一维光子晶体的有效折射率及色散特性

对有限长度一维光子晶体引入了复有效折射率的概念.它的实部描述了一维光子晶体的色散特性, 虚部反映了光在光子禁带被损耗衰减而消失的特征.从具体计算λ/4 波片堆组成的一维光子晶体的复有效折射率的结果可以看到,它的实部受到光子带结构的调制,在光子禁带及透射带中的一部分出现反常色散现象.在很大的频率范围内,有效折射率变得小于1.     

三波非共线作用参变过程的相位匹配研究

对各向异性单轴和双轴非线性晶体中三波非共线作用参变过程的相位匹配进行了详细的研究，给出了参变光在非线性晶体主平面内传播的所有非共线参变过程可能的相位匹配类型和相位匹配条件，并推出了所有可能的非共红参变过程的临界相位匹配解的解析表达式。     

Dynamical precursor of nematic order in a dense fluid of hard ellipsoids of revolution

We investigate hard ellipsoids of revolution in a parameter regime where no long range nematic order is present but already finite-size domains are formed which show orientational order. Domain formation leads to a substantial slowing down of a collective rotational mode which separates well from the usual microscopic frequency regime. A dynamic coupling of this particular mode into all other modes provides a general mechanism which explains an excess peak in spectra of molecular fluids. Using molecular dynamics simulation on up to 4096 particles and on solving the molecular mode coupling equation we investigate dynamic properties of the peak and prove its orientational origin. Received 19 September 2001 and Received in final form 19 March 2002     

Interference of circularly polarized light: contrast and application in fabrication of three-dimensional periodic microstructures

The contrast of interference pattern formed by two circularly polarized waves and by a linearly polarized wave and a circularly polarized one is discussed. The results are compared with that by two linear beams. It shows that the use of circular light in holographic fabrication of three-dimensional periodic microstructures may remove the necessity of beam ratio and polarization optimization needed in the interference of three linear noncoplanar beams and improve the uniform contrast of resultant pattern simultaneously.     

Chiral mirror and optical resonator designs for circularly polarized light: suppression of cross-polarized reflectances and transmittances

A left-handed chiral sculptured thin film (STF) that reflects strongly at the wavelength of the circular Bragg resonance tends to partially convert the handedness of incident LCP (left-circularly-polarized) light to RCP (right-circularly-polarized). We show that the cross-polarized component of the reflected RCP beam can be eliminated by interference with an additional RCP beam that is reflected at the interface of an isotropic cover and an AR (antireflecting) layer. For best results the refractive index and thickness of the AR layer need to accommodate a phase change on reflection that occurs at the chiral film. Effective suppression of the reflectances R_RR, R_RL, R_LR and the transmittances T_RL, T_LR can be achieved by sandwiching the chiral reflector between such amplitude and phase-matched AR coatings. Co-polarized chiral reflectors of this type may form efficient handed optical resonators. For LCP light the optical properties of such a handed resonator are formally the same as the properties of the isotropic passive or active Fabry–Perot resonators, but the handed resonator is transparent to RCP light.     

Nd:Ca4ReO(BO3)3(Re=Gd,Y)晶体最佳激光、最佳倍频及最佳自倍频方向的确定

介绍了Nd:Ca4ReO(BO3)3(Re=Gd,Y)晶体最佳激光方向、最佳倍频方向的确定.综合考虑激光受激发射截面、抽运光吸收系数、有效非线性系数的各向异性,分析了自倍频性质的空间分布,并就此确定出最佳自倍频方向 关键词： Nd:Ca4ReO(BO3)3(Re=Gd Y)晶体 激光发射 倍频 自倍频     

Piezoelectric activities and domain patterns of orthorhombic Ba(Zr,Ti)O3 ceramics

Ba(Zr_xTi_1?x)O₃ (0.025 ≤ x ≤ 0.065) ceramics were prepared by conventional solid-state reaction method. Crystalline structures were analyzed by X-ray diffraction. It was shown that all the Ba(Zr_xTi_1?x)O₃ (0.025 ≤ x ≤ 0.065) ceramics were of orthorhombic phase at room temperature. Piezoelectric activities and domain patterns were investigated and compared with those of BaTiO₃ ceramic. All the Ba(Zr_xTi_1?x)O₃ ceramics showed nearly the same d₃₃ values of about 265 pC/N and the same domain width of about 220 nm. By comparing the grain sizes and domain width of the Ba(Zr_xTi_1?x)O₃ ceramics with those of BaTiO₃ ceramic, it is speculated that the variation of domain width with grain sizes in orthorhombic Ba(Zr_xTi_1?x)O₃ ceramics may be different with that in tetragonal BaTiO₃ ceramic. Besides domain width, the effective inertia mass of domain wall is also considered to be a very important factor that impacts the piezoelectric activities of the Ba(Zr_xTi_1?x)O₃ ceramics.     

Phase diagrams and dielectric studies of binary mixtures exhibiting intermediate nematic and induced smectic phases

Investigations on the phase diagrams of two bi-component mixtures of liquid crystals are presented. Whereas in one of the bi-component systems, smectic A (SmA) phase is seen to be induced, in the other case the so-called nematic “island” has been observed. The dielectric properties of magnetically oriented sample forming nematic phase and induced smectic phase in one of the mixtures, and a nematic “island” and SmA phase in the other mixture, were measured in the frequency range from 1?Hz to 10?MHz at different temperatures. The transition temperatures obtained from the polarizing microscope and differential scanning calorimeter measurements agree well with the dielectric relaxation data.     

Smectic polymorphism of 4-decyloxybenzylidene- 4′-alkyloxyanilines and their mixtures with polar standards of mesophases

This article describes liquid crystalline properties of the homologous series of 4-decyloxybenzylidene-4′-alkyloxyanilines. Based on the polarization microscopy (POM and TOA methods) and the calorimetric (DSC) measurements a rich polymorphism has been detected. Investigated compounds exhibit nematic, smectic A, smectic C, smectic B, smectic I and G (smectic G) mesophases with their characteristic configurations. The presence of these mesophases was confirmed by the miscibility method, using 4-heptyloxybenxylidene-4′-pentylaniline as a mesophase reference. Nine other smectic standards with different polarity have been applied in order to investigate their influence on the mesophase stability.