光锥CCD耦合器件对提高CCD成像分辨率的探讨

成像分辨率是评价CCD成像系统的主要技术指标.提高成像分辨率可以改变CCD的成像性能.本论文以实验的方法验证了倒置光锥CCD耦合器件可提高CCD成像分辨率,同时与正置光锥CCD耦合器件实验结果对比,分别绘制了与非耦合器件的对比传递函数(CTF)曲线,直观地表示出了二者关系,与理论分析结果相吻合.     

基于固定频率激光器的低成本闭环谐振陀螺系统仿真

提出了一种使用固定频率窄线宽激光器作为干涉光源的闭环谐振式光纤陀螺系统.该系统利用相位调制器对干涉光进行移频控制,完成对谐振腔逆时针方向谐振频率的跟踪和锁定.建立了陀螺系统Simulink模型并仿真研究了不同速率点下的陀螺输出特性,结果表明,±200(°)/s速率范围内逆时针谐振频率锁定时间小于15 ms,陀螺标度因数非线性为2.41×10-4.与采用传统频率可调谐窄线宽激光器的闭环谐振式光纤陀螺系统相比,两者锁频时间和标度因数非线性基本一致.该研究为低成本闭环谐振式光纤陀螺系统的实现提供了理论和数据支撑.     

利用单光子探测器测量多光子响应时间

通过研究单光子探测器对微弱激光脉冲的暂态响 应特性,利用不同光子数的响应时间实现光 子数的分辨测量。理论上分析了光子数响应时间与微弱光脉冲探测时间的对应关系。实验上 通过测量不同光强下单光子探测器的暂态响应,测量到1550nm波段单光子、 双光子和三光子的响应时间分别为10.73±0.17、8.75±0.32和5.98±0.77ns。实现精确区分微弱光场中的光子数。分析了单光子探测器光子数统计涨落引起的 微弱激光脉冲的探测时间变化对光子数响应时间测量的影响。     

Research on Michelson interference refractive index sensing technique based on double-core microfiber

We propose a novel refractive index sensor based on Michelson interferometer by using double-core microfiber. Through the reflection of the end and taper of double-core fiber (DCF), the Michelson interference spectrum is formed. Owing to the structure characteristic of double-core microfiber, this interferometer can achieve the measurement of refractive index (RI) and temperature. The experimental results show that the refractive index sensitivity of the interferometer is 2 377.80 nm/RIU at the diameter of the taper waist of 8.76 µm. In the temperature ranges from 30 °C to 60 °C, the temperature sensitivity is 0.070 48 nm/°C. This sensor has the advantage of high refractive index sensitivity.     

Optical fiber tapers--A novel approach to self-aligned beam expansion and single-mode hardware

We investigate the performance characteristics of single-mode optical fiber tapers. These devices have a standard single-mode fiber geometry at one end and gradually increase in cross section so that the size of the core at the other end is comparable or greater to that of a multimode fiber. These tapers effectively expand the single-mode spot size and are envisioned as basic building blocks in a multitude of optical components. Analytical and experimental studies, atlambda = 0.63 mum, show that the dominant mode is preserved while traveling through the taper, from either direction. The excess coupling loss between two tapers is less than 0.1 dB. The sensitivity of the excess loss to lateral and axial displacements for two coupled tapered sections is greatly reduced compared to that between two single-mode fibers. The sensitivity to angular displacement is increased but is within practical limits. For example, for an excess loss of 0.5 dB, the maximum allowed lateral displacement is 3.1 μm for taper coupling, while only 0.73 μm is allowed in the case of fiber coupling. An axial displacement of 291 μm for taper coupling produces 0.5 dB loss while a displacement of only 16.5 μm produces a 0.5 dB loss for fiber coupling. For the same loss, angular displacements of 0.42° for the tapers and 1.77° for the fiber are allowed.     

Signal demodulation method for underwater optical wireless communication by measuring the time interval between adjacent photons

We proposed a signal demodulation method by measuring the time interval between adjacent photons and realized the recovery of the original signal from the discrete random pulse sequence output by the single-photon detector. On this basis, a new communication system model is established by comprehensively considering the photon statistical characteristics of the emitted light field, the statistical distribution of adjacent photon time interval and the performance of the detector. Finally, an underwater optical wireless communication (UOWC) system was built. The effects of the average time interval between adjacent photons, baud rate and demodulation threshold in the time-slot on the system bit error rate (BER) were verified by experiments. The experimental results show that when the baud rate is 100 Kbps and the average time interval between adjacent photons is 111 ns, the BER of the system is 2.52?×?10^?5.

