基于Bragg反射面结构的衍射光栅设计与研究

基于Bragg反射光栅是一维光子晶体的一种特例结构,本文提出利用一维光子晶体带隙理论进行Bragg反射光栅设计.通过光学仿真软件OptiFDTD对Bragg反射光栅的宽度及倾斜角度误差的仿真分析,发现Bragg光栅齿刻槽宽度变化在10%范围、倾斜角度10°以内不会引起Bragg光栅衍射效率的明显变化,说明Bragg反射光栅具有较高的工艺误差容限;根据一维光子晶体带隙理论,设计了一种罗兰圆结构的Bragg衍射双光栅结构模型,实现了两个频段之间的衍射分光,优化分析结果表明:当第一套光栅中Bragg周期层数为6、第二套光栅Bragg周期层数为10时,两频段波长的衍射效率均可以达到70%左右,明显高于传统深刻蚀的衍射光栅.基于本设计的波分复用器是一种尺寸小、衍射效率高的新型EDG波分复用器,为未来高效密集型EDG波分复用器发展提供了一种新的设计思路.

Study of the diffraction grating designed based on the Bragg reflection structure

Based on the fact that Bragg reflection grating (BRG) is a special case of one-dimensional photonic crystal, we may apply the one-dimensional photonic crystal band gap theory to design the BRG. OptiFDTD is used to simulate both the width error and tilt angle error in BRG. It turns out that the diffraction efficiency will stay high at the 10% width error or the 10° tilt angle error of the Bragg grating. These indicate that the BRG has a high fabrication tolerance. One model of a Bragg diffraction double-grating in the Rowland circle structure is proposed based on the one-dimensional photonic crystal band gap theory for achieving the two-band spectral diffraction. Result shows that the diffraction efficiency of the two incident bands can be as high as 70% when the first set of Bragg grating periods is 6 layers while the second is 10. It is significantly higher than the traditional deeply etched diffraction grating. This is the foundation of a new type of EDG-WDMer with its advantages being of small size and high diffraction efficiency. It may have great potentiality for developing high diffraction efficiency dense wavelength division multiplexer in the future.
Keywords： one-dimensioned photonic crystal Bragg etched diffraction grating diffraction efficiency Rowland circle double grating