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A 811 × 508 pixel PtSi Schottky-barrier infrared CCD image sensor which has the greatest number of pixels for a Standard TV format was developed. We achieved a 38% fill-factor of 18 × 21μm size pixel for this image sensor by using 1.0μm design rules. The noise equivalent temperature difference with f/1.2 was 0.06 K at 300 K. The responsivity nonuniformity with a 300 K background signal was estimated at 0.45%. The sensor obtained execellent thermal imaging without uniformity correction.

We have developed a 256×256-element HgCdTe hybrid infrared focal plane array for 8-10μm band that is both large scale and highly sensitive. Three new techniques were used to achieve the large scale array. First, a thin silicon readout circuit on a sapphire substrate reduced thermal stress between the HgCdTe diode array on CdZnTe and the Si readout circuit. Second, we optimized cutoff wavelength for maximum sensitivity. Third, a CMOS type readout circuit with an interlace scheme enabled a large handling capacity. We also used a HgCdTe diode array with anodic sulfide (CdS) passivation to reduce dark current and nonuniformity of the photocurrent. Our infrared focal plane array has a noise equivalent temperature difference 0.06 K with F 2.5 optics.

The low frequency noise in patterned La0.7Sr0.3MnO3 thin film bridges with different geometries was measured at 300 K in ambient magnetic field. Films were deposited by pulsed laser ablation on (100) SrTiO3 substrates. The measured 1/f noise was well described by the semiempirical Hooge relation, which indicates that the low frequency noise could be originated by resistance fluctuations. The measured noise magnitude was compared with bibliographic data for epitaxial La1−xSrxMnO3 (LSMO) and La1−xCaxMnO3 thin films. The normalized Hooge parameter α/n for our films was in the range of 2–4×10−28 m3, which is the order of magnitude of the best results reported in literature for oxygen annealed films. Finally the noise equivalent temperature of a thermometer fabricated with such LSMO films was estimated to be 3.4×10−6 K/Hz at 300 K, 10 Hz, and I=100 μA. These results demonstrate that the intrinsic low frequency noise of LSMO is not a limitation and that LSMO thin films can advantageously be used as performant t...

An E-band heterodyne Radiometer system is designed, fabricated, characterised and calibrated for sensing plasma temperature by measuring Electron Cyclotron Emission (ECE) spectrum from Aditya and SST-1 Tokamak plasma. The developed Radiometer has IF frequency 1–12 GHz, sensitivity O.2×109 V / W with a noise figures of 23.8dB and a noise equivalent temperature of 6eV.

Transmissivity is a crucial parameter for an optical system, especially for an infrared imaging system, which is commonly used for detecting and tracking dim target. NETD (Noise Equivalent Temperature Difference) is an important indicator for quality of an infrared FPA system, and it is always related with the transmissivity of its optical system, which is dealing with energy transmission of the system. So it is necessary to measure the transmissivity when optical system is fabricated. However it is usually not easily available, when the structure of IR optics is complex in particular. In this article, a new reliable method for measuring the transmissivity of optical system for cooled infrared detector is introduced. The principle of measurement is based on Etendue conservation and luminance (radiance) conservation when light travels through an ideal optical element. We put a Lambertian blackbody source attached at the cold stop of IR detector of under testing system, and get the grey-scale value of axis point of detector. Afterwards we put on the optical system for the detection and calibrate the optical path for imaging system. Then we put the Lambertian blackbody source at the position of entrance pupil of optical system, and get the grey-scale value of axis point of detector again. With proper calculation with these two grey-scale value, we could get transmissivity of this optical system. A ray tracing simulation is made to show the result for supporting correctness of this approach. A high-aperture Lambertian blackbody source is required for the embodiment of this measurement.

In this Letter, we describe the fabrication of an array of bimaterial detectors for infrared (IR) imaging that utilize SiO(2) as a structural material. All the substrate material underneath the active area of each detector element was removed. Each detector element incorporates an optical resonant cavity layer in the IR-absorbing region of the sensing element. The simplified microfabrication process requires only four photolithographic steps with no wet etching or sacrificial layers. The thermomechanical deflection sensitivity was 7.9×10(-3) rad/K, which corresponds to a noise equivalent temperature difference (NETD) of 2.9 mK. In the present work, the array was used to capture IR images while operating at room temperature and atmospheric pressure without the need for vacuum packaging. The average measured NETD of our IR detector system was approximately 200 mK, but some sensing elements exhibited an NETD of 50 mK.

A passive millimeter-wave (mmW) sensor operating at a frequency of 77 GHz is built and characterized. The sensor is a single pixel sensor that raster scans to create an image. Optical upconversion is used to convert the incident mmW signal into an optical signal for detection. Components were picked to be representative of a single element in a distributed aperture system. The performance of the system is analyzed, and the noise equivalent temperature difference is found to be 0.5 K (for a 1 s integration time) with a diffraction limited resolution of ∼8 mrad. Representative images are shown that demonstrate the phenomenology associated with this spectrum.

