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We propose an all-ZnO bilayer microbolometer, operating in the long-wave infrared regime that can be implemented by consecutive atomic layer deposition growth steps. Bilayer design of the bolometer provides very high absorption coefficients compared to the same thickness of a single ZnO layer. High absorptivity of the bilayer structure enables higher performance (lower noise equivalent temperature difference and time constant values) compared to single-layer structure. We observe these results computationally by conducting both optical and thermal simulations. (C) 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)

The simulated optical and electrical performance of the infrared HgCdTe focal plane array (FPA) for elevated operation temperature is reported. The depleted absorber layer is explored for equilibrium mode of operation up to 160 K. A resonant cavity is created to improve photon-matter interaction and hence, reduces the required absorption volume. The volume of the active region of HgCdTe detector is reduced by 70% in this manner. Dark current density is decreased without compromising the quantum efficiency. The effect of the reduced band filling effect leading to higher absorption coefficient and more efficient utilization of incident flux is employed. High quantum efficiency is achieved in a thin compositionally graded n+/ν/π/p HgCdTe photo-diode. This architecture helps to minimize the requirement of charge handling capacity in the CMOS read-out integrated circuit (ROIC) as the operation temperature is increased. Quantum efficiency ~30% or above is shown to be sufficient for Noise Equivalent Temperature Difference (NETD) less than 20 mK with the reported design.

As an optical remote sensing equipment, the thermal infrared hyperspectral imager operates in the thermal infrared spectral band and acquires about 180 wavebands in range of 8.0~12.5μm. The field of view of this imager is 13° and the spatial resolution is better than 1mrad. Its noise equivalent temperature difference (NETD) is less than 0.2K@300K(average). 1 The influence of background radiation of the thermal infrared hyperspectral imager,and a simulation model of simplified background radiation is builded. 2 The design and implementationof the Cryogenic Optics. 3 Thermal infrared focal plane array (FPA) and special dewar component for the thermal infrared hyperspectral imager. 4 Parts of test results of the thermal infrared hyperspectral imager.The hyperspectral imaging system is China’s first success in developing this type of instrument, whose flight validation experiments have already been embarked on. The thermal infrared hyperspectral data acquired will play an important role in fields such as geological exploration and air pollutant identification.

In this paper, figures of merit describing the performances of infrared (IR) bolometer sensor such as thermal response time (a#x03C4;), responsivity, detectivity (D), noise equivalent power (NEP) and noise equivalent temperature difference (NETD) are estimated using numerical simulations. The proposed model is based on the analytical formulas from Frank Niklaus, et.al. Using this model, we have evaluated the performance of two-legged, uncooled infrared bolometer sensor with 52×52 a#x03BC;m2 and 35×35 a#x03BC;m2 pixel-pitch size. The bolometer sensors were fabricated by Institut National d'Optique (INO), Canada and National Chung-Shan Institute Science of Technology (NCSIST), Taiwan. Test structures including uncooled vanadium oxide bolometer FPAs were fabricated at INO to verify the agreement between the simulated and experimental data. The performance model was used at NCSIST to evaluate the improvements on design and fabrication of bolometer FPAs with pixel pitch varying form 35 a#x03BC;m to 52 a#x03BC;m.

Searching for evidence of inflation by measuring B-modes in the cosmic microwave background (CMB) polarization at degree angular scales remains one of the most compelling experimental challenges in cosmology. BICEP2 and the Keck Array are part of a program of experiments at the South Pole whose main goal is to achieve the sensitivity and systematic control necessary for measurements of the tensor-to-scalar ratio at σ(r) ~0:01. Beam imperfections that are not sufficiently accounted for are a potential source of spurious polarization that could interfere with that goal. The strategy of BICEP2 and the Keck Array is to completely characterize their telescopes' polarized beam response with a combination of in-lab, pre-deployment, and on-site calibrations. We Sereport the status of these experiments, focusing on continued improved understanding of their beams. Far-field measurements of the BICEP2 beam with a chopped thermal source, combined with analysis improvements, show that the level of residual beam-induced systematic errors is acceptable for the goal of σ(r) ~ 0:01 measurements. Beam measurements of the Keck Array side lobes helped identify a way to reduce optical loading with interior cold baffles, which we installed in late 2013. These baffles reduced total optical loading, leading to a ~ 10% increase in mapping speed for the 2014 observing season. The sensitivity of the Keck Array continues to improve: for the 2013 season it was 9:5 μK _/s noise equivalent temperature (NET). In 2014 we converted two of the 150-GHz cameras to 100 GHz for foreground separation capability. We have shown that the BICEP2 and the Keck Array telescope technology is sufficient for the goal of σ(r) ~ 0:01 measurements. Furthermore, the program is continuing with BICEP3, a 100-GHz telescope with 2560 detectors. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

International audience; Today huge efforts are made in the research and industrial areas to design compact and cheap uncooled infrared optical systems for low-cost imagery applications. Indeed, infrared cameras are currently too expensive to be widespread. If we manage to cut their cost, we expect to open new types of markets. In this paper, we will present the cheap broadband microimager we have designed. It operates in the long-wavelength infrared range and uses only one silicon lens at a minimal cost for the manufacturing process. Our concept is based on the use of a thin optics. Therefore inexpensive unconventional materials can be used because some absorption can be tolerated. Our imager uses a thin Fresnel lens. Up to now, Fresnel lenses have not been used for broadband imagery applications because of their disastrous chromatic properties. However, we show that working in a high diffraction order can significantly reduce chromatism. A prototype has been made and the performance of our camera will be discussed. Its characterization has been carried out in terms of modulation transfer function (MTF) and noise equivalent temperature difference (NETD). Finally, experimental images will be presented.

