二步法大景深反射全息图

以开拓反射全息图的景深表达能力为目的,从反射全息图的共轭物像关系出发,利用反射全息图的均匀介质耦合波理论和布拉格条件,对其白光再现像模糊作了具体的分析和讨论,得到色模糊和线模糊的表达式.指出反射全息图上不同各点对任意白光再现像点的色模糊和线迷糊的影响均存在差异,给出反射全息图白光再现像的景深表达式.实验利用二步法制作了一张景深为83 cm的反射全息图,与大景深彩虹全息图再现像相比,其再现像的立体感更加强烈.理论分析和实验结果表明,光源的再现角度和观察距离对反射全息图的再现像景深大小影响显著.在再现光垂直于反射全息图平面照明情况下,反射全息图具有最好的景深表达能力.     

利用光致聚合物的真彩色反射全息图

本文用Ar~+-Kr~+激光器的红光(647.1nm)、绿光(574.5nm)和蓝光(488.0nm)分别对准全色的光致聚合物干板制作反射光栅,给出各个反射光栅的光谱透射率曲线,由此可得最小透射率随曝光量、再现波长随曝光量变化的情况.并采用Ar~+-Kr~+激光器全谱线输出和减色滤光片一次曝光成功地拍摄了真彩色反射全息图.本文还讨论了彩色反射全息图再现像的色度坐标和彩色控制.     

银盐干板的皱缩控制及其在彩色反射全息上的应用

分析了影响全息干板银盐乳胶在处理过程中收缩的几个因素，并通过实验，找出了在拍摄及处理体积反射全息图过程中，曝光量、漂白液温度及脱水的方式对乳胶收缩影响的规律.在此基础上提出控制乳胶的收缩，即控制反射全息图衍射波长的方法，从而达到彩色反射全息图的实现.实验结果表明该方法做出的全息图效果良好.     

拍摄白光再现全息图的一种实验方法

白光再现全息图的干涉极大值在感光介质中的分布几乎平行于乳胶表面,间距约为半个波长(在氦氖激光器波长为632.8nm的条件下,间距d约为0.3μm)。因此要求记录介质有较高的分辨率,而且要求形成反射全息图的全息实验台和有关的光学元件有极高的机械稳定性。教学用简易全息实验台常达不到要求,因此很难拍摄成功白光再现全息图。为了提高学生对于全息实验的兴趣,我们找到了一种在简易全息实验台上拍摄成功白光再现全息图的方法。现介绍如下。用一个书写投影仪上的反光装置,将其     

单色CCD记录多波长数字全息图及再现像彩色显示

对多波长数字全息图的记录和再现像的彩色显示问题进行了研究.从菲涅耳近似算法出发,对在记录距离一定情况下,不同波长全息图数字再现像的像元所表示的几何尺寸会因波长不同而不同,从而导致各波长再现像无法重合的情况进行了讨论.通过理论分析,讨论了不同波长全息图像素数与再现像像元之间的关系、不同波长全息图记录距离与再现像像元之间的关系,据此得出的解决不同波长再现像重合问题的方法及其对再现像的影响和适用范围等问题；并对合成再现像中原始色彩信息改变及其解决办法进行了分析.通过无透镜傅里叶变换数字全息方法,以632.8 nm和532.0 nm两种波长的激光为光源,用单色CCD进行记录,验证了方法的可行性.     

激光全息照相实验探讨

1962年由杰尼休克提出的反射全息图的制法至今还是实验教学的一个内容。本文介绍对干版仅仅曝光一次的条件下,将白光反射再现全息图和激光透射再现全息图同时记录于同一干版上的实验。由此得到的全息照片不仅可在白光下再现。而且可在激光下再现,且两次再现的像既可相同也可不同。图1为实验光路图。如将图中物Ⅱ去掉,该图即变成记录激光透射再现全息图的光路;而将物     

