A coupled quantum dot intersubband optical amplifier structure is reported. InGaAsP/GaAs supperlattice is used to effectively generate population inversion between the excited states and the ground state of the QD. Due to the three-dimensional quantum confinement, normal incidence optical amplification with low threshold current density can be expected. Such an intersubband optical amplifier is promising for highly-sensitive middle infrared (MWIR) and longwave infrared sensing and imaging.

An MWIR spectral imaging sensor based on dual direct vision prism (DVP) architecture is described. This sensor represents a third generation of the Chromotomographic Hyperspectral Imaging Sensor (CTHIS). In the new sensor, a direct vision prism is synthesized by the vector addition of the spectral response of two matched, but independently aligned DVP's. The resulting sensor dispersion varies from zero to twice the single prism dispersion, as a function of the angle between the dispersion axes of the two prisms. The number of resolved channels, and the related signal strength per channel, also adapts with this angle. The "synthesized prism" projects a spectral image onto the focal plane array of an infrared camera. The prism is rotated on the camera axis and the resulting spectral information is employed to form an image cube (x, y, λ), using tomographic techniques. The sensor resolves from 1 to 105 spectral channels, between 3.0μm and 5.2μm wavelength. Spectral image data and image reconstruction is provided for standard test sources and scenes.

We reported previously on full-disk observations of the sun through a layer of black polymer, used to protect the entrance aperture of a novel dualband spectrometer while transmitting discrete wavelength regions in the MWIR & LWIR¹. More recently, the spectrometer was used to assess the accuracy of recovery of unknown blackbody temperatures². Here, we briefly describe MWIR observations of the full Moon made in Jan 2008. As was the case for the solar observations, the Moon was allowed to drift across the spectrometer slit by Earth's rotation. A detailed sensor calibration performed prior to the observations accounts for sensor non-uniformities; the spectral images of the Moon therefore include atmospheric transmission features. Our plans are to repeat the observations at liquid helium temperatures, thereby allowing both MWIR & LWIR spectral coverage.

For the online characterization of fluids regarding their chemical composition, the miniaturization of an IR-absorption sensor at application-specific distinguished wavelengths for the mid-IR-region promises outstanding features. Utilizing micromachining technology facilitates the integration of all required components (including thermal emitter and detector) into a complete sensor system. The absorption is sensed in the evanescent field of an appropriately designed slab mono-mode waveguide (ZnSe, n=2.42) residing on a BaF2-substrate (n=1.44), which represents the central element of the system. A typical application for such a system is, e.g., the characterization of engine oil oxidation in terms of the absorption at 5.85 μm as an indicator for deterioration. The thermal generation and detection of mid-IR-radiation is preferred over expensive and sophisticated quantum well devices. However, the spatial and non-coherent character of thermally generated IR-radiation requires an extension of the numerical methods established for coherent light sources for a proper design of the system's grating couplers, which act as key elements determining the system performance. These couplers yield efficient coupling into and out of the sensing waveguide and provide the required spectral filtering at the same time. In the actually projected implementation, a multilayer waveguide Si/BaF2/ZnSe is used, where the silicon substrate practically represents a rear-reflector in the grating region featuring several advantages compared to simpler grating couplers. In this contribution we discuss the modelling of the coupling of non-coherent, thermally generated and detected IR-radiation by means of these multilayer grating couplers in the context of a fully integrated IR-absorption sensor system.

The Solar Bolometric Imager (SBI) is an imaging solar telescope assembly that employs a novel single-detector broadband bolometric measurement technique. An uncooled thermal IR imaging detector is coated with a thin gold-black film that absorbs over 98% of the solar spectrum. The absorbed energy is then re-radiated in the thermal IR and sampled by the detector array. This technique [4] provides an evenly weighted integrated responsivity that spans the majority of the solar spectrum (0.2-2.5μm). We present here performance results from the follow-on gold-black deposition process investigation, radiation testing results, spacecraft instrument design and some of the prototype detector/imaging system's flight performance and calibration data from our 2007 Ft. Sumner balloon flight that demonstrates the instrument met or exceeded all of its specification.