International audience; At high temperature, infra-red focal plane arrays are limited by their performance in operability, detectivity D (*) or noise equivalent temperature difference. Trap characterization and defect studies are necessary to better understand these limitations at high temperature. In this paper, we use deep level transient spectroscopy to study electrically active defects in mercury cadmium telluride n (+)/p diodes. The material investigated has a cut-off frequency (lambda (c)) of 2.5 mu m at 180 K and p doping performed with mercury vacancy. Trap energy signatures as well as capture cross-section measurements are detailed. A low temperature hole trap close to midgap is observed in the range 150-200 K with an activation energy around 0.18 +/- A 0.025 eV. A high temperature hole trap is also observed in the range 240-300 K with an activation energy of 0.68 +/- A 0.06 eV. A hole capture cross-section of 10(-19) cm(2) is obtained for both traps. The nature of the defects and their correlation with dark current are discussed.

Progress on development of lead-salt thermoelectrically-cooled (TE-cooled) imaging sensors will be presented. The imaging sensor architecture has been integrated into field-ruggedized hardware, and supports the use of lead-salt based detector material, including lead selenide and lead sulfide. Images and video are from a lead selenide focal plane array on silicon ROIC at temperatures approaching room temperature, and at high frame rates. Lead-salt imagers uniquely possess three traits: (1) Sensitive operation at high temperatures above the typical ‘cooled’ sensor maximum (2) Photonic response which enables high frame rates faster than the bolometric, thermal response time (3) Capability to reliably fabricate 2D arrays from solution-deposition directly, i. e. monolithically, on silicon. These lead-salt imagers are less expensive to produce and operate compared to other IR imagers based on II-VI HgCdTe and III-V InGaAsSb, because they do not require UHV epitaxial growth nor hybrid assembly, and no cryo-engine is needed to maintain low thermal noise. Historically, there have been challenges with lead-salt detector-to-detector non-uniformities and detector noise. Staring arrays of lead-salt imagers are promising today because of advances in ROIC technology and fabrication improvements. Non-uniformities have been addressed by on-FPA non-uniformity correction and 1/f noise has been mitigated with adjustable noise filtering without mechanical chopping. Finally, improved deposition process and measurement controls have enabled reliable fabrication of high-performance, lead-salt, large format staring arrays on the surface of large silicon ROIC wafers. The imaging array performance has achieved a Noise Equivalent Temperature Difference (NETD) of 30 mK at 2.5 millisecond integration time with an f/1 lens in the 3-5 μm wavelength band using a two-stage TE cooler to operate the FPA at 230 K. Operability of 99.6% is reproducible on 240 × 320 format arrays.

For over 30 years, the U.S. Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) has specialized in characterizing the performance of infrared (IR) imaging systems in the laboratory and field. In the late 90’s, AMRDEC developed the Automated IR Sensor Test Facility (AISTF) which allowed efficient deployment testing of aviation and missile IR sensor systems. More recently, AMRDEC has tested many uncooled infrared (UCIR) sensor systems that have size, weight, power, and cost (SWAPC) benefits for certain fielded U.S. Army imaging systems. To compensate for relatively poor detector sensitivities, most UCIR systems operate with very fast focal ratio or F-number (f/#) optics. AMRDEC has recently found that measuring the Noise Equivalent Temperature Difference (NETD) with traditional techniques used with cooled infrared systems produce biased results when applied to systems with faster f/# values or obscurations. Additionally, in order to compare these camera cores or sensor systems to one another, it is imperative to scale the NETD values for f/#, focus distance, and waveband differences accurately. This paper will outline proper measurement techniques to report UCIR camera core and system-level NETD, as well as demonstrate methods to scale the metric for these differences.

In this study, the evaluation method for the responsivity and noise characteristics of a commercial infrared thermal imaging camera and a custom-made sensor module was presented. Signal transfer functions (SiTFs) and noise equivalent temperature differences (NETDs) of the two sensor modules were obtained by using a differential mode blackbody that is able to control the temperature difference ΔT between an infrared target and its background. And we verified the suitability of our evaluation method through the comparison between the found NETD and the specification of the camera. In addition, the difference of 0.01 K of the two noise equivalent temperature differences calculated from with and without nonuniformity correction suggests that the nonuniformity correction is essential process for the evaluation of the infrared thermal imaging cameras. Finally, in case of the custom-made sensor module, only temporal NETD was found because of its higher nonuniformity characteristics.

An 8-channel E-band heterodyne radiometer system (74-86 GHz) is designed, characterized, and calibrated to measure the radial electron temperature profile by measuring Electron Cyclotron Emission spectrum at SST-1 Tokamak. The developed radiometer has a noise equivalent temperature of 1 eV and sensitivity of 5 × 10(9) V/W. In order to precisely measure the absolute value of electron temperature, a calibration measurement of the radiometer system is performed using hot-cold Dicke switch method, which confirms the system linearity.

