Folded 15-channel arrayed waveguide gratings on silicon nitride platform with loop reflector

Abstract

Silicon nitride (Si3N4) arrayed waveguide gratings (AWGs) have been widely used for dense wavelength division multiplexing systems because of their low loss and crosstalk. However, they have larger footprints because of their lower relative index compared with silicon-on-insulator (SOI) devices. In this study, a folded 1×15 Si3N4 AWG was fabricated on an SOI wafer with a silicon photonics loop reflector. The combination of the Si3N4 AWG and the Si loop reflector greatly reduced the device footprint and increased the fabrication tolerances. A layer coupler was used to connect the arrayed waveguides of the AWG to the Si loop reflector. The folded AWG consisted of a half Si3N4 AWG structure, an layer coupler array, and a Si loop reflector array. The measured insertion loss and crosstalk of the designed AWG were -5.46 dB and -17.2 dB, respectively. The integration of the half Si3N4 AWG and the arrayed Si loop reflectors can effectively reduce the large footprint of a Si3N4 AWG device with a standard complementary metal–oxide–semiconductor process while maintaining a relatively high performance.