反射型阶梯光栅的特性分析

衍射效率是评价二元光学器件质量性能的重要指标之一.针对反射性阶梯光栅,利用几何方法计算出斜入射情况下光束在台阶边缘的光程差的分布情况,根据多缝夫琅和费衍射推导出反射型阶梯光栅的衍射光强表达式.并在此基础上,讨论了台阶数N取2和N趋向于无穷两种极限情况下阶梯光栅光强公式的变化情况,得到区别于一般文献所表达的衍射效率公式.初步试验表明,反射型阶梯光栅的衍射效率与台阶数、蚀刻深度与入射波长的比值均有密切相关.

Characteristics Analysis of Reflection Step Grating

For binary optical elements, diffraction efficiency is one of the important performance indexes. Under the oblique incidence cases, the optical path difference of light beam distributed on the edge of steps can be calculated by using the geometric method. Then, according to the multi-slit Fraunhofer diffraction, the expression of diffraction intensity of reflection step grating is deduced. Under the two limit conditions that the number N of different steps changes from 2 to infinity, we discuss the expression of light intensity's change. In general case, we deduce the expression of diffraction efficiency which is different from that of other articles. Experimental results show that the step number and ratio between the etching depth and the light wavelength are closely associated with the diffraction efficiency of reflection step grating.