity between earth radiance and cold space background. As IR detector technology advances, the earth sensor has evolved from traditional scanning sensor to static sensors with uncooled infrared FPA. In order to obtain high pointing accuracy of the earth center and avoid the influence of the cloud layer, the optical system should have the following characteristics such as: excellent f-theta linearity, high MTF at corresponding frequency, and high transmittance in the 14 to 16 μm range. In addition, this earth sensor is intended to be used on a LEO satellite, so the optical system must cover a wide FOV larger than 130°, and be as light and compact as possible.

This paper contains the full design process of a wide-angle lens used for LWIR earth sensors from paraxial power allocation calculation to optimization of lens. The lens has a relative large image circle of 13mm, which is compatible with a 640×480 25μm uncooled FPA, and its full FOV is 180°. Its focal length is 4.177 and F number is 0.8. The f-theta distortion is less than 0.25%. By choosing chalcogenide glasses as lens material, the lens has a higher transmittance compare to Germanium lens. Also by analyzing the chromatic aberration of the lens, applying a DOE surface helps to improve the image quality, and pushes the modulated transfer function towards diffraction limitation.

This paper presents an approach enabling localization and identification of foreign bodies in polymer materials applying a combined approach of x-ray imaging, imaging microscopy, optical coherence tomography and Raman imaging spectroscopy. The reliable detection of even small foreign bodies in polymer materials and parts designated for use in semiconductor manufacturing and processing machines is essential. Foreign bodies can in particular be metals, burnt particles of the polymer of the work piece, or intact or degenerated foreign polymers. In either case, all surfaces of e.g. a handling equipment that get in contact with the semiconductor material or process solutions have to be free of foreign bodies to ensure the integrity of the manufacturing process. Size, localization and material of the foreign body are main parameters that decide if a work piece has to be rejected. Current inspection systems may enable the localization of the foreign body, but are not capable of identifying the material and structure of the foreign body; many components with inclusions are therefore rejected as a precaution. This work aims towards the development of a combined sensor approach as part of an automatic quality assurance procedure which can be integrated in the fabrication process. X-ray imaging is used to identify metal foreign bodies. Imaging microscopy is used to detect foreign bodies on the surface of the polymer parts. Optical coherence tomography is used to measure the three-dimensional position and size of the foreign bodies. Raman imaging spectroscopy is used to identify the composition of the foreign bodies if they are located on the surface.

It have been proposed different solutions to the problem of gas leak detection one being the use of mobile systems. An autonomous system equipped with a gas sensor (ethanol) and controlled by a microcontroller and an algorithm designed to follow the trace of smell in terms of concentration that existed in the place of taking the reading by the sensor built without considering brownouts only taken the arrangement proposed by the sensor, thus the location of the source is made and direct the system directly. In this paper the results of location system made in different workspaces, focusing primarily on the acquisition of sensor data with an analog-digital conversion 10 bits are presented whose resolution would be 4.8 mV per bit against the standard 19 mV commercial resolution. Experimental results and analytic explanation is showed below.

The image on a focal plane sensor is formed by incident radiation passing directly through the optics; although in some camera systems the light is scattered, reducing the contrast of and/or obscuring the image. Veiling Glare is the phenomena where the light entering an optical system is dispersed and partially washes out the sensor. This phenomenon can arise from many sources ranging from dirt on the lens, imperfections in the lens and anti-reflection coating to poor stray light rejection in the camera body, and the corrections can range from simply cleaning the system, rejecting a poor-quality lens or redesigning the camera. Veiling Glare Index evaluations as described in the ISO 9358 standard are difficult measurements to make. Veiling Glare Index test set ups described in the standard require a large space and/or a large integrating sphere. This paper will discuss the development of and results from a novel approach to the design and construction of a Veiling Glare Index test measurement system. The test equipment requires only 12.5% of the volume to perform the test compared to the large spheres described in the standard. The new design has additional benefits of 360° orientation of the off-axis glancing light angles. The instrument has adjustable light levels and continuous monitoring of the black and white targets so the contrast level is known at the time the measurements are made. The paper will include images obtained with the system of both excellent and marginal units under test.

