This PDF file contains the front matter associated with SPIE Proceedings Volume 8512, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Using a solution casting technique, for sample preparation, pyroelectric multi-walled carbon nanotubes in polyvinylidene fluoride composite films have been fabricated, to allow the characterization of both the pyroelectric and dielectric properties of such composites. The properties measured include: (1) dielectric constants and (2) pyroelectric coefficient as a function of temperature. From the foregoing parameters, figures-of-merit, for infrared detection and thermal-vidicons, were calculated. The results indicated figures-of-merit of composite film were higher than pristine polyvinylidene fluoride films. Additionally, composite films, composed of pyroelectric Lithium tantalate [(LiTaO₃), LT] ceramic particles and silver nanoparticles incorporated into polyvinylidene fluoride-trifluoroethylene [PVDF-TrFE) 70/30 mol%] copolymer matrix, have been prepared. The results indicate that silver nanoparticles incorporated lithium tantalate:polyvinylidene fluoride-trifluoroethylene composite films may have application for un-cooled infrared sensor.

IR Sensors and imagers using nanostructure based materials are being developed for a variety of Defense and Commercial Applications. In this paper, we will discuss recent modeling effort and the experimental work under way for development of next generation CNT and Graphene based bolometer for these applications. We will discuss detector concepts that will provide next generation high performance, high frame rate, and uncooled nano-bolometer for MWIR and LWIR bands. We will discuss the path forward to demonstrate enhanced IR sensitivity for bolometer arrays.

This paper reviews the work of several teams at ARL. In the quantum well arena we are developing bulk InAsSb material for LWIR detectors type for high performance focal plane array applications, so far we have observed that the minority carrier lifetimes in the type II SLS material have been short. Short lifetimes present a major barrier towards the realization of high performance focal plane arrays. This paper discusses photoluminescence observed in InAsSb materials and our observation that the bandgap bowing parameter is much bigger than earlier studies have shown, opening up the possibility that up to 12 micron wavelength cut-off can be achieved in InAsSb alloys. In the second section a summary of the work done by the III-V and IR device team is presented, the team is using quantum dots to enhance the efficiency of solar photovoltaic devices. We have discovered that doping the quantum dots is critical in enhancing the efficiency of the solar cells.

HgCdTe (the current infrared material of choice) lacks a scalable, sufficiently lattice-matched substrate suitable for long wave infrared focal plane array production. One possible alternative material is HgCdSe. Similar to HgCdTe, HgCdSe is a ternary alloy which can be tuned across the infrared spectrum. Unlike HgCdTe, HgCdSe is nearly lattice matched to the scalable (and commercially available) substrate GaSb. Thus long wave infrared focal plane arrays could potentially be fabricated from HgCdSe grown on GaSb, with a ZnTeSe or CdTeSe buffer layer added to alleviate the slight mismatch. Samples of HgCdSe were grown via molecular beam epitaxy using a Se thermal cracker source to compare to those grown using a simple Se valved source. This allowed us to study any differences between layers grown with predominantly Se₂ flux versus Se₆ flux. Optimal growth parameters were explored using this new effusion source for Se. All HgCdSe samples grown with the simple valved source were heavily n-type (n~1017 cm^-3) despite being nominally undoped. However, when the valved Se effusion cell was replaced with the Se cracker source, the electron concentration was reduced and began to show significant temperature dependence below 100K. Subsequent experiments suggested this may be more related to different purity in the source material between the sources than the cracking process itself. Annealing under Hg raised the electron concentration, while annealing under Se lowered the concentration.

A detailed description of a common path interferometer is given for CARS and SRS applications. In this interferometer, both probe and reference arms are separated in time and polarization by a birefringent crystal. In order to generate the pump pulse a Ti:Sa laser centered at 808 nm is used, as for the Stokes pulses a Nd:YVO centered at 1064 nm is used, both lasers are synchronized in phase and frequency at a repetition rate of 80MHz. Acetone is employed for analysis and detection in this experiment, with a extinction ratio of 1/250, a temperature heating control system is developed for the calcite birefringent crystals with a precision of de ±0.01°C as well as an analysis of the contributions of both processes CARS and SRS by using a lock-in amplifier.

