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[IEEE 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Investigation of Resonant-Cavity-Enhanced GeSn Photodetectors in Short-Wavelength Infrared Regime
摘要： GeSn with a 10% Sn content for resonant-cavity-enhanced photodetectors (RCE PDs) was grown and the RCE PDs was designed for 2000-nm operation, exhibiting a quantum efficiency up to 91%. This work shows RCE GeSn PDs can be a promising route toward high-response SWIR detection.
关键词： quantum efficiency,Resonant-cavity-enhanced photodetectors,GeSn
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Quantum-Efficiency and Bandwidth Optimized Electro-Optic Sampling
摘要： Electro-optic sampling (EOS) allows for field-sensitive detection of optical waveforms in a broad spectral range, extending from the far-infrared (THz) all the way to the near-infrared. Most recently, EOS has been employed for highly sensitive spectroscopy of liquids and gases in the mid-infrared (MIR) molecular fingerprint region, overcoming the notorious limitations of broadband detectors in this spectral range and providing a glance at the potential of this coherent detection scheme for molecular spectroscopy. In this paper, we investigate – in theory and experiment – the trade-off between quantum-efficiency/dynamic range (DR) and detection-bandwidth in EOS. The theoretical model describes the two-step-process of the EOS detection in one dimension, where the nonlinear up-conversion is calculated with the first order propagation equation, followed by heterodyne detection of the generated sum-frequency field with a strong gate pulse. In a first experiment, we sample an octave-spanning spectrum centred at 8.6 μm, using high-power, 16-fs pulses spectrally centred at 1030 nm. We show a frequency up-conversion-efficiency of 2%, which is unprecedented in EOS, measured as the maximum delay-dependent MIR power decrease behind the EOS crystal (500-μm thick GaSe). On the other hand, the maximum MIR depletion is only 0.3% for a 85-μm thick crystal, which is due to the shorter interaction length. However, this thinner crystal greatly benefits the detection bandwidth, as can be seen from the simulations. As our heterodyne detection with unprecedented local oscillator powers (450 mW at 28 MHz) is shot-noise-limited, this conversion efficiency results in an unprecedented amplitude DR of 6.5×106 (for 20 s of measurement time). This DR directly benefits spectroscopic measurements with unprecedented sensitivities. Our simulations show beneficial phase matching for sampling pulses centred at 2 μm. Therefore, the bandwidth-DR trade-off is expected to be less severe and we are currently investigating the 2 μm-based detection experimentally.
关键词： heterodyne detection,quantum-efficiency,dynamic range,bandwidth,Electro-optic sampling
更新于2025-09-16 10:30:52
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Highdetectivity AlInSb Midinfrared Photodiode Sensors with Dislocation Filter Layers for Gas Sensing
摘要： A midinfrared photodiode is developed for methane gas sensing based on the highly mismatched AlInSb/GaAs system. Inserting optimized dislocation filter layers (DFLs) in the buffer layer reduced the threading dislocation density in the active layer to less than one-third of that in the photodiode without DFLs. This improvement produces a high normal incidence detectivity of 1.8 (cid:1) 109 cm p (cid:3)1 at 3.3 μm, which is more than twice the highest detectivity previously obtained for a photodiode without DFLs.
关键词： bialkali,quantum efficiency enhancements,accelerator technologies,graphene,antimonide photocathodes
更新于2025-09-16 10:30:52
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Investigation of interference on photodetector CCD by lasers with different wavelengths
摘要： In order to study the interference mechanism about image sensor being irradiated by lasers, a monochromatic CCD and a color CCD with same type are irradiated by continuous lasers with wavelengths of 473 nm, 532 nm and 632.8 nm, respectively, and the interference phenomena are observed and the crosstalk thresholds are calculated. The digital images collected in the experiment are processed, and the interference degree curves of monochromatic CCD and color CCD under different laser powers are extracted, respectively. Analysis about experimental results indicates that the quantum efficiency of CCD material and transmittance of filter to laser will affect anti-interference ability of CCD. The higher quantum efficiency and transmittance will lead to more obvious interfering effect for CCD. Moreover, the anti-interference ability of color CCD is stronger than that of monochromatic CCD. The anti-interference ability of CCD used in the experiment to weak is: 473 m > 532 nm > 632.8 nm. Finally, the saturation point and crosstalk phenomena are simulated by analyzing the carrier overflow mode and the simulation results are basically consistent with the experimental data.
