Uncooled Detector Research Articles

Classification of black plastic types by hyperspectral imaging based on long-wave infrared emission spectroscopy

Identification of black plastics poses a significant challenge in recycling due to the absorptive nature of carbon black additives. This work introduces a method where hyperspectral imaging in the long-wave infrared regime is used to distinguish between twelve samples of commercially available black plastics encompassing nine distinct polymer types. The spectral scanner comprises a scanning Fabry-Pérot interferometer and a thermal camera based on an uncooled microbolometer detector sensitive to wavelengths from 8 μm to 15 μm. A principal component model is combined with k-nearest neighbors to differentiate between plastic samples in hyperspectral images. The model successfully classifies five (PET, POM, PMMA, PA6, and PA66) out of nine black polymers, and the overall accuracy of the model is A=73.1 %.

Spectrally Tunable Ultrafast Long Wave Infrared Detection at Room Temperature.

Room-temperature longwave infrared (LWIR) detectors are preferred over cryogenically cooled solutions due to the cost effectiveness and ease of operation. The performance of present uncooled LWIR detectors such as microbolometers, is limited by reduced sensitivity, slow response time, and the lack of dynamic spectral tunability. Here, we present a graphene-based efficient room-temperature LWIR detector with high detectivity and fast response time utilizing its tunable optical and electronic characteristics. The inherent weak light absorption is enhanced by Dirac plasmons on the patterned graphene coupled to an optical cavity. The absorbed energy is converted into photovoltage by the Seebeck effect with an asymmetric carrier generation environment. Further, dynamic spectral tunability in the 8-12 μm LWIR band is achieved by electrostatic gating. The proposed detection platform paves the path to a fresh generation of uncooled graphene-based LWIR photodetectors for wide ranging applications such as molecular sensing, medical diagnostics, military, security and space.

A Review of Thermal Detectors of THz Radiation Operated at Room Temperature.

This article concerns optical detection issues in the terahertz (THz) range. This is a kind of guide to various types of uncooled thermal detectors in the most often applications. Particular attention is paid to the principle of their operation, technology, and practical features. In addition, some detection methods were also characterized by comparing their performances. The article ends with a performance summary of the selected THz thermal detectors.

Pyroelectric Properties and Applications of Lithium Tantalate Crystals

Lithium tantalate crystals, as a type of pyroelectric material, stand out from many other pyroelectric materials due to the advantages of high Curie temperature, large pyroelectric coefficient, high figure of merits, and environmental friendliness. Due to the pyroelectric effect caused by their spontaneous polarization, lithium tantalate crystals have broad application prospects in wide spectral bandwidth and uncooled pyroelectric detectors. This article reviews the pyroelectric properties of lithium tantalate crystals and evaluates methods for pyroelectric properties, methods for modulating pyroelectric properties, and pyroelectric detectors and their applications. The prospects of lithium tantalate thin films, doped lithium tantalate crystals, and near stoichiometric lithium tantalate crystals as response components for pyroelectric detectors are also discussed.

Effect of sintering condition and Ca2+-substitution on structural and electrical properties of lead-free Ba0.46Sr0.54TiO3 piezoceramics for uncooled IR detectors application

Effect of sintering condition and Ca2+-substitution on structural and electrical properties of lead-free Ba0.46Sr0.54TiO3 piezoceramics for uncooled IR detectors application

Optical, Mechanical and Electrical Characteristics of Thermal Uncooled Bolometric Type Detector Based on Vanadium Oxide

Determination of optical, mechanical and electrical characteristics is one of the decisive factors in the design of instrumentation structures of thermal uncooled bolometer-type detectors (microbolometers). The paper presents the results of optimization calculations by means of computer simulation of absorption, transmittance and reflection spectra of device structures of microbolometers based on thermosensitive vanadium oxide film by finite-difference time-domain method (FDTD). The characteristics of the investigated microbolometer structure were checked for compliance with mechanical and electrical requirements for this class of devices.

A bolometric hyperspectral camera based on a birefringent interferometer for remote sensing in the thermal infrared

Remote sensing in thermal infrared bands (TIR) is largely dominated by cumbersome dispersive-type hyperspectral imagers, which usually require expensive and cryo-cooled quantum detectors to make up for their low optical throughput. Here, we present a compact and low-cost TIR hyperspectral camera based on the Fourier-transform approach. It combines an uncooled bolometer detector and a common-path birefringent interferometer made of calomel (Hg2Cl2). It features high optical throughput, an interferometric contrast greater than 90% even for incoherent radiation, spectral resolution tunable up to 4.5 cm-1, robust and long-term interferometric stability. Retrieving in a few minutes the infrared spectrum in all pixels of the TIR image, it could constitute a valuable tool for evaluating radiative cooling materials’ spatial and spectral properties over extended areas. We test the capabilities of the instrument by measuring the emissivity map of different butterfly wings, which provide a natural example of radiative cooling.