This paper describes the measurement principle of fluorescence spectrum on Na₂KSb film of multi-alkali photocathode and three samples were measured in the position of different radius. The data resulted shows that the peak wavelength of fluorescence spectrum on Na₂KSb film from center to edge of the photocathode surface gradually increased, while the peak fluorescence intensity gradually increased as well. The reason is that the antimony atom density of photocathode surface from the center to the edge gradually reduced. When the antimony in Na₂KSb film exceeds stoichiometry required, the fluorescence peak wavelength shifts towards the short-wave direction, while the fluorescence intensity decreased at the same time. When the antimony in Na₂KSb film achieves stoichiometry required, the fluorescence peak wavelength reaches the maximum value, while the fluorescence intensity reaches the strongest at the same time. By fluorescence test one can judge whether the stoichiometry of Na₂KSb film reaches to the ratio 2:1:1 or not, in another words whether antimony in Na₂KSb film is overdose or not. In addition by measuring the fluorescence spectra at different positions of the photocathode surface, we can measure component uniformity in the Na₂KSb photocathode film. The more uniform antimony atom density is in the photocathode surface, the more accurate the monitor method of film growth by measuring changes of the photocathode photocurrent is, thus component uniform can be better, Na₂KSb film thickness can be thicker, long-wave absorption of visible light is more, the sensitivity of the photocathode is higher. Therefore, during the manufacturing process of multi-alkali photocathode of image intensifier, one has to make the uniform antimony atoms density on photocathode window surface in order to achieve higher sensitivity.

With the availability and maturity of scanning micromirrors, a growing field of applications other than picoprojectors is emerging. The miniaturization potential of these scan based setups is most attractive for robotic vision and LIDAR imaging sensors for autonomous guided vehicles. The laser safety concept of picoprojectors is based on the eye blink reflex and high scanning frequencies (<10 kHz). However, in remote sensing applications, where infrared wavelengths and very often lower scanning frequencies are a common choice, there is a demand for robust scan failure detection. According to IEC 60825 the maximum emission time of a 100 mW CW Laser at 900 nm must be below 5 μs to be classified as a class 1 laser source. State-of-the-art scan-fail devices, which are designed for laser light shows, only feature reaction times down to 1 ms. Therefore, to enable class 1 operation of a laser scanner, based on micromirrors, a detailed examination of all possible failure scenarios was performed and consequently a fast scan-fail device with a reaction time of less than 5 μs was developed. The position of the micromirror is measured optically by focusing a laser diode to the micromirror and detecting the mirror position with a quadrant photodiode. To determine the current angular velocity of the micromirror the first derivative of the position signal is evaluated and monitored. This enables the eyesafe use of reasonably powered infrared lasers in low-cost scanning setups.

We report the demonstration of single mode AgCl_xBr_1-x channel waveguides for mid-infrared range. The waveguides were made by the deposition of AgCl_xBr_1-x layers on top of a Ag/Ti/SiO₂/Si substrate, followed by photolithographic and lift-off processing. We showed that these waveguides operate in a single mode for the 6-14 μm band. The propagation losses of 20 dB/cm were measured at λ=10.6 μm using the cut-back method. We discuss the possible propagation losses mechanisms and show that the waveguide sidewall roughness is likely the major contributor for these losses. Using this fabrication process we have also realized Y-couplers and splitters. The development of these waveguides is a crucial step towards realizing on-chip AgCl_xBr_1-x mid-infrared integrated optical circuits which will be used for applications such as chemical sensing and spectro-interferometry for planet detection.