As to visualize the leaking gas cloud which is not visible to the naked eyes, three categories of techniques have emerged, Backscatter Absorption Gas Imaging, Passive Thermal Imaging, and Imaging Spectrometer. Among these systems, Signal to Noise Ratio (SNR) is generally used to deduce gas leakage detection limit and leads to several performance evaluation parameters, such as Noise-Equivalent Spectral Radiance and Noise-Equivalent Concentration-Path Length. However, in most cases, measuring the SNR accurately is not accessible and usually needs auxiliary instruments. Therefore, we focus on researching a gas leakage detection model according to the general parameter of a thermal imager, Noise Equivalent Temperature Difference (NETD). Firstly, the Gas Equivalent Blackbody Temperature Difference (GEBTD) is obtained by calculating the attenuated radiation of the On-plume path and that of the Off-plume path respectively. A simplified form of GEBTD was derived by our previous paper, assuming that the work range was short and the affection of atmospheric transmission was omitted. But in this paper, more factors are considered to establish a more realistic and accurate detectivity model. The radiation of the gas cloud and the attenuation of the atmosphere are taken into account as well as the size of the leakage spot which inevitably affects the concentration path length. Secondly, the NETD and the GEBTD are compared to determine the detection capability. At last, an experiment is designed to verify the accuracy and reliability of this model on the basis of the gas cloud concentration cone distribution model.

Recent efforts have been paid to elevate the operating temperature of Type II superlattice Mid Infrared photon detectors. Using M-structure superlattice, novel device architectures have been developed, resulting in significant improvement of the device performances. In this paper, we will compare different photodetector architectures and discuss the optimization scheme which leads to almost one order of magnitude of improvement to the electrical performance. At 150K, single element detectors exhibit a quantum efficiency above 50%, and a specific detectivity of 1.05x1012 cm.Hz1/2/W. BLIP operation with a 300K background and 2p FOV can be reached with an operating temperature up to 130K. High quality focal plane arrays were demonstrated with a noise equivalent temperature difference (NEDT) of 11mK up to 130K. Human body imaging is achieved at 165K with NEDT of 150mK.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

This paper investigates arrays of HgCdTe photon trapping detectors. Performance of volume reduced single mesas is compared to volume reduced photon trap detectors. Good agreement with model trends is observed. Photon trap detectors exhibit improved performance compared to single mesas, with measured noise equivalent temperature difference (NEDT) of 40 mK and 100 mK at temperatures of 180 K and 200 K, with good operability. Performance as a function of temperature has also been investigated.

An effective optical readout approach based on a narrow-strip filter is presented to detect bends of a bimaterial microcantilever focal plane array, by which light intensity of the image plane (CCD image sensor plane) can be increased and its uniformity on the image plane effectively enhanced. It reduces the noise equivalent temperature difference of the microcantilever focal plane array IR imaging system and improves uniformity of the IR images. A comparative experiment is designed to verify effectiveness. The experimental results show that the proposed method has advantages of preferable effect.

International audience; We present a compact infrared cryogenic multichannel camera with a wide field of view equal to 120 degrees. By merging the optics with the detector, the concept is compatible with both cryogenic constraints and wafer-level fabrication. The design strategy of such a camera is described, as well as its fabrication and integration process. Its characterization has been carried out in terms of the modulation transfer function and the noise equivalent temperature difference (NETD). The optical system is limited by the diffraction. By cooling the optics, we achieve a very low NETD equal to 15 mK compared with traditional infrared cameras. A postprocessing algorithm that aims at reconstructing a well-sampled image from the set of undersampled raw subimages produced by the camera is proposed and validated on experimental images. (C) 2012 Optical Society of America

This paper presents a novel filtering method with a double triangular prism in an optical-readout thermal imaging system. First, the working principle of this system is described in detail, followed by the analysis of sensitivity. Then, infrared images of hands are obtained. On the basis of the analysis, it is concluded that this filtering method, whose noise equivalent temperature difference (NETD) can reach 145 mK, is effective in obtaining high-quality images. Finally, comparing the filtering method with a knife-edge filter, we can draw the conclusion that the filtering method can effectively improve image quality (the value of NETD is less than that of a knife-edge filter).

The spectral dependence of the Noise Equivalent Temperature Difference (NETD) that can be detected from the objects thermal radiation and is limited by photon fluctuations in quantum photodetectors is calculated. An absolute limit of its specific value (NETD∗) depends only on one physical variable—the temperature of the object T : NETD ∗ min = 5.07 × 10 −8 300 T [ K cm s 1 2 ] . This relationship shows that there is a decrease of the information capacity of thermal images with decreasing object temperature T . In the widely used thermal imagery wavelength region below 15μm the spectral dependence of a specific temperature difference caused by background fluctuations is expressed with acceptable precision by the relationship: NETD ∗ ideal (γ m ) ≈ kT 2 × D ∗ ideal (γ m ) . This is the so called “ kT 2 rule” where D∗ ideal (λ m ) is the specific detectivity of an ideal photodetector with cutoff wavelength λ m ) and k is Boltzmann's constant. For a particular case, considered in the Appendix, the efficiencies of thermal imagers sensitive in different spectral regions are compared, including atmospheric transmission for horizontal paths of different length.

To utilize satellite radiance sounding data, in either explicit or implicit retrieval algorithms, a proper understanding of the noise in the measurements is required. Conventionally, to define the expected accuracy of atmospheric profiles inferred from sounder data, instrument noise equivalent temperature difference (NEΔT) noise specifications have been used to simulate spacecraft data. Here it is demonstrated that NEΔT noise specifications are inappropriate for this purpose. Instead, total system noise estimates should be employed since use of sounding data in any type of physical retrieval algorithm implies application of a radiative transfer model, which in turn must be “calibrated” against in situ and satellite data. It is demonstrated that the accuracy of atmospheric retrievals inferred from the TIROS Operational Vertical Sounder radiometers is limited by the total system noise rather than NEΔT noise, and that modeled radiance temperatures perturbed by Gaussian total system noise very nearly...

