The impact of fabrication errors on a flat-top grating-based planar waveguide demultiplexer

The spectral performance of a demultiplexer is significantly affected by the phase and amplitude errors due to fabrication errors. We estimate the impact of fabrication errors on a flat-top grating-based planar waveguide demultiplexer using a design example. Simulation results show that the photomask resolution resulting in a phase error should be lower than 40 nm when a crosstalk criterion of -30 dB is given. The impact of amplitude errors is not distinct until the reduced amount of the facet width is greater than 0.5 mu m and the grating side-wall angle offset from the vertical is larger than 1 degrees.