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Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements
摘要： This study evaluates commonly used methods of extracting gravity-wave-induced temperature perturbations from lidar measurements. The spectral response of these methods is characterized with the help of a synthetic data set with known temperature perturbations added to a realistic background temperature profile. The simulations are carried out with the background temperature being either constant or varying in time to evaluate the sensitivity to temperature perturbations not caused by gravity waves. The different methods are applied to lidar measurements over New Zealand, and the performance of the algorithms is evaluated. We find that the Butterworth filter performs best if gravity waves over a wide range of periods are to be extracted from lidar temperature measurements. The running mean method gives good results if only gravity waves with short periods are to be analyzed.
关键词： running mean,sliding polynomial fit,lidar,extraction methods,temperature perturbations,spectral response,gravity waves,Butterworth filter
更新于2025-09-23 15:23:52
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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 - The Effects of VIIRS Spectral Response Differences between Suomi NPP and NOAA-20 for the Thermal Emissive Bands
摘要： The NOAA-20 satellite was successfully launched on November 18, 2017 into an afternoon orbit with local equator crossing time ~1:30pm, in the same orbital plane as that of the Suomi National Polar-orbiting Partnership (NPP) but with a time separation of half an orbit or ~50 minutes. The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard NOAA-20 will become the primary operational imager succeeding the VIIRS onboard Suomi NPP which has been in-orbit for more than six years. Although the VIIRS onboard Suomi NPP and NOAA-20 have identical design, there are small differences in the relative spectral response (RSR) in most bands. Previous studies have shown that minor differences in RSR can lead to a number of effects at detector level, such as striping. This study investigates the VIIRS RSR differences between Suomi NPP and NOAA-20 for the Thermal Emissive Bands (TEB) including M12-M16. The Line-By-Line radiative transfer model (LBLRTM) is used at very high spectral resolution for convolving with the RSR of VIIRS on both satellites. The impact of RSR difference between Suomi NPP and NOAA-20 are evaluated for radiometric biases and potential striping in TEB. This study will contribute to the measurement consistency for the long term observations in the thermal infrared bands, and ensure the quality of the data produced by VIIRS, such as sea surface temperature (SST), fire and other retrievals.
关键词： Spectral Response Function,LBLRTM,VIIRS,Thermal Emissive Band
更新于2025-09-23 15:21:21
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Self-driven all-inorganic perovskite microplatelet vertical Schottky junction photodetectors with a tunable spectral response
摘要： Wavelength-selective perovskite photodetectors (PDs) have many applications in optoelectronic field, such as machine vision, imaging and full-color display. However, the instability of organo-inorganic hybrid perovskite material severely limits the commercialization of perovskite-based PDs. In this work, a more stable all-inorganic perovskite, CsPbBr(3-x)Clx (x = 0, 1, 2, 3) microplatelets (MPs), were employed to fabricate Schottky PDs with a simple vertical structure of ITO/MP/Au. The optimized CsPbBr3 MP Schottky PDs exhibit rapid response speed (75 μs) and very low dark current (2 pA) at zero bias. Meanwhile, the device shows a high on/off ratio (>106), a large specific detectivity (>1012 Jones) and linear dynamic range (LDR = 137 dB) with excellent thermal and long-term stability. Furthermore, a tunable spectral response covering from the ultraviolet to visible range is also demonstrated. These results provide a simple avenue to realize self-driven and spectral tunable all-inorganic perovskite Schottky PDs with good stability.
关键词： all-inorganic perovskite,high temperature tolerance,tunable spectral response,vertical structure Schottky photodetector,weak-light sensitivity
更新于2025-09-23 15:19:57
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MSM-photodetector with ZnSe/ZnS/GaAs Bragg reflector
摘要： The effect of a ZnSe/ZnS/GaAs distributed Bragg reflector on the spectral response of a metal–semiconductor–metal (MSM)-diode is investigated. Good agreement is obtained between the calculated and experimental reflection spectra of the ZnSe/ZnS/GaAs heterostructure forming a distributed Bragg reflector in the MSM-diode. The MSM-detector provides a two-color response at 420 and 472 nm, a sharp decrease in photosensitivity in the long-wave part of the response signal, high quantum efficiency of 53%, and low dark current of 5 × 10?10 A. The two-color response of the detector can be adjusted to the desired wavelength by appropriately selecting the heterostructure parameters.
