Analysis of the loss resulting from point defects for an etched diffraction grating demultiplexer by using the method of moments

An effective method for analyzing the effect of point defects (e.g., dust grains and air bubbles) on an etched diffraction grating demultiplexer is presented by using the method of moments. This method leads to a deep insight into the influence of point defects on the loss of the demultiplexer. Numerical results show that strong resonance losses can be produced at some special point defects and incident light.