距离选通式半导体激光夜视系统

距离选通式半导体激光夜视系统是采用高功率脉冲半导体激光器作为夜视系统的照明光源、以微光管作为接收传感器的主动成像夜视系统。介绍了半导体激光夜视系统中所采用的高质量脉冲半导体激光光源技术及距离选通技术。其中光束准直整形技术和改善光场均匀性技术是脉冲半导体激光夜视系统的关键技术。距离选通式激光夜视系统消除了脉冲激光带来的后向散射及杂散光的干扰,提高了接收信噪比,可获取清晰的夜视图像。实验证明采用距离选通式半导体激光夜视系统可在很差的气象条件下工作,并可获得清晰图像,作用距离达5 km。该系统不仅用于军事领域也可用于边防、公安、搜救、监控等其他领域。     

飞秒激光加工半导体材料考虑电子逆韧致辐射吸收效应的烧蚀理论模型

本文对飞秒激光加工微纳器件半导体材料过程中的微观烧蚀机理进行了理论研究,基于试探粒子法,采用Fokker-Planck方程,建立了描述飞秒时间尺度内的电子非平衡态输运过程的理论模型,该模型屏弃了弛豫时间和激光吸收系数为常数的假设,给出了屏蔽coulomb势作用下电子输运的漂移系数与扩散系数表达式,考虑了电子逆韧致辐射机制对激光吸收系数的影响,通过数值模拟获得了自由电子非平衡态分布,并在此基础上计算了飞秒激光的烧蚀阀值,讨论了飞秒激光参数对烧蚀半导体材料的影响。     

MPPA光动力作用诱导人鼻咽癌细胞凋亡的实验研究

为观察MPPa光动力作用对鼻咽癌细胞凋亡的影响,应用AnnexinV—PI双染结合流式细胞仪分析MPPa光动力作用后人鼻咽癌细胞株CNE2细胞发生凋亡和继发性坏死的比率。结果显示MPPa光动力作用实验组人鼻咽癌细胞株CNE2细胞发生凋亡和继发性坏死的比率分别增加到16.43 %和4.64 % ,且均显著高于单纯光照射组、单纯MMPa光敏剂处理组和假照射组(P <0 .0 1) ,而三对照组间无明显差异(P >0 .0 5 )。表明MPPa光动力作用能有效诱导低分化人鼻咽癌细胞株CNE2细胞凋亡的发生。这也可能是MPPa光动力作用杀伤鼻咽癌的重要机制之一。     

基于边缘探测技术的激光单稳频指标分析

基于边缘探测技术的激光雷达实际应用中,激光器在工作中发射光信号的中心频率会发生漂移,激光频率的漂移过大,会直接影响边缘探测系统的测量精度。采用仿真计算的方法得到碘分子吸收滤波器在470nm~550nm范围内的吸收光谱谱线,以基于边缘探测技术的激光雷达监测大气信道和海洋水下信道环境参数为例,得到适合大气和海洋探测吸收谱线并确定发射激光信号的中心频率。通过理论分析,给出了满足探测要求的激光发射信号单稳频指标,为实际探测系统的设计奠定基础。     

激光成像雷达在飞行器避障过程中的应用

飞行器前视激光雷达通过测距得到前方距离像,由得到的距离像可以得到飞行器前面障碍物的形状、高度、宽度等信息,根据得到的信息,由飞行器惯导和飞行器在任意时刻的姿态可以决定飞行器的避障过程。根据激光成像雷达探测到的前视三维障碍物信息,推导了飞行器惯导约束下的避障算法。用该推导的算法在真实地形图上进行了模拟实验,实验结果表明算法是正确性的。     

大气中激光烧蚀铝靶冲量耦合系数实验研究

研究了激光与铝靶相互作用过程中,大气中激光功率密度与铝靶获得的冲量耦合系数的关系,通过改变激光聚焦在靶面上的光斑大小,得到冲量耦合系数与激光功率密度的关系。实验结果表明,当入射激光功率密度为3.47×106W/cm2时,铝靶获得的冲量耦合系数最高。该入射激光功率密度最佳值与理论计算值6.14×106W/cm2符合得较好。用激光支持爆轰波(LSDW)与固体靶相互作用的二维模型理论计算得到的冲量耦合系数与实验结果比较,二者趋势相同,定量比较有较大差别,原因是所用激光光斑面积偏大,不能按照该理论的点爆炸模型来计算。     

