【作者】 张昱；

【导师】 徐业彬；

【作者基本信息】 华中科技大学 ， 光学工程， 2008， 硕士

【摘要】 随着激光技术和光通信技术的飞速发展,作为光谱和空间角度滤波器件的衍射光学元件的需求量不断增加。目前,高功率激光系统的研究对于具有高破坏阈值的光学元件有着很大的需求。而传统的表面刻划式光栅,在超高功率(万瓦量级)光学系统中,将会因为光栅本身破坏阈值无法满足超大功率而被损坏。所以拥有高破坏阈值的体光栅引起广泛地关注。上世纪七十年代,在块状光敏材料中通过折射率调制可以制备体衍射光栅的优势就很清楚。几十年来,不断有各种光敏材料研制成功:卤化物银感光乳液、感光性树脂、光敏聚合物、光热塑料、掺有不同价稀土元素的氧化物、掺锗的硅玻璃以及光折变晶体等。但是这些材料在处理过程中会收缩,并且对于湿度也很敏感,不能承受高功率激光的辐射。所以制备理想的全息光栅对材料提出了很高的要求:其应该具有与使用激光波长很好匹配的光谱选择性、线性传输特性、高的分辨率以及低的噪声、高破坏阈值以及可再利用。本文针对这一问题,制备拥有良好光学性能和高破坏阈值的光致热敏折射率玻璃,使其可以用于三维全息记录,制备体布拉格光栅。我们采用掺氟化物钠玻璃体系,设计出基于SiO2-Na2O-Al2O3-ZnO为玻璃主要成份并掺杂CeO2、AgNO3和NaF等的一系列玻璃配方,在1450℃左右融化,制成拥有良好光学性质(均匀性、无气泡、无条纹、透明性好)的光学玻璃。然后对玻璃样品在520~640℃的温度条件下热处理,考察玻璃的析晶特性。并采用X射线衍射分析和差热分析等手段检测微晶成分及样品的析晶放热过程,讨论不同配方的析晶特性。我们从助熔剂,晶核剂,氟化物几个角度讨论了玻璃配方参数对样品析晶特性的影响。我们得出助溶剂B2O3,在高温条件下对粘度降低得效果不大,但是却容易降低玻璃在低温状态时的粘度,这样容易使玻璃在600℃左右的热处理温度处软化。所以在我们的PTR样品制备中就不再引入B2O3。通过不同晶核剂Ag和Ti的对样品析晶性能的对比,确定Ag是PTR玻璃晶核剂的最佳选择。通过对不同氟化物含量的样品的析晶特性测试,得到结论:当F含量较低时,热处理后参与形成NaF微晶的量将严重不足,热处理后无法观察到析晶,当F含量过高时,在浇注出炉时就发生晶化,不具有实用价值。只有将F的含量控制在一个合理的范围,才能使所制玻璃有良好的光敏微晶特性。更多还原

【Abstract】 The fast evolution of lasers and optical communications stimulated increasing demands for diffractive optical elements serving as different types of spectral and angular filters. Extensive research for high-power system make demand for optical device with high destroy threshold value. And traditional surface scored grating in super elevation power In the optical system, will be damaged that grating will destroy threshold value, because it’s destroy threshold unable to meet ultra high-power. So there is volume grating with high destroy threshold value that cause extensive attention and application.In the seventies of last century, the advantage of preparing volume grating in the bulk photosensitive material of through the refracting rate is very clear, there are a large number of patents and literatures regarding the volume grating. In these decades, various photosensitive materials are being succeeded in developing constantly: silver halide photographic emulsions, dichromated gelatin, photoresists, photopolymers, photothermoplastics, polymers with spectral hole-burning, and photo-refractive crystals. But these materials will shrink in the process of thermal development, and very sensitive to the humidity, can’t bear the radiation of the laser of high power. So the material which prepares the ideal holographic grating puts forward very high requirement to us: It should have and use spectrum alternative that the laser wavelength well match, linear transfer characteristic, high resolution ratio and low noise, high destroying threshold value and can utilize again and again. This text directs against this question, prepare Photo-Thermo-Refractive glass with good optical performance and high destroy threshold value, so that it can be used in the holographic record of the three-dimension for the preparation for Volume Bragg Grating.It is based on Stookey’s mixed fluoride sodium glass system for us to adopt, design prescriptions on the basis of SiO2-Na2O-Al2O3-ZnO for the glass main component and a series of glass doped with CeO2, AgNO3 and NaF etc. melted at about 1450℃, the glass have good optical property (homogeneity, without bubble and stripe, high transparency ). Then annealed at 520-640℃. Then we observe analyzing the crystallization characteristic of glass, use XRD and DSC to analyze the component of micro crystal, analyzing the different ability of crystallization in glass samples.We prepared a series of different formula percentage of the samples, and take the flux, nucleating agents, different fluoride formula discussed the parameters of glass samples crystallization of the impact.It show that B2O3 take little work for lowering viscosity at high temperature condition, but at a lower temperature it will reduce the viscosity of samples, it makes the samples after the heat treatment to soften. Therefore, in our sample preparation in the PTR will not introduce B2O3.Through contrast the effect of different nucleating agent Ag and Ti for the ability of crystallization in the samples, is determined Ag is the best choice for the PTR glass’s nuclei.In the use of fluoride content in a series of different samples and test contrast, we conclude that: When the F content is low, after the heat treatment involved in the formation of NaF-microcrystal will be seriously inadequate, heat treatment can not be observed after the crystallization, when the F content Too high, the sample crystallize fully when glass is poured, does not have practical value. Only when the F content control at a reasonable scope, the system can make a good photosensitive crystallization properties.更多还原