We performed experimental measurements and theoretical simulation based on an efficient half-space Green’s function method to investigate the diffraction patterns of light scattered from the biological structure on 1D reflection grating made of metal and polymer. The 1D grating provides higher-order reflected light, which can boost the image signal for off-specular reflection. This can facilitate the micro-ellipsometry imaging experiment when an incident angle of light is at a large angle, while the detection camera is placed at the upright position. The micro-ellipsometry images for s- and p-polarized reflectance and their phase difference (Rs, Rp, and Δ) was taken by a modified Optrel MULTISKOP system with rotating compensator configuration for various angles of incidence and wavelengths ranging from 450nm to 750nm. By using an 80X objective lens, the pixel size for our image is around 164nm. We can further increase the magnification and the numerical aperture by using a substrate collocated with a homemade acrylic resin lens, and the pixel size can be reduced to 50 nm. Based on the above, we study the optical properties of metallic/dielectric nanostructures and nearby biological systems including bacteria, and cancer cells via an imaging micro-ellipsometer combined with detailed theoretical modeling. By using specular and off-specular micro-ellipsometry imaging, we can achieve sufficient sensitivity to collect signals from a small area (around 10μm X 10μm and obtain a 3D image mapping of the morphology and dielectric properties of the biological system of interest.

In our research, we present a novel method for absolute angle positioning by non-distortion laser speckles imaging technique. On the surface of a circular plate, we can use a non-distortion speckles imaging device to get the nondistortion image according to its 3D profile. When the plate is rotating, we can continuously measure the speckles images, with each shot overlaps with the previous one. After the plate rotates by 360 degree, a ring-shaped speckles image is formed with several small shots will be acquired. Since the speckles image of each position is unique, the image can be directly corresponded to the angle coordinate. After getting all the images needed, database which includes all the speckles images and their corresponding angle can be built up. To measure the angle of any position on the plate surface, we can first get a real-time speckles image of that position, and thereby get the absolute angle of it after comparison to the database. In our experiment, we use SAD (Sum of Absolute Difference) to analyze the images and measure the angular displacement of the plate. The result shows that the positioning accuracy can reach 0.5 second by this method. This technique could be used to develop speckles image absolute positioning encoder.

Dark field illumination in high throughput colony selection device is reported in this paper. It improves the contrast of image in the premise of uniform illumination. Three important factors including angular distribution of light radiation, number of LED circle array and distance between the target and the LED circle source were analyzed, which affect illumination uniformity of dark field illumination. The simulation result shows that the illumination uniformity is 93.16% when the angular distribution of light radiation is 75°, the number of LED circle array is 3, and the distance between the target and the LED circle source is 61mm. In addition, Experimental system was set up in order to test designed dark field illumination, which matches with the project requirement and simulated results very well.

Tracking deep-field objects across a wide field of view requires the use of high resolution image sensors. This imposes a burden on processing systems which must detect and extract features in an image. Deep-field objects have limited spatial support within a wide field of view image and accordingly much of the recorded scene contains superfluous information about the environment. This paper explores the generation of a foveal scale space using the log-polar transform. Foveal scale space is the scale space representation of an input scene where the spatial support of the image at each scale increases with scale and the number of pixels remains constant across each slice of scale space. This paper reports the formulation of a transformation consisting of a peripheral region defined by the log-polar transform and a foveal region where resolution is constant. A method for performing diffusion in this domain is shown and the generation of the foveal scale space is presented.

Two-dimensional black phosphorous (BP) is a novel material with great potential for implementation in a new generation of flexible and optoelectronics devices. 2D BP, an intrinsically p-type semiconductor with high hole mobility, has a hexagonal honeycomb structure with strong anisotropic properties, including mechanical, thermal, electrical, and optical properties, along the zigzag against the armchair direction. In contrast with other semiconductor layered materials, such as Transition Metal Dichalcogenides (TMDs), the band gap in black phosphorous remains direct both in bulk as in monolayer. Also, as the number of layers is reduced the band gap is open up from ~ 0.3 eV in bulk to ~ 2 eV or more in monolayer, opposite effect in TMDs. BP exhibits a fast photoresponse, it can be operated in near infrared spectrum, and the photodetection can be tunable with an external electric field. In this work, we have mechanically exfoliated multilayer black phosphorus. We have conducted a stability and degradation study of the exfoliated membranes when exposed they are exposed to air and high temperatures up to 400 °C. In addition, a two-terminal broadband photodetector has been designed and fabricated based on multilayer black phosphorus. The optoelectrical measurements exhibit relatively high electrical transport levels (~ 100 uA at 1 V) compared to previous reports. The photoresponse of our device is analyzed here where the photocurrent was measured as a function of the source-drain bias voltages.

