Vortex lattice generation using interferometric techniques based on lateral shearing

Interferometric techniques that use lateral shearing for generation of a regular network of optical vortices are reported. These techniques are simple, robust, and less sensitive to vibrations compared to the existing interferometric methods of vortex lattice generation. Vortex lattice is created using three-wave interference of plane as well as spherical waves. Theory of vortex lattice formation using phasor approach is provided. The location of vortices in the interference field is described in terms of spatial frequencies of the interfering waves. The presence of the vortices in the interference field is confirmed experimentally by producing fork fringes, as vortex signatures. Results of simulation studies are presented to support experimentally recorded interferograms.     

An interferometer based on the Talbot effect

The moiré effect is very sensitive in detecting small differences between two similar gratings. These differences might be caused by an object with phase gradient placed between the two gratings. The performance of such an instrument can be understood in terms of the “Talbot effect” (also called “Fourier imaging” or “self-imaging”). Slight modifications provide shearing interferences and the second derivative of the object.     

Multiple interaction bandstop filters based on the Talbot effect

We report on two tunable, bandstop spatial filters, which are based on the Talbot effect. The light interacts with more than two gratings, arranged in series. The techniques may be considered as the analogues of the Fabry-Perot interferometer and the Lyot-Öhman filter, respectively. Some experimental results are included.     

Solitonic all-optical switch based on the fractional Talbot effect

A periodic pattern of hundreds of beams is shifted by half its transverse period as the result of excitation of parametric spatial solitons and the fractional Talbot effect. The all-optical switch that is obtained operates with 1-ps pulses.     

基于X射线塔尔博特效应的纳米光栅制作模拟研究

沿纳米多层膜生长方向切割可制成周期只有几纳米而厚度几十微米的切片多层膜光栅. 基于该切片多层膜光栅塔尔博特自成像效应的X射线光刻是一种新型的纳米图样制作方法. 已有学者用该方法完成了百纳米结构光栅的制作. 采用严格耦合波方法, 本文模拟计算了切片多层膜光栅在满足塔尔博特自成像条件下的后表面光场分布, 详细讨论三个影响光栅后表面成像质量的重要参数:光栅厚度、材料厚度所占比例和多层膜周期. 模拟结果表明, 光栅厚度不仅影响X射线透射率, 还会改变像面条纹衬比度. 材料厚度比的大小直接决定像面是否存在清晰条纹, 选取合适的材料厚度比, 得到了前人实验中近场反常成像现象. 计算还表明, 在一定条件下, 采用周期更小的多层膜光栅有望获得更高分辨率的纳米图形, 这说明使用塔尔博特效应制作更加精细的纳米结构图形具有可行性.     

Near-field hexagonal array illumination based on fractional Talbot effect

Hexagonal array is a basic structure widely exists in nature and adopted by optoelectronic device. A phase plate based on the fractional Talbot effect that converts a single expanded laser beam into a regular hexagonal array of uniformly illuminated apertures with virtually 100% efficiency is presented. The uniform hexagonal array illumination with a fill factor of 1/12 is demonstrated by the computer simulation.     

Generation of optical vortex array based on the fractional Talbot effect

A phase-only diffractive optical element (DOE) for generating array of optical vortices with high compression ratio is presented. Since it is designed according to the fractional Talbot effect, we name the DOE optical vortex Talbot array illuminator (OVTAI). As an example, an OVTAI for generating a hexagonal array of optical vortices is designed, and demonstrated through displaying the OVTAI on a programmable liquid crystal spatial light modulator. The diffraction properties of the vortex array generated by the OVTAI are observed and analyzed, and an optimal distance for generating sharp ringed vortex arrays is given.     

High-efficiency spatial color separation method based on fractional Talbot effect

Based on fractional Talbot effect, Talbot grating is adopted to realize spatial color separation with high light efficiency. For red and green colors, a two-step Talbot grating is optimized and the light efficiency reaches over 95%. The two-step Talbot grating is fabricated and tested. Experimental results show that the Talbot grating indeed has the good ability of spatial color separation.     

