二元纯位相片实现半导体激光器到单模光纤的耦合

采用二元光学位相调制的基本思想，用二元纯位相型光学系统将椭圆高斯型激光束与单模光了佳耦合。采用两块纯 位相片来进行波前变换，将椭圆型高斯激光束转变成对称圆高斯激光束，并与单我纤的基模最佳匹配耦合。     

计算机制全息图改造激光波面和模式

以变换椭圆高斯光束为圆对称高斯光束为例,本文给出了用计算机制全息图作为变换元件改造激光波面和模式的理论和方法.推导出产生计算机制全息图的数学方程.制作出计算机制全息图,并得出了实验结果.     

变间距采样及准梯度下降法实现光束整形

利用输入输出不同的变间距采样通过汉克尔变换实现圆对称纯位相片精密化设计，并发展了准梯度下降法及频谱滤波，改进了原有的混合杂化算法．模拟结果表明，考虑到热传导匀滑之后输出振幅分布顶部调制为1．1％，衍射效率为97．2％。     

应用胞腔理论计算纯物质的汽化热

1引言胞腔模型或称自由体积模型早在本世纪30年代就已经提出［’－‘］，但由于该模型的重要参数，即自由体积一直无法予以确定，以至于就无法用该模型来计算物质的一系列性质、作者曾于1985年利用胞腔型状态方程导出两个物质特性参数一内压因子和构形因子问，本文根据上述状态方程和两个特性参数导出了计算物质的自由体积公式。从此即可应用自由体积参数计算物质的热力学性质。本文是介绍应用自由体积参数计算纯物质的汽化热的方法。2自由体积模型的液体理论和自由体积的计算自由体积理论最早由Lennard－Jones和Devon－shire用来将液体的…     

成像过程的计算机模拟

按照阿贝二次成像理论,物体成像经历了两个过程：（１）物面上光场复振幅的空间分布,变换成光学系统后焦面上的频率分布;（２）后焦面上的频率分布还原成像面上的光场复振幅空间分布。本文介绍了如何用计算模拟这两个过程,设计的空间滤波器可以随意改变频谱分布,并可观察到像面上对应的变化。     

低频位相误差新校正方法模拟研究

 就多程放大系统中产生的低频位相噪声，提出用位相补偿反射镜来进行补偿的静态校正方法。用随机位相屏模拟光学元件产生的低频位相噪声，建立光传输模拟模型，引入等效位相片的概念，将数个光学元件对位相的影响简化为等效位相片，在此基础上对位相补偿反射镜的校正原理进行阐述。进而对双程光路校正过程进行了模拟研究，得到了很好的校正效果。     

多段翼型位流的准确解

本文给出了求解多段翼型位流准确解的一种方法。采用求解拉普拉斯方程把多段翼型绕流区域变换成一个有限矩形域,然后把此矩形域变换成多个圆,从而通过求绕多个圆的准确位流解来求得绕多段翼型位流的准确解。本文提供的方法能广泛应用到任意外形的多段翼型位流计算。采用这种方法计算所得的位流压力分布与用其它方法求得的压力分布非常吻合。     

高功率TE_(01)过模斜接弯头设计

设计并分析了TE01斜接弯头结构,该结构由两段相同且垂直的模式变换段及与模式变换段呈45°斜接的金属镜面组成。整个结构等效于两个模式变换段对接,但中间存在间距为波导直径的缝隙。模式变换段将纯TE01模式转换为TE01和TE02的混合模式,该混合模式在缝隙中传播时电场呈现对称分布,从而降低了模式转换损耗,提高了传输效率。对设计的Ka波段TE01斜接弯头结构的理论仿真和加工实测结果表明:中心频点转换效率在98%以上,在2 GHz带宽内传输效率95%以上,插损小于0.2 dB,驻波小于1.2。     

两平行圆柱的电容、电势和电场

运用复变函数、保角变换等理论，把横截面为两平行圆柱变换成横截面为两平行板，计算出两平行圆柱单位长度的电容、电势和电场强度．     

变换限制脉冲的研究

对增益开关分布反馈半导体激光器（ＧＳ－ＤＦＢ－ＬＤ）加法布里－珀罗共振腔滤波方法产生变换限制脉冲源进行了理论分析，设计出将不同光源变为变换限制脉冲所需的滤波器带宽，并计算出相应的输出脉冲脉宽谱宽，从实验上获得了变换限制脉冲，本文还研究了测谱仪器分辨率对测量结果的影响，导出了一套测量修正理论。     

Hollow Gaussian beam generated by beam shaping with phase-only liquid crystal spatial light modulator

Based on the refractive beam shaping system, the transformation of a quasi-Gaussian beam into a dark hollow Gaussian beam by a phase-only liquid crystal spatial light modulator (LC-SLM) is proposed. According to the energy conservation and constant optical path principle, the phase distribution of the aspheric lens and the phase-only LC-SLM can modulate the wave-front properly to generate the hollow beam. The numerical simulation results indicate that, the dark hollow intensity distribution of the output shaped beam can be maintained well for a certain propagation distance during which the dark region will not decrease whereas the ideal hollow Gaussian beam will do. By designing the phase modulation profile, which loaded into the LC-SLM carefully, the experimental results indicate that the dark hollow intensity distribution of the output shaped beam can be maintained well even at a distance much more than 550 mm from the LC-SLM, which agree with the numerical simulation results.     