Polydimethylsiloxane belongs among polymeric organosilicon compounds which find utilization in many industries. Within telecommunication technologies, the primary use is in the field of encapsulation of electronic units, circuit boards, optical splice or optical cables. This article focuses on the use of polydimethylsiloxane (below PDMS) for its optical properties. We created test samples with a defined ratio of PDMS polymer and luminophore which can to radiate part of the absorbed energy in the form of light. LED (Light-Emitting Diode) with the wavelength range of 440 nm to 470 nm, which corresponds to a blue color in the visible spectrum, was used as the source of excitation energy. Used luminophore is Yttrium Aluminium Oxide: Cerium (Y₃Al₅O₁₂:Ce). The output of the selected combination generates white light. The value of the chromaticity temperature determines the color of light. The output of article is a definition of the suitable ratio of PDMS and luminophore whose the emitted light has the range of chromaticity temperatures matching white light, for example, for lighting. A USB-650 Red Tide spectrometer and SpectraSuite software, which has chromaticity temperature and spectral characteristic as output, were used to finding the chromaticity temperature.

Modern Focal Plane Array (FPA) image sensors are highly-integrated, microelectronic processor chips comprising both analog and digital circuitry and are as complex as modern computer processor chips. A complete picture of how these devices operate requires a deep understanding of analog and digital microelectronic circuit analysis, and therefore, can be very intimidating to the engineer and/or project manager who is the end-user of the device in a system application. The overwhelming barrier to understanding how these devices work can be significantly lowered by analyzing the operation of individual sub-circuits that comprise the device. Here we will analyze a particular sub-circuit, the Source Follower (SF), which is used substantially in FPA designs as both a charge-to-voltage converter at the unit-cell (UC) input node as well as an all-purpose voltage buffering/level shifting element for driving subsequent circuit stages of low input impedance. The goal of this paper is to systematically analyze the Source Follower circuit using an equation -based approach. The analysis starts with the Sah equation which describes the DC (i.e. steady state) electrical operation of all Field Effect Transistors (FETs). Reasonable simplifications to the Sah equation then yield a tractable solution to the problem requiring only algebraic manipulation and use of the quadratic formula. Novel graphical techniques will also be used along with the resultant algebraic expressions to provide an intuitive feel for the circuit operation. The systematic approach taken here can provide useful tools and techniques for a novice in the field of microelectronic circuits who is interested in gaining a deeper understanding of FPA operation and/or analog-digital mixed-signal microelectronic designs.

Photon detection is a major issue in any high-energy astronomy instrumentation. One classical setup that has proven successful in many missions is the combination of photomultiplier tubes (PMTs) with scintillators, converting incoming high-energy photons into visible light, which in turn is converted in an electrical impulse. Although being extremely sensitive and rapid, PMTs have the drawback of being bulky, fragile, and requiring a high-voltage power supply of up to several thousand volts. The silicon photomultipliers (SiPM) appear to be a promising alternative to PMTs in essentially all their applications. We have started a R&D program to assess the possibility of using SiPMs for space-based applications in the domain of high-energy astronomy. We already presented first results of our characterization studies of SiPMs coming from three manufacturers. Each SiPM detector has been tested at low temperature and pressure to assess its performance in a representative space environment. For this purpose, we developed a dedicated vacuum chamber with a specific mechanical and thermal controlled system. After measuring dark current, dark count rate and PDE, we performed irradiation tests to understand the susceptibility of SiPM to radiation damage on two selected detectors. We report here on the results of these irradiation tests.

In view that enhancing near-infrared response of photocathodes is critical to the detection performance, we propose two technical approaches by changing the structure of buffer-layer underneath the active-layer, wherein one is to produce a graded band gap using the graded-composition structure, and the other is to produce a distributed Bragg reflector using the AlAs/GaAs supperlattice structure. Three types of reflection-mode GaAs photocathode samples grown by molecular beam epitaxy were prepared under the same condition. By comparison of activation photocurrent and spectral response among the three different samples, it is found that compared with the conventional sample, the samples with graded-composition and distributed Bragg reflector can obtain higher photocurrent and better response. The measured results of spectral response indicate that the samples without a distributed Bragg reflector exhibit a typical smooth spectral behavior, while the spectral response of the sample with a distributed Bragg reflector structure has a different resonance feature. The sample with the distributed Bragg reflector structure can obtain higher response than those without distributed Bragg reflector at some near-infrared wavelength positions. The peak positions of spectral response curve agree quite well with the dip positions in the reflectivity spectrum. This agreement demonstrates that the response enhancements are ascribed to the resonant absorption effect.