Polarization filters are commonly used as a means of increasing the contrast of a scene thereby increasing sensor range performance. The change in the signal to noise ratio (SNR) is a function of the polarization of the target and background, the type and orientation of the polarization filter(s), and the overall transparency of the filter. However, in the mid-wave and longwave infrared bands (MWIR and LWIR), the noise equivalent temperature difference (NETD), which directly affects the SNR, is a function of the filter’s re-emission and its reflected temperature radiance. This paper presents a model, by means of a Stokes vector input, that can be incorporated into the Night Vision Integrated Performance Model (NV-IPM) in order to predict the change in SNR, NETD, and noise equivalent irradiance (NEI) for infrared polarimeter imaging systems. The model is then used to conduct a SNR trade study, using a modeled Stokes vector input, for a notional system looking at a reference target. Future laboratory and field measurements conducted at Night Vision Electronic Sensors Directorate (NVESD) will be used to update, validate, and mature the model of conventional infrared systems equipped with polarization filters.

DRS history in microbolometer and uncooled focal plane array (UFPAA) development mimics that of the entire industry. The history extends over fifteen years as array pitches moved ever-smaller from 51uum to 25um to 17um, and now something smaller than 17uum. The uncooled microbolometer makers have transitioned through smaller pitches about every six years. This has been done while maintaining a noise equivalent temperature difference (NNETD) performance of 20-50mK, and maintaining a thermal time constant (TTTC) of 10-20mmSec. Once a newer pitch is developed to a performance level matching the previous pitch, development on the next smaller pitch is already underway. In this manner, the industry has progressed through smaller pitches without a fundamental performance improvement when measured in NNETD or in TTTC, or more specifically in NNETD*TTC product. Hence, a more-encompassing metric for tracking performance through time would involve the NNETD, the TTCC, and some indicator of bolometer size. Ann NETD*TTC**Area metric, as the appropriate metric for including bolometer size, will be proposed, theoretically justified, and discussed here. A rank-ordering of bolometers which have been published through 22013 is also presented in three charts, one for NETTD, one for NEETD*TTC, and lastly one for NETD*TTC**Area.

In this paper, we introduce a floating plasmonic absorber having multiple resonances in the 8 ~ 14 μm spectral range and broadband absorption characteristics by adjusting Drude relaxation rate of metal. This plasmonic broadband resonator capable of capturing light with a large optical cross-section area is able to substantially enhance the performance of micro-bolometer (response time, noise equivalent temperature difference, pixel size and so on) due to the significantly reduced thermal mass and conductance. Firstly, to adjust Drude relaxation rate, the mean crystalline size of metal was optimized by changing the deposition condition and the absorption characteristics of absorber were measured by Fourier transform infrared spectroscopy in the 8 ~ 14 μm spectral range. The measurement results show that 1.62 times of broadening in bandwidth was obtained by decreasing the crystalline size from 5.73 nm to 3.18 nm while maintaining the maximum absorption at resonant wavelength of 10 μm within 93 ~ 95%. Comparisons between measurements and CST microwave studio simulations show similar spectral absorption trends. And then, to integrate plasmonic absorber with micro-bolometer, various kinds of plasmonic absorbers which have combinations of short and long dipole resonators were designed and simulated. Based on these results, 12 μm micro-bolometer pixels integrated with plasmonic broadband Ti absorber are designed and fabricated. The optimized Ti resonators with multiple resonance and small crystalline size absorb 88 % of the unpolarized radiation in the 8 ~ 14 μm spectral range on the average.

We introduce a microwave submillimeter-wave detector based on an integrated micromesh absorber and superconducting kinetic inductance thermometer on a through-wafer released sub-micron thick membrane. Equilibrium operation achieved by thermal isolation through the membrane geometry enables operation at elevated thermal bath temperatures of 5–10 K. The bolometer operates in a phonon-noise limited regime with a measured noise equivalent temperature difference of below 10 mK at 1 s integration time, which is sufficient for radiometric imaging in terrestrial systems. We also measured and analyzed the bolometer frequency response in the band 0.1–1.4 THz. Performance improvements through further dimensional scale-down and temperature dependency are discussed.

Cataloged from PDF version of article. Microbolometers are extensively used for uncooled infrared imaging applications. These imaging units generally employ vanadium oxide or amorphous silicon as the active layer and silicon nitride as the absorber layer. However, using different materials for active and absorber layers increases the fabrication and integration complexity of the pixel structure. In order to reduce fabrication steps and therefore increase the yield and reduce the cost of the imaging arrays, a single layer can be employed both as the absorber and the active material. In this paper, we propose an all-ZnO microbolometer, where atomic layer deposition grown zinc oxide is employed both as the absorber and the active material. Optical constants of ZnO are measured and fed into finite-difference-time-domain simulations where absorption performances of microbolometers with different gap size and ZnO film thicknesses are extracted. Using the results of these optical simulations, thermal simulations are conducted using finite-element-method in order to extract the noise equivalent temperature difference (NETD) and thermal time constant values of several bolometer structures with different gap sizes, arm and film thicknesses. It is shown that the maximum performance of 171 mK can be achieved with a body thickness of 1.1 μm and arm thickness of 50 nm, while the fastest response with a time constant of 0.32 ms can be achieved with a ZnO thickness of 150 nm both in arms and body. © 2014 Elsevier B.V. All rights reserved.

