Focal Plane Array Detector Research Articles

Graphene metamaterial spatial light modulator for infrared single pixel imaging.

High-resolution and hyperspectral imaging has long been a goal for multi-dimensional data fusion sensing applications - of interest for autonomous vehicles and environmental monitoring. In the long wave infrared regime this quest has been impeded by size, weight, power, and cost issues, especially as focal-plane array detector sizes increase. Here we propose and experimentally demonstrated a new approach based on a metamaterial graphene spatial light modulator (GSLM) for infrared single pixel imaging. A frequency-division multiplexing (FDM) imaging technique is designed and implemented, and relies entirely on the electronic reconfigurability of the GSLM. We compare our approach to the more common raster-scan method and directly show FDM image frame rates can be 64 times faster with no degradation of image quality. Our device and related imaging architecture are not restricted to the infrared regime, and may be scaled to other bands of the electromagnetic spectrum. The study presented here opens a new approach for fast and efficient single pixel imaging utilizing graphene metamaterials with novel acquisition strategies.

Local delamination of InSb IRFPAs in liquid nitrogen shock tests

Both the local delamination and the local fracture, appearing in the InSb infrared focal plane arrays (IRFPAs) detectors in liquid nitrogen shock tests, restrict the final yield of the InSb IRFPAs detectors. To explore the mechanism of the local delamination appearing in the region of the negative electrode of the InSb IRFPAs detectors, basing on the created structural modeling of the InSb IRFPAs detectors, we obtain the distributions of the interfacial stresses in the different interfaces of the InSb IRFPAs detectors. After comparing the distributions of the simulated interfacial stresses with the measured local delamination region in the InSb IRFPAs detectors, we think that the local delamination originates from the interfacial shear stresses, and the crack extension is the typical sliding mode. Besides, the weakened gluing strength between the InSb chip and the underfill in the negative electrode region also causes this region to be prone to the local delamination. All these findings provide the theoretical references for both the structure design and the structure optimization of the InSb IRFPAs detectors assembly in the future.

Quantum Cascade Laser Spectral Histopathology: Breast Cancer Diagnostics Using High Throughput Chemical Imaging.

Fourier transform infrared (FT-IR) microscopy coupled with machine learning approaches has been demonstrated to be a powerful technique for identifying abnormalities in human tissue. The ability to objectively identify the prediseased state and diagnose cancer with high levels of accuracy has the potential to revolutionize current histopathological practice. Despite recent technological advances in FT-IR microscopy, sample throughput and speed of acquisition are key barriers to clinical translation. Wide-field quantum cascade laser (QCL) infrared imaging systems with large focal plane array detectors utilizing discrete frequency imaging have demonstrated that large tissue microarrays (TMA) can be imaged in a matter of minutes. However, this ground breaking technology is still in its infancy, and its applicability for routine disease diagnosis is, as yet, unproven. In light of this, we report on a large study utilizing a breast cancer TMA comprised of 207 different patients. We show that by using QCL imaging with continuous spectra acquired between 912 and 1800 cm-1, we can accurately differentiate between 4 different histological classes. We demonstrate that we can discriminate between malignant and nonmalignant stroma spectra with high sensitivity (93.56%) and specificity (85.64%) for an independent test set. Finally, we classify each core in the TMA and achieve high diagnostic accuracy on a patient basis with 100% sensitivity and 86.67% specificity. The absence of false negatives reported here opens up the possibility of utilizing high throughput chemical imaging for cancer screening, thereby reducing pathologist workload and improving patient care.

Development and Production of Array Barrier Detectors at SCD

XBn or XBp barrier detectors exhibit diffusion-limited dark currents comparable with mercury cadmium telluride Rule-07 and high quantum efficiencies. In 2011, SemiConductor Devices (SCD) introduced “HOT Pelican D”, a 640 × 512/15-μm pitch InAsSb/AlSbAs XBn mid-wave infrared (MWIR) detector with a 4.2-μm cut-off and an operating temperature of ∼150 K. Its low power (∼3 W), high pixel operability (>99.5%) and long mean time to failure make HOT Pelican D a highly reliable integrated detector-cooler product with a low size, weight and power. More recently, “HOT Hercules” was launched with a 1280 × 1024/15-μm format and similar advantages. A 3-megapixel, 10-μm pitch version (“HOT Blackbird”) is currently completing development. For long-wave infrared applications, SCD’s 640 × 512/15-μm pitch “Pelican-D LW” XBp type II superlattice (T2SL) detector has a ∼9.3-μm cut-off wavelength. The detector contains InAs/GaSb and InAs/AlSb T2SLs, and is fabricated into focal plane array (FPA) detectors using standard production processes including hybridization to a digital silicon read-out integrated circuit (ROIC), glue underfill and substrate thinning. The ROIC has been designed so that the complete detector closely follows the interfaces of SCD’s MWIR Pelican-D detector family. The Pelican-D LW FPA has a quantum efficiency of ∼50%, and operates at 77 K with a pixel operability of >99% and noise equivalent temperature difference of 13 mK at 30 Hz and F/2.7.

