光折变晶体钛酸秘的折射率和光学均匀性的测量

本文报导光折变晶体钛酸铋的折射率和光学均匀性的测量结果。     

Azimuthal dependence of the two-photon absorption coefficient for CdP2 crystals with tetragonal syngony

We studied the two-photon absorption coefficient (β) for cadmium diphosphide (CdP₂) single crystals in the tetragonal modification vs. the polarization azimuth (φ) of the incident light for intensities close to the optical breakdown (or optical damage) threshold for the crystal (11 MW/cm²). We have established that the value of β_max = 0.16 cm/MW is reached for φ = 0, i.e., for the ordinary wave. At the lasing frequency of a ruby laser, β_⊥/β_|| = 2.13, which suggests anisotropy of the two-photon absorption in the studied crystals. These dependences are needed for design and fabrication of quantum electronics and nonlinear optics elements whose operation is based on the use of the two-photon absorption effect for high radiation fluxes. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 117–121, January–February, 2009.     

利用两种响应时间不同的光折变晶体实现仅对物体变化部分成像

用两种响应时间相差很大的光折变晶体Ce:SBN和Fe:LiNbO_3作为相位共轭麦克尔逊干涉仪的两个相位共轭镜,得到同一物体的两个有时间差的相位共轭像,再对这两个像做实时“异或”运算,就能实现仅对物体随时间变化部分的成像.这种方法可以大大增加两相位共轭镜的响应时间差,具有最小可探测速度低,输出信号强、输出保持时间长的优点.文中对此作了理论分析,并提供了该系统对真实物体成像的实验结果.     

Interactions of dark solitons in photovoltaic photorefractive crystals with diffusion nonlinearity

We investigate the interaction of spatial dark optical soliton pair in open-circuit photovoltaic photorefractive crystals by considering the effect of background light and diffusion nonlinearity. We show that the spatial dark solitons repel each other and travel along different trajectories for the coherent interactions that one undergoes reflection and the other one deflects significantly when they are closely overlapped, and the dark solitons attract and deflect simultaneously along a parabolic trajectory for the case of incoherent interactions. The deflection distance depends on the intensities and the initial separation between the dark solitons.     

CRT－LCLV and photorefractive crystl BSO based real－time joint transform correlator

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648nm激光雪崩抽运掺Tm晶体的本征光学双稳特性研究

理论研究了648nm激光雪崩抽运掺Tm晶体的本征光学双稳态.根据系统的非线性速率方程理论，推导出了稳态近似下雪崩阈值的解析表达式，数值研究了光子雪崩动力学响应、本征光学双稳性以及系统参数对光学双稳态的影响等.研究结果表明，648nm激光抽运下可以观察到掺Tm激光晶体的2μm荧光辐射本征光学双稳态，通过改变可控的实验参数能够实现对光学双稳回线环的形状调节.     

Localized surface waves at the interface between the linear dielectric and photorefractive medium with drift and diffusion nonlinearity

We consider the propagation of the laser beam near the interface between the linear dielectric and photorefractive medium with drift and diffusion nonlinearity. We demonstrated the possibility of the surface waves formation, found the profiles of such surface modes and investigated waveguiding properties of the dielectric-photorefractive medium boundary. The effective particle theory was used to derive an ordinary differential equation that describes the beam center trajectory during the reflection from the interface.     

Surface electromagnetic waves at the interface of photorefractive crystals with a drift-diffusion nonlinearity mechanism

Within the accuracy of the plane-wave approximation, a solution of the boundary-value problem for the Maxwell equations is obtained for surface electromagnetic waves at the interface between a photorefractive crystal and a transparent isotropic medium. It is shown that in this case, of all the kinds of surface waves, only soliton-type waves can be generated. Characteristic parameters of these waves are determined for a photorefractive SBN (strontium-barium-niobate) crystal.     

用电磁理论说明各向异性晶体的基本光学现象

用电磁理论说明各向异性晶体为什么会产生双折射,双折射的光为什么都是线偏振光.     

Subwavelength imaging through one-dimensional metallodielectric photonic crystals at optical frequencies

We present a study of mode characteristics of multilayer metal-dielectric (M-D) structure and use the Eigen mode expansion (EME) method to simulate the subwavelength imaging effect that can be realized at the designed position. We show that the quality of the image is affected not only by absorption but also the finite width of the layers. By proper design and considering the real losses, a super lens with a resolution of about λ₀/6 (λ₀ is the wavelength in the air) can be obtained. Our researches of this structure point to that a transparent material can be composed from non-transparent materials by alternatively stacking different materials of thin nanofilms, which also provide an opportunity to expand the exploration of the wave propagation in metals, both in the linear and nonlinear regimes.     

光在两单轴晶体分界面的反射与透射系数

研究光在两单轴晶体分界面处的反射和折射情况,分析了反射光和折射光的振幅与相位,给出了光在两单轴晶体分界面处的反复和透射系数。     

增强吸收型光双稳的耦合动力学方程及动态分析

本文从唯象的角度首次提出了增强吸收到光双稳的耦合动力学方程，利用计算机模拟，描述了增强吸收型光双稳的静态和动态特性。     

Determination of the liquid crystals phase transition temperatures using optical rotation effect

Using optical rotation effect, a sensitive, simple optical analytical system is developed for determining the phase transition temperatures of liquid crystals (LCs). When a monochromatic polarized light passes through LCs sample and analyzer, the light intensity changes with temperature. Especially, during the phase transition process, the intensity varies greatly due to optical rotation effect. The variation of light intensity versus variation of temperature curve shows the phase transition temperatures of LCs clearly. The phase transition temperatures of three cholesteric liquid crystals (ChLCs) and a nematic liquid crystals (NLCs) were detected by this method, and compared with those of the differential scanning calorimetry (DSC) and polarized light microscope (PLM) methods.     