The performance of GaAs/AlGaAs multiple quantum well infrared detectors is studied theoretically and experimentally, with special emphasis on 8-12 μm thermal imaging applications. The dependence of detector performance on various factors like light coupling configurations (one and two dimensional reflection gratings or 45° polished edge), detector temperature, response wavelength and quantum well doping density is dealt with. An absorption quantum efficiency of 87% is demonstrated using a crossed grating and a waveguide (CGW). It is also found that an optimised 34 μm × 34 μm detector (a detector size suitable for large staring arrays, i.e. 256 × 256 or larger) with 9.0 μm cut-off wavelength, f# = 2 optics and 70% optical transmission reaches background limited operation at 74 K detector temperature. The potential of making highly uniform staring arrays utilising the mature GaAs material and processing technology is demonstrated by uniformity measurements of detector dark current. The experiments show that a metalorganic vapour phase epitaxy (MOVPE) grown structure can have a dark current standard deviation to mean value ratio over a 10mm long linear detector array of less than 2%. The staring array performance in terms of noise equivalent temperature difference (temporal NETD) is calculated to NETD < 20 mK at 77 K detector temperature and NETD < 10 mK at 70 K detector temperature.

The Corrugated Quantum Well Infrared Photodetector (C-QWIP) holds significant performance and other advantages over other infrared (IR) detectors. However, one disadvantage of the detector is the relatively low operating temperature needed to suppress the dark current. By coating two additional layers (thin insulator and high critical temperature (Tc) superconductor) on the top contact layer of a C-QWIP wafer, the top three layers of the detector form a high-Tc superconducting single electron tunneling junction. It could act as an electron filter because of the presence of an energy gap in superconductors. For QWIPs, the photo electrons and dark electrons are well separated in energy, most dark current is conducting below the quantum well (QW) barrier height and most photo current is conducting above the barrier height. Most dark electrons thus could be blocked by the junction while most photo electrons pass the junction by applying an appropriate voltage. Therefore, both the sensitivity and the operating temperature of the detector could be improved. Our calculation shows that the filter could provide 40% or 70% improvement in Noise Equivalent Temperature Difference (NETD) of detector focal plane arrays (FPAs) at normal operating temperature, depending on whether the detector emitter photocurrent to dark current ratio is = 1 (Emitter is background limited BLIP) or = 0.1 (Emitter is far from BLIP). For both cases, the filter could increase the detector FPAs operating temperatures up to 90K (30K improvement) with 15% to 25% NETD improvement respectively.

We report a high performance long-wavelength IR dual-band imager based on type-II superlattices with 100% cutoff wavelengths at 9.5 μm (blue channel) and 13 μm (red channel). Test pixels reveal background-limited behavior with specific detectivities as high as ∼5×1011 Jones at 7.9 μm in the blue channel and ∼1×1011 Jones at 10.2 μm in the red channel at 77 K. These performances were attributed to low dark currents thanks to the M-barrier and Fabry–Perot enhanced quantum efficiencies despite using thin 2 μm absorbing regions. In the imager, the high signal-to-noise ratio contributed to median noise equivalent temperature differences of ∼20 milli-Kelvin for both channels with integration times on the order of 0.5 ms, making it suitable for high speed applications.

An optical-readout bimaterial microcantilever-type infrared detector improving both IR absorption and pixel uniformity is proposed. A Focal Plane Array (FPA) of 128×128 pixels was fabricated using 4-inch silicon Micro-Electro Mechanical System (MEMS) processes. The FPA design and process development are discussed and the Scanning Electron Microscope (SEM) photos and imaging results of the FPA are presented. The Noise Equivalent Temperature Difference (NETD) of the proposed device was measured to be 200mK by a gray level change method and the time constant was calculated to be ~15 ms under a 10 mTorr pressure.

With the trend of developments of infrared-focal plane array (FPA) which is particularly pronounced in many applications, in this paper, we demonstrated an uncooled infrared (8~14μm) camera based on the optically read-out Bi-material Infrared FPA. We reported on the fabrication and characterization of arrays of bimaterial microcantilevers. On the basis of opto-mechanical effect and micro electromechanical system (MEMS) technology, a substrate-free FPA with the thermal isolated structure SiNx and Au for uncooled infrared imaging is developed, with 49.5μm×49.5μm of the pixel and 240×240 array, moreover, the camera had an average noise equivalent temperature difference (NETD) and a response time of 100mK and 100ms at 7Pa atmospheric pressure, respectively.

This paper introduces an optimization approach of thermal conductance for single level uncooled microbolometer detectors. An efficient detector design is required due to the limited availability of silicon area per pixel, i.e., the pixel pitch, and due to the capabilities of the fabrication line. The trade-offs between physical parameters are studied to attain the best performance, including the thermal conductance, the thermal time constant, the effective temperature coefficient of resistance (TCR), and the active area, where the main performance criterion has been selected as the Noise Equivalent Temperature Difference (NETD). A microbolometer pixel is modeled using theoretical formulations, and simulations are carried out using this model, and then, the accuracy of the model is verified by Finite Element Method (FEM) analysis. Consequently, optimum design parameters, such as the length of the support arms and the choice of interconnect metal can be extracted from the simulations for a defined process flow. Furthermore, a simple and reliable method for measuring the thermal conductance has been introduced. With this method, it is possible to accurately measure the thermal conductance in a large pixel temperature range, which is required especially for high thermal resistance microbolometers as they heat up rapidly in vacuum. The validity and accuracy of this method are also verified by comparing the simulation results with measurements performed on a single pixel microbolometer that is designed and fabricated based on the optimization approach outlined in this paper.

