- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Second Harmonic Generation under the Influence of the Earth’s Gravitational Field
摘要： The influence of the Earth’s gravitational field on a weakly relativistic electron involved in the process of generation of microwave radiation is evaluated. It is shown that such exposure leads to the generation of a second harmonic.
关键词： drift tube,electron,microwave radiation,gravity
更新于2025-09-10 09:29:36
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Charge and thermal modeling of a semiconductor-based optical refrigerator
摘要： Despite multiple attempts to achieve optical refrigeration in very high (99.5%) external quantum efficiency (EQE) GaAs, no cooling has been observed to date. In this study, we investigate optical refrigeration in GaAs by numerically solving the transient drift-diffusion equation coupled to Poisson’s equation. The charge carrier distributions we obtain, together with the heat diffusion equation, allow us to observe the spatial and temporal evolution of cooling/heating within GaAs. Our results indicate that maximum cooling occurs at a laser intensity different from that which maximizes EQE. An 11-fold difference in intensity exists with a corresponding 6-fold difference in cooling power. We ultimately find that samples suspended in vacuum using a 250 lm SiO2 fiber cool to 88 K, starting from room temperature. These results emphasize the critical importance of choosing an appropriate laser excitation intensity to achieve optical refrigeration along with minimizing the conductive heat load on the refrigerator. Furthermore, results of this study are applicable towards analyzing the optical response of other optoelectronic systems where accurate charge and/or heat diffusion modeling is critical.
关键词： drift-diffusion equation,external quantum efficiency,Poisson’s equation,cooling power,optical refrigeration,heat diffusion equation,GaAs
更新于2025-09-10 09:29:36
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Analysis and Design of an Effective Light Interference Methane Sensor Based on Three-Dimensional Optical Path Model
摘要： As an important environmental monitoring equipment, the existing methane sensors or the traditional interferometer-based methane detectors have some drawbacks, such as low accuracy, large size, and complex calibration operations. Moreover, the optical path model and analysis method for the light interference methane sensor are not practical. In this paper, an effective light interference methane sensor is proposed based on a three-dimensional optical path model with point light source. Based on this model, the interference optical system is studied to illustrate the cause of the interference fringes. Furthermore, the influencing factors of the light intensity distribution are analyzed and an adjustment method for the interference fringes is proposed, which helps to simplify the assembling and calibrating operations. In order to improve the measurement accuracy, a temperature drift compensation method which includes a mapping table, a steady-state compensator, and a dynamic compensator is proposed. The mapping table is established between the output voltages of photoelectric detector, and the methane concentration, the steady-state compensator, and the dynamic compensator are proposed to eliminate the temperature drift. Finally, an experimental device for the light interference methane sensor is constructed to validate the interference fringe adjustment method and the temperature drift compensation method.
关键词： temperature drift compensation,light interference,methane sensor,three-dimensional optical path model,interference fringes
更新于2025-09-09 09:28:46
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[IEEE 2018 International Power Electronics Conference (IPEC-Niigata 2018 –ECCE Asia) - Niigata, Japan (2018.5.20-2018.5.24)] 2018 International Power Electronics Conference (IPEC-Niigata 2018 -ECCE Asia) - Dynamic drift effects in GaN power transistors: Correlation to device technology and mission profile
摘要： GaN devices for high voltage power switching are facilitating smaller, more light-weighted and more efficient converter systems. In order to provide an optimum design of such systems it is necessary to understand dynamic GaN device performance in dependence on targeted mission profile and technological parameters. The paper shortly introduces to GaN device technology and provides a widely accepted physical interpretation of mechanisms that may adversely influence device switching properties. Then important scenarios of GaN power transistor switching are presented and correlated to biasing conditions relevant for in-system device operation. In detail, dynamic switching properties depending on off- and on-state time and voltage, substrate biasing conditions and temperature are analysed and correlated to different device technologies and manufacturers. The abovementioned parameters are influencing dynamic device properties in quite a complex manner and can often be considered as a characteristic finger print of a specific technological implementation or a specific device or epitaxial manufacturer.
