用布儒斯特角法同时测定单轴晶体的折射率和光轴方向

在理论上分析了光轴任意方向的单轴晶体的折射率．根据布儒斯特角原理,当线偏振光的电场矢量平行于入射面时,通过测出对样品三个表面的布儒斯特角,就能同时确定单轴晶体的折射率和光轴方向．并利用分光计,在光轴不确定的情况下,测定了方解石的两个主折射率和光轴方向．     

Orientation effects on the bandgap and dispersion behavior of 0.91Pb(Zn_1/3Nb_2/3)O₃-0.09PbTiO₃ single crystals

0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO 3(PZN-9%PT) single crystals with different orientations are investigated by using a spectroscopic ellipsometer,and the refractive indices and the extinction coefficients are obtained.The Sellmeier dispersion equations for the refractive indices are obtained by the least square fitting,which can be used to calculate the refractive indices in a low absorption wavelength range.Average Sellmeier oscillator parameters E o,λ o,S o,and E d are calculated by fitting with the single-term oscillator equation,which are related directly to the electronic energy band structure.The optical energy bandgaps are obtained from the absorption coefficient spectra.Our results show that the optical properties of [001] and [111] poled crystals are very similar,but quite different from those of the [011] poled crystal.     

Propagation of partially polarized, partially coherent beams in uniaxial crystals orthogonal to the optical axis

The propagation of partially polarized and partially coherent beams in uniaxial crystals orthogonal to the optical axis is investigated. The analytical formulae for the elements of the cross-spectral density matrix of partially polarized and partially coherent beams propagating through uniaxial crystals orthogonal to the optical are derived. The numerical results show that the degree of polarization decreases with the increase of the ratio of extraordinary to ordinary refractive indices at a certain propagation distance, and the influence of uniaxial crystals on the degree of coherent is not so evident. And the beams spread more rapidly in the direction parallel to the optical axis than orthogonal to the optical axis in positive crystal with the propagation distance increasing.     

Orientation effects on the bandgap and dispersion behavior of 0.91Pb（Zn_（1/3）Nb_（2/3））O_3-0.09PbTiO_3 single crystals

0.91Pb(Zn_1/3Nb_2/3)O₃--0.09PbTiO₃ (PZN--9%PT) single crystals with different orientations are investigated by using a spectroscopic ellipsometer, and the refractive indices and the extinction coefficients are obtained. The Sellmeier dispersion equations for the refractive indices are obtained by the least square fitting, which can be used to calculate the refractive indices in a low absorption wavelength range. Average Sellmeier oscillator parameters E_o, $\lambda$_o, S_o, and E_d are calculated by fitting with the single-term oscillator equation, which are related directly to the electronic energy band structure. The optical energy bandgaps are obtained from the absorption coefficient spectra. Our results show that the optical properties of [001] and [111] poled crystals are very similar, but quite different from those of the [011] poled crystal.     

基于光子晶体马赫-曾德尔干涉仪的太赫兹开关及强度调制器

通过对二维正方晶格光子晶体线缺陷模色散曲线慢光特性的研究, 利用外电场对液晶分子取向的调控作用, 在填充液晶的正方晶格波导的马赫-曾德尔干涉仪结构中实现了开关和强度调制等功能. 利用平面波展开法计算了光子晶体波导的线缺陷模, 分析了液晶折射率的变化对缺陷模的影响. 计算表明, 液晶折射率仅改变了0.1, 线缺陷模有效折射率改变达0.168, 该特性可以更为有效地实现对相位的控制, 进而实现高消光比开关和强度调制功能, 这种高效的相位调节器件在集成光系统中将有很好的应用前景.     

Precise measurement of group refractive indices and temperature dependence of refractive index for Nd-doped yttrium orthovanadate by intracavity spontaneous mode locking

We report on a novel method based on intracavity spontaneous mode locking to precisely measure the group refractive indices and temperature dependence of refractive index of Nd:YVO(4) crystal at the wavelength of 1064 nm. All the experimental results are found to agree very well with the most recent measured values. We also confirm that the developed method is applicable to measuring the group refractive indices and the temperature dependence of the refractive indices of other vanadate crystals, as well as nonlinear crystals.     

Polarimetric method for the determination of the optical axis tilt angle at boundaries of a liquid-crystal layer

A polarimetric method is proposed to determine the tilt angle of the local optical axis of a liquid crystal at layer boundaries. The method is based on the measurement of the azimuthal polarization angles of light waves passed through a liquid-crystal cell or reflected from it. This method requires neither the knowledge of the refractive indices of a liquid crystal nor the homogeneity of the layer. The method can be applied in the whole range of tilt angles. Experimental data on the measurement of the tilt angles in cells assembled by the scheme of a prism liquid-crystal polarizer are presented.     