ОПТИЧНА СПЕКТРОСКОПІЯ ДЕТЕКТОРНИХ ВИСОКООМНИХ МОНОКРИСТАЛІВ CdTe (111) ТА ТВЕРДИХ РОЗЧИНІВ Cd 1-x Zn x Te (х= 0,1)

Cadmium telluride is used for the manufacture of uncooled gamma radiation detectors, and solid solutions of Cd 1-x Zn x Te (x=0.1) are used for the manufacture of X-ray and gamma radiation detectors. The study of the effect of doping on the physical properties of semiconductors is relevant both for experimenters and for the theoretical substantiation of physical processes. This paper presents the results of the study of optical reflection spectra in the spectral range (0,2-1,7) . 10 -6 m and transmittance in the region of the fundamental optical transition E 0 of high-resistivity CdTe single crystals of (111) orientation with resistivity ρ = (2÷5)·10 9 Ohm∙cm doped with chlorine, as well as solid solutions of Cd 1-x Zn x Te (x = 0.1) with resistivity ρ = (5 ÷30)∙10 9 Ohm∙cm. Since the optical reflection coefficient R = f (λ) is related to the optical transmittance T = f (λ) and absorption D = f (λ) by the ratio R+T+D=1 (with the light (electromagnetic) wave scattering in the studied samples not taken into account), the absorption spectra D=1-(R+T) versus the light (electromagnetic) wavelength λ were also constructed in this work. It is determined that the energy of the fundamental optical transition E 0 of the studied materials at T = 300 K is as follows: for CdTe - 1.44 eV; and for Cd 1-х Zn х Te (x = 0.1) - 1.5 eV. The energy relaxation time of free charge carriers τ for p-CdTe (111) single crystals and Cd 1-х Zn х Te (x = 0.1) solid solutions was estimated to be 1.343-10 -14 s and 0,878·10 -14 s, respectively. The effective "optical" mobility for single crystals of p-CdTe (111) and solid solutions of Cd 1-х Zn х Te (x = 0.1) is 274 . 10 -4 ; 179,5 . 10 -4 , respectively. It has been shown that the investigated crystals are of high (detector) quality, which is crucial for the manufacture of highly sensitive and high-resolution ionising radiation sensors. The practical value of the obtained results lies in the determination of electronic and physical parameters of technically important semiconductors CdTe and Cd 1-х Zn х Te (x=0.1).

Calculation of Optical Parameters of Thin Films of Structural Materials of Thermal Uncooled Bolometric Type Detector

The increased interest in utilizing uncooled thermal bolometer-type detectors (microbolometers) within the infrared or terahertz detection field is justified by their operational and technological characteristics, in particular: relatively low manufacturing cost, high detection efficiency, compatibility with silicon CMOS technology, and operation at room temperature. The performance of such detectors depends on optimizing critical parameters, which are dictated by both the geometrical design and the electrical, optical, and thermal properties of the materials used. The determination of optical parameters stands as a decisive factor in the design of microbolometer structures. This article delves into the examination of optical parameters of thin films of structural materials of microbolometer based on thermosensitive vanadium oxide film manufactured at JSC “INTEGRAL”. The investigation showcases the results of determining optical constants (refractive indexes n and absorption coefficients k) of thin films from the transmission curve by applying the reflection-transmission method. Furthermore, a comparison is carried out between the results of computer modeling of the transmission, reflection and absorption spectra – taking into account the obtained values of the coefficients n and k – and the empirical data from the in-situ experiment.

Thermodynamically limited uncooled infrared detector using an ultra-low mass perforated subwavelength absorber

An uncooled detector has reached the thermodynamic temperature fluctuation limit, such that 98% of its total noise consisted of phonon and photon fluctuations of the detector body. The device has performed with a detectivity of 3.8×109cmHz/W, which is the highest reported for any room temperature device operating in the long-wave infrared (λ∼8−12µm). The device has shown a noise-equivalent temperature difference of 4.5 mK and a time constant of 7.4 ms. The detector contains a subwavelength perforated absorber with an absorption-per-unit-thermal mass-per-area of 1.54×1022kg−1m−2, which is approximately 1.6–32.1 times greater than the state-of-the-art absorbers reported for any infrared application. The perforated absorber membrane is mostly open space, and the solid portion consists of Ti, SiN x , and Ni layers with an overall fill factor of ∼28%, where subwavelength interference, cavity coupling, and evanescent field absorption among units induce the high absorption-per-unit-thermal mass-per-area. Readout of the detector occurs via infrared-absorption-induced deformation using a Mach–Zehnder interferometry technique (at λ=633nm), chosen for its long-term compatibility with array reads using a single integrated transceiver.