We report here carrier's magneto-transport properties and the band structure results for II-IV semiconductors. HgTe is a zero gap semiconductor when it is sandwiched between CdTe layers to yield to a small gap HgTe/CdTe superlattice which is the key of an infrared detector. Our sample, grown by MBE, had a period d (100 layers) of 18 nm (HgTe) / 4.4 nm (CdTe). Calculations of the spectra of energy E(k_z) and E(k_p), respectively, in the direction of growth and in the plane of the superlattice were performed in the envelope function formalism. The angular dependence of the transverse magnetoresistance follows the two-dimensional (2D) behavior with Shubnikov-de Haas oscillations. At low temperature, the sample exhibits p type conductivity with a hole mobility of 900 cm²/V.s. A reversal the sign of the weak-field Hall coefficient occurs at 25 K with an electron mobility of 3.10⁴ cm²/Vs. In intrinsic regim, the measured E_g ≈ 38 meV agrees with calculated E_g(Γ,300 K) = 34 meV which coincide with the Fermi level energy. The formalism used here predicts that this narrow gap sample is semi metallic, quasi-two-dimensional and far-infrared detector.

Backside illuminated detectors are sometimes fabricated on a thick substrates. In this work, we have calculated detector spectral response using the stack matrix approach. This matrix formulation first constructs a 2x2 "Stack Matrix" S that describes the optical properties of the complete stack from the detailed optical properties (as a function of wavelength) of each layer in the entire stack. The stack matrix relates the electric field strengths of the electromagnetic wave at the left of the stack to the electric field strengths of the electromagnetic waves at the right of the stack. The stack matrix S is constructed from the multiplication of matrices that track the phase and amplitude of the waves propagating across interfaces and from one side of a layer to the other side. From the detailed optical properties (as a function of wavelength) of each material layer, spectral response was calculated.

A new new kind of IR imaging system which is based on MEMS microcantilever has come out in recent years. The infrared radiation detection and the subsequent reconstruction of an image are based on the deflection of individual microcantilever pixels. This detection is applied in an optical way, which means there is no electrical contact to each individual pixel. This approach has drawn considerable attention due to the advantages of low cost, light weight, low power consumption, high reliability and no back-ground electrothermal noise. Firstly the incoming IR light is blocked and an image of the microcantilever array is captured by a camera as a background image before an optical readout process. Then the IR light is let in and the difference between the background image and the current image captured is calculated and exported as an IR video signal. This process has a critical demand on light power stability. A CCD of 12 bit resolution is used to achieve a high signal to noise ratio. Its resolution is 4096 which means it can detect a light power changing of 1/4096 or 0.02% theoretically. The instability of common lasers is a few percent and the long time instability of LED light sources can be about 1%. These instabilities are all larger than 1/4096. The power variation can be detected by the CCD if these lasers or LEDs are used as the light source in the system. This power variation will affect the signal to noise ratio of an output IR signal. We have done some experiments in this paper. The laser power stabilizer consists of an electro-optical modulator and an optical feedback system. The peak-to-peak instability of the laser output power reaches within 0.1% in a few minutes. The stabilized laser beam is applied to the optical readout process. The experiment shows that the output IR image is much more stable than before. The drift of light power is almost eliminated. The NETD of the whole system reaches about 2 K.