     

基于激光测量的高速非接触角度检测技术研究

提出了一种基于光学三角法测距原理的高速非接触光学角度测量方法,利用两个激光位移传感器测量物体具有角度变化时产生的位移,实时计算得到物体一维运动角度,在摇摆台上进行角度范围及精度的实验,并使用光纤陀螺进行角度实时同步测量,通过最小二乘拟合法对误差进行补偿。实验结果表明,该系统的角度测量范围±10°,角度测量精度±0.005°,测量频率2000 Hz。该角度测量技术使用非接触光学测量方法,对被测物体表面无损伤。     

Differential phase shift-quantum key distribution - [ITU-T kaleidoscope]

Quantum-key distribution has been studied as an ultimate method for secure communications, and now it is emerging as a technology that can be deployed in real fiber networks. Here, we present our QKD experiments based on the differential- phase-shift QKD protocol. A DPSQKD system has a simple configuration that is easy to implement with conventional optical communication components, and it is suitable for a high-clock rate system. Moreover, although the DPS-QKD system is implemented with an attenuated laser source, it is inherently secure against strong eavesdropping attacks called photon number-splitting attacks, which pose a serious threat to conventional QKD systems with attenuated laser sources. We also describe three types of single-photon detectors that are suitable for high-speed, long-distance QKD: an up-conversion detector, a superconducting single-photon detector, and a sinusoidally gated InGaAs avalanche photodiode. We present our recordsetting QKD experiments that employed those detectors.     

高透过率、高分辨率纳米微探针的制备

介绍了一种用于近场扫描光学显微镜(SNOM)中的高透过率光纤探针的制作方法。采用氢氟酸腐蚀低掺杂的普通单模石英光纤,选取适当比例的腐蚀液,并通过激光消融的方法得到直径、圆锥角均十分理想、表面光滑的针尖,所获探针直径变化范围为80～200nm,锥度40°～81°,透过率3.5×10-3。     

微型化自由运行InGaAs/InP单光子探测器(特邀)

单光子探测器具有最高的光探测灵敏度,在激光雷达系统中使用单光子探测器可以极大提升系统的综合性能。近红外二区(1.0～1.7μm)激光具有大气透过率高、散射弱、太阳背景辐射弱等优势,是大气遥感、三维成像等激光雷达系统的理想工作波段。研制了一种基于InGaAs/InP负反馈雪崩光电二极管的微型化自由运行单光子探测器。该探测器长宽高为116 mm×107.5 mm×80 mm,在1.5μm最大探测效率超过35%,时间抖动(半高宽)低至80 ps。为满足激光雷达系统对光子飞行时间测量的需求,探测器内部集成时间数字转换(TDC)功能,时间精度100 ps。同时,探测器集成一套后脉冲修正及计数率修正算法,可以有效降低探测器所引起的雷达信号畸变。     

Multiuser square-law detection with applications to fiber optic communications

Optimal and suboptimal multiuser noncoherent detection for square-law receivers is studied in this paper. Great potential is found for the multiuser square-law detector when compared with the conventional single-user square-law detector. We study the optimal detector and two detectors with simpler structures: the asymptotically optimal detector and the pairwise linear detector. The saddle-point approximation method is used to study the error performance and its asymptotic behavior as noise reduces. Due to difficulty in optimizing the detectors at an arbitrary noise level, we propose to use the asymptotic efficiency for detector optimization. For a low-error-rate system like a fiber optic communication system, the asymptotic efficiency is found to be an efficient way to design detectors. Numerical results show that the asymptotically optimized detectors perform as well as the optimal detector, even for nonzero noise levels of practical interest. Despite their exponential complexity, these detectors are applicable to wavelength-division multiplexed systems in which only a few neighboring channels produce strong interference.     

铌酸锂光波导器件保偏尾纤对轴工艺研究

基于采用退火质子交换工艺制备的铌酸锂光波导器件的保偏尾纤具有高偏振消光比这一特性,提出了一种通过偏振消光比测试仪测定器件保偏尾纤的偏振轴并实现与保偏连接头定位键高精度对准的方法.工艺实验证明,采用该方法制作的保偏尾纤连接头偏振轴向对准精度优于0.8°,显著优于显微成像定轴方法制作的保偏尾纤接头.     