We are developing a 350 GHz cryogenic passive video imaging system for use in standoff security applications. This demonstration system uses 800 photon-noise-limited superconducting transition edge sensor bolometers, read out using a time-division multiplexed readout system. It will image a 1 m x 1 m field of view at a standoff distance of 16 m to a resolution of approximately 1 cm at video frame rates (20 frames per second). High spatial resolution is achieved by the use of an f/2.0 Cassegrain optical system with 1.3 m primary mirror. Preliminary dark and optical testing of prototype detectors indicates that we can achieve a noise equivalent temperature difference (NETD) below 100 mK for the fully sampled 1 m x 1 m image at 20 frames per second. We report on the current status of development of this system.

Reported is a detailed analysis of the dark current versus voltage versus temperature data of planar hetero-structure P + n mid wavelength infrared MWIR photodiodes with band gap energy E g (78K) = 0.243 eV, λ g = 5.1 μm and long wavelength infrared LWIR photodiodes with E g (78K) = 0.115 eV, λ g = 10.8 μm. The purpose of the investigations is to identify the dominant carrier recombination mechanisms and in particular to determine at what temperature and voltage is the onset of Shockley Read Hall (SRH) space charge currents. The important finding is that the currents can mostly be explained by a combination of Auger (e-e) and radiative carrier recombination processes with no evidence of SRH recombination through near mid-gap states; a lower bound estimate of the SRH lifetime for LWIR photodiode is 100 μs. Intrinsic radiative recombination is found to be the dominant carrier recombination mechanisms for the MWIR photodiode with a carrier concentration N d =10 15 cm -3 , and Auger (e-e) being dominant for the LWIR photodiode. The LWIR Auger (e-e) lifetime data is well fitted with the Beattie, Landsberg and Blakemore (BLB) formulas with a constant overlap integral F1F2= 0.15, which is in accord with recent electronic band structure calculations. From the analysis of variable area LWIR photodiodes the minority carrier conductivity mobility and diffusion length at 80K are calculated to be 350 cm 2 /V-s and 23 μm respectively. The LWIR lifetime measured by the photoconductive decay method is in agreement with the expected intrinsic Auger (e-e) lifetime ≈ 2 μs at 80K and with the lifetimes obtained from device analysis. For T ≤ 40K, trap assisted tunneling is the dominant current in reversed bias LWIR photodiodes; forward bias currents are dominated by diffusion currents of origin in the n- layer. For the MWIR photodiode deviation from diffusion limited behavior to G-R is observed at T < 80K and, the SRH lifetimes ιn0 and ιp0 are estimated to be 50 ms. Measured and calculated external quantum efficiencies at the peak responsivity wavelength λpk for both MWIR and LWIR photodiodes are ≈ 70% at 78K. For imaging in the 3-5 μm spectral band scene temperature 300K, F/3 optics, the noise equivalent temperature difference NEuT of MWIR photodiodes is calculated to be near background limited performance BLIP =12.4 mK for detector temperatures Td ≤ 150K.

Recent efforts have been paid to elevate the operating temperature of Type II superlattice Mid Infrared photon detectors. Using M-structure superlattice, novel device architectures have been developed, resulting in significant improvement of the device performances. In this paper, we will compare different photodetector architectures and discuss the optimization scheme which leads to almost one order of magnitude of improvement to the electrical performance. At 150K, single element detectors exhibit a quantum efficiency above 50%, and a specific detectivity of 1.05x1012 cm.Hz1/2/W. BLIP operation with a 300K background and 2π FOV can be reached with an operating temperature up to 180K. High quality focal plane arrays were demonstrated with a noise equivalent temperature difference (NEDT) of 11mK up to 120K. Human body imaging is achieved at 150K with NEDT of 150mK.

Against a background of newly emerged security threats the well-established idea of utilizing submillimeter-wave radiation for personal security screening applications has recently evolved into a promising technology. Possible application scenarios demand sensitive, fast, flexible and high-quality imaging techniques. At present, best results are obtained by passive imaging using cryogenic microbolometers as radiation detectors. Building upon the concept of a passive submillimeter-wave stand-off video camera introduced previously, we present the evolution of this concept in a practical application-ready imaging device. This has been achieved using a variety of measures such as optimizing the detector parameters, improving the scanning mechanism, increasing the sampling speed, and enhancing the camera software. The image generation algorithm has been improved and an automatic sensor calibration technique has been implemented taking advantage of redundancy in the sensor data. The concept is based on a Cassegrain-type mirror optics, an opto-mechanical scanner providing spiraliform scanning traces, and an array of 20 superconducting transition-edge sensors (TES) operated at a temperature of 450-650 mK. The TES are cooled by a closed-cycle cooling system and read out by superconducting quantum interference devices (SQUIDs). The frequency band of operation centers around 350 GHz. The camera can operate at an object distance of 7-10 m. At 9m distance it covers a field of view of 110 cm diameter, achieves a spatial resolution of 2 cm and a pixel NETD (noise equivalent temperature difference) of 0.1-0.4 K. The maximum frame rate is 10 frames per second.

This work explores the influence of head window thickness on the performance of a mid-wave infrared, panoramic periscope imager. Our focus is on transparent spinel ceramic as the head window material. Spinel is an attractive material for IR applications due to its good strength and transmission properties (visible through mid-wave). However, there is some degradation in spinel transmission near the high end of the mid-wave band ( 5μm) as the head window thickness increases. In this work we predict the relationship between head window thickness and imager performance, as quantified by the Noise Equivalent Temperature Difference, and compare these predictions to values estimated from experimental data. We then discuss the implications for imager design and demonstrate a possible approach to correcting for the headwindow-induced losses. The imager used in this study is a compact, catadioptric, camera that provides a 360 o horizontal azimuth by -10 o to +30 o elevation field of view and uses a 2048 x 2048, 15μm pitch InSb detector.

