Hybrid Scandium Aluminum Nitride/Silicon Nitride Integrated Photonic Circuits

TL;DR

This paper introduces a hybrid silicon nitride and scandium aluminum nitride waveguide platform that significantly reduces optical loss, enabling scalable, functional quantum photonic circuits with potential for advanced optical applications.

Contribution

It presents a monolithic integration of Si3N4 and ScAlN waveguides achieving low loss and high quality factors, overcoming previous limitations of scandium-doped aluminum nitride.

Findings

Achieved an intrinsic quality factor of 3.35 x 10^5.

Reduced propagation loss to 1.03 dB/cm, comparable to commercial waveguides.

Demonstrated a scalable platform retaining ScAlN functionalities.

Abstract

Scandium-doped aluminum nitride has recently emerged as a promising material for quantum photonic integrated circuits (PICs) due to its unique combination of strong second-order nonlinearity, ferroelectricity, piezoelectricity, and complementary metal-oxide-semiconductor (CMOS) compatibility. However, the relatively high optical loss reported to date-typically above 2.4 dB/cm-remains a key challenge that limits its widespread application in low-loss PICs. Here, we present a monolithically integrated $\mathrm{Si}_3\mathrm{N}_4$-ScAlN waveguide platform that overcomes this limitation. By confining light within an etched $\mathrm{Si}_3\mathrm{N}_4$ waveguide while preserving the functional properties of the underlying ScAlN layer, we achieve an intrinsic quality factor of $Q_{\mathrm{i}} = 3.35 \times 10^5$, corresponding to a propagation loss of 1.03 dB/cm-comparable to that of commercial single-mode silicon-on-insulator (SOI) waveguides. This hybrid architecture enables low-loss and scalable fabrication while retaining the advanced functionalities offered by ScAlN, such as ferroelectricity and piezoelectricity. Our results establish a new pathway for ScAlN-based PICs with potential applications in high-speed optical communication, modulation, sensing, nonlinear optics, and quantum optics within CMOS-compatible platforms.