空间锥形目标的红外成像仿真

由于应用需求的驱使,红外成像仿真技术越来越受到国际社会的关注,并已成为现代国防科技的关键技术之一。针对深空背景条件下的锥形目标,可利用结点热网络法求解其表面温度分布,然后计算目标与背景的红外辐射,再将探测器接收的辐射照度转化为灰度,并加入探测器自身效应的影响,就可仿真得到锥形目标不同成像状态的图像。此方法完整地实现了空间锥形目标在红外探测器上的成像过程,同时考虑了多种因素的影响,具有很高的真实性与逼真度,可为红外成像系统的研制及目标检测识别算法提供测试场景与依据。     

SLED光源的恒温恒流控制系统研究

采用以单片机为核心的控制电路和PID控制算法,对SLED的温度和驱动电流进行高精度的控制,使工作温度可在0℃～30℃设定范围内稳定到±0.01℃以内,驱动电流在20mA～200mA设定范围内可稳定在±0.02mA以内,满足了光纤传感系统对光源光谱分布和输出功率稳定性的需要。     

Recombination dynamics of single quantum dots in a fiber system at telecommunication wavelengths

Coupling the emitted light from single quantum dots into an optic fiber has been demonstrated as a ‘plug and play’ single-photon source. In this work, lifetime dynamics measurements were performed with two time-delayed femtosecond optical pulses at different wavelengths. When the energy of the pumping light is less than the energy of the wetting layer (i.e. quasi-resonant excitation), the single-photon sources can be operated at a speed of 1 GHz.     

管腐蚀法制作纳米光纤探针

根据优质探针的理论模型,利用管腐蚀法制作了可用于光纤生物传感器的纳米光纤探针,该制作方法操作方便,成本低廉,易于批量生产,且受环境的影响较小,制作的光纤探针具有较高的重复率。所获探针锥径小于50nm,锥角为45°。最后讨论了在管腐蚀实验中不良因素对光纤探针形貌的影响。     

Integration of thin film optoelectronic devices onto micromachinedmovable platforms

The integration of a thin film optoelectronic device onto a micromachined movable platform is reported in this letter. This micro-opto-mechanical system, consisting of a thin film AlGaAs/GaAs double heterostructure p-i-n detector integrated onto a polyimide micromachined platform on silicon, has applications which range from fiber optic coupling to sensors. Fiber optic coupling is demonstrated using a stationary fiber positioned above the thin film detector. By applying a voltage between the platform and actuation strips, the platform moves and a change in fiber to detector coupling is observed     

3×1高效率紫外光纤耦合器的研究

介绍了一种在深紫外波长下工作的特种光纤耦合器,它采用改良的三根光纤一次拉锥成型技术制造,利用旋转的光纤夹具和可移动的火炬获得的低损耗熔融锥区,通过选择不同数值孔径的输入和输出光纤降低熔接损耗。测试结果表明,该方法有助于提高产品的耦合效率,采用芯径为100μm的紫外光纤可以获得大于70%的耦合区传输效率,远高于其他3×1耦合器。     

基于棱镜的激光周视接收系统的设计

为了实现对目标全向探测和精确定位,采用成像光学与非成像光学相结合的方法,设计了一种可用于周视探测的非对称激光回波接收光学系统。由于子午和弧矢两方向视场差异很大,需加入特殊的非对称结构来平衡两方向的视场差异,该系统采用阶梯棱镜和倒置柱面望远镜对弧矢方向大视场进行角度压缩,后经过对称聚焦子系统将光能量收集到直径为1.5mm的圆形探测器上。系统由1块阶梯棱镜、1片非球面镜、2片柱面镜和2片球面镜组成,其光圈数达到0.56。结果表明,单套接收系统完成±30°视场探测,6套接收系统组合起来可实现360°周视无盲点探测。整体系统体积小、结构简单,有良好的适用性。     

基于FPGA马赫－泽德干涉仪的光谱数据采集系统

针对马赫-泽德(M-Z)干涉仪中干涉条纹采集和处理的要求,为了使其具有高速实时光谱数据处理能力,设计了一种通过FPGA硬件编程实现干涉条纹采集处理的方法.系统由CMOS探测器采集马赫-泽德干涉仪获取的干涉图像,再将干涉图像中的灰度信息输入到FPGA芯片中,通过去噪、切趾、快速傅里叶变换、标定等求解入射激光的光谱特征.系...