The NiTiNOL diaphragm, under two geometries, were simulated on a Silicon wafer and controlled by an external heat source. As the substrate bottom wall heats and conducts heat, the thermal expansion raises the thin layer which can be used as an actuator. The case of heat source applied on the top walls was also considered. The simulations were realized by means of the mechanical and thermal properties of materials. A comparison among the performance of the diaphragm based on the geometries with a plane layer, a layer with a primary boss, and finally with primary and secondary bosses is presented. Each process was simulated in COMSOL Multiphysics. The distribution of deformation using bosses is similar to the analyzed cases using pressure instead of heat. The maximum obtained displacement for NiTiNOL is of approximately 2.5 micrometers at 343°K, at the same conditions, Silicon case reaches 0.9 μm. The diaphragm behavior is also compared with the cases of Silicon and Cu-Al-Ni. Our interest in the development of MEM actuators only controlled by external heat sources is due to several reasons. At first, because these clean energy sources sometimes reaches high density values, but they have not been well-spent. The most of MEMS thermal actuators need a current flow to heat the MEM device, by means of the Joule effect, and produce the corresponding thermal expansion. In this paper, the displacement depends on the external source, in accordance with the mechanical and electrical properties of the used materials.

Compared with traditional infrared imaging, infrared polarization imaging system can detect and identify the man-made or camouflaged target more efficiently by using the difference in the degree of polarization (DoP) between the target and background. The scene’s radiation is attenuated by the path atmosphere firstly, and then modulated by the polarizer and the optical system. Because of the effect of the atmosphere (such as absorption, radiation, diffusion etc.), the final radiation intensity the sensor received changes, which affects the result of detection and identification. In this paper, the component characteristic of particles in atmosphere was discussed particularly. And the propagation of signal was described by analyzing the scattering effect between atmospheric particles and photons. After the process of free path sampling, selecting the radius of the colliding particles, the scattering angle and azimuth sampling, and particle collision and extinction judgment, a Monte Carlo model of polarized light propagation in atmosphere was present by use of the Stokes/Mueller formalism and Meridian planes method. Then two different methods (the radiation intensity and the DoP) used for target recognition in atmosphere were simulated. The relationship between the received radiation intensity, the DoP and the distance was developed. The contrast showed that the DoP had a better performance than the intensity measurements on the whole. However, there was a maximum distance for polarization imaging system using short wavelength to make the most of the advantage. When beyond this distance, the polarization imaging advantage will disappear. Polarized light with longer wavelengths had a better ability to maintain the state of polarization after propagation in the atmosphere.

The closely lattice-matched material system of InAs, GaSb, and AlSb, commonly referred to as the 6.1Å material system, enables many unique approaches for producing high performance infrared detectors. The flexibility of the materials system allows for superlattice structures that can be tailored to have cutoff wavelengths ranging from the short wave infrared to the very long wave infrared. The type-II superlattice design promises high optical properties due to normal incidence absorption, high uniformity, low tunneling currents, and suppressed Auger recombination. The antimonide material system also allows for the design of high performance barrier structures. In particular, unipolar barriers, which blocks one carrier type without impeding the flow of the other, have been implemented in the design of SL photodetectors to realize complex heterodiodes with improved performance. Here we report on growth and device performance of infrared photodetectors based on type II InAs/Ga(In)Sb strain layer superlattices (SLs) using the complementary barrier infrared detector (CBIRD) design.

Two type-II superlattice structures with 15 monolayer (ML) InAs/12ML GaSb and 17ML InAs/7ML GaSb grown on GaSb (100) substrates by solid-source molecular beam epitaxy (MBE) have been investigated. The X-ray diffraction (XRD) measurements of both the 15ML InAs/12ML GaSb and 17MLInAs/7ML GaSb superlattices indicated excellent material and interface qualities and very narrow full width at half maximum (FWHM) of the zeroth-order peaks which were 22 arcsec and 20 arcsec respectively. The cutoff wavelengths of 15ML InAs/12ML GaSb and 17ML InAs/7ML GaSb superlattices photodetectors were measured at 6.6 μm and 10.2 μm, respectively. These different spectral ranges were achieved by growing alternating layers of variable thicknesses and in addition, the band gap engineering offered by the superlattices of InAs and GaSb. A zero-bias Johnson-noise-limited detectivity of 1.2x10¹¹cmHz^1/2/W at temperature 80K and wavelength of 6 μm was achieved for an unpassivated photodiode of 15ML InAs/12ML GaSb superlattice, and the detectivity at 80K and 9 μm was 2.2x10¹⁰cmHz^1/2/W for the device of 17ML InAs/7ML GaSb superlattice. Also, the optical and electrical characteristics of 15ML InAs/12ML GaSb superlattice photodiode were investigated from 80K to 280K. A zero-bias Johnson-noise-limited detectivity at temperature of 210K and wavelength of 6 μm was 1.2x10⁸cmHz^1/2/W.

