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Dark current in long-wave cascade-transport infrared up-converters
摘要： Reducing the dark current in an infrared (IR) photodetector is one of the most important aspects in improving the detector’s performance. This article attempts to clarify the dominant paths of dark current and reduce it in a long-wave cascade-transport IR up-converter (CIUP), which has been reported to be a potential candidate for very-large-scale IR detection/imaging. The four paths of the dark current are considered, including the ground state sequential tunneling, thermionic emission onto the continuum, thermally-assisted transition onto the excited state of the absorption quantum well (QW) or some energy levels in the transport region. Accordingly three designs of the band structure are proposed for long-wave CIUPs, with miniband-to-miniband intersubband transition, bound-to-miniband transition and step-bound-to-miniband transition. Samples based on these designs are fabricated and measured. Both the calculated electron concentration distributions and the measured dark currents show that the step-bound-to-miniband structure is the most effective in cutting down the dark current, in which the superlattice barrier and InGaAs absorption QWs help to reduce dark current related to tunneling, thermionic emission and thermally-assisted tunneling.
关键词： Dark current,Up-converter,Step-bound-to-miniband,Long-wave infrared,Cascade
更新于2025-09-23 15:23:52
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Mid- to long-wave infrared computational spectroscopy with a graphene metasurface modulator
摘要： In recent years there has been much interest concerning the development of modulators in the mid- to long-wave infrared, based on emerging materials such as graphene. these have been frequently pursued for optical communications, though also for other specialized applications such as infrared scene projectors. Here we investigate a new application for graphene modulators in the mid- to long-wave infrared. We demonstrate, for the first time, computational spectroscopy in the mid- to long-wave infrared using a graphene-based metasurface modulator. furthermore, our metasurface device operates at low gate voltage. to demonstrate computational spectroscopy, we provide our algorithm with the measured reflection spectra of the modulator at different gate voltages. We also provide it with the measured reflected light power as a function of the gate voltage. The algorithm then estimates the input spectrum. We show that the reconstructed spectrum is in good agreement with that measured directly by a fourier transform infrared spectrometer, with a normalized mean-absolute-error (nMAe) of 0.021.
关键词： metasurface,modulator,mid- to long-wave infrared,graphene,computational spectroscopy
更新于2025-09-23 15:21:01
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High-power long-wave infrared laser based on polarization beam coupling technique
摘要： We demonstrated a high-power long-wave infrared laser based on a polarization beam coupling technique. An average output power at 8.3 μm of 7.0 W was achieved at a maximum available pump power of 107.6 W, corresponding to an optical-to-optical conversion of 6.5%. The coupling ef?ciency of the polarization coupling system was calculated to be approximately 97.2%. With idler single resonance operation, a good beam quality factor of ～1.8 combined with an output wavelength of 8.3 μm was obtained at the maximum output power.
关键词： optical parametric ampli?er,long-wave infrared laser,polarization coupling,optical parametric oscillator
更新于2025-09-23 15:21:01
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The long-wave infrared (8-12 μm) spectral features of selected rare earth element—Bearing carbonate, phosphate and silicate minerals
摘要： Rare earth elements (REEs) are a group of metals essential to high technology industries. This high demand, combined with a high supply risk, has led to an understanding that REEs are critical to society. Despite the potential that hyperspectral imaging (HSI) data offers for a fast and non-invasive characterization of the REEs, it is still poorly understood whether REEs have some information in the long-wave infrared (LWIR; 8–12 μm) wavelength range that can be used for their identification. To partially fill this gap, we have investigated the spectroscopy of twelve REE-bearing mineral samples using relatively high spatial and spectral resolution LWIR hyperspectral imaging data. These samples were formerly characterized using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and hyperspectral imaging data acquired in the 0.4–2.5 μm wavelength range. Results from these analyses were compared to and used to guide the analysis of the HSI data recorded in the LWIR range. This information was further compared to a reference spectral library of rare earth oxides. Our findings suggest that the spectral features of the samples can generally be traced to the asymmetric degenerate stretching and bending modes of the X-O (X = C, Si, P) groups. Moreover and contrary to what has been observed in the shorter wavelengths, there are no definitive spectral features in the LWIR wavelength region that could be assigned to any specific REE.
