Numerical Simulation of Refractive-Microlensed HgCdTe Infrared Focal Plane Arrays Operating in Optical Systems

The optoelectronic performance of the mid-wavelength HgCdTe infrared focal plane array (IRFPA) with refractive microlenses integrated on its CdZnTe substrate has been numerically simulated. A reduced light-distribution model based on scalar Kirchhoff diffraction theory was adopted to reveal the true behavior of IRFPAs operating in an optical system under imaging conditions. The pixel crosstalk obtained and the energy-gathering characteristics demonstrated that the microlenses can delay the rise in crosstalk when the image point shifts toward pixel boundaries, and can restrict the major optical absorption process in any case within a narrow region around the pixel center. The dependence of the microlenses’ effects on the system's properties was also analyzed; this showed that intermediate relative aperture and small microlens radius are required for optimized device performance. Simulation results also indicated that for detectors farther from the center of the field of view, the efficacy of microlenses in crosstalk suppression and energy gathering is still maintained, except for a negligible difference in the lateral magnification from an ordinary array without microlenses.     

High‐Responsivity Graphene/InAs Nanowire Heterojunction Near‐Infrared Photodetectors with Distinct Photocurrent On/Off Ratios

Graphene is a promising candidate material for high‐speed and ultra‐broadband photodetectors. However, graphene‐based photodetectors suffer from low photoreponsivity and I_light/I_dark ratios due to their negligible‐gap nature and small optical absorption. Here, a new type of graphene/InAs nanowire (NW) vertically stacked heterojunction infrared photodetector is reported, with a large photoresponsivity of 0.5 AW^?1 and I_light/I_dark ratio of 5 × 10², while the photoresponsivity and I_light/I_dark ratio of graphene infrared photodetectors are 0.1 mAW^?1 and 1, respectively. The Fermi level (E_F ) of graphene can be widely tuned by the gate voltage owing to its 2D nature. As a result, the back‐gated bias can modulate the Schottky barrier (SB) height at the interface between graphene and InAs NWs. Simulations further demonstrate the rectification behavior of graphene/InAs NW heterojunctions and the tunable SB controls charge transport across the vertically stacked heterostructure. The results address key challenges for graphene‐based infrared detectors, and are promising for the development of graphene electronic and optoelectronic applications.     

Surface Plasmon‐Enhanced Photodetection in Few Layer MoS2 Phototransistors with Au Nanostructure Arrays

2D Molybdenum disulfide (MoS₂) is a promising candidate material for high‐speed and flexible optoelectronic devices, but only with low photoresponsivity. Here, a large enhancement of photocurrent response is obtained by coupling few‐layer MoS₂ with Au plasmonic nanostructure arrays. Au nanoparticles or nanoplates placed onto few‐layer MoS₂ surface can enhance the local optical field in the MoS₂ layer, due to the localized surface plasmon (LSP) resonance. After depositing 4 nm thick Au nanoparticles sparsely onto few‐layer MoS₂ phototransistors, a doubled increase in the photocurrent response is observed. The photocurrent of few‐layer MoS₂ phototransistors exhibits a threefold enhancement with periodic Au nanoarrays. The simulated optical field distribution confirms that light can be trapped and enhanced near the Au nanoplates. These findings offer an avenue for practical applications of high performance MoS₂‐based optoelectronic devices or systems in the future.     

ReS2‐Based Field‐Effect Transistors and Photodetectors

Atomically thin 2D layered transition metal dichalcogenides (TMDs) have been extensively studied in recent years because of their appealing electrical and optical properties. Here, the fabrication of ReS₂ field‐effect transistors is reported via the encapsulation of ReS₂ nanosheets in a high‐κ Al₂O₃ dielectric environment. Low‐temperature transport measurements allow to observe a direct metal‐to‐insulator transition originating from strong electron–electron interactions. Remarkably, the photodetectors based on ReS₂ exhibit gate‐tunable photoresponsivity up to 16.14 A W^?1 and external quantum efficiency reaching 3168%, showing a competitive device performance to those reported in graphene, MoSe₂, GaS, and GaSe‐based photodetectors. This study unambiguously distinguishes ReS₂ as a new candidate for future applications in electronics and optoelectronics.     

