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设计了一种具有波长和偏振模式选择特性的GaAs材料的亚波长抗反射光栅,工作波长为976nm。采用等效介质理论与薄膜理论对光栅进行初步设计,基于严格耦合波法依次对光栅占空比、脊高和周期进行优化确定,同时分析了各个参数对光栅透射率的影响。所设计的抗反射光栅分别具有99.99%(横电模)和99.86%(横磁模)的高透射率,并且在976nm±30nm的范围内保持99%以上的高透射率,满足器件应用要求。最后研究了工艺误差导致的光栅非矩形形貌对光栅透射率以及偏振优势模式的影响。
A subwavelength anti-reflection grating of GaAs material with wavelength and polarization mode selection is designed. The working wavelength is 976 nm. The grating was preliminarily designed by using equivalent medium theory and thin film theory, and the grating duty cycle, ridge height and period were optimized and determined in turn based on the strict coupled wave method. Meanwhile, the influence of each parameter on the grating transmittance was analyzed. The designed anti-reflection grating has high transmittance of 99.99% (transverse electric mode) and 99.86% (transverse magnetic mode), respectively, and maintains high transmittance of 99% or more in the range of 976nm ± 30nm to meet the device application requirements. Finally, the influence of the non-rectangular shape of the grating caused by the process error on the grating transmissivity and the predominant mode of polarization is studied.