Aluminum nitride integration on silicon nitride photonic circuits: a new hybrid approach towards on-chip nonlinear optics

TL;DR

This paper presents a novel hybrid integration method of aluminum nitride on silicon nitride photonic circuits, significantly simplifying fabrication and enhancing optical performance for on-chip nonlinear optics applications.

Contribution

It introduces a patterning-free hybrid integration approach of AlN on SiN photonic chips, improving quality factors and reducing propagation losses.

Findings

Hybrid resonators show tenfold increase in quality factor.

Propagation losses are reduced to 0.7 dB/cm.

Phase matching conditions are explored via simulations.

Abstract

Aluminum nitride (AlN) is an emerging material for integrated quantum photonics due to its large $\chi^{(2)}$ nonlinearity. Here we demonstrate the hybrid integration of AlN on silicon nitride (SiN) photonic chips. Composite microrings are fabricated by reactive DC sputtering of c-axis oriented AlN on top of pre-patterned SiN. This new approach does not require any patterning of AlN and depends only on reliable SiN nanofabrication. This simplifies the nanofabrication process drastically. Optical characteristics, such as the quality factor, propagation losses and group index, are obtained. Our hybrid resonators can have a one order of magnitude increase in quality factor after the AlN integration, with propagation losses down to \SI{0.7}{dB/cm}. Using finite-element simulations, phase matching in these waveguides is explored.