DEVELOPMENT OF A PORTABLE GAMMA PROBE FOR REGISTRATION AND LOCALIZATION OF RADIATION SOURCE, INCLUDING MEDICAL APPLICATION

Self-powered portable gamma probe has been developed on the base of silicon planar uncooled detector and CsI(Tl) scintillator. The device is designed for interoperative and extraoperative search for differences in the concentration of radiopharmaceuticals in the energy range from 100 to 360 keV. Test stand was developed for determining the angular resolution of the gamma probe.

DEVELOPMENT OF A SOFTWARE AND TECHNICAL COMPLEX FOR A TWO-CHANNEL DETECTING SYSTEM FOR CONTINUOUS REGISTRATION OF X-RAY AND GAMMA RADIATION

A compact spectrometric tract and software for work as part of a two-channel detecting system for continuous registration of X-ray and gamma radiation in a wide range of energies have been developed. The complex is designed to work with silicon planar uncooled detectors. The software allows you to process information from each spectrometric channel and provide information in the form of a integrated spectrum. The design of the detecting module, which combines low-energy and high-energy detectors in one housing has been developed.

Wafer-Scale High-Detectivity Near-Infrared PbS Detectors Fabricated from Vapor Phase Deposition

The commercialization of uncooled lead-salt photoconductive (PbX PC) detectors has been restricted by the low-yield of standard chemical bath deposition (CBD) manufacturing technology. As an iterative solution, herein, a novel vapor phase deposition (VPD) route is demonstrated by fabricating the 3 in. wafer-scale uniform PbS sensitized films with high detectivity. The morphological evolution suggests that the self-assembled rod-like microstructure, which is dominated by the I2/PbS flux ratio in the VPD process, is the key to triggering the near-infrared (NIR, 1–3 μm) response of the PbS-sensitized films. The maximum peak detectivity of VPD-PbS NIR detector of 1.9 × 1011 cm Hz1/2 W–1 is achieved after optimizing the sensitization-condition dependence of PbS detector’s performance. The high performance of wafer-scale VPD-PbS PC detectors, which attains the same performance as standard CBD-PbS detectors, manifests that the VPD technology opens up a new avenue to the industrialization of uncooled lead-salt PC detectors.

Millimeter-wave to near-terahertz sensors based on reversible insulator-to-metal transition in VO2

In the quest for low power bio-inspired spiking sensors, functional oxides like vanadium dioxide are expected to enable future energy efficient sensing. Here, we report uncooled millimeter-wave spiking detectors based on the sensitivity of insulator-to-metal transition threshold voltage to the incident wave. The detection concept is demonstrated through actuation of biased VO2 switches encapsulated in a pair of coupled antennas by interrupting coplanar waveguides for broadband measurements, on silicon substrates. Ultimately, we propose an electromagnetic-wave-sensitive voltage-controlled spike generator based on VO2 switches in an astable spiking circuit. The fabricated sensors show responsivities of around 66.3 MHz.W−1 at 1 μW, with a low noise equivalent power of 5 nW.Hz−0.5 at room temperature, for a footprint of 2.5 × 10−5 mm2. The responsivity in static characterizations is 76 kV.W−1. Based on experimental statistical data measured on robust fabricated devices, we discuss stochastic behavior and noise limits of VO2 -based spiking sensors applicable for wave power sensing in mm-wave and sub-terahertz range.

Design and Performance of Amorphous Silicon Based on Uncooled Bolometer-Type Infrared Focal Plane Arrays

Uncooled bolometric type thermal detectors , combined into a matrix and placed into a focal plane array have the following characteristics : low cost , operation at room temperature , compatibility with the silicon CMOS technology , and high detecting performance ; therefore recently it became a hot spot in infrared or terahertz detection field . The performance of uncooled infrared focal plane detector arrays depends on the optimization of critical parameters which are determined by geometrical design and the electrical , optical , and thermal physical properties of the detector materials . We report the study of a fabrication process and characterization of two (2D) dimensional arrays of uncooled microbolometers based on silicon (α- Si ) thermo-sensing films . Because these arrays substantially reduce sensor size , they are becoming the preferred format for most modern applications .