基于分数泰伯效应的激光损伤阈值测量

 介绍了一种基于分数泰伯效应的单脉冲激光损伤阈值测量方法。该方法是根据六角相位光栅的分数泰伯效应,将激光光束整形成许多不同能量密度的高斯形状光斑,通过比较光斑分布图和损伤分布图即可统计计算得到各个能量密度区间的损伤概率。根据角谱传输理论数值模拟得到了六角相位光栅的分数泰伯像并得到实验验证。用该方法和传统的1on1测得HfO₂/SiO₂高反介质膜的激光零损伤阈值分别为7.9和8.0 J/cm²,并进行了误差分析。     

基于塔尔博特效应测量液体中的声速

通过移动凸透镜的纵向位置来调整像面上自成像级次,测得相邻2次自成像时凸透镜的距离,确定液体中的超声波长,再经计算给出声速,从而将类塔尔博特效应用于液体中声速的测量.给出了基于类塔尔博特效应的超声光栅测声速实验设计与验证,拓展了自成像技术的应用范围.     

Wavefront sensor using the Talbot effect

A method for measuring optical wavefronts is proposed by properly sampling the light amplitude distribution with a two-dimensional periodic mask. At the Talbot planes, where a reference wavefront (spherical or plane) would originate replicas of the aperture, distortions of the resulting selfimages take place. These intensity patterns are detected and processed for obtaining the required wavefront information. The approach is illustrated with some experimental results.     

Talbot effect with Cantor transmittances

We show the Talbot effect for Cantor transmittances, which are obtained as a product superposition of periodic components. The self-images for each periodic component can be superimposed with the self-images or the optical noise corresponding to the remaining components. Due to the integer scaling factor among periodic components, there are also self-images positions for the complete fractal structure.     

Talbot效应的空间方法

对于照明光束方向与物光栅平面法线方向呈任意角度的情况作了研究。证明了Talbot像平面与物光栅平面平行。还给出了特殊情况下的Talbot像强度的分布。     

Talbot effect in cylindrical waveguides

We extend the theory of Talbot revivals for planar or rectangular geometry to the case of cylindrical waveguides. We derive a list of conditions that are necessary to obtain revivals in cylindrical geometry. A phase space approach based on the Wigner and the Kirkwood-Rihaczek functions provides a pictorial representation of interference phenomena that lead to the Talbot effect.     

Influence of the size of the grating on Talbot effect

The Fresnel theory of the Talbot effect of the grating is reviewed in this paper, and the general formula of the Fresnel diffraction of the grating with finite aperture size is presented. The aperture effect of the grating on the Talbot image is discussed and a number of numerical calculations are performed. The variation rule of the diffraction intensity distribution at the Talbot distance with the aperture size of the grating and the case at different Talbot distances are obtained through the calculations, and the corresponding explanations of these phenomena are given in this paper. We think that these discussions provide the theoretic basis for the practical application of the Talbot effect of the actual grating.     

High-efficiency color separation method based on fractional Talbot effect for color liquid crystal display

Based on the fractional Talbot effect of Talbot grating, a new method with high light efficiency for color separation in color liquid crystal displays (LCDs) is proposed. The light efficiency of 85% and 89% are obtained by three- and four-step Talbot gratings, respectively, which are rather higher than that of using color filter, the traditional color separation method in color LCDs. This method has large tolerance to the position error of the color separation plane, the wavelength changes of red, green and blue colors, and the step height errors of the gratings.     

Pulse loading ~(87)Rb Bose-Einstein condensation in optical lattice:the Kapitza-Dirac scattering and temporal matter-wave-dispersion Talbot effect

<正>We study ~(87)Rb Bose-Einstein condensation(BEC) loading into the pulse of the one-dimensional(1D) optical lattice experimentally.The lattice is turned on abruptly,held constant for a variable time,and then turned off abruptly.The measurement of the depth of the optical lattice is obtained by Kapitza-Dirac scattering.The temporal matter-wave-dispersion Talbot effect with ~(87)Rb BEC is observed by applying a pair of pulsed standing waves(as pulsed phase gratings) with the separation of a variable delay.     

Transform spectrometer based on measuring the periodicity of Talbot self-images

We demonstrate a compact transform spectrometer based on measuring the periodicity of Talbot self-images. The system has no moving parts; it contains only a tilted absorption grating that is imaged onto a CCD camera. The linear architecture of the system makes it possible to use this design in imaging arrays of spectrometers. Unlike other transform spectrometers, its resolution is independent of wavelength.     

Observation of the Talbot effect for ultrasonic waves

The diffraction of ultrasonic radiation on an amplitude diffraction grating in the near-field area (Fresnel diffraction) has been studied. The effect of self-imaging of the grating (Talbot effect) has been detected for ultrasonic radiation at distances from the grating in the range from z = 0 to z = 2L _T, where L _T is the Talbot length. The fractional Talbot effect, i.e., the ultrasonic image of the grating with the period d/2, has been observed.