Signal-to-noise ratio (SNR) depends on how the signal is generated above the noise level at the detector. For QWIP (Quantum Well Infrard Photoconductor) photoconductive gain, noise gain and quantum efficiency are important properties that determine the operating parameters in a background-limited operation. At high bias the photoconductive and noise gain becomes comparable, and this allows for the experimental extraction of its value and quantum efficiency. It is important that signal and noise at the detector are the dominant values that determine the SNR of the entire system. In addition, the amplifier gain on Read Out Integrated Circuit (ROIC) is required to be large enough in order for input referred noises from subsequent amplifiers to be insignificant. Temporal and spatial noise limits the performance of the Focal plane Array (FPA). It is assumed that the time-independent noises can be calibrated out using linear two-point non-uniformity correction (NUC). The origin of spatial noise is ROIC's fixed pattern, Cosine⁴ (aperture effect), dark current, pixel response variation, etc. Unfortunately, gain and offset matrices from a finite time data capture do not represent detector array and ROIC behavior at time scale much larger than the gain and offset data capture time, and therefore 1/f noises can corrupt the images at larger time scale. Thus, an investigation of spatial and temporal noise has shown dependence on the number of frames collected. Non-linearity on some QWIP FPAs makes two-point NUC inapplicable, but it is not observed on some FPAs. The origin of this is not completely understood.

Infrared imaging in the 3-5 and 8-12 μm bands is demonstrated to be extremely fast and spatially resolved characterization technology for testing light and heat in micron-size light emitting devices. It is shown how this high-speed contactless technology coupled with the CCD micro vision can be used to monitor both light and parasitic heat evolution in space (10-μm resolution step) and time (~10 μs temporal scale) in white, near IR, mid-wave IR, and long-wave IR LEDs. The technology appears to be the best way to find out if and where the excess heat emerges and how it affect on the light pattern and device performance. We experimentally demonstrate the non-uniformity in light pattern and local heat traps with giant temperature gradients (>10³ K/cm), which affect LED parameters and cause these devices to degrade.

Ultra-fast laser has been used in laser sensing and laser communication systems as well as for raison d'etre of Target-to-Noise Ratio (TNR or SNR) remote control. Foundation of these quite different applications is in unique ability of ultrafast laser to change photonic characteristics when ultra-short laser pulse interacts with photonic semiconductor. Ultrafast laser is capable to sweep potential free carriers for period of time that is comparable with free carrier's life time and thereto, ultra-short pulse is able to "bleach" photonic bandgap semiconductor making it temporally insensitive to its genuine in-band irradiance. Energy transfer into semiconductor lattice follows the "bleaching". Energy transfer may have different physical mechanisms-direct thermal as well as non-thermal or electronic transfer, leading initially to temporal lattice structure changes, and, with respect to pulse intensity, eventually to band gap collapse and even phase changes in the semiconductor. However, for the purpose of fine sensing the only mild lattice disturbance is important. That will limit focus of our consideration of laser-semiconductor interaction by relatively low intensity ultra-fast and fast laser pulses. Ultra-fast and fast lasers open almost unlimited opportunities in band gap photonic applications by allowing remotely engineer the characteristics of active and passive systems such as bandwidth, spectral responsivity, detectivity, response time etc. In this paper we will discuss applications of ultra-fast lasers-lasers with femto-seconds pulse width and, to some extend-fast lasers-with picoseconds pulse width, to remote engineering of photonic characteristics of active and passive IR and electro-optical systems.

A laser processing method was used to microstructure the surface of position-sensitive silicon avalanche photodiodes (PSAPDs) and enhance their near-infrared response. Following laser microstructuring and high-temperature annealing, experiments were performed on PSAPDs to determine their performance at 1064 nm. As a result of this processing method, we fabricated APDs with quantum efficiencies as high as 58% at 1064 nm. The enhanced near-infrared response has now been realized in both lateral effect and quadrant-type PSAPDs without altering their electronic noise, avalanche gain or position resolution. A near-infrared-enhanced PSAPD module with temperature control and position output was assembled and tested.

We have demonstrated the operation of a far-infrared frontside-illuminated GaAs/AlGaAs quantum well photodetector based on intersubband absorption in a quantum well (QW) with a targeted peak frequency of 3 THz (wavelength: ~100 μm). A multiple quantum well structure consists of 20 periods of 18 nm QWs interleaved by 80 nm barriers with an Al alloy content of 2%. We measured the following performance characteristics: dark current, responsivity, and spectral response. A responsivity of 13 mA/W at an electric bias of 40 mV and an operating temperature of 3 K was obtained with a peak response close to the designed detection frequency. The dark current density was a few μA/cm² and was limited by thermally assisted tunneling through the barriers. We looked also at possible designs to optimize the device's performance.

