scholarly journals Research Progress on Terahertz Quantum-Well Photodetector and Its Application

2021 ◽  
Vol 9 ◽  
Author(s):  
Dixiang Shao ◽  
Zhanglong Fu ◽  
Zhiyong Tan ◽  
Chang Wang ◽  
Fucheng Qiu ◽  
...  
Keyword(s):  
Quantum Well ◽  
High Speed ◽  
Theoretical Calculations ◽  
Material Design ◽  
Response Speed ◽  
Peak Frequency ◽  
Fast Response ◽  
Detection Sensitivity ◽  
Research Progress ◽  
Frequency Error

Compared with other typical terahertz (THz) detectors, the quantum-well photodetector (QWP) has the advantages of high detection sensitivity, fast response, mature fabrication, small size, and easy integration. Therefore, it is suitable for high-speed detection and imaging applications at the THz band. Researchers, both domestic and overseas, have systematically studied material design and device performance of the THz QWP. The design of the device is such that the peak frequency error is within 8%, the maximum peak responsibility is 5.5 A/W, the fastest response speed is 6.2 GHz, the best noise equivalent power is ∼10−13 W/Hz0.5, and the spectrum range is 2.5–6.5 THz. In this article, firstly the basic principles and theoretical calculations of the THz QWP are described, and then the research progress of the THz QWP in our research group at imaging and communication is reviewed, which looks forward to its future development.

Study of the Squeeze Film Damper of Larger Flow Rate High-Speed On/Off Valve

2011 ◽  
Vol 130-134 ◽  
pp. 594-598
Author(s):  
Hai Bing Jiang ◽  
Jian Ruan ◽  
Ming Ming Wu ◽  
Tao Wang
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Response Speed ◽  
Fast Response ◽  
Squeeze Film ◽  
Squeeze Film Damper ◽  
Perfect Performance ◽  
Sealing Performance ◽  
New Type ◽  
Off Time

A new type of squeeze film damper (SFD) is designed to reduce spool’s impact and vibration which happen in the two-stage larger flow rate high-speed on/off valve with the 450 L/min flow rate and 8ms turn-off time, the valve’s sealing performance、reliability and service life improve largely, and the valve’s response speed doesn’t drop. The simulated and experimental results show: The damper has optimum buffering performance when oil film thickness is 0.1mm, and the spool closing process approach ideal state. The valve will has a great potential application in the powerful occasions because of it's perfect performance: larger flow rate、fast response and novel damper.

System Frequency Stabilization Using Doubly Fed Induction Generators Based Wind Energy Conversion Systems

2011 ◽  
Vol 347-353 ◽  
pp. 1442-1453
Author(s):  
Ying Cheng Xue ◽  
Neng Ling Tai
Keyword(s):  
Wind Turbines ◽  
Frequency Control ◽  
Wind Farms ◽  
Response Speed ◽  
Fast Response ◽  
Frequency Regulation ◽  
Frequency Error ◽  
Inertial Response ◽  
Doubly Fed ◽  
System Frequency

The conventional decoupling controls of variable-speed doubly fed wind turbines provide minimal support to the regulation of system frequency. The characteristics of doubly fed induction generator (DFIG) wind turbines and conventional power plans are compared, and the contributions of DFIG to system inertial response and frequency regulation are investigated. The influence of auxiliary loop parameters on the inertial response is illustrated. We also introduce a novel algorithm to enhance the participation of DFIG in existing frequency regulation mechanisms. The proposed approach takes advantage of the fast responses associated with DFIGs. The control system consists of four functional modules, namely, frequency control, rotational speed delay recovery, speed protection, and coordination control with conventional generators. The simulation results show that the control strategy has a fast response speed to the transient frequency error, thereby proving that wind farms can participate in system frequency regulation to a certain extent.

scholarly journals Fast Response GaAs Photodetector Based on Constructing Electron Transmission Channel

Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1160
Author(s):  
Shuai Guo ◽  
Xue Chen ◽  
Dengkui Wang ◽  
Xuan Fang ◽  
Dan Fang ◽  
...  
Keyword(s):  
High Speed ◽  
Surface States ◽  
Response Speed ◽  
Fast Response ◽  
Transmission Channel ◽  
Electron Transmission ◽  
Speed Performance ◽  
Gaas Nanowire ◽  
Low Dimensional ◽  
Low Dimensional Materials

Low-dimensional GaAs photodetectors have drawn a great deal of attention because of their unique absorption properties and superior responsivity. However, their slow response speed caused by surface states presents challenges. In this paper, a mixed-dimensional GaAs photodetector is fabricated utilizing a single GaAs nanowire (NW) and a GaAs 2D non-layer sheet (2DNLS). The photodetector exhibits a fast response with a rise time of ~4.7 ms and decay time of ~6.1 ms. The high-speed performance is attributed to an electron transmission channel at the interface between the GaAs NW and GaAs 2DNLS. Furthermore, the fast electron channel is confirmed by eliminating interface states via wet passivation. This work puts forward an effective way to realize a high-speed photodetector by utilizing the surface states of low-dimensional materials.

