An Eight-Channel 400 GHz-Spacing Etched Diffraction Grating Multi/Demultiplexer on a Nanophotonic Silicon-on-Insulator Platform

An eight-channel 400 GHz-spacing planar waveguide multi/demultiplexer employing etched diffraction grating is designed and fabricated on a silicon-on-insulator platform with a 220 nm thick top layer. The design parameters are optimized by scalar diffraction simulation to obtain optimal performance with a small footprint of only 0.75 mm². A bi-level adiabatic taper is used to connect the input/output waveguide and the slab waveguide so as to reduce the insertion loss and the broadening of the diffraction angle of the propagating light. The device is fabricated in a two-step process with E-beam lithography and dry etching, and the alignment accuracy is 10 nm or even better. Measurements show that the insertion loss is 7.35 dB and the crosstalk between adjacent channels is about ?15 dB. Ways to improve the performance are also investigated in detail.