Investigation of a UV-laser generated waveguide in a planar polymer chip using an improved interferometric method

Polymeric integrated-optical waveguides are prepared in a planar polymer chip by UV-laser lithographic methods. The waveguide samples are irradiated by an excimer laser at a wavelength Λ=248 nm with various irradiation parameters (different fluencies and irradiation doses). Mach-Zehnder interferometer is employed and the refractive index depth profiles of the waveguide samples are obtained. This profile covers two regions having exponential and Gaussian shapes. The model field distributions strongly depend on the refractive index of each region. The mode field distribution and the effective mode indices for each region have been calculated on the basis of a theoretical model and the experimentally measured data.     

Investigation of a UV-laser generated planar polymeric waveguide directly and after five years of preparation using an interferometric method

Polymeric integrated-optical waveguides were prepared in a planar chip using UV-laser lithographic method. Five waveguide samples were irradiated by an excimer laser of wavelength 248 nm with different irradiation parameters (fluence and irradiation doses). Using Mach–Zehnder interferometer, the refractive index depth profiles of these samples are determined in two cases, directly and five years later of preparation. A crucial change of refractive indices profiles has been recorded after five years of preparation. In the first case we got double region waveguides fitted a Gaussian shape, while in the second one we observe a single region waveguide which has exponential shape. The photochemical reactions responsible for these changes in the two cases are demonstrated. This is quite important when such waveguides are used in the applications. Also it was interesting to investigate the aging impact on mode field distributions and the effective mode indices. The mode parameters are determined based on a theoretical model and the experimentally obtained data. The results show a notable change in the mode field distributions and the propagation coefficients as influence of aging.     

γ辐射对光纤波导电磁场分布的影响

开展了光纤波导中的电磁场传输理论分析,得到了光纤折射率变化对波导中电磁场分布的影响规律,建立了块状融石英材料及光纤光栅在60Co 辐射作用下折射率变化的测量系统,开展了折射率随辐射剂量变化及光纤模场测量实验。结果表明:光纤的折射率随辐射剂量的增加而增大,折射率的变化会引起波导中传输模式的场强分布变化,从而导致光纤的辐射感生波导损耗;在一定的辐射剂量范围（0～2000 Gy）内,光纤仍满足弱导边界条件,能够维持对传输模式的约束能力。     

γ辐射对光纤波导电磁场分布的影响

开展了光纤波导中的电磁场传输理论分析,得到了光纤折射率变化对波导中电磁场分布的影响规律,建立了块状融石英材料及光纤光栅在60Co 辐射作用下折射率变化的测量系统,开展了折射率随辐射剂量变化及光纤模场测量实验。结果表明:光纤的折射率随辐射剂量的增加而增大,折射率的变化会引起波导中传输模式的场强分布变化,从而导致光纤的辐射感生波导损耗;在一定的辐射剂量范围（0～2000 Gy）内,光纤仍满足弱导边界条件,能够维持对传输模式的约束能力。     

Analysis of arbitrary index profile planar optical waveguides and multilayer nonlinear structures: a simple finite difference algorithm

we present here a simple numerical method to obtain the mode effective indices as well as field distributions of modes of any arbitrary profile planar optical waveguide. The method is based on the solutions of scalar and semivectorial Helmoltz’s equation by finite difference algorithm and devised with a field convergence technique. This approach is quite general and can be applied straightforwardly to calculate the guided as well as quasi- or leaky modes of any arbitrary planar structure without the need to solve any eigenvalue equation or any complex matrix formalism. Besides providing the ease of application, the algorithm is particularly useful for waveguides with any graded index profile or with irregular multilayered structure and multilayered waveguides with a localised arbitrary nonlinear film. The performance of our method is verified against typical problems with analytical solutions or having results known otherwise, and is shown to yield results with good accuracy.     