We describe optical characterisation of a Strained Silicon Cold Electron Bolometer (CEB), operating on a $350~\mathrm{mK}$ stage, designed for absorption of millimetre-wave radiation. The silicon Cold Electron Bolometer utilises Schottky contacts between a superconductor and an n++ doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to $160~\mathrm{GHz}$ and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of $50~\%$ for radiation coupled into the device by the planar antenna and an overall noise equivalent power (NEP), referred to absorbed optical power, of $1.1 \times 10^{-16}~\mathrm{\mbox{W Hz}^{-1/2}}$ when the detector is observing a $300~\mathrm{K}$ source through a $4~\mathrm{K}$ throughput limiting aperture. Even though this optical system is not optimised we measure a system noise equivalent temperature difference (NETD) of $6~\mathrm{\mbox{mK Hz}^{-1/2}}$. We measure the noise of the device using a cross-correlation of time stream data measured simultaneously with two junction field-effect transistor (JFET) amplifiers, with a base correlated noise level of $300~\mathrm{\mbox{pV Hz}^{-1/2}}$ and find that the total noise is consistent with a combination of photon noise, current shot noise and electron-phonon thermal noise., Comment: Published in Applied Physics Letters, 105, pp. 043509

A new micromachined microbolometer array structure is presented that utilizes a self-supporting semiconducting yttrium barium copper oxide (Y-Ba-Cu-O) thin film thermometer. The Y-Ba-Cu-O thermometer is held above the substrate only by the electrode arms without the need of any underlying supporting membrane. This represents a significant improvement in the state-of-the-art for microbolometers by eliminating the thermal mass associated with the supporting membrane. The reduced thermal mass permits lowering the thermal conductance to the substrate to obtain increased responsivity or having a shorter thermal time constant to allow for higher frame rate camera. The simple structure does not suffer from warping problems associated with stress imbalances in multilayer microbolometer structures that utilize a supporting membrane such as Si/sub 3/N/sub 4/. Devices were fabricated by growing Y-Ba-Cu-O films on a conventional polyimide sacrificial layer mesa. Subsequent etching of the sacrificial layer provides the air gap that thermally isolates the microbolometer. Y-Ba-Cu-O possesses a relatively high temperature coefficient of resistance of 3.1%/K at room temperature. The 400-nm-thick Y-Ba-Cu-O film exhibited absorptivity of about 30%. The responsivity and detectivity approached 10/sup 4/ V/W and 10/sup 8/ cm Hz/sup 1/2//W to filtered blackbody infrared (IR) radiation covering the 2.5 to 13.5 /spl mu/m band. This extrapolates to noise equivalent temperature difference (NETD) less than 100 mK. The micromachining techniques employed are post-complementary metal-oxide-semiconductor (CMOS) compatible, allowing for the fabrication of focal plane arrays for IR cameras.

An optically readable bi-material infrared detector has been developed. In this paper, the basic operating principle of this detector, the structure of the test device, and the optical read-out system are described. The thermal-bending property of the test device is also reported. We measured the infrared responsivity of this detector. A noise equivalent temperature difference (NETD) of 0.25 K was obtained with the test device, which had an element size of 75μm×75 μm.

The main idea of this paper is to compare the readout architectures for uncooled microbolometer focal plane detector arrays with respect to the detector and readout circuit noise. The comparison is done keeping the total power consumption of all architectures constant. Three CMOS readout architectures with different degree of parallelism are described in this paper: pixelwise, columnwise and serial. The noise model of the readout circuit is given. Also, the optimization for the lowest NETD (noise equivalent temperature difference) and estimation of the self-heating effect is presented.

We have designed and fabricated an optimized long-wavelength/very-long wavelength two-color quantum well infrared photodetector (QWIP) device structure. The device structure was grown on a 3-in semi-insulating GaAs substrate by molecular beam epitaxy (MBE). The wafer was processed into several 640/spl times/486 format monolithically integrated 8-9 and 14-15 /spl mu/m two-color (or dual wavelength) QWIP focal plane arrays (FPAs). These FPAs were then hybridized to 640/spl times/486 silicon CMOS readout multiplexers. A thinned (i.e., substrate removed) FPA hybrid was integrated into a liquid helium cooled dewar for electrical and optical characterization and to demonstrate simultaneous two-color imagery. The 8-9 /spl mu/m detectors in the FPA have shown background limited performance (BLIP) at 70 K operating temperature for 300 K background with f/2 cold stop. The 14-15 /spl mu/m detectors of the FPA reaches BLIP at 40 K operating temperature under the same background conditions. In this paper we discuss the performance of this long-wavelength dualband QWIP FPA in terms of quantum efficiency, detectivity, noise equivalent temperature difference (NE/spl Delta/T), uniformity, and operability.

The noise equivalent temperature difference(NETD)is one of the most important performance indices of mechanical scanning thermograph, as well as the minimum detectable size as the resolution of the measuring object. This index shows the ability of thermograph that presents the possibility of more precise temperature measurement. It is defined in traditional standard, in which the noise is defined by peak to peak noise voltage. This paper presents a new method to obtain NETD by standard deviation of radiance temperature at individual pixels in thermogram. As this method depends upon statistical treatment, we can treat the NETD quantitatively and objectively. We can also apply this method to another type of thermograph.