Spectral investigation of nematic liquid crystals with high optical anisotropy at THz frequency range

Liquid crystals (LCs) with high optical anisotropy are very desirable for different applications in devices, such as filters, phase shifters, or phase gratings [T. Göbel, P. Meissner, A. Gaebler, M. Koeberle, S. Mueller, and R. Jakoby, Dual-Frequency Switching Liquid Crystal Based Tunable THz Filter, CLEO, Baltimore, MD, 2009; C.-Y. Chen, T.-R. Tsai, C.-L. Pan, and R.-P. Pan, Room temperature terahertz phase shifter based on magnetically controlled birefringence in liquid crystals, Appl. Phys. Lett. 83 (2003), pp. 4497–4499; and C.-J. Lin, C.-H. Lin, Y.-T. Li, R.-P. Pan, and C.-L. Pan, Electrically controlled liquid crystal phase grating for terahertz waves, IEEE Photon. Technol. Lett. 21 (2009), pp. 730–732]. We present spectral studies of LCs with large optical anisotropy in the range from 0.3 to 3?THz. Nematic LC mixtures which have Δn?>?0.30 for visible frequency range, i.e., 1825 (Δn?=?0.42 at 633?nm) were measured. Properties of LC materials like birefringence, absorption coefficients, and refractive indices for ordinary and extraordinary polarization in THz range were obtained. Orientation of LC was done by a high electric field. Measurements were performed using a TDS spectra 3000 spectrometer.     

Design of wavelength adjustable lasers with photonic crystal based Fabry-Perot etalon for applications in optical network units of wavelength-division-multiplexed passive optical network systems

We propose a novel wavelength adjustable laser (WAL) with a photonic crystal based Fabry-Perot (FP) etalon. This laser will be a promising light source for optical network units (ONUs) of conventional wavelength-division-multiplexed passive optical network (WDM-PON) systems for up-stream transmission. It has the merits of a relatively simple fabrication and operation, wide process tolerance, low-cost, high side-mode suppression ratio, and wavelength-tunable characteristics. The optimization of the device structure and the implementation methods for this type of laser are discussed. Although the WALs in WDM-PON systems are not colorless, each laser can cover several wavelengths. Thus, the required number of different ONUs can be reduced. This approach may be necessary for 10 Gbps upstream transmission in next-generation optical access networks because the 10 Gbps data rate is difficult to achieve by using current colorless schemes.     

Nd3+:LiNbO3 晶体的坩埚下降法生长及光谱特性

以同成分化学组分比(Li2O:48.6mol%,Nb2O5:51.4mol%)为原料,Nd2O3为掺杂剂,应用坩埚下降法技术,生长了Nd3+初始掺杂为0.2mol%的LiNbO3晶体。测定了晶体的差热曲线、红外吸收光谱、紫外-可见吸收光谱,并与用提拉法技术生长的晶体性质进行了比较。观测到了Nd3+的特征吸收峰。在800nm的半导体激光激发下研究了晶体在1.06μm附近的荧光曲线和荧光寿命,观测到了1067,1080,1085,1093,1106nm五个分裂的4F3/2→4I11/2能级跃迁发射峰。测定了最强荧光峰(1085nm)的荧光寿命为351μs。与用提拉法技术生长的晶体相比,其荧光寿命得到了大幅度的变长,约为3.5倍。在密封条件下用坩埚下降法技术生长的晶体,由于在生长过程中隔绝了空气和水汽,所以在获得的晶体中具有低的OH-离子浓度,获得了长的荧光寿命。     

Optical computation based on nonlinear total reflectional optical switch at the interface

A new scheme of binary half adder and full adder is proposed. It realizes a kind of all-optical computation which is based on the polarization coding technique and the nonlinear total reflectional optical switches.      

Nonlinear Schrödinger equation for optical media with quintic nonlinearity

A nonlinear quintic Schrödinger equation (NLQSE) is developed and studied in detail. It is found that the NLQSE has soliton solutions, the stability of which is analysed using variational method. It is also found that the soliton pulse width in the materials supporting NLQSE is small compared to soliton pulse width of the commonly studied nonlinear cubic Schrödinger equation (NLCSE).     

On the interface at the equilibrium crystallization

Properties of an interface, created at some experimental conditions in the course of the equilibrium crystallization process, are theoretically investigated. Influence of quantum and thermal fluctuations on smoothing-roughening phase transitions is considered. The phase diagram illustrating these properties is found.     

一组新型络合物晶体结构与光学性能的研究

研究了二氯三烯丙基硫脲合镉(ATCC),二氯三烯丙基硫脲合汞(ATMC)和二溴三烯丙基硫脲合镉(ATCB)三种晶体的结构特点.首次报道了ATMC和ATCB晶体的非线性光学系数及倍频性能;文中分析比较了三种晶体的非线性光学性能;讨论了晶体结构与性能的关系,为探索高效非线性光学新材料提供依据.