Effects of surface roughness on the performance of an etched diffraction grating demultiplexer.
The fabrication tolerance of surface roughness on the performance [such as the insertion loss, the polarization-dependent loss (PDL), and the chromatic dispersion] of an etched diffraction grating demultiplexer is analyzed by using an accurate method of moments. The results show that both the insertion loss and the chromatic dispersion rapidly increase as the roughness of the grating facets increases. Appropriate residual roughness of the shaded facets can reduce the PDL of the demultiplexer, and the mechanism for the existence of an optimal residual roughness is explained.
Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Joint Research Center of Photonics of the Royal Institute of Technology, Stockholm, Sweden. songjun@coer.zju.edu.cn
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