Polarisation insensitive and tuneable optical add and drop multiplexer utilising vertically stacked buried semiconductor waveguides

A polarisation insensitive and tuneable optical add and drop multiplexer ha s been realised by utilising vertically stacked buried semiconductor wavegu ides. The difference in peak wavelength of the dropped light between the tw o orthogonal polarisations was as small as 0.03nm, which is much smaller th an the 3dB bandwidth of 0.4nm. The difference in peak power was also as sma ll as 0.7dB. Furthermore, polarisation insensitivity was maintained even du ring wavelength tuning.