Annealing effect on the quality of long wavelength infrared (LWIR) InAs/GaSb superlattices (SLs) has been investigated using atomic force microscopy (AFM), photoconductivity, temperature dependent Hall, and time-resolved differential transmission measurements using an electronically delayed pump-probe technique. Quarters of a single SL wafer were annealed at 440, 480, and 515 °C, respectively for 30 minutes under a Sb-over pressure. Morphological qualities of the SL surface observed by AFM did not show any indication of improvement with annealing. However, the spectral intensity measured by photoconductivity showed an approximately 25 % improvement, while the band gap energy remained at ~107 meV for each anneal, The electron mobility was nearly unaffected by the 440 and 480 °C anneals, however showed the improvement with the 515°C anneal, where the mobility increased from ~4500 to 6300 cm²/Vs. The minority carrier lifetime measured at 77 K also showed the improvement with annealing, increasing from 12.0 to 15.4 nanoseconds. In addition to the longer lifetimes, the annealed samples had a larger radiative decay component than that of unannealed sample. Both the longer measured lifetime and the larger radiative decay component are consistent with the modest improvement in the quality of the annealed SL sample. Overall the qualities of LWIR SL materials can be benefit from a post growth annealing technique we applied.

Temperature-dependent minority carrier lifetimes of InAs/InAs_1-xSb_x type-II superlattices are presented. The longest lifetime at 11 K is 504 ± 40 ns and at 77 K is 412 ± 25 ns. Samples with long periods and small wave function overlaps have both non-radiative and radiative recombination mechanisms apparent, with comparable contributions from both near 77 K, and radiative recombination dominating at low temperatures. Samples with short periods and large wave function overlaps have radiative recombination dominating from 10 K until ~200 K. The improved lifetimes observed will enable long minority carrier lifetime superlattices to be designed for high quantum efficiency, low dark current infrared detectors.

We present the performance of a unipolar barrier long-wave type-II InAs/GaSb superlattice (SLS) photodetector with a 50% cut-off wavelength of approximately 8.7 microns. In this study, the ability to lower dark current densities over traditional PIN diodes is presented by way of hetero-structure engineering of a pBiBn structure utilizing superlattice Ptype (P) and N-type (N) contacts, Intrinsic (I) superlattice active (absorber) region, and unipolar superlattice electron and hole blocking (b) layers. The spectral response of this pBiBn detector structure was determined using a Fourier Transform Infrared (FTIR) Spectrometer and the quantum efficiency (QE) was determined using a narrow 6250 nm narrow band filter and a 500K blackbody source. A diode structure designed, grown, and fabricated in this study yielded a dark current density of less than one (1) mA/cm² at a reverse bias of 150 mV and a specific detectivity value of greater than 10¹¹ Jones at 77K. In addition to single point temperature measurements, a variable temperature study (80K-300K) of the dark current is presented for a diode demonstrating diffusion limited dark current from 160K down to 80K.

DRS is the inventor and a leading developer of Blocked Impurity Band detector technology for ground, airborne and space-based observing applications and the sole developer of antimony doped silicon (Si:Sb) blocked impurity band (BIB) FPAs. Arsenic doped silicon (Si:As) and Si:Sb arrays in 128² pixel formats were developed by DRS for use on the Spitzer Space telescope. In the subsequent years these arrays were extended in both format and capability. 1024² pixel format, low flux Si:As arrays were developed for the NASA WISE mission, and Si:As and Si:Sb arrays were developed for higher flux applications such as JPL’s MegaMIR camera and Cornell’s FORCAST instrument for SOFIA, in both 256² and 1024² pixel array formats. Si:Sb arrays have advanced to offer similar responsivity, response uniformity, high operability and low dark currents long associated with Si:As BIB arrays but with high quantum efficiency that extends to 40 μm, compared to only 28 μm for Si:As. Recently, Si:Sb detector material has been further developed for low flux astronomy applications. Specifically, Si:Sb material has been grown to satisfy exceptionally low dark current requirements (such as < 0.5 e^-/s/pixel at 5 K) for large format focal plane arrays for future infrared telescopes. This paper will focus on the characterization of this low flux Si:Sb detector material