The IR antenna-pair coupled micro-bolometers has demonstrated its unique power response features compared to the single antenna coupled micro-bolometers. The response pattern is determined by that of the single antenna and an interference oscillation term of the antenna-pair with respective to the angle of incidence of the radiation field, and can be steered by shifting the location of the bolometer. This paper explores the potential application of antenna-pair coupled detector in beam synthesis. It describes an array configuration based upon these micro-bolometers, and discusses the corresponding coherent data processing method for the purpose of obtaining response pattern narrowing effects from such an array. This directional gain enhancement, together with the beam steering control, could potentially lead to an array capable of providing a novel IR lensless imaging technique.

In this study, we develop a new 3D miniature blood vessel searching system by using near-infrared LED light, a CMOS camera module with an image processing unit for a health monitoring system (HMS), a drug delivery system (DDS) which requires very high performance for automatic micro blood volume extraction and automatic blood examination. Our objective is to fabricate a highly reliable micro detection system by utilizing image capturing, image processing, and micro blood extraction devices. For the searching system to determine 3D blood vessel location, we employ the stereo method. The stereo method is a common photogrammetric method. It employs the optical path principle to detect 3D location of the disparity between two cameras. The principle for blood vessel visualization is derived from the ratio of hemoglobin's absorption of the near-infrared LED light. To get a high quality blood vessel image, we adopted an LED, with peak a wavelength of 940nm. The LED is set on the dorsal side of the finger and it irradiates the human finger. A blood vessel image is captured by a CMOS camera module, which is set below the palmer side of the finger. 2D blood vessel location can be detected by the luminance distribution of a one pixel line. To examine the accuracy of our detecting system, we carried out experiments using finger phantoms with blood vessel diameters of 0.5, 0.75, 1.0mm, at the depths of 0.5 ~ 2.0 mm from the phantom's surface. The experimental results of the estimated depth obtained by our detecting system shows good agreements with the given depths, and the viability of this system is confirmed.

Within this work a 28 pixels line sensor for distance measurement applications is presented based on the time-of-flight principle and the double-correlator circuit concept. An on-chip oscillator block generates 15-phase steps of the fundamental 10 MHz clock with σ = 1.28 %, which is necessary for calculating the triangular correlation function out of which the distance information is obtained. Measurement results in a range up to 3 m with a standard deviation ≥ 3.5 cm are achieved. The pixel autonomous background light suppression is capable of managing background illumination > 100 kLux. A smart bus concept reduces the number of control signals to the pixels and guarantees 80 dB attenuation from the oscillator signals to the analog differential outputs of the chip. The line sensor was realized in a single-chip solution embodying the silicon PIN photodiode detectors.

Sensitive ultraviolet photodetectors are essential components for a growing number of civilian and military applications. In this paper, we report 4H Silicon Carbide (SiC) avalanche photodiodes (APDs) with a p-i-n structure. These APDs, range in diameter from 180 μm to 250μm, exhibit very low dark current (10s of pA at avalanche gain of 1000) and high gain in linear-mode operation. An external quantum efficiency of 48% at 280 nm is achieved at unity gain with a recessed-window structure. The differential resistance of a 250 μm recessed-window device at zero bias is estimated to be 6×10¹⁴ ohms. As a result of high external quantum efficiency, large area, and large differential resistance, a record high specific detectivity of 4.1×10¹⁴ cmHz ^1/2 W^-1, has been achieved. Single ultraviolet photon detection in Geiger-mode operation with gated quenching is also described. In this paper, we report single photon detection efficiency (SPDE) of 30% at 280 nm with a dark count probability (DCP) of 8×10^-4.