用于圆对称光束波前变换的位相型光学系统

由两个位相型衍射光学元件构成的光学变换系统可以实现一般圆对称光束的波前变换。在只需满足菲涅耳衍射近似条件下,采用稳相法与输入输出法相结合,可以设计出具有较高精度的光学变换系统。 关键词：     

Correction to: Generation of amplitude- and phase-modulated signal beam with a phase-only spatial light modulator and its detection by the transport of intensity equation method for holographic data storage

This study evaluates a novel holographic data storage (HDS) that uses a phase-only spatial light modulator (SLM) for the multilevel complex amplitude modulation of a signal beam and the transport of intensity equation (TIE) method to detect the signal beam without interferometry, to increase the capacity of the HDS, simplifying its optical system, and improving the stability of the signal beam modulation and detection. Both the amplitude and phase of the signal beam were modulated by a computer-generated hologram displayed in a phase-only SLM, a 4-f optical system, and a pinhole placed in the Fourier plane. The complex amplitude-modulated signal beam generated by this scheme does not always perfectly match the target complex amplitude, and deviations from the amplitude and phase of the target complex amplitude may exist. It is unclear whether the TIE method, which is sensitive to the state of the beam intensity and the phase distributions to be detected (such as zero-intensity points and phase discontinuities), can accurately detect a signal beam whose complex amplitude is modulated by the modulation scheme with a phase-only SLM. Here, we demonstrate via numerical simulations and experiments that several methods of complex amplitude generation using a phase-only SLM can achieve multilevel modulation of the amplitude and phase of a signal beam and are suitable for detection by the TIE method in HDS.

     

利用纯相位型液晶空间光调制器实现空心光束

为了提高激光系统的整体效率,需要将出射光强整形为空心分布。采用纯相位型液晶空间光调制器整形近高斯分布光强到空心分布。基于能量守恒定律和等光程原理,分析了纯相位型液晶空间光调制器光束整形系统,得出了整形系统所需的相位分布。采用衍射光学方法,数值模拟了整形效果,讨论了入射光束束腰半径和强度分布等因素对整形效果的影响。利用纯相位型液晶空间光调制器实验实现了空心光束,实验测得的转换效率大于99%。     

Wavelength tunable laser beam shaping

Laser beam shaping by phase-only transformations, often referred to as field mapping, has for a long time been considered wavelength dependent. In this Letter we outline a simple mathematical argument that shows how the problem may be formulated in a wavelength tunable manner, requiring only a minor adjustment in the observation plane. We verify the theoretical prediction by experiment using the example of a Gaussian-to-flattop-beam transformation, and we show that the shaping is valid across a wide range of wavelengths for a single diffractive optical element.     

A New Fourier Iterative Algorithm for the Design of Phase－only Diffractive Optical Element Used in Laser Beam Shaping

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基于模拟退火算法的自适应近场光束整形

在激光实际应用中,为了提高系统的利用效率,常常需要将激光器的输出光束整形为特定光强分布光束.基于纯相位液晶空间光调制器的高空间分辨率、实时可编程控制等特性,结合模拟退火算法搭建了一套自适应近场光束整形系统.理论模拟了该系统对于理想高斯光束的近场整形效果,并基于这一闭环系统,对固体激光器输出的近高斯光束进行了近场光束整形...     

非高斯光束的传输

提出一种能处理非高斯非轴对称光束传输的张量方法,引入三个表征任意分布光束的特征张量,运用非对称光学系统的惠更斯衍射积分公式导出了它们的变换规律.讨论了任意光束的质量因子.作为一个实例,分析了高阶厄米-高斯光束通过柱面透镜的变换.     

Intensity control of the focal spot by vectorial beam shaping

A vectorial beam shaping algorithm is presented for the design of a phase-only diffractive optical element to achieve a given target intensity profile in the focal plane under tight focusing conditions. The underlying iterative optimization scheme is based on the Richards-Wolf vectorial diffraction theory and the Gerchberg-Saxton method, and is suitable for an arbitrary incoming polarization distribution, since only the magnitudes of the field vectors in the focal plane are reshaped. The efficiency of the method is numerically demonstrated for flat-top beam shaping examples of linear and circular incoming beam polarizations and square and circular flat-top region shape. A diffraction efficiency of 97.1% and a uniformity error of 4.8% were achieved in the case of focusing a Gaussian input beam onto a 50λ × 50λ square flat-top region with a 1.4-NA lens.     

遗传算法在激光束整形中的应用

采用遗传算法设计了一个8台阶二元光学元件,可用菲涅耳变换系统将高斯光束变换成均匀圆光束,均匀区能量转换效率达到87％,输出波形比较理想。将遗传算法设计的结果同稳相法和输入输出法设计的结果进行比较,发现在同时降低量化台阶数和增大最细线条宽度的条件下,用遗传算法进行设计并制作出的激光束整形元件仍可以得到满意的变换结果。 关键词：