一种近红外探测器的光谱响应率测量

对近红外辐射功率光谱绝对响应率的定标技术进行了研究。设计了一种制冷扩展波长型的InGaAs探测器，为了使其能够作为功率传递的标准探测器工作在（1.2～2.5）μm波长范围，对探测器的光谱响应率进行了测量。首先在1260nm波长下进行绝对功率传递的标定试验，然后用基于红外单色仪的光谱比较系统（SCF）测量了探测器的相对光谱响应率。结合2个步骤的数据，最终可以得到探测器的绝对光谱响应率。     

飞秒激光-等离子体相互作用中快电子能量分布

 采用不同量程的电子谱仪与LiF热释光探测器相配合，测量了飞秒激光 等离子体相互作用中产生的快电子能量分布。结果显示快电子能量分布的一致性和多个重要特征与国外同类实验和计算机模拟结果相似。快电子能谱在低能处产生凹陷是由于冷电子的回流产生的；几种加速机制共同作用是能谱在100~350 keV范围内出现平台的原因；快电子的有效温度较好地满足共振吸收的温度定标律是由于反射激光加速与共振吸收机制均是通过朗道阻尼或波破对电子进行加速的。     

Optical characterization of the silicon photodiodes for the establishment of national radiometric standards

Optical properties of the silicon photodiodes are investigated in the visible spectral regime. Non-linearity measurement standard was established by using Hamamatsu S1337-11 type windowless silicon photodiode whose non-linearity value was found to be better than 6×10⁻⁵ at photocurrent level of 10⁻⁹ to 10⁻⁴ A. Temperature effects on the spectral responsivity for S1337-11, S1337-1010BQ and S1227-1010BQ type photodiodes were analyzed between 20°C and 40°C at 488.1, 514.7 and 632.8 nm vacuum wavelengths. The spatial uniformities of the responsivity for three type photodiodes are performed with a laser beam having 1 mm diameter by using home made two-axis micro translation system. Results of the reflectance measurements for three elements of reflection-based trap detectors were compared with the predicted values obtained from Fresnel equations.     

Curvature Inspired Cosmological Scenario

Using modified gravity with non-linear terms of curvature, R ² and R ^(2+r) (with r being a positive real number and R being the scalar curvature), cosmological scenario, beginning at the Planck scale, is obtained. Here a unified picture of cosmology is obtained from f(R)-gravity. In this scenario, universe begins with power-law inflation followed by deceleration and acceleration in the late universe as well as possible collapse of the universe in future. It is different from f(R)-dark energy models with non-linear curvature terms assumed as dark energy. Here, dark energy terms are induced by linear as well as non-linear terms of curvature in Friedmann equation being derived from modified gravity. It is also interesting to see that, in this model, dark radiation and dark matter terms emerge spontaneously from the gravitational sector. It is found that dark energy, obtained here, behaves as quintessence in the early universe and phantom in the late universe. Moreover, analogous to brane-tension in brane-gravity inspired Friedmann equation, a tension term λ arises here being called as cosmic tension, It is found that, in the late universe, Friedmann equation (obtained here) contains a term −ρ ²/2λ (ρ being the phantom energy density) analogous to a similar term in Friedmann equation with loop quantum effects, if λ>0 and brane-gravity correction when λ<0.     

High‐Responsivity Photodetectors Based on Formamidinium Lead Halide Perovskite Quantum Dot–Graphene Hybrid

Highly performance photodetector requires a wide range of responses of the incident photons and converts them to electrical signals efficiently. Here, a photodetector based on formamidinium lead halide perovskite quantum dots (e.g., FAPbBr₃ QDs)–graphene hybrid, aiming to take the both advantages of the two constituents. The FAPbBr₃ QD–graphene layer not only benefits from the high mobility and wide spectral absorption of the graphene material but also from the long charge carrier lifetime and low dark carrier concentration of the FAPbBr₃ QDs. The photodetector based on FAPbBr₃ QD–graphene hybrid exhibits a broad spectral photoresponse ranging from 405 to 980 nm. A photoresponsivity of 1.15 × 10⁵AW⁻¹ and an external quantum efficiency as high as 3.42 × 10⁷% are obtained under an illumination power of 3 µW at 520 nm wavelength. In detail, a high responsivity is achieved in 405–538 nm, while a relatively low but fast response is observed in 538–980 nm. The photoelectric conversion mechanism of this hybrid photodetector is investigated in the view of built‐in electric field from the QD–graphene contact which improves the photoconductive gain.     