关键词： Metal–semiconductor–metal (MSM) diode,Dark current,Heterostructure,Infrared detectors,Bragg reflector,Spectral response
更新于2025-09-19 17:13:59
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Incorporation of metal selenide thin films as the secondary absorber in the CdTe solar cells
摘要： The introduction of selenium in the CdTe solar cells has been responsible for high performance CdTe thin film solar cells in recent years. It is an approach to form CdSexTe1-x alloys by the interdiffusion using precursor CdSe layer during the CdTe high-temperature deposition process. Nevertheless, the compositionally gradient CdSexTe1-x formed by the diffusion makes it difficult to absorb long-wavelength photons adequately. So close-spaced sublimation deposited CdSexTe1-x interlayer was incorporated in the CdTe thin film solar cells. It is found that 600 nm CdSexTe1-x absorber is useful to increase long-wavelength photons absorption and extend the long-wavelength QE response. Meanwhile, the synergetic effects of the primary absorber deposition processing on CdTe solar cell performance were investigated. The substrate temperature of CdTe deposition has an obvious impact on the cell efficiency. The much higher substrate temperature can efficiently gain larger grain size, increase the crystal quality and promote the interdiffusion of different semiconductor layers. These improvements can efficiently decrease the carrier recombination to obtain a much higher fill factor and open-circuit voltage.
关键词： Spectral response,CdTe solar cells,Carrier recombination,CdSexTe1-x,CdSe
更新于2025-09-19 17:13:59
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ZnO‐Based Ultraviolet Photodetectors with Tunable Spectral Responses
摘要： Conventionally, wavelength-selective ultraviolet photodetection is achieved by using broadband inorganic photodiodes coupled with optical ?lters, which signi?cantly increases the complexity and fabricating cost of devices for high pixel density imaging systems. Here, a facile approach to achieve tunable spectral response without ?lters is demonstrated. The devices are based on ZnO heterojunctions, and the response spectra are effectively modulated by tuning the position of charge generation, which results in distinct charge-collection ef?ciencies. After optimization, the ZnO/poly[bis(4-phenyl)(2,4,6-trimethylphenyl) amine] (PTAA) photodiodes exhibit narrowband ultraviolet (UV) response with a full width at half maximum (FWHM) of <25 nm, and the NiOx/ZnO devices reveal relatively broader photoresponse. All of these devices demonstrate relatively low dark currents and noises, high responsivities and detectivities, and fast response speeds. This work proves the great potential of ZnO thin ?lms for UV detection and also ?rst provides an alternative approach to effectively tune the spectral response.
关键词： atomic layer deposition,narrowband,tunable spectral response,ZnO-based photodiodes,ultraviolet photodetectors
更新于2025-09-19 17:13:59
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In-Situ Tailoring of Vertically Coupled InAs p-i-p Quantum-Dot Infrared Photodetectors: Toward Homogeneous Dot Size Distribution and Minimization of Ina??Ga Intermixing
摘要： The authors report a detailed analysis of an epitaxial growth technique for Indium Arsenide (InAs) Quantum-dot infrared photodetectors to circumvent the detrimental effects arising from the progressively increasing dot-size in vertically coupled heterostructures. Constant overgrowth percentage of the vertically coupled dot-layers has been achieved with the implementation of the growth strategy, which has been validated by cross-sectional transmission electron microscopy (X-TEM) images of the samples. The optical characteristics of these samples have been analyzed through photoluminescence spectroscopy and photoluminescence excitation spectroscopy (PL and PLE) measurements which show longer wavelength response and reduced full width at half-maxima (FWHM) upon implementation of the growth strategy. X-TEM, in-plane and out-of-plane high resolution X-ray diffraction (HR-XRD) measurements suggest morphological improvement upon implementation of the growth strategy, with a reduction in the Indium desorption and lowering of defects and dislocation densities. Excellent correlation has been found between the different experimental results and also their theoretical simulations. The fabricated single-pixel photodetectors at low temperature (T=14K) show a broad response extending up to the MWIR region (~4.5μm) for one of the samples. Also, a strong spectral response in the SWIR region is obtained even at room temperature (T=300K). The highest responsivity (Rp) and specific detectivity (D*) values obtained are 166.17 A/W and 8.39 x 1010 cmHz1/2W-1 at a bias of 5V and 300K temperature.