Operation limitation of CMP in back-thinning process of InSb IRFPAs

InSb infrared focal plane arrays (IRFPAs) detector, active in 3–5 μm range, has been widely used in military fields. In the fabrication of InSb IRFPAs, the InSb chip is usually thinned down to 10 μm by means of both the chemical mechanical polishing (CMP) process and the wet chemical etching process. In order to confirm the operation limitation of the CMP process, in light of the proposed equivalent method, we create the deformation analysis modeling of InSb IRFPAs. In order to learn the evolving tendency of the deformation distribution characteristic appearing on the top surface of InSb IRFPAs during the thinning process of InSb chip, we reduce the thickness of InSb chip from 300 μm down to 6 μm in a suitable step. And the simulated Z-components of strain distribution are identical with the measured deformation distribution, appearing on the top surface of InSb IRFPAs with different InSb chip thickness values. According to the dependence of the deformation distribution characteristic of InSb IRFPAs on the thickness of InSb chip, we conclude that the thickness of InSb chip should not be thinner than 30 μm after the CMP process is executed completely. A series of thickness values of GaSb substrate, which is thinned down to 60, 50 or 30–40 μm by CMP process in the fabrication of type-IIsuperlattice IRPFAs, support our conclusion. All these cases prove that the operation limitation of the CMP process proposed in this paper is accurate and acceptable in the fabrication of IRFPAs.

Nanoantenna-Enhanced Infrared Spectroscopic Chemical Imaging.

Spectroscopic infrared chemical imaging is ideally suited for label-free and spatially resolved characterization of molecular species, but often suffers from low infrared absorption cross sections. Here, we overcome this limitation by utilizing confined electromagnetic near-fields of resonantly excited plasmonic nanoantennas, which enhance the molecular absorption by orders of magnitude. In the experiments, we evaporate microstructured chemical patterns of C60 and pentacene with nanometer thickness on top of homogeneous arrays of tailored nanoantennas. Broadband mid-infrared spectra containing plasmonic and vibrational information were acquired with diffraction-limited resolution using a two-dimensional focal plane array detector. Evaluating the enhanced infrared absorption at the respective frequencies, spatially resolved chemical images were obtained. In these chemical images, the microstructured chemical patterns are only visible if nanoantennas are used. This confirms the superior performance of our approach over conventional spectroscopic infrared imaging. In addition to the improved sensitivity, our technique provides chemical selectivity, which would not be available with plasmonic imaging that is based on refractive index sensing. To extend the accessible spectral bandwidth of nanoantenna-enhanced spectroscopic imaging, we employed nanostructures with dual-band resonances, providing broadband plasmonic enhancement and sensitivity. Our results demonstrate the potential of nanoantenna-enhanced spectroscopic infrared chemical imaging for spatially resolved characterization of organic layers with thicknesses of several nanometers. This is of potential interest for medical applications which are currently hampered by state-of-art infrared techniques, e.g., for distinguishing cancerous from healthy tissues.

Preflight Radiometric Calibration of Orbiting Carbon Observatory 2

The imaging spectrometers of the second orbiting carbon observatory were radiometrically calibrated before launch during instrumentlevel ground testing. The gain and dark responses were characterized for each focal plane array detector element. An integrating sphere source with an integrated monitoring spectroradiometer illuminated the OCO-2 spectrometers at many light levels. Instrument output was compared with the calibrated output of the source to derive gain coefficients. This source was calibrated in situ with respect to the National Institute of Standards and Technology reference standards, and the instrument met its absolute performance requirement of 5%. Matching fields of view for the internal monitor detectors and the external instrument under test was found to be particularly important, as observed in the results and supported by modeling. Temperature-dependent dark offsets were corrected in a separate process. Solar spectra with varying neutral density filters were used to validate the linearity of the spectrometers.

Direct mapping and characterization of dry etch damage-induced PN junction for long-wavelength HgCdTe infrared detector arrays.