The revolutionary charge-coupled device (CCD) was first described by George Smith and Willard Boyle of Bell Laboratories in 1969. Hubert Burke and Gerald Michon of General Electric (GE) followed with the invention of the charge-injection device (CID) in 1973. In the 1970s and 1980s, CID-based cameras were widely used in machine vision applications. By the 1990s, as CMOS sensors were gaining popularity, CIDs were adapted for applications demanding high dynamic range and superior antiblooming performance. CID-based cameras have found their niche in applications requiring extreme radiation tolerance and the high dynamic range scientific imaging. CID imagers have progressed from passive pixel designs using proprietary silicon processes to active pixel devices using conventional CMOS processing. Scientific cameras utilizing active pixel CID sensors have achieved a factor of 7 improvement in read noise (30 electrons (rms) versus 225 electrons (rms)) at vastly increased pixel frequencies (2.1 MHz versus 50 kHz) when compared to passive pixel devices. Radiation-hardened video cameras employing active pixel CIDs is the enabling technology in the world's only solid-state radiation-hardened color camera, which is tolerant to total ionizing radiation doses of more than 5 Mega-rad. Performance-based CID imaging concentrates on leveraging the advantages that CIDs provide for demanding applications.

Geiger-mode photodiodes (GPD) act as binary photon detectors that convert analog light intensity into digital pulses. Fabrication of arrays of GPD in a CMOS environment simplifies the integration of signal-processing electronics to enhance the performance and provide a low-cost detector-on-a-chip platform. Such an instrument facilitates imaging applications with extremely low light and confined volumes. High sensitivity reading of small samples enables twodimensional imaging of DNA arrays and for tracking single molecules, and observing their dynamic behavior. In this work, we describe the performance of a prototype imaging detector of GPD pixels, with integrated active quenching for use in imaging of 2D objects using fluorescent labels. We demonstrate the integration of on-chip memory and a parallel readout interface for an array of CMOS GPD pixels as progress toward an all-digital detector on a chip. We also describe advances in pixel-level signal processing and solid-state photomultiplier developments.

Presented is a comprehensive, physics-based model for microbolometer detector and sensor performance prediction. The model combines equations found in the literature and various standard models that generate NETD, MRTD, 3-D noise statistics and atmosphere characteristics (MODTRAN-based), with a comprehensive microbolometer model and HgCdTe model developed by the author to provide an end-to-end detector/FPA/sensor analysis and design tool, as well as a realistic image sequence generation tool. The model characterizes the individual pixel element based on the structure used, the various layer thicknesses, the electrical and thermal characteristics of the bolometer material and the biasing and readout circuit, and uses these results to calculate response and noise, NEP and NETD. The NETD, MTF and MRTD are predicted from the optics, detector and readout. Predicted NETD has been compared and verified with values found in literature, results from other models, and to uncooled camera measurements. The MRTD prediction has been verified with camera measurements and with standard industry MRTD model outputs. The model also calculates atmospheric path radiance and transmittance for horizontal paths based on MODTRAN outputs for the LWIR band at altitudes from 0 to 10km and ranges from 1 to 50km for assessments of air-to-air engagement SNR's. The model in matlab utililizes a 3-D noise model to provide accurate realistic imagery used to present realistic sensor images and to further validate the NETD and MRTD routines.(1) Images at 30Hz and 60Hz have been generated for visual assessment by the user and have mirrored industry model results and real-time camera images for MRTD's for the temporal noise case. The model's 3-D noise generation feature allows the prediction of MRTD vs. frequency under any 3-D noise combination. This model provides an end-to-end performance prediction tool useful in bolometer element design, readout design and for system level trade studies.

The short- and mid-wavelength infrared detectors based on short period type II superlattices (SLs) InAs (2ML) / GaSb (8ML) and InAs (8ML) / GaSb (8ML) were grown by molecular-beam epitaxy on semi-insulating GaAs substrates. An interfacial misfit mode AlSb quantum dot layer and a thick GaSb layer were grown as buffer layers. Room-temperature optical transmittance spectra showed clear absorption edge at ~2μm and ~5μm. The 50% cutoff wavelength of the two photoconductors was 2.1μm and 5.05μm in photoresponse at 77K respectively. The blackbody detectivity was beyond 2×10⁸ cmHz^1/2/W at 77K and 1×10⁸ cmHz^1/2/W at room temperature with 8 V/cm bias.

