EAST中快离子Dα诊断光电检测系统的设计

设计了具有高时间和空间分辨率EAST 快离子D_α 的光电检测系统,它由16 路光电倍增管(PMT)和电流放大器(采用蓝宝石材料代替传统印刷板电路)构成。为了使快离子D_α (FIDA)信号在中性束注入时能从其他光源的在同一光谱范围内的谱线中检测出来,系统参数设计为整体光子-电压增益5.0×10⁹、电流放大器增益10⁶V/A、-3dB 带宽500kHz。实验结果表明,该光电检测系统可以很好的检测到快离子D_α (FIDA)信号,并有助于从D_α 光的多普勒偏移光谱推断快离子特性。     

Anomalous flattening of the fast-ion profile during Alfvén-Eigenmode activity

Neutral-beam injection into plasmas with negative central shear produces a rich spectrum of toroidicity-induced and reversed-shear Alfvén eigenmodes in the DIII-D tokamak. The first application of fast-ion D_{alpha} (FIDA) spectroscopy to Alfvén-eigenmode physics shows that the central fast-ion profile is anomalously flat in the inner half of the discharge. Neutron and equilibrium measurements corroborate the FIDA data. The current density driven by fast ions is also strongly modified. Calculations based on the measured mode amplitudes do not explain the observed fast-ion transport.     

制备工艺对掺杂NaYF4:Er3+,Yb3+发光纳米晶的聚合物光波导放大器性能的影响

制备了NaYF₄：Er³⁺,Yb³⁺纳米晶,表征了纳米晶的形貌,通过物理掺杂的方式将纳米粒子掺杂到SU-8中作为光波导放大器的芯层材料,优化了波导放大器的尺寸,利用旋涂、刻蚀等工艺,在二氧化硅衬底上制备了光波导放大器。实验中用光漂白法和湿法刻蚀两种方法制备光波导放大器,分别给出了两种方法制备的器件的结构、工艺流程、光场模拟结果,并对两种方法制备的器件的放大特性进行了测试。测试结果表明,当980 nm波长的泵浦光功率为241 mW且1 550 nm波长的信号光功率为0.1 mW时,使用湿法刻蚀法制备的放大器得到2.7 dB的相对增益。当980 nm波长的泵浦光功率为235 mW且1 550 nm波长的信号光功率为0.1 mW时,使用光漂白法制备的放大器得到4.5 dB的相对增益。根据以上测试结果,分析了两种工艺对器件性能的影响。     

基于近红外光电技术的脑水肿无创监测方法

提出了基于近红外光电技术的脑水肿无创监测方法,对大鼠脑水肿的程度进行无创监测.阐述了监测设备的测量原理和系统组成,并对大鼠实验数据结果进行了分析.监测系统光源选用760 nm和程序850 nm的双波长发光二极管,通过恒流源电路驱动进行驱动.选用OPT101作为检测器,用锁相放大电路和滤波电路对所测信号进行处理.在LabVIEW环境下通过数据采集卡进行数据采集,并进行后期处理,该系统能够实时测量大鼠脑组织的血氧变化.利用该系统测量脑水肿模型的大鼠,分析了光强、血氧参量的变化与脑水肿变化的关系.研究结果表明近红外光电技术可应用于对大鼠脑水肿程度进行无损监测.     

Slotted third-harmonic gyro-TWT amplifier experiment

The first operation of a slotted third-harmonic gyrotron traveling-wave amplifier is reported. The low-magnetic-field moderate-voltage gyrotron amplifier's 62-keV 2.5-A υ_⊥ /υ_∥=1.2 axis-encircling electron beam was supplied by a gyroresonant RF accelerator. The 10-GHz 1.3-kG single-section slotted third-harmonic amplifier is stable and yielded 12.5 dB of small signal gain with a bandwidth of 2.5%. The experiment was performed as a scaled proof-of-principle test of the 95-GHz multisection slotted amplifier under development at CPI (formerly Varian)     

Optimized photoelectric receiver to enhance modulation bandwidth of visible light communication system