激光光热辐射技术测量不透明复合材料的热扩散率

报道了一种用激光光热辐射技术测量不透明材料热扩散率的方法。根据红外探测器在不同频率下测得试样光热信号的振幅和相位 ,采用非线性拟合法 ,由振幅和相位分别对频率进行非线性拟合 ,由此可得材料的热扩散率 ,并对单向氧化铝纤维基复合材料进行了测量 ,给出了任一方向上的热扩散率的实验结果     

Resonant Tunneling through Monolayer Si Colloidal Quantum Dots and Ge Nanocrystals

Resonant tunneling through a 4 nm nanocrystal Ge (nc‐Ge) layer and a 2.4 nm monolayer of Si colloidal quantum dots (QD) is achieved with 0.7 nm amorphous Al₂O₃ (a‐Al₂O₃) barriers. The nc‐Ge resonant tunneling diode (RTD) demonstrates a peak‐to‐valley current ratio (PVCR) of 8 and a full width at half maximum (FWHM) of 30 mV at 300 K, the best performance among RTDs based on annealed nanocrystals. The Si QD RTD is first achieved with PVCRs up to 47 and FWHMs as small as 10 mV at room temperature, confirming theoretically expected excellences of 3D carrier confinements. The high performances are partially due to the smooth profile of nc‐Ge layer and the uniform distribution of Si QDs, which reduce the adverse influences of many‐body effects. More importantly, carrier decoherence is avoided in the 0.7 nm a‐Al₂O₃ barriers thinner than the phase coherence length (≈1.5 nm). Ultrathin a‐Al₂O₃ also passivates well materials and suppresses leakage currents. Additionally, the interfacial bandgap of ultrathin a‐Al₂O₃ is found to be similar to the bulk, forming deep potential wells to sharpen transmission curves. This work can be easily extended to other materials, which may enable resonant tunneling in various nanosystems for diverse purposes.     

可调谐激光痕量气体检测中的数字滤波技术的优选

为改善可调谐二极管激光吸收光谱(TDLAS)系统的检测性能,以浓度为50×10-6和17×10-6的H2S气体检测为例,根据TDLAS系统的噪声特征,选择了4种数字滤波技术并利用Visual C++软件分别编写了程序对二次谐波原始信号进行压噪和有效信号的提取。结果表明,采用非线性最小二乘法与数字平均滤波技术相结合,使系统理论检测极限由原来的30×10-6提高到了5×10-6量级;对于反演后气体的浓度信号则采用Kalman滤波进行再去噪,使信噪比提高了近8倍。比较结果表明,经过上述滤波处理,TDLAS系统的信噪比和检测极限性能有明显改善。本文的上述方法实际应用到我们的TDLAS在线工业排放气体的测量系统中,取得了良好的效果。     

Gas Sensing of NiO‐SCCNT Core–Shell Heterostructures: Optimization by Radial Modulation of the Hole‐Accumulation Layer

Hierarchical core–shell (C–S) heterostructures composed of a NiO shell deposited onto stacked‐cup carbon nanotubes (SCCNTs) are synthesized by atomic layer deposition (ALD). A film of NiO particles (0.80–21.8 nm in thickness) is uniformly deposited onto the inner and outer walls of the SCCNTs. The electrical resistance of the samples is found to increase of many orders of magnitude with the increasing of the NiO thickness. The response of NiO–SCCNT sensors toward low concentrations of acetone and ethanol at 200 °C is studied. The sensing mechanism is based on the modulation of the hole‐accumulation region in the NiO shell layer upon chemisorption of the reducing gas molecules. The electrical conduction mechanism is further studied by the incorporation of an Al₂O₃ dielectric layer at NiO and SCCNT interfaces. The investigations on NiO–Al₂O₃–SCCNT, Al₂O₃–SCCNT, and NiO–SCCNT coaxial heterostructures reveal that the sensing mechanism is strictly related to the NiO shell layer. The remarkable performance of the NiO–SCCNT sensors toward acetone and ethanol benefits from the conformal coating by ALD, large surface area of the SCCNTs, and the optimized p‐NiO shell layer thickness followed by the radial modulation of the space‐charge region.