Mercury cadmium telluride is the standard material to fabricate high-performance infrared focal plane array (FPA) detectors. However, etch-induced damage is a serious obstacle for realizing highly uniform and damage-free FPA detectors. In this Letter, the high signal-to-noise ratio and high spatial resolution scanning photocurrent microscopy (SPCM) is used to characterize the dry etch-induced inversion layer of vacancy-doped p-type Hg1-xCdxTe (x=0.22) material under different etching temperatures. It is found that the peak-to-peak magnitude of the SPCM profile decreases with a decrease in etching temperature, showing direct proof of controlling dry etch-induced type conversion. Our work paves the way toward seeking optimal etching processes in large-scale infrared FPAs.

Long Wave Infrared Type II Superlattice Focal Plane Array Detector

The XBn/XBp family of barrier detectors enables diffusion limited dark currents comparable with HgxCd1-xTe Rule-07 and high quantum efficiencies. SCD’s XBp type II superlattice (T2SL) detector contains InAs/GaSb and InAs/AlSb T2SLs, and was designed for the long wave infrared (LWIR) atmospheric window using k · p based modeling of the energy bands and photo-response. Wafers are grown by molecular beam epitaxy and are fabricated into focal plane array (FPA) detectors using standard FPA processes, including wet and dry etching, indium bump hybridisation, under-fill, and back-side polishing. The 640 × 512 pixel, 15 μm pitch, detector goes by the name of ‘Pelican-D LW’ and exhibits a quantum efficiency of ~ 50 per cent with background limited performance at an operating temperature of 77 K. It has a cut-off wave length of ~ 9.5 μm, with a pixel operability of above 99 per cent. The detector gives a very stable image with a residual non uniformity of below 0.04 per cent over its useful dynamic range. A new digital read-out integrated circuit has been designed so that the complete detector closely follows the configuration of SCD’s MWIR Pelican-D detector.

Optical de-scanning technique in search and track systems using focal plane array detectors

Optical de-scanning technique in search and track systems using focal plane array detectors

Structural model of InSb IRFPAs including underfill curing process

InSb infrared focal plane array(IRFPA) detector, active in 3-5 m range, has been widely used in military fields. Higher fracture probability appearing in InSb infrared focal plane arrays(IRFPAs) subjected to thermal shock test, restricts its final yield. In order to analyze and optimize the structure of InSb IRFPAs, it is necessary to create the three-dimensional structural model of InSb IRFPAs, which is employed to estimate its strain distribution appearing in the different fabricating processes. In this paper, the curing model of underfill is described by its volume contraction percentage combined with the elastic modulus of the completely cured underfill. Thus, both the von Mises stress and the Z-components of strain accumulated in the curing process of underfill are calculated. When InSb IRFPAs is naturally cooled to room temperature from the curing temperature of underfill, the Z-component of strain distribution appearing on the top surface of InSb IRFPAs is obtained with our structural model, which is identical to the deformation distribution on the top surface of InSb IRFPAs measured at room temperature. In the following thermal shock simulation, we find that the maximal von Mises stress appears at 100 K and the maximal Z-component of strain appears at 150 K, these two temperature points are located in the second half of the thermal shock process, these results indicate that the fracture of InSb chip happens more easily in liquid nitrogen shock test. This inference is consistent with the fact appearing in liquid nitrogen shock test. All these findings suggest that the proposed model is suitable to estimate the deformation distribution of InSb IRFPAs and its changing rule in its different fabricating stages.

数字化中波红外焦平面探测器组件研究进展

数字化中波红外焦平面探测器组件研究进展

数字化中波红外焦平面探测器组件研究进展

数字化中波红外焦平面探测器组件研究进展

Impact of high-conductivity n-type anti-debiasing layer on the photoresponse of “leaking” and “non-leaking” FPA elements in photovoltaic MCT-based n-on-p infrared FPA detectors

Impact of high-conductivity n-type anti-debiasing layer (ADL) on the photoresponse of focal plane array (FPA) elements in mercury-cadmium-tellurium based photovoltaic n-on-p infrared FPA detectors is analyzed via consideration of, first, measured current-voltage characteristics of FPA elements with “leaking” and “non-leaking” array photodiodes and, second, spatial photoresponse profiles measured using FPA elements of both types. A most pronounced manifestation of the parasitic diode with the p-n junction at the absorber layer/ADL interface consists in the emergence of negative photoresponses produced by the “leaking” FPA elements.