关键词： power switching,dynamic on-state resistance,drift effects,gallium nitride
更新于2025-09-09 09:28:46
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Modeling of degradation in normal and inverted OSC devices
摘要： Degradation of organic solar cells (OSC) remains a problem which has prevented its commercial exploitation. While there are several experimental studies pointing towards different reasons behind the atmospheric degradation of these devices, yet a microscopic understanding is lacking. Here, we present a combined experimental and modeling study to understand the degradation in the electrical characteristics of OSC in normal and inverted architectures, further correlated with the interfacial degradation. Our investigations show that degradation of current density – voltage (J-V) characteristics of normal devices is extremely fast i.e. 50% in 9 h as against 21 days for inverted devices. Interestingly, degradation in normal devices is driven primarily by a decrease in short circuit current density (Jsc) without appearance of S-shape in J-V characteristics while degraded inverted devices exhibit S-shaped J-V characteristics. Modeling of J-V data along with time dependent capacitance-voltage (C-V) analysis suggests that the degradation in normal OSC devices can be modeled using degradation induced reduced effective area theory supporting the formation of Al2O3 pockets at the cathode-active layer interface which grow exponentially with storage time eventually forming a continuous layer. In contrast, inverted devices degrade much slowly, via deterioration of hole transporting MoO3 layer resulting in increased anode barrier height and reduced surface recombination velocity (Sp) at anode causing a S shaped J-V curve due to decreased carrier extraction rate. The study clearly highlights the differences between the way two differences architectures and elucidates the underlying reasons.
关键词： Drift diffusion,Degradation,Organic solar cells,Modeling
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Research of the AlGaAs Impulse Properties
摘要： The impulse properties of AlxGa1-xAs (at x = 0.225) are investigated by research of the "overshoot" effect of the charge carriers drift velocity. The effect of the rectangular electric field pulse parameters on the temporal and spatial distribution of the drift velocity is carried out by the numerical experiment. The impulse properties of Al0.225Ga0.775As and gallium arsenide are compared.
关键词： the effect of the drift velocity "overshoot",AlGaAs,impulse properties
更新于2025-09-09 09:28:46
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Transmission Spectroscopy in Noninvasive Blood Glucose Measurement
摘要： The use of laser diodes and photodiodes in transmission spectroscopy has some effects (temperature, time, spectral, and spatial) reducing the accuracy of glucose measurement. These effects can be reduced by using a (1600 ± 3) nm laser in combination with fixation and occlusion of the tissue area under examination. In this work, a method is suggested that allows spatial displacements of the system to be taken into account. A number of methods for reducing the effect of the thermal drift of the diodes are also suggested. A portable noninvasive optical glucose meter implemented using these methods provides high clinical performance: more than 97% of the measurements are in the A and B zones of the Parkes error grid.
关键词： photodiodes,transmission spectroscopy,noninvasive blood glucose measurement,laser diodes,thermal drift,spatial displacements
更新于2025-09-04 15:30:14
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Investigation of moments-based transport models applied to plasma waves and the Dyakonov–Shur instability
摘要： Transport models based on balance equations with different degrees of numerical complexity can be derived from the Boltzmann transport equation (BTE). In this paper two different drift-diffusion models based on the first two moments of the BTE as well as two hydrodynamic models based on four moments are derived and analyzed for their accuracy in the THz frequency range with emphasis on the generation of plasma waves. To this end, they are compared to the BTE in the small-signal regime under homogeneous bulk conditions where harmonic waves were assumed, which reveals that the hydrodynamic models provide a higher accuracy. It is also shown that the anisotropy of the distribution function must be taken into account in the closure relations. This leads to convective derivatives in the balance equations, which are very difficult to treat by numerical means in the case of semiconductor devices and are neglected in commercial TCAD suites. But without them a meaningful simulation of the Dyakonov–Shur plasma instability will not be possible.
关键词： Boltzmann transport equation,THz,drift-diffusion,plasma instability,hydrodynamic
更新于2025-09-04 15:30:14