关键词： p-i-p infrared photodetectors,InAs Quantum Dots,MBE growth strategy,homogenous dot size distribution,room temperature spectral response,In-Ga inter-diffusion
更新于2025-09-19 17:13:59
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Improved spectral and temporal response of MSM photodetectors fabricated on MOCVD grown spontaneous AlGaAs superlattice
摘要： A co-planar metal-semiconductor-metal nonsymmetrical back to back Schottky diode photodetector using natural superlattice AlGaAs grown by metalorganic vapor phase epitaxy on GaAs (100) has been reported. The detection efficiency and photoresponse of the superlattice based device are found significantly superior compared to the one based on high temperature annealed homogeneous AlGaAs. Under a forward bias of 1 V, the peak values of responsivity, detectivity and sensitivity were 10.133 mA/W, 7.6 × 1011 cmHz1/2W?1, 81.06 cm2/W for the device with as-grown natural superlattice and 1.14 mA/W, 7.05 × 1010 cmHz1/2W?1, 2.82 cm2/W for the device with homogeneous composition of AlGaAs, respectively. Besides, the device with natural superlattice structure showed much faster response to the pulsed light with rise and decay time of 560 μs and 1 ms as compared to 2 and 7 ms, respectively for the device with disordered bulk AlGaAs. The superior spectral and temporal characteristics of the device are explained by a model based on a third diode representing the net effect due to the superlattice modulations along with two Schottky diodes at the metal-semiconductor junctions. The third barrier, which is basically due to the periodic modulation in aluminium composition, plays an important role in enhancement of the photocurrent owing to the activation of the superlattice channels under light while keeping the dark current small. The fast sweeping of the photogenerated carries by the intrinsic electric field at the heterointerfaces in the active semiconducting layer makes the characteristic times of the device with the superlattice structures much smaller than one with homogeneous AlGaAs. Degradation in photoresponse and speed is attributed to the interdiffusion as an effect of thermal annealing.
关键词： AlGaAs/GaAs,Spectral response,Metal-semiconductor-metal photodetector,Natural superlattice,Temporal response
更新于2025-09-12 10:27:22
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Patterned resist on flat silver achieving saturated plasmonic colors with sub-20-nm spectral linewidth
摘要： Plasmonic color generation is a promising field of study that have the potential to produce paradigm-shifts in display and printing technologies. To produce vibrant colors, plasmonic surfaces decorated with complex corrugated or protruding structures have been the commonly adopted strategy for saturated structural color generation. However, it is particularly challenging to cover the full sRGB color gamut due to difficulty in achieving narrowband spectral response via plasmonic structures. Here we report a flat silver film decorated with 90 nm-thick resist nanostructures of low aspect-ratio feature (0.25–0.55). With such a facile and close-to-uniform morphology, we experimentally demonstrate sub-20-nm linewidth of full-width-half-maxima (FWHM) of reflection spectra in the visible range, realizing a color gamut comparable to that of ultra-high definition TV (UHDTV) in the chromaticity diagram. Our work breaks the conventional notion that sophisticated and high aspect-ratio plasmonic and dielectric nanostructures are indispensable, and highly saturated color are impossible for plasmonic nanoprinting. The unique structure enables an etch-free fabrication and recycling recipe, with the potential for mass production by nanoimprinting lithography and other applications including multicolor holographic projection.
关键词： sRGB color gamut,narrowband spectral response,Plasmonic color generation,nanoimprinting lithography,structural color
更新于2025-09-12 10:27:22
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Optical Characterization of III-V Multijunction Solar Cells for Temperature-Independent Band Gap Features
摘要： A recently developed method to characterize the band gap energies of III-V optosemiconductors was utilized to determine temperature-invariant band gap features of multijunction solar cells. The method is based on measuring electroluminescent spectra of the solar cells at different temperatures. The normalized spectra reveal temperature-invariant energy values of the different junctions which are further converted to band gap energies. The method utilization requires a calibrated spectroradiometer and a temperature controlled mounting base for the solar cell under test, however, no knowledge about the absolute temperature of the cell under measurement. The method was tested on GaAs and GaInP solar cells that consist of single and dual junctions. The band gap energies were also derived from spectral response measurements. The differences of the determined band gap energies from the literature values were smaller than 1.1%. Compared with other band gap determination methods, the developed method yields temperature-invariant band gap characteristics; with a known uncertainty, that separated the different junctions in a multijunction device without individual biasing for the different junctions. In addition, a temperature-independent characterization parameter ensures that the operating conditions of the device under test do not affect the results.
关键词： III-V solar cells,light-emitting diode (LED),spectral response,temperature,Band gap
更新于2025-09-12 10:27:22