GaN/AlGaN双带红外探测及光子频率上转换研究

研究了GaN/AlGaN异质结构中的双带（中、远）红外探测及光子频率上转换特性.通过光致发光光谱确认GaN/AlGaN探测器结构中AlGaN本征层的Al组分,讨论了不同Al组分GaN/AlGaN异质结的导带带阶界面功函数差.在拟合单周期GaN/AlGaN探测器中红外和远红外波段响应谱的基础上,研究多周期GaN/AlGaN探测器与GaN/AlGaN发光二极管集成结构的中红外和远红外光子频率上转换效率与GaN发射层厚度、AlGaN本征层厚度、紫光光子出射效率、内量子效率、空间频率和发射层掺杂浓度间的关系,优化 关键词： 双带红外探测 光子频率上转换 响应谱 GaN/AlGaN     

红外光谱发射率测量系统的温漂修正方法

针对探测器光谱响应度温漂现象对红外光谱发射率测量系统重复性的影响,分析探测器温度与输出电压之间的变化规律,提出了基于多项式拟合的光谱响应度温漂修正方法。研究探测器自身温度与其光谱响应度的函数关系,对探测器光谱响应度随温度变化的曲线进行数据拟合,得到探测器温度-光谱响应度的拟合方程,计算光谱响应度的温漂修正系数,修正探测器的输出电压,消除光谱响应度温漂现象对探测器输出电压造成的影响。研制光谱响应度温漂修正装置,测得探测器光谱响度的温漂曲线,对比指数拟合曲线和多项式拟合曲线与测量曲线的吻合度,结果表明6阶多项式拟合曲线的一致性较好,提高了基于积分球反射计的光谱发射率测量系统的重复性。     

激光点阵扫描法绝对定标太阳辐射计直射通道研究

利用可调谐激光器作为光源,以溯源于低温绝对辐射计的标准传递探测器作为激光束功率测量探测器,采用激光点阵扫描方法在太阳辐射计有效孔径光阑面形成均匀照度场,精确测量太阳辐射计870 nm无偏直射通道中心波长处绝对辐照度响应度。利用灯-单色仪系统扫描获得该通道相对光谱辐照度响应度,最终在实验室条件下获得该通道绝对光谱辐照度响应度,联合大气层外太阳照度谱数据通道内积分得到该通道大气层外响应常数V₀值,与NASA的GSFC中心的2009年定标结果差异仅为3.75%,定标不确定度达到2.06%,验证了这一新技术的原理可行性。     

基于光谱响应定标的辐射测温方法

辐射测温是通过测量物体发出的辐射来反演温度,辐射测量方程中含有与空间位置相关的非光谱参数,通常需通过辐射标定予以确认。而该研究将非光谱参数归入有限项级数形式的光谱发射率中,这既不会影响多通道测温方程组的封闭性,又不会影响真温求解,从而在无需测量数据归一化的条件下,实现了无需空间位置标定的辐射测温,该方法仅需要标定仪器的绝对光谱响应或相对光谱响应,但不能解得发射率。以两个特例分别对多波长测温方法和多谱段测温方法的求解特性进行了研究。结果表明：对于任意的测量矢量,有效波长不相同的多波长测温唯一解是存在的;而多谱段测温时,存在无解区域,双解直线,甚至可能存在三解直线。     

Optically controlled SiCGe/SiC heterojunction transistor with charge-compensation layer

A novel optically controlled SiCGe/SiC heterojunction transistor with charge-compensation technique has been simulated by using commercial simulator.This paper discusses the electric field distribution,spectral response and transient response of the device.Due to utilizing p-SiCGe charge-compensation layer,the responsivity increases nearly two times and breakdown voltage increases 33%.The switching characteristic illustrates that the device is latch-free and its fall time is much longer than the rise time.With an increase of the light power density and wavelength,the rise time and fall time will become shorter and longer,respectively.In terms of carrier lifetime,a compromise should be made between the responsivity and switching speed,the ratio of them reaches maximum value when the minority carrier lifetime equals 90 ns.