- 标题
- 摘要
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- 实验方案
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[IEEE 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Va?ster?s (2018.9.3-2018.9.6)] 2018 IEEE Conference on Antenna Measurements & Applications (CAMA) - Train Communication System with Distributed Antenna System using Optical Frequency Doubler in 90 GHz Band
摘要： A MilliMeter Wave (MMW) backhaul technology for advanced high-speed trains running a tunnel for a long distance is under development for the communication gathering a large number of passenger communications transmitting to the ground. The authors are studying a system that realizes large capacity communication between trains and the ground by arranging Distributed Antenna System (DAS) along with a long distance railway. In order to transmit a radio signal between distant antennas and the main frame of base station physically, it is necessary to avoid the influence of fiber dispersion for Radio over Fiber (RoF) which transmits a radio signal over the light. We are investigating RoF system with optical multiplication which can obtain doubled frequency after transmission. In this paper, we develop the vector modulation signal transmission by the RoF used for the downlink of the base station and report on the result of the packet communication experiment with the base station and the terminal.
关键词： DAS,RoF,millimeter wave,Frequency multiplication
更新于2025-11-28 14:23:57
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Temperature dependence simulation and characterization for InP/InGaAs avalanche photodiodes
摘要： Based on the newly proposed temperature dependent dead space model, the breakdown voltage and bandwidth of InP/InGaAs avalanche photodiode (APD) have been investigated in the temperature range from -50°C to 100°C. It was demonstrated that our proposed model is consistent with the experimental results. Our work may provide a guidance to the design of APDs with controllably low temperature coefficient.
关键词： separate absorption, grading, charge, and multiplication avalanche photodiode (SAGCM APD),optical communication,temperature coefficient,dead space effect
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - Austin, TX, USA (2018.9.24-2018.9.26)] 2018 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD) - An Improved Random Path Length Algorithm for p-i-n and Staircase Avalanche Photodiodes
摘要： We present an improved Random Path Length algorithm to accurately and efficiently estimate the design space of heterostructure avalanche photodiodes (APDs) in terms of gain, noise and bandwidth without any need of full Monte Carlo transport simulations. The underlying nonlocal model for impact ionization goes beyond the Dead Space concept and it is suited to handle staircase structures composed by a superlattice of III-V compounds as well as thick and thin p-i-n APDs. The model parameters have been calibrated on GaAs and Al_xGa_{1-x}As p-i-n APDs in a previous work. In this work GaAs p-i-n APDs are compared to staircase structures in terms of noise and bandwidth.
关键词： Impact Ionization,Avalanche Multiplication,Random Path Length,Staircase APDs,Bandwidth,Excess Noise Factor,Simulation
更新于2025-09-23 15:22:29
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Model To Determine a Distinct Rate Constant for Carrier Multiplication from Experiments
摘要： Carrier multiplication (CM) is the process in which multiple electron?hole pairs are created upon absorption of a single photon in a semiconductor. CM by an initially hot charge carrier occurs in competition with cooling by phonon emission, with the respective rates determining the CM e?ciency. Up until now, CM rates have only been calculated theoretically. We show for the ?rst time how to extract a distinct CM rate constant from experimental data of the relaxation time of hot charge carriers and the yield of CM. We illustrate this method for PbSe quantum dots. Additionally, we provide a simpli?ed method using an estimated energy loss rate to estimate the CM rate constant just above the onset of CM, when detailed experimental data of the relaxation time is missing.
关键词： carrier multiplication,quantum yield,quantum dots,semiconductor,electron?hole pairs
更新于2025-09-23 15:22:29
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Initial evaluation of proportional scintillation in liquid Xenon for direct dark matter detection
摘要： The Liquid Xenon Time Projection Chamber (LXeTPC) is often seen as an ideal detector for the direct Dark Matter (DM) search. In such experiments an efficient γ-ray background discrimination is essential. This can be achieved by distinguishing the ionization density, different for γ-rays and Nuclear Recoils. Two quantities are used for this measurement, the direct scintillation light generated by the ionizing event, and the free charges swept away by an electric field before recombination occurs. Present LXe detectors apply the Dual Phase principle, i.e. the charges are extracted into the gas phase and are measured by the proportional light they produce in a strong electric field in the gas. With ever growing dimensions of the detectors it is difficult to meet the tight mechanical tolerances required. Proportional scintillation also occurs in the liquid phase, although at much higher field strengths. Such field strengths can be reached in the 1/r field close to thin wires. All the limitations due to the extraction of electrons into the gas phase are avoided. Since the liquid level has not to be crossed, the design of the detector becomes simpler with many advantages over Dual Phase detectors. Our initial tests clearly show the pulses. They are much shorter, and their length is limited by longitudinal diffusion of the drifting charges. The threshold for proportional light production seems significantly lower, and estimates of the gain are more favorable than previously predicted. We attribute these discrepancies to our improved liquid purity.
关键词： Time projection Chambers (TPC),Dark Matter detectors (WIMPs,multiplication and electroluminescence in rare gases and liquids,ionization,Charge transport,double-phase),axions,etc.),Noble liquid detectors (scintillation
更新于2025-09-23 15:22:29
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Strain Effect Enhanced Ultrasensitive MoS2 Nanoscrolls Avalanche Photodetector
摘要： 2D materials and their derived quasi one-dimensional structure bring incredible possibilities for the field of photoelectric detection due to the intrinsic optical and electrical properties. However, the photo-generated carriers in atomically thin media are poor due to the low optical absorption, which extremely limits the performance. Here, in the MoS2 nanoscrolls photodetector, we meticulously investigated the avalanche multiplication effect. The results show that by employing the nanoscrolls structure, the required threshold electrical field to trigger avalanche multiplication is significantly lowered compared with MoS2 flake due to the modulation of energy band and intervalley scattering through the strain effect. Consequently, the avalanche multiplication could efficiently enhance the photoresponsivity exceeding 104 A/W. Furthermore, enhanced avalanche multiplication could be generalized to other TMDCs through theoretical prediction. The results are not only significant for the understanding of intrinsic nature in 2D materials but also exhibit meaningful advance in high performance and low-power consumption photodetection.