石英晶体的色散方程及折射率温度系数

研究了石英晶体在不同温度下折射率随波长的变化规律.通过对Sellmeier方程严格求解，得出了其系数表达式，计算出了不同波长对应的折射率，经验证与实验值符合得很好.通过曲线拟合求解出了折射率温度系数表达式，由此式可计算出不同波长折射率温度系数；进一步求解出了Sellmeier方程常量随温度变化地数值，得到求解不同温度任意波长的石英晶体主折射率的一种方法.     

Tunable Dielectric Metasurfaces Based on the Variation of the Refractive Index of the Environment

A dielectric metasurface at the variation of the refractive index of the environment has been numerically simulated. The optical response of the metasurface contacting both a homogeneous medium with different refractive indices and a liquid crystal controlled by the temperature and applied electric field has been considered. The results can be used to produce optical devices for various aims. Numerical simulations have been performed for the parameters of the liquid crystal E7 widely used in industry.     

用光纤白光干涉技术测量晶体的弹光系数

运用折射率椭球分析晶体的弹光效应,给出了三方晶系沿光轴方向的应力与折射率的变化关系.针对晶体的各向异性和折射率随应力变化很小的因素,利用白光干涉技术空间分辨率高的特点,将白光干涉技术拓展到研究各向异性材料的光学性质. 并对测量群折射率的光纤迈克尔逊白光干涉技术进行了改进.采用光栅位移传感器和全保偏光纤提高反射扫描镜的位移准确度.通过测量石英晶体在不同外力下折射率的变化情况,确定了晶体的弹光系数. 石英晶体的弹光系数P33和P13分别为0.110和0.279,其准确度达到0.001.     

Can the optically uniaxial crystal be made optically isotropic?

A problem of variation in the refractive indices of the optically uniaxial crystal during its elastic deformation has been considered. The stress has been applied along the optical axis of the crystal. It has been shown that, under uniaxial compression of corundum and quartz, refractive indices of the ordinary and extraordinary rays converge but cannot be equal to each other.     

去除光学器件弹光双折射的方法

在电光、磁光调制器和传感器等光学器件的制作和使用过程中,经常会产生影响器件性能的弹光双折射.根据折射率椭球分析法,通过系统分析各晶系晶体的弹光效应,提出了若干去除光学器件中静态弹光双折射的方法.主要结论包括:对于正交晶系的双轴晶体,当光波沿着晶体任意一个主轴方向传播时,如果作用于晶体另外两个主轴方向的应力能够满足某一与晶体自身参数有关的倍数关系且不存在剪切应力,则可以去除这两个应力引起的弹光双折射;对利用所有单轴晶体,ˉ43m,432,m3m点群的立方晶体和匀质光学玻璃制作的光学器件,如果能够保持晶体沿着x1,x2轴方向的正应力相等且不存在剪切应力,或只对晶体施加x3方向的正应力,也可以避免沿着晶体主光轴x3方向传播光波的弹光双折射.上述去除弹光双折射的方法对光学器件的设计、制作和使用具有重要参考价值.     

二维点缺陷正方光子晶体的微腔结构

通过平面波展开法对由Al₂O₃介质棒在空气背景介质中构成含有点缺陷的二维正方光子晶体微腔结构进行研究,计算得出缺陷态能带以及缺陷态模场分布。缺陷模对应的电磁波波长为470~476nm。对该微腔结构的品质因数的求解,得出缺陷态光谱曲线。在光谱曲线中,随着传输波长的增大,将产生几个峰值,并且在475nm处的波动最为明显,反映出在475nm附近的电磁波段在缺陷处的光强较大。进一步利用全矢量等效折射率法研究该结构缺陷模频率的稳定性,得出等效折射率的变化曲线。从等效折射率变化曲线可以看出,当传输波长达到475nm时,该结构已经达到稳定传输的区域。含缺陷模的二维光子晶体微腔结构在光子晶体发光二极管以及高阈值半导体激光器等方面有着重要的应用价值。     

光子晶体中基于有效折射率接近零的光束准直出射

利用平面波展开法(PWM)和时域有限差分法(FDTD)研究了二维正方格子光子晶体靠近禁带边沿附近频率光波的传输特性.研究发现,若有效折射率接近于零,可出现光束从晶体表面准直出射的现象,且光束的出射方向只与晶体表面的取向有关,而与晶格取向无关.这种现象与自准直现象有很大不同.     