We investigated silicon as a promising material for a IR transparent window platform of IR(Infrared Ray) sensors with WLP(wafer level package), because silicon has advantages in price and CMOS process compatibility compared to Ge window although Ge exhibits higher IR transmittance than Si. Having comparable transmittance to Ge is the key to use silicon as a IR transparent window platform. We compared several types of AR coating films, SiN, SiO2, only ZnS, and Ge/ZnS for finding the condition of maximizing transmittance of Si in the range of 8 ~12 um , LW-IR(Longwave IR). Also we investigated changing of transmittance for LW-IR after thermal treatments in several ambient gases and several temperatures.

Silicon photon detectors and focal plane arrays (FPAs) are fabricated in many varieties^1,2. Their function depends on the detector architecture, dopants, and operating temperature. DRS has fabricated silicon pin detectors that cover the visible spectral range and blocked impurity band (BIB) detectors that cover the very-long-wavelength infrared (VLWIR) region³. Imaging arrays of silicon pin-diodes utilize the intrinsic bandgap of silicon to provide high photo response over the 0.4 – 1.0 μm spectral range. The detectors operate at or near room temperature as required. Silicon pin-diode arrays are particularly attractive as an alternative to charge-coupled devices (CCDs) for space applications where radiation hardening is needed. Pros and cons of CCD and pin diode architectures are listed in Reference⁴.

Electro-optical/infrared nanosensors are being developed for a variety of defense and commercial systems applications. One of the critical technologies that will enhance EO/IR sensor performance is the development of advanced antireflection coatings with both broadband and omnidirectional characteristics. In this paper, we review our latest work on high quality nanostructure-based antireflection structures, including recent efforts to deposit nanostructured antireflection coatings on large area substrates. Nanostructured antireflection coatings fabricated via oblique angle deposition are shown to enhance the optical transmission through transparent windows by minimizing broadband reflection losses to less than one percent, a substantial improvement over conventional thin-film antireflection coating technologies. Step-graded antireflection structures also exhibit excellent omnidirectional performance, and have recently been demonstrated on 3-inch diameter substrates.

Thermal injuries are a serious medical problem in the China. The accurate determination of burn degree is difficult for scatheless diagnose and a precondition of treating burn wounds. Multi-spectral photographic analysis is expected to play an important role in determining burn wound degree, the Liquid Crystal Tunable Filter has a capability of selecting the observing wavelength instaneously with high spectral resolution and excellent imaging quality in visible and near-infrared spectrum band. Taking advantage of this filter, we have developed a LCTF imaging spectrometer prototype instrument at visible wavelength bands for burn wound diagnose. In this paper, spectral analysis experiments were first performed on KUNMING mice and burn injury patients to find the characteristic reflective spectral curves at 400nm-1800nm, the imaging spectrometer prototype instrument using LCTFs which are sensitive to radiation in 420nm-750nmwavelength bands was built based on spectral analysis results. The spectral imaging experiments on burn injury patients have verified the excellent properties of the prototype instrument, including high quality spectral images with spectral resolution of less than 7nm and continuous selection of the output wavelength. The burn areas of patients were marked with different colors which represents as different burn degree and the spectral imaging system has thus been proven to have the ability to classify the burn areas through comparing their reflective spectral curves with characteristic spectrum of the different burn degree in spectral database in the future. Finally, the application of the LCTF imaging spectrometer to burn wound diagnose are summarized based on the results of spectral imaging experiments on burn injuries.