无透镜傅里叶变换全息图数值再现中的图像处理

针对无透镜傅里叶变换全息图数值再现过程的特点，提出了一套不同于以往的削弱或消除全息图0级衍射和孪生像的数字图像处理算法。该算法分为三步。首先，对所拍摄的数字全息图通过高通滤波实现衬比度增强预处理，以提高全息图的衍射效率并消除再现图像的0级衍射斑；其次，对再现图像进行带通及Ⅴ型滤波，以降低背景噪声并使再现视场均匀；最后，对所得到的再现像进行平滑处理，通过小波滤噪和中值滤波进一步提高再现像的信噪比。实验结果表明，该方法只需记录一幅数字全息图，通过简单的数字图像处理，便可明显改善图像质量，尤其适用于无透镜傅里叶变换全息图的数值再现，并且更加实用化。     

共轭读出法消除光致变色材料全息记录中的相位畸变

采用有机光致变色材料-吲哚俘精酰胺/PMMA薄膜作为可擦写全息记录介质,建立了一种能消除全息光存储中相位畸变的光路.此光路采用参考光的相位共轭光再现全息图,能有效消除物光路中由于光学元件失调和记录材料缺陷引起的相位畸变,是全息光存储中提高再现像像质的一种有用光路.     

用DCG制作彩色反射全息图的研究

本文介绍了采用重铬酸盐明胶制作彩色全息的方法,并对影响彩色全息图的因素进行了研究,通过选择适宜的实验参数、实验条件及显影处理工艺,获得了满意的彩色反射全息图.     

国产KL全色全息干板感光特性研究

为了用国产KL型全色全息干板制作真彩色反射全息图,对KL全息干板的感光特性进行了实验研究.介绍了实验的光路,化学处理方法,三基色的选择.测试了底片单波长记录的感光特性和波长灵敏度,对三基色波长记录的特性进行了实验和分析,结果表明KL全息干板可用于记录真彩色反射全息图.     

用亚甲蓝敏化的重铬酸铵明胶全息图的工艺研究

研究了用亚甲蓝敏化的重铬酸铵明胶（ＭＢＤＣＧ）全息图的工艺，提出了提高脱水温度并将急剧脱水过程改为逐步脱水过程的制作方法，提高了衍射光栅的角度（波长）灵敏度，避免了在制作过程中明胶发生霜现的现象。研究了明胶中重铬酸铵和亚甲蓝的浓度、曝光量和脱水温度对全息图像衍射效率的影响。实验结果能较好地符合由Ｋｏｇｅｌｎｉｋ的耦合波理论导出的理论值。     

Measurement of birefringence in integrated optical waveguides by use of a microwave-modulated optical wave

We present a technique for measuring birefringence (B) in integrated optical waveguides by use of a microwave-modulated optical wave. It is shown that the technique is able to yield an accurate measurement of birefringence. In addition, an approximate estimate of birefringence dispersion (dB/dlambda) can be achieved by means of tuning the wavelength of the light source and measuring the dependence of the birefringence on the wavelength. As an example of the use of the technique, we show how to evaluate an innovative Ti:LiNbO (3) waveguide. The results show that such a Ti:LiNbO (3) waveguide has a birefringence of 0.0783+/-0.0001 and a birefringence dispersion of 0.05+/-0.01mum (-1) when the optical wavelength is approximately 1.560mum .     

Wavelength tunable optical time-domain reflectometry based on wavelength swept fiber laser employing two-dimensional digital micro-mirror array

We demonstrate a cost effective wavelength tunable optical time-domain reflectometry (OTDR) for wavelength division multiplexing passive optical networks (WDM-PON). In order to realize the unique wavelength tunable optical time-domain reflectometry (OTDR), the wavelength swept fiber laser was developed by a digital micro-mirror array device (DMD), and the correlation OTDR (COTDR) technique was used. We successfully detected the fault location at the remote node fibers with 20 m resolution and fast wavelength setting speed of ∼15 μs in conventional band (C-band).     

New technique to record and playback holographic color video memories

A low-cost and simple color-encoding technique for holographic video memories is proposed and designated as a “stripe-coded” method. The playback system requires a laser of a single wavelength, a black-and-white vidicon installed TV camera and a common color TV monitor. One frame can be stored in a hologram of 4-mm diameter, and the storage density is several times higher than that of the conventional TV films. Color images of satisfactory hue and saturation were successfully restored.     