The noise equivalent temperature difference (NETD) and the minimum detectable size (MDS) as a spatial resolution, are most important performance indices of thermograph. For such indices, a wide variety of standards and test/evaluation methods have been defined until now, but, it is very important to establish more objective standards for the quantification of thermographs. This paper presents two matters, one is a new method to obtain noise equivalent temperature difference by standard deviation of radiance temperature at individual pixels in thermogram and the another is the necessity to clarify the relationship between the size of an object to be measured and the temperature reading. In the former, we can treat the noise equivalent temperature difference quantitatively and objectively, as this method depends upon statistical treatment, while in the latter we can quantitatively measure the temperature of the measuring object in the detectable size

In order to estimate the ultimate sensitivity of thin film colossal magnetoresistors regarding to magnetic field and temperature, we have studied low frequency noise in La 0.8 Sr 0.2 MnO 3 , La 0.75 Sr 0.25 MnO 3 and La 0.7 Pb 0.3 MnO 3 pulse laser deposited thin epitaxial films. Excess noise has been found to be caused by resistance fluctuations, defect related and haven't magnetic origin. Ex situ annealing effectively reduces electrical noise about one order of magnitude without any change of transport properties. The signal to noise ratio was found to be almost temperature independent in wide range near the phase transition. These properties are common for all the films, which are of epitaxial quality. La 0.8 Sr 0.2 MnO 3 film exhibits superior performances: the noise equivalent temperature difference (NETD) and magnetic field (NEMFD) difference are 100 nK/√Hz at 30 Hz and 75 μOe/√Hz at 1 kHz correspondingly.

A W-band monolithic microwave integrated circuit (MMIC), including an Sb-heterostructure diode on a GaAs substrate, has been demonstrated. The MMIC also includes the RF choke and output shorting capacitor essential to detector circuits. Additional input matching has yielded peak sensitivities on the order of 10 000 V/W and equivalent bandwidths of 40 GHz. Using these circuits in conjunction with current W-band low-noise amplifier technology can achieve the sub-1degK noise equivalent temperature difference necessary for producing discernible images with W-band passive imaging cameras.

We demonstrated a 256 times 256 voltage-tunable two- color corrugated quantum-well infrared-photodetector focal plane array. The detector operation is based on photocurrent asymmetry in a double-superlattice quantum well structure. By using a broadband corrugated light coupling scheme, we obtained a quantum efficiency of 24% in the mid-wave (MW) band and 26% in the long-wave (LW) band without AR coating. Operating at 50 K, the measured noise equivalent temperature difference is 27 mK at 33-ms integration time for the MW and 90 mK at 2 ms for the LW with f/2.44 optics. The NETD operability values are 98.4% and 95.9%, respectively.

We report a large-format (640 times 512) voltage-tunable quantum-well infrared photodetector (QWIP) focal plane array (FPA) for dual-color imaging in the midwavelength infrared (3-5 mum) band. Voltage-tunable spectral response has been achieved through series connection of two eight-well stacks of AlGaAs-InGaAs epilayers grown by molecular beam epitaxy on GaAs substrate. The peak responsivity wavelength of the detectors is shifted from 4.1 mum (color 1) to 4.7 mum (color 2) as the bias is increased within the limit applicable by commercial read-out integrated circuits. The operability of the FPA is ~99.5% with noise equivalent temperature differences of ~60 and 30 mK (f/1.5) in color modes 1 and 2, respectively. To our knowledge, this is the first large-format voltage-tunable dual-color QWIP FPA reported for midwavelength thermal imaging.

We report the first large format (640times512) AlInAs-InGaAs quantum-well infrared photodetector (QWIP) focal plane array (FPA), and investigate the characteristics of AlInAs-InGaAs QWIPs both at pixel and FPA level. The measurements on the detectors fabricated with molecular beam epitaxy grown epilayer structure including 30 InGaAs quantum wells (26 Aring thick, ND=2times1018 cm-3) yielded very promising characteristics. The detectors with lambdap=4.2 mum and Deltalambda/lambdap=25% displayed a background-limited performance temperature as high as 105 K with f/2 aperture. The noise equivalent temperature difference of the FPA is as low as 23 mK (f/1.5) at 105-K sensor temperature with 99.6% operability. These results are comparable to the best results reported for AlGaAs-InGaAs midwavelength infrared QWIPs showing the promise of this material system for completely lattice-matched multiband QWIP FPAs.

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASA's Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NE/spl Delta/T) of /spl les/0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTER's TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities and then calculating emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should be able to recover temperatures within about /spl plusmn/1.5 K and emissivities within about /spl plusmn/0.015. Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations. The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTER's precision, calibration, and atmospheric compensation.

Two Si Wafers were bonded using SiO2//Si3N4 direct bonding technology, where a bridge structure of a composite dielectric film (SiO2//Si3N4/SiO2) was formed in the bond area. In the center of this bridge structure, a single crystal Si was left in the shape of an island, on which a Schottky Barrier Diode (SBD) with Cr silicide was fabricated and used as a detector part. On the other hand, another Si wafer was used as a cap wafer having anti-reflection coating to improve the light transmittivity in the wavelength range from 8 to 12μm up to more than 90%. This cap wafer and the above mentioned main wafer were bonded together using water glass bonding technology at 80°C to encapsulate the detector part in a vacuum. A bolometer type infrared radiation microsensor was thus made on an experiment basis. It has a self-package type structure to protect the detector part from mechanical damages and secure the operational environment. Its size and weight could be extremely reduced down to 2.0mm×2.0mm×0.8mm and 10mg, respectively. The response time is as fast as 4ms which is about 1/100 of that of a conventional bolometer. Other important electric characteristics of this element are as follows: NEP (noise equivalent power)=5.90×10-10W/Hz1/2, NETD200-205 (noise equivalent temperature difference)=0.02°C, R (sensitivity)=1.69×105V/W.

