Compact Silicon Nitride Arrayed Waveguide Gratings for Very Near-Infrared Wavelengths

In this letter, we report a novel high-index-contrast silicon nitride arrayed waveguide grating (AWG) for very near-infrared wavelengths. This device is fabricated through a process compatible with a complementary metal-oxide-semiconductor fabrication line and is therefore suitable for mass fabrication. The large phase errors that usually accompany high-index-platform AWGs are partly mitigated through design and fabrication adaptions, in particular the implementation of a two-level etch scheme. Multiple devices are reported, among which a 0.3-mm² device which, after the subtraction of waveguides loss, has a -1.2 dB on-chip insertion loss at the peak of the central channel and 20-dB crosstalk for operation $\sim 900$ nm with a channel spacing of 2 nm. These AWGs pave the way for numerous large-scale on-chip applications pertaining to spectroscopy and sensing.