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。     

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.     

Tunable All-Optical Microwave Filters Based on Fiber Loop and Chirped Fiber Bragg Gratings

All-optical microwave filters are important parts of fiber-optic microwave/millimeter wave processing systems. In this paper, two novel passive tunable all-optical microwave filters based on fiber loop and chirped fiber Bragg gratings (CFBGs) are demonstrated, where the frequency response of the both filters can be continuously tuned by adjusting the wavelength of the input light. The required free spectral range (FSR) of the filters can be obtained by carefully controlling the length of fiber loop and the positions of the CFBGs in the fiber loop. Experimental results prove the feasibility of the proposed filtering structures.     

Characteristics of a Grating-Folded Optical Directional Coupler

We developed a new optical add/drop multiplexer composed only of a grating-folded directional coupler. We found that in this multiplexer, the power drop becomes maximal when the grating-coupling strength is equal to that of directional coupling. At this maximum power, both power transfer between the waveguides and power reflection take place simultaneously at the grating. The power drop approaches 1 when the grating length increases.     

Design of a Resonant-Cavity-Enhanced p-i-n GaN/AlxGa1-xN Photodetector

A resonant-cavity-enhanced p-i-n photodetector has been designed and analyzed to operate at a wavelength of 360 nm based on the Al_xGa_1-xN material system. The novel approach has been adopted of using epitaxial AlN/Al_xGa_1-xN quarter-wave stacks as the distributed Bragg reflector that serves as the front mirror. An Al_xGa_1-xN absorptive filter layer is incorporated to suppress all but one resonant mode to ensure single, narrow-band operation. This device structure is projected to achieve wavelength selective, high speed, and high quantum efficiency operation in the ultraviolet. MOCVD-grown 6 1/2-pair AlN/Al_xGa_1-x     

High Temperature Sensitive Fiber Bragg Grating with Polymer Jacket

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