Low-Crosstalk Fabrication-Insensitive Echelle Grating Demultiplexers on Silicon-on-Insulator

In this letter, we report about design, fabrication, and testing of echelle grating (EG) demultiplexers in the O-band (1.31-mu m) for silicon-based photonic integrated circuits. In detail, flat band perfectly chirped EGs and two-point stigmatic EGs on the 300-nm thick silicon-on-insulator platform designed for 4 x 800-GHz spaced wavelength-division multiplexing featuring a low average crosstalk (-30 dB), a precise channel spacing, optimized interchannel uniformity (0.7 dB) and insertion losses (3-3.5 dB) are presented. Wafer-level statistical performance analysis shows the EG spectral response to be stable over the wafer in terms of crosstalk, channel spacing, and bandwidth with minimal wavelength dispersion (<0.8 nm), thus highlighting the intrinsic robustness of high-order gratings and chosen fab pathways as well as the full reliability of 3-D vectorial modeling tools.