In recent years, some companies take a dual-camera system to improve the magnification ability and zoomed image’s quality in multi-function imaging devices. The solution comprises two apertures to perform a large zooming range without any mechanism moving optical elements: one with a wide-angle lens for lower magnification and the other with a telephoto lens for higher magnification. Nevertheless, this dual-camera system still needs to interpolate the digital zoomed image between the lower and higher magnification images results in a discontinuous quality of zoomed image. We propose a distorted lens (DL) dual-camera system with varying focal length for higher magnification performance and smoother optical zoom. The proposed optical system has a greater pixel count per field angle at the center of sensor than at the periphery of sensor. Therefore, we sacrifice some resolution of the peripheral FOV to enhance the resolution of the center FOV for improving the capability of magnification. For instance, using a 20 MP sensor and displaying a Full HD zoomed image, the maximum magnification factor of 7.54 is achieved in our distorted lens system, but this factor of 3.12 in the distortionless lens system. In other words, we raise the capability of magnification up to 242%.

In this paper, we propose a pixel averaging current calibration algorithm for reducing fixed pattern noise due to the deviation of bolometer resistance. To reduce fixed pattern noise (FPN), averaging current calibration algorithm by which output current of each bolometer reference pixel is averaged by the averaging current calibration is suggested. The principle of algorithm is that average dark current of reference pixel array is subtracted by a dark current of each active pixel array. After that, the current difference with information of pixel deviation is converted to voltage signal through signal processing. To control the current difference of pixel deviation, a proper calibration current is required. Through this calibration algorithm, nano-ampere order dark currents with small deviations can be obtained. Sensor signal processing is based on a pipeline technique which results in parallel processing leading to very high operation. The proposed calibration algorithm has been implemented by a chip which is consisted of a bolometer active pixel array, a bolometer reference pixel array, average current generators, line memories, buffer memories, current-to-voltage converters (IVCs), a digital-to-analog converters (DACs), and analog-to-digital converters (ADCs). Proposed bolometerresistor pixel array and readout circuit has been simulated and fabricated by 0.35μm standard CMOS process.

The Panoramic Vehicular Imaging System (PaVIS) is the system providing a see-through solution for all confined members inside armored vehicles. PaVIS incorporates an around view monitoring system, panoramic cameras and an EO/IR payload. It enlarges the vision for each one of the crew simultaneously, and thereby significantly improves fighting efficiency.

The around view monitoring system (AVM) provides nearby surrounding images and aerial photos to the driver that makes turning, backing and parking safe and easy.

Panoramic cameras provide 360° view to dismounted soldiers with in-situ video, which is interchangeable among visible, IR and fused images. By wearing the head-mounted displays, each dismounted soldier can observe the outside battlefield on the direction they are facing. This enables the soldiers to alert the commander immediately if a danger appears. Moreover, when dismounted, the soldiers are already aware of the outside situation and are therefore better prepared to complete the assigned mission.

PaVIS not only assists the commander in making precise decision by panoramic view reported from dismounted soldiers, but also the image provided by a variable zoom payload for long distance observation. Once an engagement is confirmed, the commander can guide the gunner to the right direction for shooting.

X-ray imaging is popular in medical imaging, non-destructive testing and security. The main techniques of x-ray imaging with semiconductor detector are charge accumulation and photon counting, and the photon counting is expected to identify materials at the same time with taking x-ray photograph by using energy information of x-ray photons. We proposed direct charge handling method to build photon counting system with energy information for x-ray imaging. This method operates the charge from x-ray detector and converts it to encoded digital bit pattern directly without dead time of front end circuit. We simulated and built proposed system to prove operating principals.

Regenerative dampers for vehicle suspension systems that can harvest power at low frequencies efficiently are challenging to realise. To increase their energy harvesting efficiency, a type of high volumetric Figure of Merit magnetoelectric regenerative damper is proposed. To increase the magnetic linkage gradient of its coil in the moving direction and in its motion region, lumped parameter equivalent magnetic circuit model is adopted in its magnetic structural parameter optimization. Finite element analysis is then used to verify the analytical model and theoretical results. Finally, 3 prototypes with different parametric combinations are manufactured and fabricated to do experiments. The experiments indicate that the optimised megnetoelectric regenerative damper can harvest vibration power of 16.3 watts and provide an adjustable damping coefficient that can reach 1605Ns/m when the damper in a relative velocity of 0.2m/s. The corresponding volumetric Figure of Merit can reach 8.3%, which is higher than most of the works presented in recent literatures. This type of regenerative damper can be used in vehicle suspension systems and meet their requirements. It also offers the opportunity to be applied in semi-active vehicle suspensions.