Application of Cad Systems to Accounting for Mechanical Stresses in the Development of Uncooled Thermal Detectors of the Bolometric Type

A comparative analysis of the characteristics of the main types of bolometers is indicated in the article. The constructive solution of an uncooled thermal detector of the bolometric type, formed using the technology of microelectromechanical systems, is studied. By means of computer simulation in modern computer-aided design systems in microelectronics, a static mechanical analysis was performed to assess the effect of mechanical stresses arising in structural materials during their formation on the magnitude of deformation. It has been established that to ensure the normal functioning of the microbolometer (to reduce the maximum deviation value of the film from the nominal value), it is necessary to reduce the internal mechanical stresses in the NiCr film. For the Si3N4 films, on the contrary, this value should be increased.

Design of MIR Dispersive Spectrograph System with Uncooled Microbolometer.

To make the mid-infrared (MIR) dispersive spectrograph a practical tool in industrial food processing lines, we designed a dispersive spectrograph system with an uncooled microbolometer focal plane array (FPA) detector for MIR spectral acquisition. To precisely regulate the angle of a rotatable grating to acquire the MIR spectrum, the spectral resolution and spatial resolution of the system were rigorously controlled to improve system performance. In the reflectance operation mode of the MIR dispersive spectrograph, the uncooled microbolometer FPA detector offered a maximum spectral resolution of 12 nm for the MIR, when a 300 grooves/mm blazed grating was used. Utilizing an optical parametric oscillator (OPO) pulse laser source, the wavelengths of the first-order diffraction were validated, and the system's spectral resolution limit was determined. As a line-scanning source, a Globar broadband source was installed, and the USAF 1951 Resolution Calculator was used to establish the spatial resolution of the imaging spectrograph. Using NI LabView, the logical operational technique for controlling the MIR dispersive spectrograph was encoded into system firmware. The GUI and test results are thoroughly described.

Research on Electro-Optical Characteristics of Infrared Detectors with HgCdTe Operating at Room Temperature.

This paper presents a thorough analysis of the current-voltage characteristics of uncooled HgCdTe detectors optimized for different spectral ranges. HgCdTe heterostructures were grown by means of metal-organic chemical vapor deposition (MOCVD) on GaAs substrates. The obtained detector structures were measured using a Keysight B1500A semiconductor device analyser controlled via LabVIEW for automation. The experimental characteristics were compared with numerical calculations performed using the commercial platform SimuAPSYS (Crosslight). SimuAPSYS supports detector design and allows one to understand different mechanisms occurring in the analysed structures. The dark current density experimental data were compared with theoretical results at a temperature of 300 K for short, medium, and long wavelength infrared ranges. The dark current density of detectors optimized for different wavelengths was determined using various generation-recombination mechanisms. Proper matching between experimental and theoretical data was obtained by shifting the Shockley-Read-Hall carrier lifetime and the Auger-1 and Auger-7 recombination rates. Exemplary spectral responses were also discussed, giving a better insight into detector performance. The matching level was proven with a theoretical evaluation of the zero-bias dynamic resistance-area product (R0A) and the current responsivity of the designed detectors.

Chemical Gas Telemetry System Based on Multispectral Infrared Imaging.

Environmental monitoring, public safety, safe production, and other areas all benefit greatly from the use of gas detection technologies. The infrared image of a gas could be used to determine its type from a long distance in gas detection. The infrared image can show the spatial distribution of the gas cloud and the background, allowing for long-distance and non-contact detection during safety production and hazardous chemical accident rescue. In this study, a gas detection system based on multispectral infrared imaging is devised, which can detect a variety of gases and determine the types of gas by separating the infrared radiation. It is made up of an imaging optical system, an uncooled focal plane detector, a filter controller, and a data gathering and processing system. The resolution of the infrared image is 640 × 512 and the working band of the system is 6.5~15 μm. The system can detect traces of pollutants in ambient air or gas clouds at higher concentrations. Ammonia, sulfur hexafluoride, methane, sulfur dioxide, and dimethyl methyl phosphonate were all successfully detected in real time. Ammonia clouds could be detected at a distance of 1124.5 m.

Zoom Optical System for Thermal Camera in Optical Range 8-14 µm

Continuous infrared zoom systems with image quality and image stabilisation maintained throughout the workflow are increasingly being used. A long-wave infrared continuous zoom optical system with a 6x zoom ratio operating with an uncooled detector was designed. The optical system has a focal length from 37,5 mm to 225 mm, and the F/# is 1,5. The system includes 7 lenses with 3 even aspheres. The results show that the MTF function is very close to the diffraction limit curve over the entire focal range, proving that the system meets the specifications.