关键词： Imaging spectroscopy,Long-wave infrared,Rare earth element,Hyperspectral,Mineral
更新于2025-09-23 15:21:01
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Analysis of dark current generated by long-wave infrared HgCdTe photodiodes with different implantation shapes
摘要： Resistance-voltage curves of B+-implanted n-on-p Hg1-xCdxTe long-wavelength infrared photodiodes with different implantation unit shapes were measured for temperatures in the 20–140 K range. The response spectrum of the device was measured, and the response cutoff wavelength was 11.45 μm. By fitting the experimental data, R0A at different temperatures and the dark current at different bias voltages of the two long-wavelength diodes were calculated theoretically. The results demonstrate that the response spectrum of the device is affected by the implantation shape. The temperature transformation point of the dominant dark current was 40 K, and correlations between some parameters were also demonstrated.
关键词： dark current,long-wave infrared,HgCdTe,photosensors
更新于2025-09-11 14:15:04
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Long-Wave Hyperspectral Imaging for Lithological Mapping: A Case Study
摘要： Hyperspectral long-wave infrared imaging (LWIR HSI) adds a promising complement to visible, near infrared, and shortwave infrared (VNIR and SWIR) HSI data in the field of mineral mapping. It enables characterization of rock-forming minerals such as silicates and carbonates, which show no detectable or extremely weak features in VNIR and SWIR. In the last decades, there has been a steady increase of publications on satellite, aerial, and laboratory LWIR data. However, the application of LWIR HSI for ground-based, close-range remote sensing of vertical geological outcrops is sparsely researched and will be the focus of the current study. We present a workflow for acquisition, mosaicking, and radiometric correction of LWIR HSI data. We demonstrate the applicability of this workflow using a case study from a gravel quarry in Germany. Library spectra are used for spectral unmixing and mapping of the main lithological units, which are validated using sample X-ray diffraction (XRD) and thin section analysis as well as FTIR point spectrometer data.
关键词： thermal infrared,mineral mapping,hyperspectral,long wave infrared
更新于2025-09-10 09:29:36
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High-frequency very long wave infrared quantum cascade detectors
摘要： High speed quantum cascade detectors (QCDs) in a very long wave infrared range have been fabricated and characterized. Based on the resonant longitudinal optical-phonon scattering extraction relaxation mechanism, the QCD material behaves at an intrinsically high speed. In order to achieve high speed operation, we integrated microwave technology into the device process to reduce the parasitic parameters and ensure a low time constant of the effective resistance, inductance, capacitance (RLC) circuit. The peak response is located at 14.2 μm at 77 K. The electrical response characteristics of these QCDs was tested using a microwave rectification technique. The ?3 dB cutoff frequency of a 100×100 μm2 QCD is 3.2 GHz. The cutoff behavior of our devices were modeled with a second order filter RLC circuit model and showed good agreement with the experimental data.
关键词： very long wave infrared,high speed,quantum cascade detectors
更新于2025-09-09 09:28:46
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[IEEE 2018 33rd Symposium on Microelectronics Technology and Devices (SBMicro) - Bento Gon?alves, Brazil (2018.8.27-2018.8.31)] 2018 33rd Symposium on Microelectronics Technology and Devices (SBMicro) - Non uniformity correction in a Long Wave Infrared Focal Plane Array as a function of the higher calibration temperature
摘要： It is well known that every detector in a Focal Plane Array (FPA) has a different responsivity and offset. These variations result in a specific kind of noise, the Fixed Pattern Noise (FPN) or spatial noise. During the image processing, those pixels who has a large deviation in responsivity are considered a bad pixel, and has its value removed of FPA. Knowing the answer of in a FPA all those pixels are the first test procedure characterization. However, during the bad pixels analysis it is necessary to choose two reference temperatures, calibration points, and those temperature affects important parameters such as Uniformity, Noise Equivalent Temperature Difference (NETD) and Signal Transfer Function (SiTF). This work will study the influence of higher calibration temperature on the Non-Uniformity Correction (NUC) quality.
关键词： Focal Plane Array,Uniformity,Signal Transfer Function,Noise Equivalent Temperature Difference,Long Wave Infrared
更新于2025-09-04 15:30:14