关键词： CCD,Quantum efficiency,Saturation threshold,Interference simulation,Jamming phenomenon
更新于2025-09-16 10:30:52
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Lithium ion doping triggered splendid quantum efficiency and thermal stability in Li <sub/>2</sub> SrSiO <sub/>4</sub> : <i>x</i> Eu <sup>2+</sup> phosphors for optical thermometry and high luminous efficiency white-LED
摘要： Eu2+/Li+-Codoped Li2SrSiO4 orange-yellow phosphors were developed for the applications of white light-emitting diodes (white-LEDs) and optical thermometry. Under near-ultraviolet and blue light excitation, the resultant phosphors exhibited the emissions of Eu2+ ions with an optimal doping concentration of 5 mol% and the concentration quenching mechanism was prevailed to be the dipole–quadrupole interaction. Through the incorporation of Li+ ions into the host lattices, the thermal stability and internal quantum efficiency of the synthesized phosphors were boosted. When the excitation wavelengths were 419 and 449 nm, the internal quantum efficiencies of the Eu2+/Li+-codoped Li2SrSiO4 phosphors were increased to 73% and 69%, respectively. The temperature dependent emission spectra were employed to characterize the thermal stability of the studied samples. The white-LED lamps utilizing the Eu2+/Li+-codoped Li2SrSiO4 phosphors as the orange-yellow component exhibited enhanced photoelectric properties. Furthermore, based on the temperature dependent bandwidth of Eu2+ ions, the thermometric performance of the resultant compounds was studied in detail and the maximum sensitivity was 0.049 K?1. The phosphors with multi-excitation wavelengths were suitable for high luminous efficiency white-LEDs and optical thermometers.
关键词： Li2SrSiO4,Eu2+/Li+-codoped,thermal stability,quantum efficiency,phosphors,white-LEDs,optical thermometry
更新于2025-09-16 10:30:52
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Luminescent silver–lithium-zeolite phosphors for near-ultraviolet LED applications
摘要： Silver clusters (AgCLs) confined in zeolites show remarkable luminescence properties, displaying high photoluminescence quantum efficiencies combined with tunable visible light emission characteristics, making them highly promising phosphors in lighting devices. However, to date the lack of efficient near-ultraviolet (NUV) and blue excitable silver zeolites has hindered their use in remote LEDs. In this report, we show the utilization of Ag-zeolites in a NUV-LED device, displaying highly efficient green emission with an external quantum efficiency of 83% and a broad excitation range between 300 and 400 nm. This phosphor material was obtained by confining AgCLs in a dehydrated fully Li-exchanged Linde-type A (LTA) zeolite. The unique effect of Li+ ions and dehydration, on the luminescence properties of AgCLs, originates from the structural changes of both the zeolite framework, and the ligand coordinated tetrahedral Ag4 clusters, as observed by X-ray diffraction analysis and X-ray excited optical luminescence–X-ray absorption fine structure (XEOL-XAFS) method, respectively. Moreover, photophysical evidence showed long decay times for these samples in the order of 210 ms, responsible for the steady-state emission, which most likely originates from the decay of the triplet state with a charge transfer character of Ag4(O2) tetrahedral clusters surrounded by 6 lithium cations confined in the sodalite cages of LTA zeolites.
关键词： luminescence,NUV-LED,Silver clusters,quantum efficiency,phosphors,zeolites
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Miramar Beach, FL, USA (2019.8.19-2019.8.21)] 2019 IEEE Research and Applications of Photonics in Defense Conference (RAPID) - Ultra-Thin MSM Photodetectors with Nano-Structured Surface
摘要： The photon trapping structure helps to enhance the quantum efficiency (QE) in ultra-thin metal-semiconductor-metal (MSM) photodetectors so that they can achieve high speed while maintaining less than 1 micron thickness. The study shows that the short pulse response is shorter if the device is thinner. For the thin layer of Si with thickness 250nm the pulse response is 2ps, while for 400nm and 700nm the pulse responses are 3ps and 5ps, respectively. The QE for the thin layer of Si with nano-holes is higher than the flat Si with the same thickness. The QE for 250nm Si with nano-holes is 60% at 850nm wavelength, while for flat Si with the same thickness is 20%. The QE for 400nm Si with nano-holes is 80% at 850nm wavelength, while for flat Si with the same thickness is 40%. The QE for 700nm Si with nano-holes is 90% at 850nm wavelength, while for flat Si with the same thickness is 60%. The QE for 1500nm Si with nano-holes is 95% at 850nm wavelength, while for flat Si with the same thickness is 80%. The QE for the thin layer of Si with nano-holes is higher than the flat Si with the same thickness. The QE for 250nm Si with nano-holes is 60% at 850nm wavelength, while for flat Si with the same thickness is 20%. The QE for 400nm Si with nano-holes is 80% at 850nm wavelength, while for flat Si with the same thickness is 40%. The QE for 700nm Si with nano-holes is 90% at 850nm wavelength, while for flat Si with the same thickness is 60%. The QE for 1500nm Si with nano-holes is 95% at 850nm wavelength, while for flat Si with the same thickness is 80%.
