Simple method of fabricating polarisation-insensitiveand very low crosstalkAWG grating devices

A simple method of fabricating polarisation insensitive and very low crosstalk dense-WDM devices has been developed. The matching of the thermal coefficient of expansion (TCE) of the overcladding layer to the silicon substrate, for a 16 channel arrayed-waveguide demultiplexer, resulted in very low polarisation sensitivity (0.03 nm). The TCE of the undercladding and the core layers, on the other hand, were found to have negligible effect on the polarisation sensitivity. PECVD was used for depositing all the oxide layers.