Improving the heat dissipation in Quantum Cascade Lasers (QCLs) is important from the point of view of a growing number of their applications, which require better performance. In this paper, we propose and experimentally demonstrate the possibility of a significant reduction of Active Region (AR) temperature without sophisticated and fabrication-intensive means. We have examined the influence of electroplated gold thickness on thermal and electro-optical properties of InP-based QCLs. Numerical modeling, that we have performed, predicts a significant reduction of the laser core temperature of epi-side up mounted ridge waveguide QCLs with increased thickness of electroplated gold. Predictions of the numerical model have been confirmed experimentally by means of electro-optical, spectral, and thermal characterization.
Single mode emission is one of the crucial requirements for Quantum Cascade Lasers (QCLs), which are compact laser sources of infrared radiation in the mid-IR range (3–20 micrometers) and in the THz range (1–5 THz). This feature is particularly important in all spectroscopic applications such as industrial process monitoring, remote sensing, breath analysis for medical diagnostic or industrial process monitoring.
In this paper, we have proposed a modified approach to coupled cavity QCLs, based on multisection (three section) coupled cavity QCLs. The range of spectral tuning is very important from the point of view of applications in optical sensing techniques based on the intrapulse tuning of the laser emission.
We have designed and fabricated 3-section CC QCLs characterized by intrapulse wavelength tuning of 2.8 cm-1, obtained for 2 mirosecond pulse width. The device operates above room temperature. The improvement of the spectral tuning of 3-section device is compared to 2-section laser. The third section improved significantly the performance of the laser in terms of single mode intrapulse wavelength tuning.
The paper focuses on the design, fabrication and characterization of monolithic, coupled cavity two-section quantum cascade lasers. The devices were fabricated by reactive ion etching from InP-based heterostructure designed for emission in 9.x micrometer range. To make the device attractive for sensing applications, the idea of the coupled-cavity device was employed, giving the possibility of single longitudinal mode operation. We have previously presented devices fabricated by means of focused ion beam post-processing. However, FIB etching is challenging and time-consuming. In order to overcome the relatively low throughput of the FIB process, in this work, gaps separating sections were defined by dry etching during the fabrication process. Careful optimization of the dry etching process resulted in very good control of gap geometry. Quality of mirrors formed by RIE did not introduce high scattering loss into the cavity, as the threshold current density was not increased significantly. Devices routinely exhibited side mode suppression ratio of more than 20 dB. Approach to fabricate two-section devices by dry etching resulted in improved yield as well as high repeatability of the performance of individual devices.
Monolithic, electrically isolated, two-section devices were also fabricated and characterized. We will present a comparison of the performance of different designs and discuss their characteristics, fabrication challenges and stability against operating conditions.
We report recent results of works on quantum cascade lasers at the Institute of Electron Technology. During that time we have developed technology of lasers emitting at wavelengths 9.0–9.5 μm and 4.7 μm, based on InGaAs/AlGaAs/GaAs and InAlAs/InGaAs/InP heterostructures; both lattice matched and strain compensated. The structures were grown by molecular beam epitaxy MBE and by metalorganic vapor phase epitaxy MOVPE. The InGaAs/AlGaAs/GaAs lasers were grown by MBE. For InP based lasers three types of structures were investigated; the one grown exclusively by MBE without MOVPE overgrowth, the second fabricated by hybrid approach combining MBE grown AlInAs/InGaAs active region with MOVPE grown InP top waveguide layer and the third one with both the top and the bottom InP waveguide grown by MOVPE. Regardless of the waveguide construction, the active region was grown by MBE in every case. The lasers were fabricated in double trench geometry using standard processing technology. The buried heterostructure lasers were also investigated.
KEYWORDS: Sensors, Signal to noise ratio, Cameras, Microbolometers, Black bodies, Temperature metrology, Field programmable gate arrays, Signal detection
Microbolometer belongs to the group of thermal detectors and consist of temperature sensitive resistor which is exposed to measured radiation flux. Bolometer array employs a pixel structure prepared in silicon technology. The detecting area is defined by a size of thin membrane, usually made of amorphous silicon (a-Si) or vanadium oxide (VOx). FPAs are made of a multitude of detector elements (for example 384 × 288 ), where each individual detector has different sensitivity and offset due to detector-to-detector spread in the FPA fabrication process, and additionally can change with sensor operating temperature, biasing voltage variation or temperature of the observed scene. The difference in sensitivity and offset among detectors (which is called non-uniformity) additionally with its high sensitivity, produces fixed pattern noise (FPN) on produced image. Fixed pattern noise degrades parameters of infrared cameras like sensitivity or NETD. Additionally it degrades image quality, radiometric accuracy and temperature resolution. In order to objectively compare the two infrared cameras ones must measure and compare their parameters on a laboratory test stand. One of the basic parameters for the evaluation of a designed camera is NETD. In order to examine the NETD, parameters such as sensitivity and pixels noise must be measured. To do so, ones should register the output signal from the camera in response to the radiation of black bodies at two different temperatures. The article presets an application and measuring stand for determining the parameters of microbolometers camera. Prepared measurements were compared with the result of the measurements in the Institute of Optoelectronics, MUT on a METS test stand by CI SYSTEM. This test stand consists of IR collimator, IR standard source, rotating wheel with test patterns, a computer with a video grabber card and specialized software. The parameters of thermals cameras were measure according to norms and method described in literature.