关键词： MSM photodetectors,ultra-thin,quantum efficiency,nano-holes,photon trapping
更新于2025-09-16 10:30:52
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Oblique-Angle Deposited SiO <sub/>2</sub> /Al Omnidirectional Reflector for Enhancing the Performance of AlGaN-Based Ultraviolet Light-Emitting Diode
摘要： We report the improvement of the performance of AlGaN-based ultraviolet (UV)-light-emitting diodes (LEDs) using oblique-angle deposited SiO2-based omnidirectional reflectors (ODRs). The electron-beam (e-beam) deposition at angles of 60° and 80° resulted in the formation of porous SiO2 films. The refractive index (n) varied from 1.49 to 1.25 at 365 nm with changing angle from 0 to 80°. Simulation based on the transfer matrix method showed that the porous SiO2 (n = 1.25)/Al ODR gave the normal incidence reflectance of 95.4% at 365 nm, whereas the conventional SiO2 (n = 1.49)/Al and ITO/Al reflectors have the normal incidence reflectance of 93.8% and 79%, respectively. The UV-LED with different reflectors had a forward voltage in the range of 3.40–3.51 V at 20 mA. The UV-LEDs with porous SiO2/Al ODRs (40% mesh ohmic area) yielded 21% higher light output at 100 mA and 24% relative external quantum efficiency (EQE) at 6 mA compared with the one with a reference ITO/Al reflector. The plan-view emission images showed that the SiO2/Al ODR UV-LED displayed better current spreading than the reference one with the ITO/Al reflector experiencing current crowding near the p-pad.
关键词： refractive index,SiO2-based omnidirectional reflectors,AlGaN-based ultraviolet light-emitting diodes,external quantum efficiency,oblique-angle deposition
更新于2025-09-16 10:30:52
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Organic tandem solar cells with 18.6% efficiency
摘要： Tandem organic photovoltaic (TOPV) cell is one of the technologies to harvest more solar power by staking two or more OPV devices on top of each other. Recently, the highest power conversion efficiency (PCE) ever achieved was 17.3%. Herein, this paper simulates the response of 676 different TOPV devices that consists front and back OPV cells. For this purpose, this paper uses the best 26 single-cell OPV devices to form the TOPV front and back cells combinations. The results show that there are some new TOPVs that can exceed 17.3% efficiency limit for TOPV. Also, in this work thickness optimization was performed for these new TOPV devices with an objective of efficiency maximization. As a result, using PBDTS-TDZ: ITIC in the front cells and PTB7-Th: O6T-4F:PC71BM in the back cell gives 18.6% efficiency. Likewise, the TOPV of PBDB-T-2F:TfIF-4FIC in the front cell with PTB7-Th:O6T-4F:PC71BM in the back cell gives 18.06% efficiency.
关键词： Organic materials,External quantum efficiency,Tandem organic solar cells,Optimization,Simulation
更新于2025-09-16 10:30:52
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The role of photon recycling in perovskite light-emitting diodes
摘要： Perovskite light-emitting diodes have recently broken the 20% barrier for external quantum efficiency. These values cannot be explained with classical models for optical outcoupling. Here, we analyse the role of photon recycling (PR) in assisting light extraction from perovskite light-emitting diodes. Spatially-resolved photoluminescence and electroluminescence measurements combined with optical modelling show that repetitive re-absorption and re-emission of photons trapped in substrate and waveguide modes significantly enhance light extraction when the radiation efficiency is sufficiently high. In this manner, PR can contribute more than 70% to the overall emission, in agreement with recently-reported high efficiencies. While an outcoupling efficiency of 100% is theoretically possible with PR, parasitic absorption losses due to absorption from the electrodes are shown to limit practical efficiencies in current device architectures. To overcome the present limits, we propose a future configuration with a reduced injection electrode area to drive the efficiency toward 100%.
关键词： external quantum efficiency,light-emitting diodes,photon recycling,optical outcoupling,perovskite
更新于2025-09-16 10:30:52