Fabrication of low-loss and polarisation-insensitive256 channelarrayed-waveguide grating with 25 GHz spacing using 1.5% Δwaveguides

A 256 channel arrayed waveguide grating with a 25 GHz spacing was fabricated on a 4 inch Si wafer using 1.5% Δ silica-based waveguides with a minimum bending radius of 2 mm. By improving the fabrication methods of 1.5% Δ waveguides, we have obtained an on-chip loss of 2.7 – 4.7 dB, a far-end crosstalk of < –40 dB and a polarisation-dependent wavelength shift of < 0.025 nm.