The development and application of single-photon detectors are introduced. The operating principles of photomultiplier tube (PMT), avalanche photodiode (APD) and superconducting, single-photon detector (SSPD) are expounded. The characteristic, advantages and disadvantages of them are discussed. Then give a view for the perspective and the development of these devices. In the above types of single-photon detectors, the PMT can't detect photon in near-infrared while the APD has great advantage on it, so it is the most preponderant detector in the single-photon detection. The capability of SSPD are excelled the former single-photon detectors, besides, it can detect the arriving time and energy of the photon, so it has great potential in the astronomical observation and the high-speed quantum communication and so on.

According to the randomness of multiplication of the carrier for the avalanche photodiode (APD), a mathematic model of the false alarm ratio (FAR) and the multiplication factor of APD were established based on the statistics. Through monitoring FAR for avalanche noise, the curve between bias voltage and temperature characteristic and the temperature coefficient of breakdown voltage have been obtained. The experiment shows that false alarm method not only can gain the breakdown voltage of APD in different temperature accurately, but also can determine the degree of avalanche breakdown. The temperature compensating circuit designed for the bias of APD can guarantee the normal operating of APD in a large variation of temperature, it is suitable for the photoelectric system that the high-frequency continuous signal detect.

An uncooled thermal detector array with low NETD is designed and fabricated using MEMS bimaterial microcantilever structures that bend in response to thermal change. The IR images of objects obtained by these FPAs are readout by an optical method. For the IR images, processed by a sparse representation-based image denoising and inpainting algorithm, which generalizing the K-Means clustering process, for adapting dictionaries in order to achieve sparse signal representations. The processed image quality is improved obviously. Great compute and analysis have been realized by using the discussed algorithm to the simulated data and in applications on real data. The experimental results demonstrate, better RMSE and highest Peak Signal-to-Noise Ratio (PSNR) compared with traditional methods can be obtained. At last we discuss the factors that determine the ultimate performance of the FPA. And we indicated that one of the unique advantages of the present approach is the scalability to larger imaging arrays.

In this work, based on the advanced drift and diffusion model with commercial software, the Crosslight APSYS, twodimensional photoresponsivity behavior for the InP/InGaAs separate absorption, grading, charge and multiplication avalanche photodiodes have been modeled to analyze suppressing premature edge breakdown. Basic physical quantities like band diagram, photon absorption, carrier generation and electric field as well as performance characteristics such as photocurrent, multiplication gain, and breakdown voltage etc., are obtained and selectively presented. Modeling results indicate that an etched mesa structure with the charge sheet layer can effectively suppress the premature edge breakdown in the device periphery region. Optimization modeling results with mesa step height are also demonstrated. Approach to model complex guard ring structure with double diffusion is further explored. Possible combination of Crosslight CSuprem diffusion profile is also discussed.

Several active and passive methods have been proposed for recovering 3-D shape of objects from their 2-D images Shape-from-focus is one of the passive methods. An important advantage of shape/depth from focus is that, unlike stereo and motion, it is not confronted with the correspondence problem. A lot of research has been done on the image focus analysis to automatically focus the imaging system, or to obtain the sparse depth information from the observed scene. In our method, the images are taken by varying the focus value in different steps, and each pixel in the image is taken as a single measurement. According to Thin Lens Model, the pixel's energy attains the maximum at the focused plane and decreases else where. This change in pixel's energy follows a 'Generalized Gaussian' curve. For the initial stage, we modified the pixel intensity in the images and found the maximum value in the modified pixel intensity vector and its corresponding frame, repeating for all the pixels to compute Raw Depth Map (RDM). The proposed algorithm is fast and precise, as compared to previous methods. The rigid body assumption reduces the number of pixels in the image, which are to be considered for the shape reconstruction.