In this letter, we report the electrical and optical characteristics of a superconducting vacuum-bridge microbolometer with an electrical noise equivalent power of 26fW radicHz and an effective time constant of 380 ns, when operated at a bath temperature of 4K. We employ a novel room temperature external negative feedback readout architecture, that allows for noise matching to the device without bulky stepup transformers or cooled electronics. Both the detector and the readout lend themselves to be scaled to imaging arrays. The directly measured noise equivalent temperature difference over a 100-1000-GHz bandwidth is 125 mK in a 30-ms integration time

A high-performance 801×512-element PtSi Schottky-barrier infrared image sensor has been developed with an enhanced Charge Sweep Device (CSD) readout architecture. In the enhanced CSD, the power consumption of the CSD has been reduced by employing a multiphase CSD with an on-chip multiphase CMOS clock generator. Flexible vertical scan is also possible using a newly developed transfer gate scanner. A large fill factor of 61% is obtained in spite of the small pixel size of 17×20μm2. The differential temperature response and noise equivalent temperature difference with f/1.2 optics at 300K were 2.2×104 electrons/K and 0.037K, respectively. The saturation signal level was 2.1×106 electrons and the total power consumption of the device was less than 50mW.

Infrared chopper elements have been fabricated, utilizing the transient light scattering effect of ferroelectric liquid crystal with asymmetric waveform voltage drive. New elements can performed 12% of modulation degrees in around 10 microns region. A combination of an IR-chopper and a pyroelectric sensor is used to measure radiation intensity from black body at various temperatures to detect human body stationary. The new type of IR detector allows a pyroelectric sensor array easily to be developed to measure temperature distribution over large area. The detection has achieved 0.55°C noise equivalent temperature difference (NETD).

Noise equivalent temperature difference (NETD) is the key parameter characterizing the detectivity of infrared systems. Our developed pushbroom longwave infrared imaging spectrometer works in a waveband between 8μm to 10.5 μm. Its temperature sensitivity property is not only affected by atmosphere attenuation, transmittance of the optical system and the characteristics of electric circuit, but also restricted by the self-radiation. The NETD accurate calculation formula is derived according to its definition. Radiation analysis model of a pushbroom image spectrometer is set up, and its self-radiation is analyzed and calculated at different temperatures, such as 300K, 150K and 120K. Based on the obtained accurate formula, the relationships between the NETD of imaging spectrometer and atmospheric attenuation, F-number, effective pixel area of detector, equivalent noise bandwidth and CCD detectivity are analyzed in detail, and self-radiation is particularly discussed. The work we have done is to provide the basis for parameters determination in spectrometer system.

Muzzle smoke produced by weapons shooting has important influence on infrared (IR) system while detecting targets. Based on the theoretical model of detecting spot targets and surface targets of IR system while there is muzzle smoke, the function range for detecting spot targets and surface targets are deduced separately according to the definition of noise equivalent temperature difference(NETD) and minimum resolution temperature difference(MRTD). Also parameters of muzzle smoke affecting function range of IR system are analyzed. Base on measured data of muzzle smoke for single shot, the function range of an IR system for detecting typical targets are calculated separately while there is muzzle smoke and there is no muzzle smoke at 8～12 micron waveband. For our IR system function range has reduced by over 10% for detecting tank if muzzle smoke exists. The results will provide evidence for evaluating the influence of muzzle smoke on IR system and will help researchers to improve ammo craftwork.

We have developed a low-cost uncooled infrared radiation focal plane array (FPA) requiring no thermoelectric cooler (TEC), which has 320 x 240 detection pixels with 22 um pitch. The silicon single-crystal series p-n junction diodes and the low-noise readout circuit on the same SOI wafer fabricated by 0.13 um CMOS technology were utilized for infrared (IR) detection. The temperature dependence in the readout circuit was eliminated by correlated double sampling (CDS) operation with reference pixel that was insensitive to infrared radiation. In order to reduce the temperature dependence, we improved the reference pixel and the readout circuit. Although the reference pixels should be completely insensitive to IR radiation, prior reference pixels showed measurable sensitivity. The improved reference pixel was formed by partially releasing with bulk-micromachining and was verified to be insensitive to IR radiation by an object of 400°C. The readout circuit had a differential amplifier instead of a singletransistor amplifier and an analog-to-digital converter (ADC). In each portion, CDS was applied to reduce temperature dependence. The first CDS operation was used for eliminating the pixel output variation and the second operation was used for canceling the variation of the differential amplifier. The output variation referred to input was reduced to 1/30 compared with that of the prior circuit. Moreover, the residual variation of output voltage was reduced by CDS operation in ADC and stable output data was obtained with ambient temperature variation. With these improvements, the sensitivity variation of the FPA was improved to 10% in the range of -30 degrees to 80 degrees and noise equivalent temperature difference (NETD) of 40 mK was achieved.

Quantitative temperature measurements of large-scale fires are of key interest to FM Global’s researchers and engineers. In this study, the effectiveness of extending an uncooled fixed-integration-time IR camera’s temperature range via a reduced aperture was investigated. The corresponding calibration of the focal plane array (FPA) was performed, in situ, by investigating spatially resolved radiance levels with and without the aperture present. In-the-field calibration results were compared and validated using a blackbody (e = 1) source. The effect of reduced radiant intensity on the noise equivalent temperature difference (NETD) was investigated over a wide temperature range. This study shows the effective temperature extension of a fixed-integration-time (microbolometer) IR camera from 1200oF (650oC) to 2192oF (1200oC), making this camera particularly suitable for studying fires. The temperature extension was accomplished at low cost without changing the integration time of the focal plane array (FPA), removing the camera’s lens, or by using a neutral density (ND) filter.

