Bragg反射齿型平面凹面衍射光栅性能研究

Study on planar concave diffraction grating with Bragg reflector facets

本文基于Bragg反射光栅是一维光子晶体的一种特例结构,提出利用一维光子晶体理论进行Bragg衍射光栅的设计并对其性能进行研究分析.根据一维光子晶体理论,建立了罗兰圆结构的凹面椭圆Bragg蚀刻衍射光栅,研究了TE/TM模式下器件的分光特性以及入射角度改变对器件角色散造成的影响;同时,文中对比了空气介质型和金属铝线型椭圆Bragg蚀刻衍射光栅的光学性能.研究结果表明:选择合适的器件参数,可以实现TE/TM模式下1.465—1.615μm范围内波长衍射效率在95%以上,且空气介质型结构光栅的通道均匀性要优于金属铝线型结构光栅;入射角在30?—60?范围内变化时,相同入射角度下,TM模式下器件角色散大于TE模式.基于Bragg衍射光栅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,为未来密集型EDG波分复用器发展提供了一种新的设计思路.

Based on the fact that Bragg reflection grating（BRG） is a special one-dimensional photonic crystal, we propose to apply the one-dimensional photonic crystal band gap theory to the design of Bragg reflection grating and then to make an analysis of its optical performance. According to the above band gap theory, FDTD solution is used to build the elliptical Bragg etched diffraction grating（EDG） based on the Rowland circle. We have studied the spectral characteristics for both TE and TM modes and the angle dispersion due to the variation of the incident angle, at the same time, the optical performances in the air dielectric type Bragg grating and the Al metallic line type Bragg grating are also made to compare with each other. It turns out that by choosing appropriate parameters the diffraction efficiency can be got more than 95% within the scope of 1.465–1.615 μm in both TE and TM modes, and the air dielectric type Bragg grating structure behaves better in the uniformity throughout the whole channel than in the Al metallic line type Bragg grating structure. When the incident angle varies from 30° to 60°, the angle dispersion in TM mode is larger than that in TE mode. This is the foundation of a new type of EDG wavelength division multiplexer with advantages of small size and high diffraction efficiency. It may have the potential to promote the development of high diffraction efficiency dense wavelength division multiplexer in the future.