We review and present additional results from our work on multilayer silicon nitride (SiN) on silicon-on-insulator (SOI) integrated photonic platforms over the telecommunication wavelength bands near 1550 and 1310 nm. SiN-on-SOI platforms open the possibility for passive optical functionalities implemented in the SiN layer to be combined with active functionalities in the SOI. SiN layers can be integrated onto SOI using a front-end or back-end of line integration process flow. These photonic platforms support low-loss SiN waveguides, low-loss and low-crosstalk waveguide crossings, and low-loss interlayer transitions using adiabatic tapers. Novel ultra-broadband and efficient grating couplers as well as polarization management devices are enabled by the close coupling between the silicon and SiN layers.

This paper discusses multilayer platforms using silicon nitride and silicon waveguides. This technology allows 3-D photonic circuits to be created.

We propose and experimentally demonstrate fiber-to-chip grating couplers with aligned silicon nitride (Si(3)N(4)) and silicon (Si) grating teeth for wide bandwidths and high coupling efficiencies without the use of bottom reflectors. The measured 1-dB bandwidth is a record 80 nm, and the measured peak coupling efficiency is -1.3 dB, which is competitive with the best Si-only grating couplers. The grating couplers are integrated in a Si(3)N(4) on silicon-on-insulator (SOI) integrated optics platform with aligned waveguides in both the Si(3)N(4) and Si, and we demonstrate a 1 × 4 tunable multiplexer/demultiplexer using the Si(3)N(4)-on-SOI dual-level grating couplers and thermally-tuned Si microring resonators.