Control of the distribution of surface plasmon local field by altering the surrounding material

The field distribution of the surface plasmon (SP) around a silver nanowire greatly influences its applications for both spectrum enhancement and nano-waveguide. This paper demonstrates the change of the SP local field distribution of a silver nanowire on glass substrate with the refractive index of the covering medium by numerical simulation. The hot energy site is observed focusing on the interface between the nanowire and the surround material of larger refractive index. Moreover, we also find that the surface plasmon field becomes more confined as the refractive index between the substrate and medium has a larger gap, while a homogeneous distribution of the surrounding dielectric material around the nanowire shows a uniform local field distribution with a larger surface plasmon propagation length. The change of related parameters, such as effective index, mode area, and propagation length are also comprehensively investigated against the refractive index for nanowires with 100, 200, 300 nm diameter. Considering the wide use of polymethyl methacrylate (PMMA) material, the field distribution of silver nanowire partially imbedded in PMMA against the PMMA thickness is also studied.     

用光辐照法在SBN:Cr晶体中写入动态阵列平面光波导

利用扩展的准直He-Ne激光束通过菲涅耳双棱镜所形成的干涉光场辐照SBN:Cr晶体， 同时沿晶体光轴方向施加适当的直流电场，可在晶体中形成类似于体相位光栅结构的阵列平 面光波导. 采用马赫-曾德干涉仪光路实时测量了所写入阵列平面光波导的横向折射率分布 ，其峰值接近10-4. 初步的导光测试结果表明，利用周期结构光辐照并辅以适当的外加电场在SBN:Cr晶体中写入阵列平面光波导是可行的. 并且由于SBN:Cr晶体的快速响应特性，所写入的光波导是动态的，可随着写入光的撤除而快速消失，或通过改变双光束夹角 关键词： SBN:Cr晶体 结构光辐照 阵列平面光波导 折射率分布 外电场     

Biaxial behaviour of an optical waveguide fabricated by ion implantation in a uniaxial BaTiO3 substrate

Biaxial behaviour has been observed in a waveguide fabricated by the technique of ion-beam implantation (H⁺ ions: 1 MeV at a rather high dose of 6 × 10¹⁶ ions/cm²) in a uniaxial BaTiO₃ single crystal. For the first time to our knowledge this phenomenon has been connected to the elasto-optic properties of the material. The index profile reconstructions both for TE and TM modes are led with two methods and we compare the results. The computation technique to connect the latter with the elasto-optic properties is presented. Then the calculations are successfully compared with the measured values.     

Acoustic field imaging by light reflection at the free surface of a liquid

In this paper we present a novel technique for acoustic field imaging. This technique is based on reflection of a collimated laser beam at the free surface of a liquid. The reflected beam becomes phase modulated by the acoustic wave as in acoustical holographic systems. We do not use a reference acoustical beam for holographic reconstruction but we observe this phase modulation using dark-field techniques. It gives a measurement of the acoustic field power as a function of the position. The authors have built an optical imaging system and carried out experiments with piezocomposite transducers. The technique presented in this work is able to give fast quantitative information about the performance of individual ceramic rods of the piezocomposite.     

Destabilizing effect of a surface electric field generated by ionic adsorption on the molecular orientation of nematic liquid crystals

The destabilizing effect of a surface electric field, produced by selective ionic adsorption, on the molecular orientation of a nematic-liquid-crystal sample is analyzed for a cell in the shape of a slab of thickness d. The electric-field distribution considered in the analysis is the one obtained in the limit in which essentially all the positive ions are adsorbed. Because of the coupling of this surface field with the nematic director, the surface anchoring energy depends on the thickness of the sample as well as on the adsorption energy characterizing the surfaces. A relation connecting the threshold field for the destabilization of the homeotropic pattern to the adsorption energy and to the thickness of the sample is established in closed form, after solving a set of two coupled non-linear equations determining the electric-field distribution across the sample. It is shown that the values of surface electric field generated by adsorbed ions that can lead to a destabilization of the homeotropic alignment can be attained by real samples.     

两种均匀磁介质分界面上有长载流导线的场和电流分布

分析两种均匀磁介质分界面上有长载流导线的场和电流分布，指出磁感应强度B=B(r)φ径向对称分布是由径向对称分布的总电流j=j(r)ez(包括传导电流和磁化电流)所激发,探讨了传导电流的分布与磁感应强度B、磁场强度H和磁化电流的分布的关系。