Systematic characterization of various types of intersubband transitions in the quantum dots in a well (DWELL) infrared photodetectors has been presented. By changing the thickness of the quantum well, the excited state energy can be tuned with respect to the barrier, without altering the quantum dot ground state. Bound to continuum transitions offer very high extraction probability for photoexcited electrons but poor absorption coefficient, while the bound to bound transitions have higher absorption but poorer extraction probability. Bound to quasibound transition is optimum for intermediate values of electric fields with superior signal to noise ratio. The bound to quasibound device has the detectivity of 4×10 11 cm.Hz 1/2 W -1 (+3V, f /2 optics) at 77 K and 7.4×10 8 cm.Hz 1/2 W -1 at 200 K, which is highest reported detectivity at 200 K for detector with long wave cutoff wavelength. High performance focal plane arrays have been fabricated with noise equivalent temperature difference of 44 mK at 80 K for 6.1μm peak wavelength.

Standoff detection of gas leakage is a fundamental need in petrochemical and power industries. The passive gas imaging system using thermal imager has been proven to be efficient to visualize leaking gas which is not visible to the naked eye. The detection probability of gas leakage is the basis for designing a gas imaging system. Supposing the performance parameters of the thermal imager are known, the detectivity based on electromagnetic radiation transfer model to image gas leakage is analyzed. This model takes into consideration a physical analysis of the gas plume spread in the atmosphere-the interaction processes between the gas and its surrounding environment, the temperature of the gas and the background, the background surface emissivity, and also gas concentration, etc. Under a certain environmental conditions, through calculating the radiation reaching to the detector from the camera's optical field of view, we obtain an entity "Gas Equivalent Blackbody Temperature Difference (GEBTD)" which is the radiation difference between the on-plume and off-plume regions. Comparing the GEBTD with the Noise Equivalent Temperature Difference (NETD) of the thermal imager, we can know whether the system can image the gas leakage. At last, an example of detecting CO 2 gas by JADE MWIR thermal imager with a narrow band-pass filter is presented.

The Jet Propulsion Laboratory has developed the Hyperspectral Thermal Emission Spectrometer (HyTES).12 It is an airborne pushbroom imaging spectrometer based on the Dyson optical configuration. First low altitude test flights are scheduled for later this year. HyTES uses a compact 7.5–12□m hyperspectral grating spectrometer in combination with a Quantum Well Infrared Photodetector (QWIP) and grating based spectrometer. The Dyson design allows for a very compact and optically fast system (F/1.6). Cooling requirements are minimized due to the single monolithic prism-like grating design. The configuration has the potential to be the optimal science-grade imaging spectroscopy solution for high altitude, lighter-than-air (HAA, LTA) vehicles and unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The QWIP sensor allows for optimum spatial and spectral uniformity and provides adequate responsivity which allows for near 100mK noise equivalent temperature difference (NEDT) operation across the LWIR passband. The QWIP's repeatability and uniformity will be helpful for data integrity since currently an onboard calibrator is not planned. A calibration will be done before and after eight hour flights to gage any inconsistencies. This has been demonstrated with lab testing. Further test results show adequate NEDT, linearity as well as applicable earth science emissivity target results (Silicates, water) measured in direct sunlight.

We investigate in this paper the potential of carbon nanotubes for infrared bolometers. A method to obtain CNT film layer and technological processes to obtain matrix of devices are presented. The electrical characterization of samples establishes the quality of our technology i.e. low contact resistance, and weak dispersion between devices. The potential of carbon nanotub es films as bolometric material is investigated by measuring the thermal dependence of their resistance and by comparison with amorphous silicon (one of the leading material for bolometric applications). Optical measurements of CNT films in the infrared and THz ranges show a relatively high absorption for a few hundreds nanometers thick material. Eventually the infrared (8-12 m) photo-response of a first demonstrator is presented and discussed. Keywords : uncooled IR detector, microbolometer, single wall carbon nanotube. INTRODUCTION Over the last decade, the market of infrared bolometer’s focal plane array (FPA) has shown a rapid growth. The vanadium oxides originally developed by Honeywell, and the amorphous silicon pushed forward by ULIS and CEA-LETI are the main technologies [1]. Since the first generation of FPA, various improvements have been made. In the case of ULIS, they gradually decrease the pitch of their pixels from 50 P m in 1998 [2], to 17 P m in 2009 [3]. This enables the realization of large format FPA: 1024*768 pixels and decrease of manufacturing costs. In order to compensate the inherent decrease of the Noise Equivalent Temperature Detectivity (NETD) due to the reduction of the pitch, improvements were made on the thermal insulation of the suspended membranes by means of advanced UV-photolithography processes. Attention was also paid to the reduction of the noise by an improvement of the fabrication process of the amorphous silicon and by advanced design of pixels. Nevertheless this roadmap will be in the next future less and less relevant, especially because further reduction of the pitch will reach the diffraction limit for the LWIR (8-14 P m). Absorption and fill factor of the FPA are already closed to their ideal values. Improvement of performance or reduction of the cost can still be made by progress in smart and efficient read-out integrated circuit ROIC, which is a key point of the uncooled FPA success. Recently progress has been reported in the packaging, by pixel level encapsulation [4]. Improvement of the performances can also be made by a change of the bolometric materials [5]. It is worth noticing that the two same materials have been driving the market for tw enty years. Recently, following th e results shown by Itkis et al. [6] on the bolometric behavior of carbon nanotube (C NT) films, ONERA, the French aerospace labs and LPN-CNRS founded by the French MOD, have chosen to investigate the potential of carbon nanotubes films as bolometers. First we will present the fabrication and report processes of our material: Single Wall Carbon Nanotubes (SWCNT) films. Then we will focus on the fabrication processes developed in our clean room facilities, and the electrical characterization of the fabricated devices. The next part will deal with the potential of SWCNT films as a thermistor. Then we will detail the optical characterization of our material, and eventually show the infrared (8-12 m) photo-response of our first generation of bolometric sensors.