红外探测器信息获取系统噪声特性

理论上完成了红外图像传感器信息获取电路的噪声建模,并且分别从仿真和测试两个方面对电路的噪声进行分析.三种分析方法的结果基本相同,均为0.11 m V左右.从原理和实验两个方面证明了基于仪放的模拟信号调理电路可以满足噪声低至0.2 m V的红外探测器航天应用需求.在完成噪声量大小分析的同时进行了噪声频谱特性分析,证明了信息获取电路噪声主要成分是1/f噪声和白噪声,二者均满足高斯分布.     

甚长波量子阱红外探测器中的双激发态工作机理

通过对甚长波量子阱红外探测器的变温变偏压光谱实验,发现了光电流谱峰值响应波长与半高宽随偏置电压和温度变化均会发生变化,尤其以小偏压下峰值移动明显.结合器件能带结构计算的结果,提出了甚长波量子阱红外探测器中双激发态工作模型,并阐明了其中束缚态-准束缚态跃迁模式中准束缚态的物理特性,包括隧穿特性和热离化特性,以及不同工作条件下这两种物理过程在形成光电流时的主导性.同时,验证了甚长波量子阱红外探测器件的第一激发态随外界工作条件的变化会呈现出准束缚到准连续的变化特性.最后,揭示了在甚长波量子阱红外探测器工作中束缚态-准束缚态跃迁工作模式对于降低器件暗电流、提升器件工作温度、提高器件探测率的有效性.     

聚合物含量对锆钛酸铅多层膜光学特性的影响

利用溶胶-凝胶法,由添加高分子聚合物聚乙烯吡咯烷酮(PVP)的化学溶液制备了锆钛酸铅(Pb Zr0.4Ti0.6O3,PZT)多层膜,研究了溶液中聚合物PVP的含量对多层膜光学性能的影响.测试表明,PZT多层膜呈现出由致密层和多孔层交替排布的层状结构,在可见光区具有单一的高反射率带,且反射带中心波长在一定范围内随着溶液中PVP浓度的升高向长波方向移动.在PVP的相对摩尔比为x=1.0时,多层膜反射性能达到最优,室温绝对反射率高达89%,反射带宽为44 nm.     

一种大测距动态范围高重频相干测距测速激光雷达(Ⅱ): 信号调制

针对"双频双调制双本振(DFDMDL)"大测距动态范围高重频相干测距测速体制,分析了该体制信号调制需要考虑的调频线性度、发射光和本振光信号的"幅-频"特性、对称三角线性调频(STLFM)信号的周期稳定性等因素,通过参数的对比、仿真及实测,提出了适合本系统的信号调制方案.实测结果表明,采用声光移频器(AOFS)外调制提供高线性度STLFM信号,直接数字频率合成(DDS)驱动AOFS,通过DAC调节射频驱动源功率补偿AOFS非平坦的"幅-频"特性,以及基于FPGA的高精度时间测量系统监测STLFM信号周期及测量多个STLFM周期间的时间差,可以使该"双频双调制双本振"体制具有较高的距离测量精度,并为通过脉冲积累减小发射能量的途径提供了可能.     

基于实时视轴跟踪的像移补偿技术研究

为解决画幅式扫描红外成像技术中翼展摆扫引起的严重像移问题,提出了一种基于实时视轴跟踪的像移补偿技术,对于瞬时视场为100μrad的成像系统,像移补偿精度可达±0.005°(±87.3μrad),补偿效果优于1个像元。该技术能够实现翼展摆扫像移的高频补偿,研究成果对推动机载红外成像技术向宽视场、高空间分辨率方向进一步发展具有重要意义。     

用于空间领域的太赫兹技术研究概况

作为电磁波中从红外光到微波的过渡区,太赫兹波所具有的独特性能已得到了人们的广泛认识。随着太赫兹辐射源、太赫兹探测器等单元技术研究的不断成熟,美国、欧洲和日本已率先将其应用于空间天文观测、深空探测和对地气象环境监测等领域。重点总结了这些应用中的技术发展情况,并简要分析了太赫兹雷达与通信技术的研究状况和应用前景。