In the visible light communication (VLC) system which combines lighting and communication functions, the 3-dB modulation bandwidth is mainly limited by the light-emitting diode (LED) suffered high-frequency response attenuation. An optimized photoelectric receiver was proposed to enhance the 3-dB modulation bandwidth. The frequency response of the photoelectric receiver was derived. Theoretical analysis predicted that a gain peak would appear in the high-frequency response of the photoelectric receiver. The value of the gain and the frequency point of the gain peak can be adjusted by selecting appropriate values of feedback resistor and capacitor. Then, the measurement platform of 3-dB modulation bandwidth for blue-LED VLC system was established. Experimental measurements demonstrated that the photoelectric receiver with proper sets of feedback resistor and capacitor can compensate the high-frequency response attenuation of a normal LED. The 3-dB modulation bandwidth obtains 56% enhancement if the photoelectric receiver was replaced from a commercial one to our optimized design. In order to further expand the 3-dB modulation bandwidth, an equalization circuit consists of two-stage transistor amplifier and an emitter-follower was introduced to suppress the low-frequency response. The 3-dB modulation bandwidth for the VLC system with our optimized photoelectric receiver can be expanded to 241 or 281 MHz, while the circuit was, respectively, arranged as pre-equalization or post-equalization.     

Detection of scattered light pulses at femto-Joule level by using a picosecond BBO optical parametric amplifier

We report a technique for detecting weak scattered light pulses based on a 532 nm pumped picosecond β-barium-borate collinear optical parametric amplifier. The measured maximum slope gain factor of the amplifier was found to be around 10⁷, and the energy detection limit was of the order of fJ/pulse for the signal of 730 nm and the idler of 1.5 μm at a pumping intensity of 2.83 GW/cm². The linearity of the gain for this amplifier was found to be excellent for a seeding level of lower than 420 fJ per pulse. The maximum gains and the energy detection limits for the scattered light pulses from various scattering targets were found to be poorer than that from the reflective mirror, owing to the degraded beam quality and the depolarization of the scattered light. A reduction of the maximum gain for the scattered light with the increase of the angle of incidence, which causes pulse broadening and reduces the photon flux of the signal, was investigated. The feasibility of detecting weak scattered light in the infrared by using idler-to-signal frequency up-conversion was also demonstrated, in which the infrared seeder located in the idler branch of the amplifier was injected as the seeding beam and was then parametrically up-converted into the visible signal branch, with an even higher gain.     

基于AsP/MoS2异质结的偏振光电探测器

线偏振光的探测能力是评价偏振光电探测器件的重要指标。黑砷磷(AsP)是一种较为稳定的平面内各向异性材料,由于其面内结构各向异性,其对线偏振光较为敏感,在偏振探测领域有着重要的应用潜力。本文介绍了一种基于AsP/MoS2的高度偏振敏感光电探测器。由于AsP各向异性的光吸收、MoS2有效的载流子收集和输运能力以及范德华异质结对暗电流的抑制作用,该光电探测器实现了大于300的电流开关比,0.27 A/W的电流光响应度以及2×10^10 Jones的比探测率。更重要的是,此类光电探测器在638 nm波段实现了高达3.06二向色性比的偏振特性。这些实验结果表明AsP/MoS2异质结构在偏振光电探测领域有着广阔的应用前景。     

基于石墨烯-钙钛矿量子点场效应晶体管的光电探测器

以等离子增强化学气相沉积法制备的石墨烯作为导电沟道材料,将其与无机CsPbI_3钙钛矿量子点结合,设计并制备了石墨烯-钙钛矿量子点场效应晶体管光电探测器.研究和分析了石墨烯作为场效应晶体管的电学特性及其与钙钛矿量子点结合作为光电探测器的光电特性.结果表明,石墨烯在场效应晶体管中表现出良好的电学性质,其与钙钛矿量子点的结合对波长为400 nm的光辐射具有明显的光响应,在光强为12μW时器件光生电流最大为64μA,响应率达6.4 A·W~(-1),对应的光电导增益和探测率分别为3.7×10~4,6×10~7Jones(1 Jones=1 cm·Hz~(1/2)·W~(-1)).