Infrared (IR) Focal plane array (IRFPA) cameras are nowadays both, more accessible and with a broad variety in terms of detectors design. In many cases, the IRFPA characterization is not completely given by the manufacturer. In this paper a long wave 8-12 [μm] microbolometer IRFPA is characterized by means of calculating the Noise Equivalent Temperature Difference (NETD) and the Correctability performance parameters. The Correctability parameter has been evaluated by using a black body radiator and Two-Points calibration technique. Also, the Transfer Function of the microbolometer IR camera has been experimentally obtained as well as the NETD by the evaluation of radiometric data from a blackbody radiator. The obtained parameters are the key for any successful application of IR imaging pattern recognition.

This report explores the geometrical effects of a cylindrical chopper wheel on calculations of power coupling efficiency and noise equivalent temperature difference (NETD) of array elements. The overall efficiency of the cylindrical chopper wheel is found to be about 53% from geometrical arguments. In the limit that a detector beam fills the chopper aperture, if this efficiency is not accounted for, it can lead to detector NETD values that are a factor of 1.9 too high when calculated using standard double-modulation measurement techniques. For the particular geometry used with this setup, a power coupling efficiency of 78% was calculated for typical detector elements, resulting in values of detector NETD that were too large by a factor of 1.3 when the coupling efficiency was unaccounted for. This factor plays a role in accounting for some of the discrepancy between NETD values calculated based on diode sensitivity estimates and NETDs measured for individual array elements using double-modulation measurements.

A new silicon-diode-based infrared thermal detector array (1 × 4) has been developed. The silicon diode, as a temperature-sensing device, is built on a thin cantilever structure that is formed by micromachining. The thickness of the cantilever is about 5 μm. A thin layer of bismuth is evaporated on the cantilever as an infrared radiation absorber. With a cantilever measuring 264 μm × 112 pm × 5 gm and an active area measuring 102 μm × 102 μm, the fabricated detector array yields a responsivity of 5.3 V/W, a detectivity of 2.7 × 10 7 cm Hz 1/2 /W, and a noise equivalent temperature difference (NETD) of 1.7 °C.

Using careful measurements of the I-V curve of a YBCO thin-film microbridge under light irradiation at 780 nm and temperature close to 77 K, it is shown that the critical current versus temperature dependence is a good thermometer for estimating bolometric effects in the film. A novel dynamic voltage bias is introduced which directly gives the device current responsitivity and greatly reduces risks of thermal runaway. Detectivity is very low but it is predicted that a noise equivalent temperature of less than 10/sup -7/ K/ square root Hz would be achievable in a wide temperature range (10-80 K), which is an improvement over thermometry at the resistive transition. >

Potassium tantalum niobate (KTN) films, 10- mu m thick, with a nominal Curie temperature of -20 degrees C were formed on polished platinum-coated sacrificial yttria substrates by metalorganic deposition (MOD). These KTN films were used to fabricate focal plane arrays consisting of 128*128 pixels with each pixel on 50- mu m centers and 50- mu m/sup 2/. Using f/1 optics and a 2.5-V/ mu m/sup 2/ detector bias, a noise equivalent temperature (NE Delta T) of 0.65 degrees C was obtained for the best 1% of the pixels when the detector and blackbody source operated at 25 degrees C. >

This paper presents the design, fabrication, and characterization of temperature sensitive quartz resonators fabricated using heterogeneous integration methods for realizing high-density, thermal conductance fluctuation limited thermal sensors for infrared imaging and biochemical sensing applications. An integrated quartz sensor array using CMOS-compatible micromachining techniques has been designed and fabricated. 241 MHz micromachined resonators from F-cut quartz crystal cuts were fabricated with a temperature sensitivity of 22.162 kHz/°C. Infrared measurements on the resonator pixel resulted in a noise equivalent power (NEP) of 3.90 nW/Hz1/2, detectivity D* of 9.17 ×107 cmHz1/2/W, and noise equivalent temperature difference (NETD) in the 8–12 µm wavelength region of 4 mK and a response time of < 30 Hz. In a unique new application a remotely coupled thermal sensor configuration was used to monitor biochemical reactions in real time.

An increasing need for high-precision atmospheric data especially in the long wavelength infrared (LWIR) and very long wavelength infrared (VLWIR) spectral ranges has arisen in the past years not only for the analysis of climate change and its effect on the earth's ecosystem, but also for weather forecast and atmospheric monitoring purposes. Spatially and spectrally resolved atmospheric emission data are advantageously gathered through limb or nadir sounding using an imaging Fourier transform (FT) interferometer with a two-dimensional (2D) high-speed focal plane detector array (FPA). In this paper, AIM reports on its latest results on MCT VLWIR FPAs for Fourier transform infrared sounding applications in the 8-15μm spectral range. The performance of a (112x112) pixel photodiode array with a 40μm pixel pitch incorporating extrinsic p-doping for low dark current, a technique for linearity improvement at high photon fluxes, pixel guards, pixel select/de-select, and a (2x2) super-pixel architecture is discussed. The customized read-out integrated circuit (ROIC) supporting integrate while-read (IWR) operation has a buffered direct injection (BDI) input stage and a full well capacity (FWC) of 143 Megaelectrons per super-pixel. It consists of two independently operating halves with two analog video outputs each. The full frame rate is typically 4k frames/sec, making it suitable for use with rapid scan FT infrared spectrometers. At a 55K operating temperature and an ~14.4μm cut-off wavelength, a photo response of 12.1mV/K and a noise equivalent temperature difference of 24.8mK at half well filling are demonstrated for a 286K reference scene. The nonlinearity error is