关键词： Ultra-sensitivity,Nanoscrolls,2D materials,Avalanche multiplication effect,Photodetector
更新于2025-09-23 15:21:01
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Hund excitations and the efficiency of Mott solar cells
摘要： We study the dynamics of photoinduced charge carriers in semirealistic models of LaVO3 and YTiO3 polar heterostructures. It is shown that two types of impact ionization processes contribute to the carrier multiplication in these strongly correlated multiorbital systems: The first mechanism involves local spin state transitions, while the second mechanism involves the scattering of high-kinetic-energy carriers. Both processes act on the 10-fs timescale and play an important role in the harvesting of high-energy photons in solar cell applications. As a consequence, the optimal gap size for Mott solar cells is substantially smaller than for semiconductor devices.
关键词： LaVO3,Mott solar cells,impact ionization,YTiO3,carrier multiplication
更新于2025-09-23 15:19:57
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Direct vs Delayed Triplet Energy Transfer from Organic Semiconductors to Quantum Dots and Implications for Luminescent Harvesting of Triplet Excitons
摘要： Hybrid inorganic-organic materials such as quantum dots (QDs) coupled with organic semiconductors have a wide range of optoelectronic applications, taking advantage of the respective materials strengths. A key area of investigation in such systems is the transfer of triplet exciton states to and from QDs, which has potential applications in the luminescent harvesting of triplet excitons generated by singlet fission, in photocatalysis and photochemical upconversion. While the transfer of energy from QDs to the triplet state of organic semiconductors has been intensely studied in recent years, the mechanism and materials parameters controlling the reverse process, triplet transfer to QDs have not been well investigated. Here, through a combination of steady state and time-resolved optical spectroscopy we study the mechanism and energetic dependence of triplet energy transfer from an organic ligand (TIPS-tetracene carboxylic acid) to PbS QDs. Over and energetic range spanning from exothermic (-0.3 eV) to endothermic (+0.1 eV) triplet energy transfer we find that the triplet energy transfer to the QD occurs through a single step process with a clear energy dependence that is consistent with an electron exchange mechanism as described by Marcus-Hush theory. In contrast, the reverse process, energy transfer from the QD to the triplet state of the ligand does not show any energy dependence in the studied energy range, interestingly a delayed formation of the triplet state occurs relative to the quantum dots decay. Based on the energetic dependence of triplet energy transfer we also suggest design criteria for future materials systems where triplet excitons from organic semiconductors are harvested via QDs, for instance in light emitting structures or the harvesting of triplet excitons generated via singlet fission.
关键词： singlet fission,quantum dots,solar energy,photon multiplication,triplet energy transfer
更新于2025-09-23 15:19:57
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High performance flexible organic photomultiplication photodetector based on ultra-thin silver film transparent electrode
摘要： Flexible and lightweight photomultiplication-type organic photodetectors (PM-OPDs) have attracted wide attention for their broad application prospects, especially in the field of wearable electronic products. However, the common used indium tin oxide (ITO) conductive anode is not conducive to realize high-performance flexible PM-OPD due to its rigidity and fragility. Here, on the flexible polyethylene terephthalate (PET) substrate, we successfully fabricate highly sensitive poly 3-hexylthiophene:phenyl-C70-butyric acid methyl ester (P3HT:PC70BM, 100:1) based PM-OPDs using ultra-thin silver films as the transparent anode. Specifically, a 1 nm thick MoO3 layer is utilized as the wetting layer for facilitating the silver film percolation, and a 2 nm thick MoO3 layer, as the hole transport layer, is coated on top of the ultra-thin silver film before coating the P3HT:PC70BM film. The as-prepared flexible PM-OPDs based on the ultra-thin silver film exhibit the optimal external quantum efficiency (EQE) and responsivity (R) of 1.3×105 % and 388.4 A/W, respectively, under -15 V bias, which are 1.98 times and 2.15 times greater than those of the ITO anode based device. More importantly, the device has good flexibility with the EQE maintaining 70.6% of its initial value after 10 times of bending, and 51.4% of its initial value after 1000 times of bending. This work paves the way for developing flexible PM-OPDs as well as other flexible optoelectronic devices.
关键词： multiplication,transparent electrode,photodetectors,silver film,flexible
更新于2025-09-19 17:13:59
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Extremely Efficient Photocurrent Generation in Carbon Nanotube Photodiodes Enabled by a Strong Axial Electric Field
摘要： Carbon nanotube (CNT) photodiodes have potential to convert light into electrical current with high efficiency. However, previous experiments have revealed photocurrent quantum yield (PCQY) well below 100%. In this work, we show that axial electric field increases the PCQY of CNT photodiodes. In optimal conditions our data suggest PCQY > 100%. We studied, both experimentally and theoretically, CNT photodiodes at room temperature using optical excitation corresponding to the S22, S33 and S44 exciton resonances. The axial electric field inside the pn junction was controlled using split gates that are capacitively coupled to the suspended CNT. Our results give new insight into the photocurrent generation pathways in CNTs, and the field dependence and diameter dependence of PCQY.
关键词： scanning photocurrent microscopy,carbon nanotube,carrier multiplication,exciton dissociation
更新于2025-09-16 10:30:52