A simple and comprehensive electromagnetic theory uncovering complete picture of light transport in birefringent crystals

Birefringence production of light by natural birefringent crystal has long been studied and well understood. Here, we develop a simple and comprehensive rigorous electromagnetic theory that allows one to build up the complete picture about the optics of crystals in a friendly way. This theory not only yields the well-known refraction angle and index of ellipse for birefringence crystal, but also discloses many relevant physical and optical quantities that are rarely studied and less understood. We obtain the reflection and transmission coefficient for amplitude and intensity of light at the crystal surface under a given incident angle and show the electromagnetic field distribution within the crystal. We derive the wavefront and energy flux refraction angle of light and the corresponding phase and ray refractive index. We find big difference between them, where the phase refractive index satisfies the classical index of ellipse and Snell's law, while the ray refractive index does not. Moreover, we disclose the explicit expressions for the zero-reflection Brewster angle and the critical angle for total internal reflection. For better concept demonstration, we take a weak birefringent crystal of lithium niobate and a strong birefringent crystal tellurium as examples and perform simple theoretical calculations. In addition, we perform experimental measurement upon z-cut lithium niobate plate and find excellent agreement between theory and experiment in regard to the Brewster angle. Our theoretical and experimental results can help to construct a clear and complete picture about light transport characteristics in birefringent crystals, and may greatly facilitate people to find rigorous solution to many light-matter interaction processes happening within birefringent crystals, e.g., nonlinear optical interactions, with electromagnetic theory.     

硫酸钡改性β-环糊精气相色谱手性毛细管柱制备与研究

β-环糊精(β-cyclodextrin，β-CD)是由7个葡萄糖单元通过α-(1，4)糖苷键连接而成的环状低聚合物。近年来。环糊精衍生物以其高选择性，适用范围广而成为气相色谱手性分离研究中发展最快的固定相。本研究采用全烷基化和部分酰基化方法合成了两种环糊精衍生物，2，3，6-O-三丁基-β-CD(TB-β-CD)和2，6-O-3-O-三氟乙酰基β-CD(DB-TFA-β-CD)，硫酸钡微晶对玻璃毛细管内壁进行改性，用上述两种固定相和中等极性的聚硅氧烷OV-1701混合制备出柱效高、热稳定性好的手性石英毛细管柱，并研究了色谱柱的选择性能。     

钙镁负载型固体碱催化剂制备生物柴油

固体碱催化剂;酯交换反应;脂肪酸甲酯;生物柴油