Modeling of waveguide UV-induced Bragg gratings with arbitrary apodization function: Tools for designing high-performance related devices

We present a semi-analytical modeling suitable for the investigation of the spectral characteristics of UV-waveguide Bragg gratings (UV-WBGs) having arbitrary apodization function and extending both in the film layer and in the overlayer. The modeling is based on a proper combination of coupled mode theory and transfer matrix formalism and provides a powerful tool for designing and simulation of complex UV-grating based structures. The results of a detailed investigation of UV-WBGs in doped silica based channel optical waveguides are presented and critical issues for upgrading the performances of related device are discussed. Validation of the modeling is provided by means of an extensive comparison between theoretical and experimental results relevant to UV-WBGs realized in phosphorous (P)- and boron (B)-doped silica based waveguides.     

BD-1型高精度Bragg衍射仪θ角微位移驱动系统

研制出一种角度微位移驱动系统,并成功地用于BD-1高精度布拉格衍射仪。该系统精度高,稳定可靠,既可手工调节,亦可计算机控制,控制灵敏度0.29″/V,精度V=±0.12″。文中介绍了进行角度精密微调的原理和方法,介绍了线路原理。     

有序混合光束和迷宫式多次反射光学系统

本文给出有序混合光束结构和多程光学系统的具体考虑,并指出它们在多波长高激发态激光光谱学研究和其它领域中的意义.     

显示反射全息图单光束相干复制技术

描述用单光束激光复活制银盐白光显示反射全息图的技术，本技术的关键：１）母全息图的颜色必须恢复到满足其布拉格条件；２）复制所用的光波与记录母全息图时的参考的相同；（３）复制所用的激光采用平行偏振，以减少界面反射；９４）采用白糖溶液作为折射率匹配液，取得极佳效果。     

XPM-induced intensity distortion due to dispersion in fibre Bragg grating filters

We investigate the conversion of cross-phase modulation (XPM) to intensity distortion due to dispersion in fibre Bragg grating (FBG) filters. We find that there can be significant XPM-induced intensity distortion, especially near the edges of the filter passband where the in-band dispersion is increasingly pronounced. Since FBG filter dispersion occurs above and beyond that in standard single-mode fibre, this enhances XPM-induced intensity distortion arising from dispersion and should be accounted for in system design.     

Scattering experiments on the structure of concentrated dispersions

 In this work the Couette cell is compared with a more recently constructed disk shear cell. There are distinct advantages of the disk over the Couette cell, in particular, when it comes to the determination of the intensity along certain Bragg rods. Received: 12 December 2000 Accepted: 31 January 2001     

Low-temperature, solution processing of TiO2 thin films and fabrication of multilayer dielectric optical elements

High-quality TiO₂ thin films have been deposited from aqueous titanium-peroxo solutions via spin coating. The effects of precursor solution pH on the crystallization behavior, morphology, density, and refractive index of the films are reported. From X-ray diffraction measurements, the amorphous as-deposited films are found to crystallize in the anatase phase at 250 °C. Surface and cross-section SEM images reveal that films deposited from an acidic precursor are more uniform and denser than those deposited from a basic precursor. X-ray reflectivity measurements show that films with smooth surfaces and high densities (up to 87% of single-crystal anatase) can be produced at temperatures as low as 300 °C. Measured densities are consistent with high refractive indices at 633 nm of 2.24 and 2.11 for films derived from acidic and basic precursors, respectively. The uniformity and dense nature of the films have allowed fabrication of multilayer dielectric optical elements with thermal processing at only 300 °C. The distributed Bragg reflector with four bilayers exhibits a reflectance of 92% and a stop band width of 150 nm. The optical microcavity has a quality factor of 20. The optical properties of all elements agree well with theoretical models, indicating good optical quality. Use of the precursor chemistry for direct photopatterning of TiO₂ films without a polymer resist is also demonstrated.     

Appearance of pseudo-band-gaps in a disordered quantum wire array

The density of states and the conductivity are calculated in lateral superlattices with disorder in the period within a self-consistent Born approximation. Although the potential loses its periodicity on average due to disorder, it leads to an opening up of a pseudo-band-gap and modifies the conductivity perpendicular to the superlattice even qualitatively, when the energy reaches the zone boundary.