Direct Current Deadbeat Predictive Controller for BLDC Motor Using Single DC-Link Current Sensor

2020 ◽  
Vol 38 (8A) ◽  
pp. 1187-1199
Author(s):  
Qaed M. Ali ◽  
Mohammed M. Ezzalden
Keyword(s):  
Control System ◽  
High Speed ◽  
Fast Response ◽  
Bldc Motor ◽  
Current Controller ◽  
Three Phase ◽  
Predictive Controller ◽  
Two Phases ◽  
Dc Current ◽  
Three Phase Inverter

BLDC motors are characterized by electronic commutation, which is performed by using an electric three-phase inverter. The direct control system of the BLDC motor consists of double loops; including the inner-loop for current regulating and outer-loop for speed control. The operation of the current controller requires feedback of motor currents; the conventional current controller uses two current sensors on the ac side of the inverter to measure the currents of two phases, while the third current would be accordingly calculated. These two sensors should have the same characteristics, to achieve balanced current measurements. It should be noted that the sensitivity of these sensors changes with time. In the case of one sensor fails, both of them must be replaced. To overcome this problem, it is preferable to use one sensor instead of two. The proposed control system is based on a deadbeat predictive controller, which is used to regulate the DC current of the BLDC motor. Such a controller can be considered as digital controller mode, which has fast response, high precision and can be easily implemented with microprocessor. The proposed control system has been simulated using Matlab software, and the system is tested at a different operating condition such as low speed and high speed.

scholarly journals Tin Disulfide-Coated Microfiber for Humidity Sensing with Fast Response and High Sensitivity

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 648
Author(s):  
Aijie Liang ◽  
Jingyuan Ming ◽  
Wenguo Zhu ◽  
Heyuan Guan ◽  
Xinyang Han ◽  
...  
Keyword(s):  
Humidity Sensor ◽  
Small Diameter ◽  
High Sensitivity ◽  
Large Change ◽  
Small Variation ◽  
Response Speed ◽  
Fast Response ◽  
Tin Disulfide ◽  
Recovery Times ◽  
Response And Recovery

Breath monitoring is significant in assessing human body conditions, such as cardiac and pulmonary symptoms. Optical fiber-based sensors have attracted much attention since they are immune to electromagnetic radiation, thus are safe for patients. Here, a microfiber (MF) humidity sensor is fabricated by coating tin disulfide (SnS2) nanosheets onto the surface of MF. The small diameter (~8 μm) and the long length (~5 mm) of the MF promise strong interaction between guiding light and SnS2. Thus, a small variation in the relative humidity (RH) will lead to a large change in optical transmitted power. A high RH sensitivity of 0.57 dB/%RH is therefore achieved. The response and recovery times are estimated to be 0.08 and 0.28 s, respectively. The high sensitivity and fast response speed enable our SnS2-MF sensor to monitor human breath in real time.

scholarly journals Asymmetric Ge/SiGe coupled quantum well modulators

Nanophotonics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1765-1773
Author(s):  
Yi Zhang ◽  
Jianfeng Gao ◽  
Senbiao Qin ◽  
Ming Cheng ◽  
Kang Wang ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Quantum Well ◽  
Quantum Wells ◽  
High Speed ◽  
Low Voltage ◽  
Extinction Ratio ◽  
High Frequency Response ◽  
Modulation Format ◽  
Silicon Photonic ◽  
Coupled Quantum Well

Abstract We design and demonstrate an asymmetric Ge/SiGe coupled quantum well (CQW) waveguide modulator for both intensity and phase modulation with a low bias voltage in silicon photonic integration. The asymmetric CQWs consisting of two quantum wells with different widths are employed as the active region to enhance the electro-optical characteristics of the device by controlling the coupling of the wave functions. The fabricated device can realize 5 dB extinction ratio at 1446 nm and 1.4 × 10−3 electrorefractive index variation at 1530 nm with the associated modulation efficiency V π L π of 0.055 V cm under 1 V reverse bias. The 3 dB bandwidth for high frequency response is 27 GHz under 1 V bias and the energy consumption per bit is less than 100 fJ/bit. The proposed device offers a pathway towards a low voltage, low energy consumption, high speed and compact modulator for silicon photonic integrated devices, as well as opens possibilities for achieving advanced modulation format in a more compact and simple frame.

scholarly journals Self-Powered All-Inorganic Perovskite Photodetectors with Fast Response Speed

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Ting Zhang ◽  
Shibin Li
Keyword(s):  
High Performance ◽  
Solution Process ◽  
Response Speed ◽  
Fast Response ◽  
Single Step ◽  
Inorganic Perovskite ◽  
Perovskite Materials ◽  
Photoactive Materials ◽  
Self Powered ◽  
Solvent Processing

AbstractIn this manuscript, the inorganic perovskite CsPbI2Br and CsPbIBr2 are investigated as photoactive materials that offer higher stability than the organometal trihalide perovskite materials. The fabrication methods allow anti-solvent processing the CsPbIxBr3−x films, overcoming the poor film quality that always occur in a single-step solution process. The introduced diethyl ether in spin-coating process is demonstrated to be successful, and the effects of the anti-solvent on film quality are studied. The devices fabricated using the methods achieve high-performance, self-powered and the stabilized photodetectors show fast response speed. The results illustrate a great potential of all-inorganic CsPbIxBr3−x perovskites in visible photodetection and provide an effective way to achieve high performance devices with self-powered capability.

High performance self-powered CuZnS/GaN UV photodetectors with ultrahigh on/off ratio (3 × 108)

2021 ◽  
Vol 9 (14) ◽  
pp. 4799-4807
Author(s):  
Yong Zhang ◽  
Weidong Song
Keyword(s):  
Chemical Bath Deposition ◽  
High Performance ◽  
Response Speed ◽  
Fast Response ◽  
Uv Photodetector ◽  
Uv Photodetectors ◽  
Simple Chemical ◽  
Self Powered

P-CuZnS/n-GaN UV photodetector is prepared by a simple chemical bath deposition, showing excellent self-powered properties, including ultrahigh on/off ratio (3 × 108), fast response speed (0.14/40 ms) and large detectivity of 3 × 1013 Jones.

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