Fiber optic sensors are a mature choice for highly sensitive applications. Most modern pressure sensors are based on the piezoelectric effect (pressure causes a material to conduct electricity at a certain rate, leading to a specific level of charge flow associated with a specific level of pressure). In this paper, we describe theoretical calculations which predict encouraging experimental results on pressure sensing with optical fibers. These results may be used in applications for distributed sensors in structural health monitoring (SHM). The sensing fiber is capable of propagating 3 modes with a straight fiber length of 30cm at a lambda of 1550nm. In our experiments, a perpendicular force of F=200gr cause a core compression of nearly 2um, according to Poisson’s elastic coefficient for silica, which in turn provoked the loss of half the number of modes indicating a 50% sensitivity as shown in our results included here. The proposed set-up intends to measure force vs propagating modes in a standard single mode fiber. A full set of results will be included in our presentation.

There are two important parts in Microbolometer: the high TCR sensing material and low thermal conductance. The high TCR material cytochrome c protein is a good candidate for infrared detection. Our group already demonstrated cytochrome c thin film has high TCR on the top of SU8 surface that has been published in Proc. of SPIE (2011). Because the very low thermal conductivity of SU-8, we proposed a new concept of SU-8 photoresist thermal insulation desk structure, and used the exposure dose method to establish it. Although exposure dose method is very sensitive to exposure time and PEB time, we successfully investigated the right recipe to create new desk insulation structure which with different height. We also explored the relationship between mask II exposure time and desktop thickness, and how the post-exposure baking (PEB) time influenced our structure. Our SU-8 photoresist insulation structure fabrication process is much easier and cheaper than present SiNx fabrication process. The desk shape structure can have low thermal conductance of 6.681*10^-6 W/K. The easy-made SU-8 microstructures and cytochrome c thin films that and can reduce the cost of IR microbolometer. We believe that it is possible to fabricate a new generation of microbolometer based on cytochrome c protein and SU-8 photoresist microstructures.

Full waveform lidar systems are capable of recording the complete return signal from the laser illuminated target. By making use of the return full waveform, one can obtain more detailed information about the target of interest than the simple target range. The development of better methods to extract information from the return signal can lead to better target characterization. Several methods have been proposed in the literature to obtain the complete range profile or radar cross section of the target.^{1, 2} In a previous work, we proposed to use a compressive sensing scheme to acquire and compress the received signal, and at a post-processing stage reconstruct the signal to obtain the range profile of the target. We extend this previous work on full waveform lidar using chaotic signal by including additive white Gaussian noise into the acquisition stage of the lidar system. The objective is to test the robustness of the previously developed approach based on compressive sensing to different noise level intensities. The simulation software Digital Imaging and Remote Sensing Image Generation (DIRSIG) was used to simulate the range profile corresponding to a three-dimensional scene. The simulation results indicate that the full range profile can be reconstructed with a compressive sensing acquisition as low as 25 percent of the total number of samples and with low root-mean-square error (RMSE). The proposed lidar system with compressive sensing can be used to sense with compression and recover the range target profile.

Onera, the French Aerospace Lab, develops and models 2D and 3D active imaging systems to understand the relevant physical phenomena impacting on their performances. As a consequence, efforts have been done both on the propagation of a pulse through the atmosphere (scintillation and turbulence effects) and, on target geometries and their surface properties (radiometric and speckle effects). But these imaging systems must operate at night in all ambient illuminations and weather conditions in order to perform the strategic surveillance of the environment for various worldwide operations or to perform the enhanced navigation of an aircraft (A/C). Onera has implemented codes for 2D and 3D laser imaging systems. As we aim to image a scene even in the presence of rain, snow, fog or haze, Onera introduces such meteorological effects in these numerical models and compares simulated images with measurements provided by commercial imaging systems.

A tunable resonant photoresponse to millimeter-waves is demonstrated in a grating-gated high electron mobility transistor (HEMT) formed by an InGaAs/InP heterostructure. The gate consists of a metal grating with 9 μm period, which was designed to couple mm-radiation to plasmons in the two-dimensional electron gas (2DEG) of the HEMT. The resonant excitation of plasmons, which shifts with gate-bias, changes the channel conductance. These devices have potential as chip-scale frequency-agile mm-wave detectors, which may be scaled to THz frequencies.

The possibility of single-cycle infrared pulses generation by for-wave mixing of visible seed radiation with high power femtosecond filament field with central wavelength of 800 nm is shown. It is determined that phase synchronism does not play a significant role in this ultrafast nonlinear optical process.