CEA-Leti MINATEC has been involved in infrared focal plane array (IRFPA) development since many years, with performing HgCdTe in-house process from SWIR to LWIR and more recently in focusing its work on new ROIC architectures. The trend is to integrate advanced functions into the CMOS design for the purpose of applications demanding a breakthrough in Noise Equivalent Temperature Difference (NETD) performances (reaching the mK in LWIR band) or a high dynamic range (HDR) with high-gain APDs. In this paper, we present a mid-TV format focal plane array (FPA) operating in LWIR with 25μm pixel pitch, including a new readout IC (ROIC) architecture based on pixel-level charge packets counting. The ROIC has been designed in a standard 0.18μm 6-metal CMOS process, LWIR n/p HgCdTe detectors were fabricated with CEA-Leti in-house process. The FPA operates at 50Hz frame rate in a snapshot integrate-while-read (IWR) mode, allowing a large integration time. While classical pixel architectures are limited by the charge well capacity, this architecture exhibits a large well capacity (near 3Ge-) and the 15-bit pixel level ADC preserves an excellent signal-to-noise ratio (SNR) at full well. These characteristics are essential for LWIR FPAs as broad intra-scene dynamic range imaging requires high sensitivity. The main design challenges for this digital pixel array (SNR, power consumption and layout density) are discussed. The electro-optical results demonstrating a peak NETD value of 2mK and images taken with the FPA are presented. They validate both the pixel-level ADC concept and its circuit implementation. A previously unreleased SNR of 90dB is achieved.

Some parameter testing standards of Infrared Focal Plane Array performances were analyzed in this paper, the performance parameters testing systems of uncooled infrared focal plane device are developed, testing systems are established, including the radiation sources, the UFPA modules, signal acquisition module and the host computer program, the system can real-time transfer data through PCIE bus, stores, statistics and analysis the parameters, such as noise, responsivity, detectivity, noise equivalent power (NEP) and noise equivalent temperature difference (NETD). It can accurately determine the number of blind pixels and located them, quantitatively statistics non-uniformity, and to assess the performance of focal plane devices.

We are developing a 350 GHz cryogenic passive video imaging system. This demonstration system uses 800 photon-noise-limited superconducting transition edge sensor bolometers. It will image a 1 m x 1 m area at a standoff distance of 16 m to a resolution of approximately 1 cm at video frame rates (20 frames per second). High spatial resolution is achieved by the use of an f/2.0 Cassegrain optical system with 1.3 m primary mirror. Preliminary testing of prototype detectors indicates that we can achieve a noise equivalent temperature difference (NETD) of 70 mK for the fully sampled 1 m × 1 m image at 20 frames per second.

The Thermal Infrared Sensor (TIRS) is a QWIP based instrument intended to supplement the Operational Land Imager (OLI) for the Landsat Data Continuity Mission (LDCM). The TIRS instrument is a dual channel far infrared imager with the two bands centered at 10.8[mu]m and 12.0[mu]m. The focal plane assembly (FPA) consists of three 640x512 GaAs Quantum Well Infrared Photodetector (QWIP) arrays precisely mounted to a silicon carrier substrate that is mounted on an invar baseplate. The two spectral bands are defined by bandpass filters mounted in close proximity to the detector surfaces. The focal plane operating temperature is 43K. The QWIP arrays are hybridized to Indigo ISC9803 readout integrated circuits (ROICs). Two varieties of QWIP detector arrays are being developed for this project, a corrugated surface structure QWIP and a grating surface structure QWIP. This paper will describe the TIRS system noise equivalent temperature difference sensitivity as it affects the QWIP focal plane performance requirements: spectral response, dark current, conversion efficiency, read noise, temperature stability, pixel uniformity, optical crosstalk and pixel yield. Additional mechanical constraints as well as qualification through Technology Readiness Level 6 (TRL 6) will also be discussed.

In this paper, the performance enhancing method by increasing optical fill factor of a μ-bolometer is proposed. The main idea of increasing optical fill factor of a μ-bolometer is the reducing the leg area without deteriorating the thermal and electrical properties of its legs. We propose 'the self align leg' structure in order to reduce the leg area without deteriorating electrical and thermal properties. From the analysis, this method can give some benefits, the improvement of responsivity up to 9% and noise equivalent temperature difference 13% through fill factor increasing by 5 to 7%. A new plausible method of increasing fill factor can easily be incorporated with a conventional process without considerable change of process.

We have developed a 22um pitch and 320 × 240 pixel uncooled infrared radiation focal plane array on the silicon-oninsulator (SOI) substrate by means of 0.35um CMOS technology and bulk-micromachining. For IR detection, we use silicon single-crystal series p-n junctions that can realize high uniformity of sensitivity and low voltage drift. The supporting beam shrinkage enabled the pixel pitch shrinkage from 32um to 22um and 320 × 240 pixel number without deteriorating NETD. We also developed a SOI low-noise CMOS readout circuit that can calibrate chip temperature and introduced a noise canceling digital algorithm to cancel the reset noise generated in the readout circuit. The dominant noise source, SOI MOSFET noise, was decreased by optimizing the gate design. Finally the FPA has realized noise equivalent temperature difference (NETD) of 0.12K and requires no thermo-electric cooler (TEC) and is mounted on a low-cost standard ceramic package.