We report the realization of coalescent free-standing ultra-thin (as thin as 5.5 nm) platinum layers deposited via plasma-enhanced atomic layer deposition and their characterization as an uncooled infrared detector. Such thin platinum thermistors enable a responsivity as high as 2 · 107 V/WA, an estimated noise equivalent temperature difference of 163 mK and thermal time constants on the order of 1 ms.

InAs/GaSb shortperiod superlattices have proven their large potential for highperformance focal plane array infrared detectors. They are fabricated as monospectral and bispectral infrared detectors for a wavelength range between 3�30 !m with very high responsivity and thus comparable to stateof� theart CdHgTe and InSb detectors. Dualcolor, midwavelength infrared InAs/GaSb superlattice camera systems offer simultaneous and spatially coincident detection on a millisecond time scale in both spectral channels between 3�4 !m and 4�5 !m. Thus, these cameras are very sensitive to the spectral signature of carbon dioxide at approximately 4.3 !m and can be used for remote imaging of CO2. In a molecular beam epitaxy based process, eleven 288 × 384 dualcolor detector arrays are fabri cated on 3" GaSb substrates. Very homogeneous detector arrays with an excellent noise equivalent temperature difference have been realized. This article presents the InAs/GaSb typeII superlattice dualcolor concept, its results, and delivers insights into a range of test methodologies which ensure that the basic requirements for achieving high detector performance are fulfilled.

The Hyperspectral Thermal Emission Spectrometer (HyTES) is being developed as part of the risk reduction activities associated with the Hyperspectral Infrared Imager (HyspIRI). HyspIRI is one of the NASA’s Tier 2 Decadal Survey Missions for earth science. HyTES will provide information on how to place the spectral filters on the HyspIRI Thermal Infrared Instrument as well as provide antecedent science data. The HyTES pushbroom design has 512 spatial pixels over a 50-degree field of view and 256 contiguous spectral bands between 7.5 and 12 μm in the thermal infrared (TIR) wavelength region. HyTES includes many key enabling state-of-the-art technologies including a high performance concave diffraction grating, a quantum well infrared photodetector (QWIP) focal plane array, and a compact Dyson-based optical design. The Dyson optical design allows for a very compact and optically fast system (F/1.6). It also minimizes cooling requirements due to the fact it has a single monolithic prism-like grating design which allows baffling for stray light suppression. The monolithic configuration eases mechanical tolerancing requirements which are a concern since the complete optical assembly is operated at cryogenic temperatures. The QWIP allows for optimum spatial and spectral uniformity and provides adequate responsivity or D-star to allow 200 mK noise equivalent temperature difference (NEDT) operation across the TIR passband. The system uses two mechanical cryocoolers to maintain instrument temperature. The first cooler holds the focal plane array at 40 K and the second cooler holds the remainder of the cryovacuum system at 100 K. Assembly of the system is now complete and the system is undergoing alignment and laboratory testing. Once laboratory testing is complete the system will be used to acquire airborne data from a Twin Otter aircraft over the southwestern USA in late 2012.

A newly designed infrared radiation sensor for a clinical tympanic thermometer has been developed. A very small packaging size (2.2 mm × 2.3 mm × 0.8 mm) is achieved so that the sensor can be used in the human auricle. To realize high sensitivity, infrared sensing regions in the shape of a pair of micro-air-bridges are encapsulated in a vacuum microchamber through a successive silicon batch process using micromachining techniques. The sensor shows a sensitivity R v of 5000 V W −1 and a noise equivalent temperature difference (NETD) of 0.062 °C at a d.c. bias voltage of 1.56 V.

A quartz crystal resonator's resonance frequency is sensitive to temperature. This sensitivity has been exploited in the past in thermometers made of single, macroscopic quartz resonators that can accurately detect temperature changes of /spl mu/K. Using semiconductor microfabrication techniques, it is now possible to fabricate a large number of microresonators from a single quartz wafer. It is shown that combining the small thermal mass and high thermal isolation capability of such microresonators, the steep frequency versus temperature characteristics of resonators made of certain cuts of quartz and the low-noise characteristics of quartz crystal oscillators can result in high-performance infrared (IR) sensors and sensor arrays. In a microresonator sensor, the temperature change produced by the absorption of IR energy results in a frequency change that can be measured with a resolution that corresponds to a change in the resonator's temperature of less than a /spl mu/K. Calculation shows that an array of microresonators in the 200 MHz-1 GHz range can be the basis of an uncooled IR imaging system with a noise equivalent temperature difference, NETD, of

A detailed study of bipolar transport under forward‐bias conditions is evaluated by Ensemble Monte Carlo simulation in two structures (p+n and pn+ junctions). The static characteristics of both structures are presented. In particular, this study focuses on a microscopic analysis of current fluctuations. A decomposition of the autocorrelation function of the total current fluctuations in electron, hole and crossed contributions is performed. In this way, the importance of each type of carrier in the spectral density of current fluctuations in both structures for a wide frequency range is determined. In the low frequency range, the presence of shot, thermal and excess noise was found. The Ensemble Monte Carlo method also permits ready evaluation of the noise equivalent temperature in both structures.

