梯形介质膜光栅衍射特性分析

基于严格耦合波理论建立了梯形介质膜光栅的衍射机理模型,利用该模型讨论了底角为70°的梯形介质膜光栅-1级的衍射行为.通过对梯形介质膜光栅的占空比、槽深和剩余厚度的优化,设计了应用于1053 nm和51.2°角度入射的梯形介质膜光栅.对于顶层为HfO2的介质膜光栅,当槽深为200 nm,剩余厚度为100 nm,占空比为0.35时.其衍射效率优于99.5%,而对于顶层为SiO2的梯形光栅,为获得99.5%的衍射效率.其槽深为800 nm,剩余厚度为320 nm.而且,获得同样的衍射效率,顶层为HfO2的梯形光栅具有更宽的光谱特性.数值计算表明,严格耦合波理论模型对梯形介质膜光栅衍射效率的计算具有很好的收敛性和稳定性.

Diffraction Property of Multi-Layer Dielectric Grating with Trapezium Groove

The rigorous coupled-wave analysis is used to describe the diffraction of multi-layer diffraction grating (MDG) with trapezium groove. The diffraction performance of multi-layer dielectric grating with the trapezium groove of 70° is discussed. Trapezium MDG used for wavelength of 1053 nm and incident angle of 51.2° is designed by optimizing the duty cycle, depth and residual thickness of the top layer. For gratings etched into the top HfO2 layer, diffraction efficiency of 99.5% can be attained when the duty cycle is 0.35, groove depth is 200 nm and the residual thickness of HfO2 is 50nm. Whereas for SiO2 as the top corrugated layer, the groove depth is 800 nm and the top SiO2 residual layer is 320 nm in order to obtain the same diffraction efficiency as 99.5%. Furthermore, the trapezium MDG with HfO2 on the top has wider wavebandth compared with the design of SiO2 on the top of MDG to obtain the same diffraction efficiency. Numerical calculation indicates that the coupled-wave analysis model has excellent convergence and stable performance to analyze the diffraction of trapezium MDG.