We present field results showing excellent performance for a compact earth observing thermal infrared (EOTIR) hyperspectral grating spectrometer using a combination of a Quantum Well Infrared Photodetector (QWIP) and grating based Dyson spectrometer. 12The Dyson design allows for a very compact and optically fast system (F/1.6). Cooling requirements are minimized due to the single monolithic prism-like grating design. The configuration has the potential to be the optimal sciencegrade imaging spectroscopy solution for lighter-than-air (LTA) vehicles and unmanned aerial vehicles (UAV) due to its small form factor and relatively low power requirements. The QWIP allows for optimum spatial and spectral uniformity and provides adequate responsivity to allow for near 100mK noise equivalent temperature difference (NEDT) operation across the EOTIR passband. These tests are in preparation for the deployment of the Hypserspectral Thermal Infrared Spectrometer (HyTES) which is currently being funded under NASA's instrument incubator program (IIP). Test results show NEDT, linearity as well as applicable earth science emissivity target results (silicates, water) measured in direct sunlight. A calibration is also performed to derive direct water temperature using a well calibrated transfer radiometer operating simultaneously.

Recent efforts have been paid to elevate the operating temperature of Type II InAs/GaSb superlattice Mid Infrared photon detectors. Optimized growth parameters and interface engineering technique enable high quality material with a quantum efficiency above 50%. Intensive study on device architecture and doping profile has resulted in almost one order of magnitude of improvement to the electrical performance and lifted up the 300K-background BLIP operation temperature to 166K. At 77K, the ~4.2 m cut-off devices exhibit a differential reP sistance area product in excess of the measurement system limit (10 6 Ohm.cm 2 ) and a detectivity of 3x10 13 cm.Hz 1/2 /W. High quality focal plane arrays were demonstrated with a noise equivalent temperature of 10mK at 77K. Uncooled camera is capable to capture hot objects such as soldering iron. Keywords: Type II superlattice, InAs/GaS b, M-structure, photodetector s, MWIR, focal plane arrays. INTRODUCTION: TYPE II ANTIMONIDE BASED SUPERLATTICES

To address the growing needs of the automotive industry for low cost solutions to far infrared imaging, a silicon - silicon germanium (Si/SiGe) quantum well resistive bolometer technology is presented. The Si/SiGe thermistor structure is epitaxially grown and combines a high temperature coefficient of resistance (TCR) with low flicker noise. A TCR of approximately 3%/K for a Ge fraction of 32% is demonstrated. Quantum mechanical calculations show that a minimum SiGe layer thickness of 8 nm is needed to avoid degradation caused by ground state shift due to carrier confinement in the SiGe potential wells. In contrast to most of today's bolometer designs, the optical quarter wave cavity needed to achieve high absorption of radiation is an integral part of the quantum well thermistor structure. Optimization of the full bolometer design is made where the interaction between optical absorption, heat capacity and electrical properties is considered and a design approach targeting the lowest noise equivalent temperature difference is presented. As part of the optimization, it was found that for the best overall solution, optical absorption can be sacrificed in favor for a smaller heat capacity.

A photovoltaic detector design based on the graded band gap HgCdTe MBE structure with high conductivity layer (HCL) at interface, which provides photodiodes series resistance and a shortwave cut.off filter is developed. The optimal HCL parameters giving high quantum efficiency and minimal noise equivalent temperature difference were determined by calculations and experimentally confirmed. The hybrid 320×256 IR FPA operating in 8–12 μm spectral range was fabricated. The threshold power responsivity and minimal noise equivalent temperature difference values at wavelength maximum were 1.02×10−7 W/cm2, 4.1×108 V/W and 27 mK, respectively.

This paper described an infrared (IR) radiation sensor based on Film Bulk Acoustic-wave Resonator (FBAR). The resonant frequency of FBAR sensor downshifts linearly when there is IR (peak wavelength at 780nm) illumination on the device. This effect attributed to the temperature sensitivity of the FBAR. The noise equivalent temperature difference (NETD) and the detection limit for 780 nm IR of the sensor is 25 mK at 25 °C and 19 μW/mm2, respectively. This study has proven the feasibility of detection of IR using ZnO film based FBAR.

Describes a 648*487 pixel PtSi Schottky-barrier infrared CCD image sensor. Due to the development of the modified inverted-LOCOS process, which can minimize dead regions, and the two-dopant concentration structure, which achieves both a large charge capability and high transfer efficiency, a 40% fill factor in a 21- mu m*21- mu m pixel and a 0.1-K noise equivalent temperature difference were obtained. >

It has recently been suggested1 that by operating a ferroelectric pyroelectric under a d.c. field its dielectric response can be modified to improve its sensitivity as a pyroelectric imager target. In light of this, a knowledge of how the various classes of pyroelectrics respond to field would be useful. Lead scandium tantalate (PST) materials were chosen as the subject of the present study. Samples were synthesized by a conventional ceramic route, and subjected to extensive measurements in order to determine the response of their relative permittivity, loss tangent, and pyroelectric coefficient to applied d.c. fields. Using these data the predicted performance of a thermal imager operated with a PST target has been calculated: the highest performance was obtained with the most ordered material, which gave a thermal resolution (noise equivalent temperature difference) of 0.11 K.