On-chip unidirectional dual-band fiber-chip grating coupler in silicon nitride

Abstract

We report, for the first time, a single state polarization (TE) dual-band grating fiber-chip coupler on a 700 nm thick silicon nitride platform that couples to both O and C band channels. Dual-band coupling with a single grating coupler is achieved using cross mode k-space equalization. By phase matching the first-order vertical TE01 mode and the fundamental TE00 mode in two distinct bands, we observe simultaneous co-directional dual-band coupling to a single waveguide. Experimental peak efficiency per coupler is measured to be −7.3 dB in the O-band and −8.2 dB in the C-band and the combined 1 dB bandwidth is observed to be 82 nm.