高掺镁LiNbO3晶体折射率温度系数的表示式

推导了掺５ｍｏｌ％ＭｇＯ的ＬｉＮｂＯ３晶体折射率温度系数的表示式。利用这些表示式可以计算２９３～４２８Ｋ温度和０．５３９８μｍ～１．３４１４μｍ波长范围内的折射率温度系度，结果表明：计算值和实验值的最大相对偏差是１２％，用具有最大相对偏差的折射率温度系数的计算值，计算１．０７９５μｍ波长的非临界相位匹配温度，其值为３８２．４Ｋ，它与实验值仅差６Ｋ。因此，本文得到的表示式，对于采用这种晶体，设计在上     

Negative thermo-optical coefficients and athermal directions in monoclinic KGd(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> and KY(WO<Subscript>4</Subscript>)<Subscript>2</Subscript> laser host crystals in the visible region

The temperature dependence of three principal refractive indices of the biaxial KGd(WO₄)₂ and KY(WO₄)₂ crystals in the temperature range of 288–673 K was measured at wavelengths of 438.5 and 632.8 nm. Their thermo-optical coefficients (TOC) of the first and second orders were determined on the basis of the experimental data obtained. TOC were found to be negative for the n_g and n_p refractive indices of the KY(WO₄)₂ crystal and for the n_g refractive index of the KGd(WO₄)₂ crystal. It was established that in a fairly wide temperature range contributions of the positive and negative TOC to the refractive index of a light wave propagating in these crystals in certain directions compensate each other. Such athermal directions were determined for the index ellipsoid principal planes of these crystals on the basis of experimental data. PACS 78.20.Ci; 78.20.Nv     

Characteristics of paraxial propagation of a super Lorentz-Gauss SLG₀₁ mode in uniaxial crystal orthogonal to the optical axis

Analytical propagation expression of a super Lorentz-Gauss(SLG) 01 mode in uniaxial crystal orthogonal to the optical axis is derived.The SLG 01 mode propagating in uniaxial crystal orthogonal to the optical axis mainly depends on the ratio of the extraordinary refractive index to the ordinary refractive index.The SLG 01 mode propagating in uniaxial crystals becomes an astigmatic beam.The beam spot of the SLG 01 mode in the uniaxial crystal is elongated in the x-or y-direction,which is determined by the ratio of the extraordinary refractive index to the ordinary refractive index.With the increase of the deviation of the ratio of the extraordinary refractive index to the ordinary refractive index from unity,the elongation of the beam spot also augments.In different observation planes,the phase distribution of an SLG 01 mode in the uniaxial crystal takes on different shapes.With the variation of the ratio of the extraordinary refractive index to the ordinary refractive index,the phase distribution is elongated in one transversal direction and is contracted in the other perpendicular direction.This research is beneficial to the practical applications of an SLG mode.     

Calculations of spontaneous emission rates of a single-impurity molecule in uniaxial host crystals

In a uniaxial host crystal the spontaneous emission rate of the dipole transition of the zero-phonon line of a single-impurity molecule depends on the angle between the transition dipole moment and the optical axis of a crystal and as well as on the ordinary and extraordinary refractive indices. The relative spontaneous emission rate (the spontaneous emission rate divided by the spontaneous emission rate in the case when the transition dipole moment is parallel to the optical axis) is determined through a simple formula by one coefficient. Here this coefficient is calculated as a function of the extraordinary refractive index for 40 values of the ordinary refractive index on the interval from 1.25 to 3.20. For comparison, the effects caused by the nearness to the plane interface between cinnabar crystal (HgS) and air, as an example, are calculated.     

BiB3O6晶体主轴折射率及其温度系数

利用自准直法，在30℃到170℃温度范围内分别测量0.4880 μm、0.6328 μm、1.0640 μm、1.3414 μm等波长下BiB₃O₆(BIBO)晶体的主轴折射率.得到不同温度下的Sellmeier方程及各主轴折射率的温度系数.计算了1.0795 μm下BIBO晶体的的主轴折射率.与实验测量的结果进行比较，两者的差异不大于2×10－4.     

高掺镁铌酸钾晶体的主折射率及其温度系数的测量

本文报道掺5mol%MgO的铌酸锂(liNbO_3)晶体的主折射率n_o、n_o及其温度系数.用自准直法在0.5398μm、0.6328μm、1.0795μm和1.3414μm波长上,并在20℃～160℃温度范周内,测量了该晶体的主折射率,并获得在这些波长上的折射率温度系数.修正的Sellmeier方程的常数也在20℃～160℃温度内推算出.用此结果计算室温的二次谐波I类临界相位匹配角与实验值符合得很好,又计算二次谐波的非临界相位匹配温度,其结果也与实验值较符合.