Spatial Temporal Analysis of Electrically-Addressable Phase-Only Spatial Light Modulator

An optically addressed parallel-aligned nematic-liquid-crystal spatial light modulator (PAL-SLM) has been studied as a dynamic phase-only modulation device. A computer control feature of the spatial light modulator is strongly desired for practical applications. For those demands, an electrically-addressable phase-only spatial light modulator has been developed to combine a liquid crystal display (LCD) with a PAL-SLM (LCD-coupled PAL-SLM) and its performance has been reported. However, a temporal characteristic especially two-dimensional (2D) response has not been discussed before. In this paper, 2D response analysis system has been constructed by using a high-speed complementary Metal-Oxide-Semiconductor (CMOS) camera (1000 frames/sec) and the 2D-modulation characteristic of the LCD-coupled PAL-SLM has been observed. As a result, the LCD has a spatially non-uniform modulation characteristic due to a scanning addressing. It has the potential to cause problems in high speed switching for a computer generated hologram. On the other hand, the spatial non-uniformity has not been observed with the LCD-coupled PAL-SLM.     

在光学相关器中测试滤波空间光调制器的相位调制特性

研究了在范德卢格特型光电混合相关器中,利用朗奇光栅图像替代实物光栅测试滤波空间光调制器相位调制特性的原理和方法.对XGA2L11型空间光调制器的相位调制特性进行了现场测试,并对测试结果进行了误差分析和光学相关实验验证.结果表明,该方法不需要单独构建测量装置而是完全在相关器的工作状态下测试,保证了空间光调制器的特性测试结果和实际工作性能的一致性.     

空间光强自动测试装置的研究

通过对灯具空间光强测试方法的研究，提出了一种空间光强测试新方法。建立了灯具空间光强自动对中的数据模型，介绍了空间光强自动测试装置的组成和测试原理。借助二维扫描系统和专用测试软件绘制出空间光强的三维图形，从而可快速求出灯具x和y轴的光强分布曲线以及发散角，故而可获得所需的测试信息，并可通过全过程测试得到更加丰富的测试信息及测试报告。最后给出将一投影灯置于离探测器5m处的测试结果，按文中所述测试原理测得的峰值光强为2634.4cd，发散角为15.25°。     

Statistical similarity and cross-spectral purity of stationary stochastic fields

In practical situations, one often generates a beam by superposition of two or more light beams. The beam generated by superposition displays, in general, different spectral properties than do the original beams. However, there are some optical beams, called cross-spectrally pure beams, which can generate a light beam of identical spectral distribution on superposition. The relationship between cross-spectral purity and spatial coherence has been the subject of investigations for some time. Recently, a concept of so-called statistical similarity has been introduced which provides a new way to elucidate complete spatial coherence. In this Letter, we discuss some implications of statistical similarity of an optical field on its cross-spectral purity.     

The coherency of synchrotron radiation at Pohang Accelerator Laboratory

The coherency of the synchrotron radiation at Pohang Accelerator Laboratory has been investigated using Young's interferometer. The electron beam size can be measured precisely using the interferometer. An interferogram using 650 nm light at the diagnostics beamline at Pohang Light Source (PLS) has been measured to determine the electron beam distribution and the spatial coherence length. Interferograms obtained by numerical study are compared with experimental results in order to understand the measured data. From this comparison, the electron beam at PLS is revealed to be a Gaussian distribution with a standard deviation of 210 µm. The spatial coherency length of 650 nm light at PLS is measured to be 0.57 cm, and that of 0.1 nm light at PLS is predicted to be 0.88 µm by the same numerical study.     

Bistable properties of spatial light modulator with internal feedback

A bistable spatial optical device has been developed on the basis of a spatial light modulator which contains photosensitive and electrooptical liquid crystal layers, where an internal feedback loop is established.     

Multistability in optical transmittance of spatial light modulators with internal feedback

A multistable spatial optical device has been developed on the basis of a spatial light modulator which contains photosensitive and electrooptical liquid crystal layers where an internal feedback loop is established.     

随机激光器中准态腔的阈值与其局域化程度的关系

基于光波在有限随机介质中的局域化理论，利用有限时域差分法数值求解Maxwell方程 组，研究了随机介质中的激光现象，分析了准态模的放大与其 空间局域性的关系. 通过研究二维非增益随机介质中光波的局域化，确定了准态模的空间分 布和频谱特征. 通过引入增益，研究了准态模的放大过程和阈值特性. 结果表明空间局域化 强的准态模在增益介质中被优先放大，且有较低的阈值. 关键词： 随机激光器 准态模 随机介质中的光学特性     

二维机械准直器准直光束的衍射

把入射光作为从不同方向入射的空间光,应用傅里叶光学的方法分析了通过机械准直器中一组不同间距的栅格挡光片的物理过程。建立了准直光束的理论计算公式,给出了采用数值方法精确计算准直光束的主要步骤和计算中应注意的问题,计算了空间频率分布。对于从各方向入射的光辐射,证明了机械准直器的准直性能,对于平行光入射,计算了通过机械准直器的光辐射衍射,衍射超出了准直器的几何阴影区,得到了准直光束空间频率的二维分布图形。与国外一维的方法相比,该方法更准确、快捷,计算结果与实验数据比较,更接近实验结果。     