A thermistor bolometer (an infrared radiation sensor) for a clinical tympanic thermometer has been newly developed and quantitatively evaluated. In order to mount the sensor on a tip of a flexible probe and to insert it into human's auricle, the sensor iscompleted in a very small size (2.2mm×2.3mm×0.8mm) using silicon micromachining technologies. Further the sensor can selectively detect the infrared radiation only from a tympanic membrane.The sensor has been designed especially concerning the reduction of heat loss. To realize high sensitivity, a pair of infrared sensing regions of the sensor is made inthe shape of micro-air-bridge. It is encapsulated in a vacuum micro-chamber conformed between silicon substrates. The effectiveness of vacuum encapsulation is clearly proved by experiment.The sensor shows the sufficient performance for the tympanic thermometer with the sensitivity of 5000V/W and the noise equivalent temperature difference (NETD) of 0.062°C at a D.C. bias voltage of 1.56V.

We report a demonstration of an infrared focal plane array based on InGaAs/InGaP quantum dot infrared photodetectors. The middle-wavelength infrared quantum-dot infrared photodetector (QDIP) structure was grown via low-pressure metal organic chemical vapor deposition. A detectivity of 3.6×1010 cm Hz1/2/W was achieved at T=95 K and a bias of −1.4 V. The background limited temperature of our QDIP was 140 K with a 45° field of view. A 256×256 detector array was fabricated with dry etching, and hybridized to a Litton readout chip by indium bumps. Thermal imaging was achieved at temperatures up to 120 K. At T=77 K, the noise equivalent temperature difference was measured as 0.509 K with a 300 K background and f/2.3 optics.

Theoretical expressions to calculate the signal-to-noise ratio of an IR detector in a direct injection readout hybrid focal plane array (FPA) are developed in this paper. The theory takes into account the effect of shift of operating point of the pixel with small variations in scene temperature and contribution of shunt resistance due to surface leakage currents in the photodiode. These expressions are then used to calculate the noise equivalent temperature difference (NETD) performance of the IR detector in the FPA. The role of buffered direct injection (BDI) circuit in improving the NETD performance of hybrid pixels in a LWIR mercury cadmium telluride FPA array is analyzed. The results of our calculations show that the individual pixels in a LWIR HgCdTe FPA would not function to their ultimate performance and in certain conditions may even exhibit erratic behaviour in the absence of BDI interface.

Thomson-CSF/LCR and TCS have carried out research in the field of IR sensors working at room temperature using ferroelectric and pyroelectric copolymers of poly(vinylidene fluoride) and trifluo-roethylene. The copolymers are soluble and easy to process by the standard technique of CCD silicon circuits. This paper describes the realization of a matrix array detector (128 × 128 pixel) associating the P(VF2-VF3) copolymer with a silicon CCD matrix. The performance of this detector, i.e. the Noise Equivalent Temperature Difference, is equal to 0.6 K for an optical aperture of f/1 and an image frequency of 50 Hz.

Our results measuring I-V characteristics of YBCO/MgO microbridges show that large current sensitivities (10 mA/K) as a function of temperature can be obtained, roughly independently of the applied voltage V up to a few hundred mV. This offers the possibility of working with high values of the dynamic resistance so that the phonon noise associated to the thermal boundary resistance, located at the YBCO/MgO interface, becomes dominant. A noise equivalent temperature of 10/sup -8/ K//spl radic/Hz (T=85 K, f>1 kHz) has already been obtained in a 0.2/spl times/12/spl times/10 /spl mu/m/sup 3/ microbridge. We describe a process involving the periodical sampling of the I-V characteristics that eliminates 1/f amplifier noise and returns the current value (temperature dependent) at fixed voltage bias (/spl plusmn/1 mV). This output, locked to a reference voltage through a commercial temperature regulator, leads to temperature fluctuations less than 100 /spl mu/K/sub pp/ in a 10 Hz bandwidth. These results are promising to enhance performances of high-T/sub c/ microbolometers as infrared detectors. >

Because of obvious drawbacks including serious artefacts and noise in a decoded image, the existing wavefront coding infrared imaging systems are seriously restricted in application. The proposed ultra-precision diamond machining technique manufactures an optical phase mask with a form manufacturing errors of approximately 770 nm and a surface roughness value Ra of 5.44 nm. The proposed decoding method outperforms the classical Wiener filtering method in three indices of mean square errors, mean structural similarity index and noise equivalent temperature difference. Based on the results mentioned above and a basic principle of wavefront coding technique, this paper further develops a wavefront coding infrared imaging system. Experimental results prove that our wavefront coding infrared imaging system yields a decoded image with good quality over a temperature range from −40 °C to +70 °C.

A back surface illuminated 130/spl times/130 pixel PtSi Schottky-barrier (SB) IR-CCD image sensor has been developed by using new wiring technology, referred to as CLOSE Wiring, CLOSE Wiring, designed to effectively utilize the space over the SB photodiodes, brings about flexibility in clock line designing, high fill factor, and large charge handling capability in a vertical CCD (VCCD). This image sensor uses a progressive scanned interline-scheme, and has a 64.4% fill factor in a 30 /spl mu/m/spl times/30 /spl mu/m pixel, a 3.9 mm/spl times/3.9 mm image area, and a 5.5 mm/spl times/5.5 mm chip size. The charge handling capability for the 3.3 /spl mu/m wide VCCD achieves 9.8/spl times/10/sup 5/ electrons, The noise equivalent temperature difference obtained was 0.099 K for operation at 120 frames/sec with a 50 mm f/1.3 lens. >