Design of a panoramic long-wave infrared athermal system

A panoramic long-wave infrared athermal system is introduced in this paper. The proposed system includes a panoramic annular lens (PAL) block providing a stereo field of view of (30 deg – 100 deg) × 360 deg without the need to move its components. Moreover, to ensure the imaging quality at different temperatures, a refractive/diffractive hybrid lens is introduced to achieve optical passive athermalization. The system operates in a spectral band between 8 and 12 μm, with a total length of 175 mm and a focal length of 3.4 mm. To get a bright and clear image, the aperture of the system was set to f/1.15. The introduction of aspherical surface and even-order diffractive surface not only eliminates the differential thermal but also makes the structure simple and lightweight and improves the image quality. The results show that the modulation transfer function below 20 lp/mm of the system is above 0.2 at each temperature ranging from −20°C to +60°C, which is close to the diffraction limit. The system is suitable to be applied in an uncooled infrared focal plane array detector and will serve as a static alert system. It has a number of pixels of 640×480, and the pixel size is 25 μm.

A Strategy of Transparent Conductive Oxide for UV Focal Plane Array Detector: Two‐Step Thermodynamic Process

A deep UV transparent Al:Mg0.43Zn0.57O (AMZO) film with high electrical conductivity (406.6 S cm−1) and high UV light transmittance is prepared via a designed two-step method controlling the thermodynamic process of doping. The method proposed here can provide a reference for the production of deep UV luminescent materials. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The analysis of scalp irritation by coacervates produced in hair shampoo via FTIR with focal plane array detector, X-ray photoelectron microscopy and HaCaT cells.

Coacervates are inevitably formed on scalp on using hair washing products. Our goal was to analyse the coacervates in detail to identify the part responsible for scalp stimulation. Shampoo that increases coacervate formation was applied to in vitro skin and was washed. The residue was then analysed using Fourier transform infrared spectroscopy-focal plane array (FTIR-FPA) and X-ray photoelectron microscopy (XPS). And HaCaT cells were used for irritant test of coacervate. Through this research, it was confirmed that the coacervate was a macromolecule structurally similar to a cationic polymer and contains an anionic surfactant. Its anionic surfactant was structurally semi-stable so that it released onto scalp when it absorbs moisture. Coacervate releases sulphate bonding into the matrix when it is exposed to water. Thus, the scalp stimulation would be expected.

Terahertz 3D printed diffractive lens matrices for field-effect transistor detector focal plane arrays.

We present the concept, the fabrication processes and the experimental results for materials and optics that can be used for terahertz field-effect transistor detector focal plane arrays. More specifically, we propose 3D printed arrays of a new type - diffractive multi-zone lenses of which the performance is superior to that of previously used mono-zone diffractive or refractive elements and evaluate them with GaN/AlGaN field-effect transistor terahertz detectors. Experiments performed in the 300-GHz atmospheric window show that the lens arrays offer both a good efficiency and good uniformity, and may improve the signal-to-noise ratio of the terahertz field-effect transistor detectors by more than one order of magnitude. In practice, we tested 3 × 12 lens linear arrays with printed circuit board THz detector arrays used in postal security scanners and observed significant signal-to-noise improvements. Our results clearly show that the proposed technology provides a way to produce cost-effective, reproducible, flat optics for large-size field-effect transistor THz-detector focal plane arrays.

Annealing of CdZnTe materials to reduce inclusion defects

Annealing of (CdZn)Te substrate material is an important technology to enhance the quality of HgCdTe epitaxial material as well as the performance of infrared focal plane array detectors. In this paper, the size variations of inclusions defects in (CdZn)Te material after annealing were investigated. And the quantitative dependencies of the inclusion defect sizes on the sample temperature, Cd partial pressure and annealing time were obtained. Some properties of inclusion defects and rules of inclusion defect evolution in annealing were revealed. The models of the inclusion defects and the physical mechanism of annealing process based on atom diffusions were proposed to describe the experimental results. The research results can help us to better understand the evolution process of the inclusion defects in annealing and find suitable annealing technology to obtain high-quality (CdZn)Te materials.

Chemical imaging of secondary cell wall development in cotton fibers using a mid-infrared focal-plane array detector

Market demands for cotton varieties with improved fiber properties also call for the development of fast, reliable analytical methods for monitoring fiber development and measuring their properties. Currently, cotton breeders rely on instrumentation that can require significant amounts of sample, which complicates fiber development studies. Herein, we explored the use of high-resolution, Fourier-transform infrared (FT-IR) microscopy to examine cotton fiber secondary cell wall development in single fibers. Notably, there was a marked intensity increase for the C-O bending region near 1015 cm–1 and the C-H stretch at 2900 cm–1. These changes agree with those observed with macroscopic FT-IR tests. Chemical distribution maps and principal component analysis plots visually depict these spectral changes. Our results suggest the FT-IR microscopy can potentially be utilized as a tool to monitor and assess important fiber properties, such as cotton maturity, during fiber development.