窄线宽准分子激光腔内棱镜扩束器的优化设计

棱镜扩束器(PBE)广泛用在准分子激光腔内光谱压窄系统中,可以有效降低光束发散角和系统内能量密度。为了实现窄线宽激光输出并降低腔内损耗,需要对棱镜扩束器的棱镜个数、单棱镜扩束倍数和棱镜顶角进行优化设计。根据棱镜扩束倍数的理论,数值分析了入射角、顶角和出射角对棱镜扩束倍数的影响,并在实验上很好地验证了扩束倍数与入射角的关系。此外,推导了激光器线宽压窄系统实现一定激光线宽输出所需的总棱镜扩束倍数。优化设计了扩束倍数M为13.3的氟化钙消色散棱镜扩束器,在此基础上,实现了0.915pm的窄线宽ArF激光输出,实验结果与理论设计吻合。     

Pulsed Laser Deposition of Ba0.6Sr0.4TiO3 Thin Films and Their Optical Properties

ABSTRACT

Barium strontium titanate [Ba_0.6Sr_0.4TiO₃ or BST (60/40)] thin films were deposited on MgO (100) substrates using pulsed laser deposition. X-ray diffraction (XRD) measurements revealed that the BST thin films had epitaxially grown on the MgO (100) substrates. The surface morphology of the thin films was observed using an atomic force microscope and the grain size was found to be about 100–150 nm. The surface roughness was around 4.9 nm for a 250 nm thick film. The optical transmittance of the BST thin film was measured using a transmission mode ellipsometer. The BST/MgO configuration was highly transparent in the visible region. The optical band gap energy of the BST film, calculated by applying the Tauc relation, was 3.56 eV. Optical waveguide characteristics of the BST (60/40) thin film were determined using a prism coupler. The electro-optic (E-O) properties were measured at 632.8 nm wavelength using a phase modulation detection method. The BST film exhibited a predominately quadratic E-O behavior and the quadratic E-O coefficient was found to be 0.58 × 10^{? 17} m²/V².     

热处理对共聚氟化聚酰亚胺薄膜折射率的影响

研究了高温热处理对4,4′-六氟亚异丙基-邻苯二甲酸酐(6FDA)/均苯四甲酸二酐(PMDA)-4,4′-二氨基二苯醚(ODA)共聚氟化聚酰亚胺折射率的影响。随热处理温度升高,在完成亚胺化后,共聚氟化聚酰亚胺薄膜折射率的变化趋势取决于柔性链段/刚性链段(6FDA/PMDA)比例,刚性链段多,折射率随固化温度升高而增加,反之,折射率随固化温度升高而减小,即可以通过调节柔性链段/刚性链段比例实现热处理折射率的恒定。此外,只有当完成亚胺化且最高热处理温度相同时,共聚氟化聚酰亚胺折射率与含氟量才呈严格的线性关系。     

角度误差影响运动角锥棱镜反射特性的理论分析

角度误差对运动角锥棱镜反射特性有何影响,国内未见报导。本文根据矩阵光学理论证明了,角度制造误差将引起运动角锥棱镜反射光束空间方位的随机改变,但其改变属于高阶小量。这个结论对于将角锥棱镜作为He-Ne激光频率分裂位移传感器动镜使用,具有指导意义。     

恒偏向棱镜的光线变换矩阵和传输特性分析

恒偏向棱镜是指能恒定改变光束传输方向的转向元件。本文分析了恒偏向棱镜,导出了它的光线变换矩阵及失调矩阵,进一步导出了棱镜存在制造公差情况下的变换矩阵,并指出它只是二维失调不灵敏元件。最后分析了它对一般离轴像离散高斯光束的传输变换特性,给出了复曲率和离轴参数的张量变换规律。     

外差干涉仪中光路调整的分析

分析了共光路外差干涉仪光路中几个组成元件的调整方法 ,包括入射光位置的调整、渥拉斯顿棱镜位置的调整、被测表面位置的调整等。     

新式CT型索结构的研究

ＣＴ型（Ｃｏｍｐｒｅｓｓｉｏｎ－Ｔｅｎｓｅｇｒｉｔｙ）索结构（简称ＣＴ结构）是在研究了张拉整体（Ｔｅｎｓｅｇｒｉｔｙ）结构（简称Ｔ结构）优缺点的基础上开发的一种新型索结构。它保留了Ｔ结构的优点,结构效率高于Ｔ结构,材料用量低于Ｔ结构,节点构造易实现,施工方法简单,屋面系统选型范围宽,造价较低。此结构属线性时不变系统。力学分析和结构设计较方便,是一种值得推广的结构形式。     

Precise measurements of the dispersion of the index of refraction for Cd1−xZnxTe alloys

By using a prism coupler technique in conjunction with reflectivity measurements, we have obtained highly accurate relations for the dispersion of the indices of refraction n for a series of MBE-grown Cd_1−xZn_xTe alloys. Initially, the prism coupler technique was used to determine n at discrete wavelengths with an accuracy of at least 0.1%, and also to concurrently determine the epilayer thicknesses with an uncertainty of less than 0.5%. Having obtained precise values for both n (at discrete wavelengths) and the thicknesses of the Cd_1−xZn_xTe epilayers, we were then able to correctly decipher the values for n at the maxima and minima of the reflectivity spectra observed on the above epilayers, and thereby generate a continuous variation of the indices of refraction as a function of wavelength. Fitting the dispersion of n in each alloy to a Sellmeier-type dispersion relation, we have obtained the dependence of the constants appearing in this relation on the alloy concentration. This enables one to predict n not only as a function of wavelength, but also as a function of alloy composition.     

Converting a tetrahedral mesh to a prism–tetrahedral hybrid mesh for FEM accuracy and efficiency

This paper presents a computational method for converting a tetrahedral mesh to a prism–tetrahedral hybrid mesh for improved solution accuracy and computational efficiency of finite element analysis. The proposed method performs this conversion by inserting layers of prism elements and deleting tetrahedral elements in sweepable sub‐domains, in which cross‐sections remain topologically identical and geometrically similar along a certain sweeping path. The total number of finite elements is reduced because roughly three tetrahedral elements are converted to one prism element. The solution accuracy of the finite element analysis improves since a prism element yields a more accurate solution than a tetrahedral element due to the presence of higher‐order terms in the shape function. Only previously known method for creating such a prism–tetrahedral hybrid mesh was to manually decompose a target volume into sweepable and non‐sweepable sub‐volumes and mesh each of the sub‐volumes separately. Unlike the previous method, the proposed method starts from a cross‐section of a tetrahedral mesh and replaces the tetrahedral elements with layers of prism elements until prescribed quality criteria can no longer be satisfied. A series of computational fluid dynamics simulations and structural analyses have been conducted, and the results verified a better performance of prism–tetrahedral hybrid mesh. Copyright © 2009 John Wiley & Sons, Ltd.     

定向棱镜改善Cr4+:YAG调Q输出稳定性的研究

为了改善Cr4+:YAG被动调Q激光器的输出稳定性,采用了定向棱镜谐振腔,通过实验得到了以下结果:单脉冲能量稳定度由7.3%提高到2.2%,脉宽稳定度由13.5%提高到6.5%,频率精度由0.01%提高到0.005%,输出脉冲波形稳定光滑。研究表明,采用定向棱镜谐振腔技术的Cr4+:YAG被动调Q激光器的输出稳定性较原平平腔激光器得到了显著改善。另外还报道了定向棱镜谐振腔技术消除Cr4+:YAG被动调Q激光器子脉冲的现象。