An Advanced Signal Processing Technique Designed for Multilevel Signal Optical Disc System

We propose a novel signal processing technique by which we can increase the effective signal to noise ratio of optical discs. This technique is capable of reducing the influence of random noise even when the playback signal contains a distortion. We apply this signal processing technique to single carrier independent pit edge recording optical disc system. When a linear recording density of 0.2 μm/bit and a track pitch of 0.8 μm for an optical pickup is used in a DVD pickup (γ =635 nm, NA=0.6), the experimental results show that the system can obtain tangential and radial skew margins of ±0.5° and ±0.75°, respectively. From the experimental results, we estimate that the proposed method is capable of increasing the capacity of DVD by a factor of about 1.2.     

A novel all optical method of implementing an n-bit wavelength encoded complete digital data comparator using nonlinear semiconductor optical amplifiers

Data comparator is the integral part of arithmetic and logical unit of any electronic or optical data processor. Due to some inherent limitations of electronics it cannot be possible to obtain a super fast operation (over terahertz limit) from electronic comparators. Again wavelength encoding technique has been established as an excellent one over other existing optical data encoding techniques. Semiconductor optical amplifier (SOA) technologies have shown their strong potentiality of realizing many all-optical systems. In this communication the authors have proposed a new scheme of developing all-optical wavelength encoded n bit binary comparator exploiting the four-wave mixing, wavelength filtering, wavelength conversion and nonlinear polarization rotation capabilities property of nonlinear semiconductor optical amplifiers. The scheme can be used for comparing signed and unsigned optical binary data of any bit wide numbers as well. The comparator is especially suitable for use as a building block in a larger optical circuit, such as in an all optical telecommunications switch.     

Use of state of polarization transparent scheme for polarization shift keying signal as optical phase conjugator to improve the transmission performance

Transmission characteristics of polarization shift keying (PolSK) signal is experimentally demonstrated in this work. Performance degradation due to transmission is improved using optical phase conjugation (OPC) technique. The wavelength converter based on the proposed state of polarization (SOP) transparent scheme for PolSK signal is effective to use it as mid-link optical phase conjugator and which is difficult to achieve using conventional wavelength conversion scheme. It is found that for fiber transmission, the performance of both of the orthogonal SOPs of the PolSK signal is different for their respective chirping characteristics which can be optimized to be similar using proposed OPC technique.     

Wideband tunable wavelength conversion of 10-Gbit/s return-to-zero signals by optical time gating of a highly chirped rectangular supercontinuum light source

We propose a novel technique for wideband tunable wavelength conversion of return-to-zero signals by optical time gating of a supercontinuum (SC) light source. A SC pulse generated by nonlinear propagation in a normal-dispersion fiber has a rectangular shape with highly linear upchirping. By control of the optical time-gating position, the center wavelength of time-gated SC pulse can be precisely tuned. Error-free 10-Gbit/s wavelength conversion with a tuning range of 27.1 nm is experimentally demonstrated.     

基于可调谐滤波器的带中心波长自动跟踪光纤光栅动态波长解调技术的研究

研究了基于可调谐滤波器(TOF)的带中心波长自动跟踪光纤光栅动态波长解调技术。实验表明,解调仪特别适合在传感FBG(fiber Bragg grating)存在大幅度静态波长变化时对微幅度动态波长变化进行检测,动态波长检测分辨率为0.007pm/Hz。上电时,TOF对中心波长为1292.50~1308.50nm范围内的光纤光栅具有自动跟踪的能力,克服了TOF不稳定对系统的影响。     

基于拉曼光谱散射的新型分布式光纤温度传感器及应用

介绍了分布式光纤拉曼温度传感器(DTS)的基本原理、发展趋势和工程应用研究状况,研究了分布式光纤拉曼温度传感器的关键技术,全面提升了DTS的性能。将拉曼放大技术应用于DTS系统,用拉曼增益部分抵偿光纤的传输损耗,使系统的传感长度达到50 km;对脉冲激光器进行211位循环编码,在接收时采用相关运算解调,显著提高系统的信噪比,使测温不确定度达到1 ℃;采用双波长自校正技术提高了系统的空间分辨率,达到2 m;在DTS系统中嵌入光开关,使测温通道成倍扩展,有效延伸了传感光纤的总长度,组成光纤传感网络。