反射式液晶光阀用于激光束空间整形可行性研究

 从理论和实验两方面对一种反射式液晶光阀（LCOS）的调制特性进行了研究。着重研究了在高功率激光系统中,反射式液晶光阀作为空间整形器件面临的一些应用问题,特别是它的各种调制特性、整形能力以及对于光束质量的影响。研究发现,与透射式液晶光阀相比,反射式液晶光阀有着明显的优势,效率达到42%,远远优于透射式液晶光阀10%的效率,从而能够实现系统的大幅度简化,是一种非常有潜力的空间光调制器件。     

Interference of additional modes in spectra of opal-like photonic crystals in the multiple diffraction regime

The mechanisms of formation of Bragg reflectance and transmittance spectra have been investigated for films of three-dimensional opal-like photonic crystals. Attention has been drawn to the fact that the spectra exhibit an additional short-period interference structure of the novel type due to the multiple Bragg diffraction of light. The spectra have been calculated in the framework of the dynamical three-wave diffraction model taking into account strong spatial modulation of the dielectric function. It has been found that short-period oscillations appear in the spectra due to the spatial quantization of additional modes with a low group velocity.     

Hypothesis of the spatial adjustment of optical inhomogeneities of water and its confirmation through experiments on measurements of light scattering

To explain the features of the scattering and propagation of light in liquid water, a hypothesis of the spatial adjustment of global optical inhomogeneities of water has been proposed. An analytical expression for the intensity of light singly scattered on randomly distributed clusters filling the entire water bulk has been obtained in the Rayleigh-Gans approximation. It has been shown that theoretical estimates are in good agreement with the experimental data on the volume scattering function in pure filtered water.     

Study of modulation instability in a temporally incoherent photorefractive ring resonator below the threshold with incoherent light

Modulation instability (MI) and evolution of pattern formation inside a passive non-linear photorefractive ring resonator having cavity-length longer than the coherence length of the light circulating in the resonating cavity has been theoretically analyzed. Dynamics of the system below the threshold conditions have also been analyzed, numerically using linear perturbation theory for the Kerr-type non-linearity. The process of modulation instability in a temporally incoherent cavity below the cavity threshold and the influence of various parameters such as the cavity-length, intensity feedback of the perturbed wave field, amplitude of the incoming beam and spatial frequency on the gain factor and the spatial spectral density have also been studied. For the perturbed wave field, it has been found that the growth rate of MI increases with increase in the intensity feedback as well as the spatial frequency. It has also been found that increasing the intensity feedback of the perturbed wave field, for a given value of the spatial frequency, the spatial spectral density of the perturbation at the output of the non-linear medium increases with the shifting peak positions to the higher spatial frequency side.     

Phase-shift interferometry combined with surface plasmon resonance effect for two-dimensional bio-surface analysis

The phase-shift interferometry combined with surface plasmon resonance (SPR) effect has been studied as a novel technique used to analyze the bio-surface, which measures the spatial phase variation of SPR reflected light. The spatial sensitivity of the SPR imaging sensor is improved over the conventional SPR imaging systems based on optical intensity.     

Non-steady-state photoelectromotive force in SiC crystals irradiated by reactor neutrons

The effect of the non-steady-state photoelectromotive force in 6H-SiC crystals irradiated by reactor neutrons has been investigated experimentally. The dependences of the signal amplitude on the phase modulation frequency, spatial frequency, light intensity, and amplitude of an external alternating-current (ac) electric field have been analyzed. The unusual frequency dependence of the signal has been explained in terms of the two-level semiconductor model taking into account shallow traps. The photoelectric parameters of the crystals have been determined for the light wavelength λ = 532 nm.     

液晶电视空间光调制器对比度的研究

本文分析了影响液晶显示屏对比度的种种因素,根据偏振光在液晶中传输的性质,提出了一种有效改进液晶电视空间光调制器对比度的新方法。通过实验得到了液晶电视最佳对比度的条件,从而使原来4∶1的最佳对比度提高到19∶1。     

Modulation transfer function of a liquid crystal spatial light modulator

The modulation transfer function (MTF) of a pixelated liquid crystal spatial light modulator (LC-SLM) has been derived as a function of the fill factor. Based on the formula, we have investigated the dependence of the MTF on the orientations and spatial frequency of the input patterns. Furthermore, we have proposed and demonstrated a method for improving the MTF of a LC-SLM.     

飞秒脉冲展宽器的设计

以群速度色散展宽脉冲理论和基尔霍夫－菲涅耳积分为基础，合理地设计了一种紧凑有效的飞秒脉冲展宽器，不仅获得了较大的脉冲展宽比，而且光束通过展宽器后其空间特性也得到恢复。     

KrF准分子激光空间相干性测量

设计制作了一套反转剪切干涉仪,测量了ＫｒＦ准分子激光的空间相干性。用这种方法能够一次测量激光的空间相干度,并且在不同条纹相机的条件下能够实时测量相干度随时间的变化过程,在有注入、无注入锁定及百非稳腔中经过不同路程条件下对激光的空间相干性进行测量,并且和利用变换矩阵分析了相干度在非稳腔中的传播及其演变过程,计算了激光在不同往返次数的相干带宽度。     

Influence of operating conditions and interface properties on dynamic characteristics of liquid-crystal spatial light modulators

The effects of both varying the alignment films and the operating conditions on the dynamic characteristics of liquid-crystal spatial light modulators (LC-SLMs) have been investigated. The optimum operating conditions of LC-SLMs have been determined, and a proper choice of alignment films has been made. To interpret the high speed obtained for polyimide systems retaining their high resolution, a simulation of speed enhancement has been proposed.