The aim of research was determination of composition and nature of superficial deposits, cumulated at the selected mosaic’s tesserae from Lebanon. Selected were three series of objects from different locations, namely from the seaside and mountain archaeological sites as well as from the mosaics exposed in the city center. Analyzed were stone and ceramic tesserae. The selection of objects was dictated by wide diversification of factors influencing the state of preservation and composition of deposits in given location. Investigations were performed including LIBS, FT-IR, Raman spectroscopy and optical 3D microscopy. The experimental results included composition and kind of deposit at the tesserae surfaces, and composition of tesserae itself. Compounds in the superficial deposits were identified. Confirmed was occurrence of different encrustations in dependence on geographic localization of a given sample. The interpretation of results was supported by multivariate statistical techniques, especially by the factor analysis. Performed analyses constitute the pioneer realization in terms of determination of deposits composition at the surface of mosaics from the Lebanon territory.
In order to objectively compare the two infrared cameras ones must to measure and compare their parameters on a laboratory. One of the basic parameters for the evaluation of the designed camera is NEDT (noise equivalent delta temperature). In order to examine the NEDT ,parameters such as sensitivity and pixels noise must be measured. To do so, ones should register the output signal from the camera in response to the radiation of black bodies at two different temperatures. The article presents an application and measuring stand for determining the parameters of microbolometers camera. In addition to determination of parameters of a cameras the measuring stand allow to determine defective pixel map, the non uniformity correction (NUC) coefficients: 1-point and 2-point. Additionally, developed test stand serves as a test system to read the raw data from microbolometer detector. Captured image can be corrected with calculated non-uniformity correction coefficients. In a next step the image is processed and visualized on a monitor. Developed test stand allows for an initial assessment of the quality of designed readout circuit. It also allows for efficient testing and comparison of the number of sensors or readout circuits.
Laser cleaning technique has been thoroughly compared to traditional chemical and mechanical procedures in the several
case studies of wooden artworks, particularly when conventional cleaning tests showed that none of the methods known
to experienced restorers met all the requirements. Laser cleaning tool, included into conservation projects, appeared to be
very successful in the removal of old overpaintings, dirt clusters in deep artworks fractures and hollows as well as
removal of sootiness formed by mixture of soot, wax, stearin and dust from coloured polychrome. Moreover, laser
cleaning appeared to be much faster and safer for original wooden artwork substrates, especially in deeper fragments of
sculptured areas. Four case studies of different historical objects with wood as an original substrate material will be
presented. In all cases, conservation treatments followed detailed structural stratigraphy of layers and identification of
materials. For comparison, paper includes also some citations from authors earlier published works1-2.
KEYWORDS: Acoustics, Signal detection, Land mines, Signal analysis, Signal analyzers, Sensors, Reconnaissance systems, Classification systems, Signal generators, Mining
The methods of detection and identification of objects based on acoustic signal analysis are used in many applications, e.g., alarm systems, military battlefield reconnaissance systems, intelligent ammunition, and others. The construction of technical objects such as vehicle or helicopter gives some possibilities to identify them on the basis of acoustic signals generated by those objects. In this paper a method of automatic detection, classification and identification of military vehicles and helicopters using a digital analysis of acoustic signals is presented. The method offers a relatively high probability of object detection in attendance of other disturbing acoustic signals. Moreover, it provides low probability of false classification and identification of object. The application of this method to acoustic sensor for the anti-helicopter mine is also presented.
The meter of average energy of holmium laser radiation is a digital measuring instrument, made on the basis of a pyroelectric detector and single-system microprocessor from the MCS- 51 family. This device enables a measurement of a defined number of light pulses, total energy of n-laser pulses as well as the number of pulses received by a detector. The frequency of sampling signal is 25 Hz, the accuracy of measurement is 5%. This meter also enables introducing the defined transmission coefficient (measurement at the back mirror of the laser resonator) to the measurement results as well as control of operation of the output diaphragm of the laser (TTL levels).
The paper presents a description of a construction of the ophthalmological set LH-58 with the holmium laser. Results of preliminary medical tests of eye lens curvature correction carried out by means of this set are given.
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