Abstract

Silicon nitride is a dielectric material widely used for applications in linear and nonlinear optics. It has an ultra-broad transparency window, low intrinsic loss, and a refractive index that allows for moderate optical field confinement in waveguides. The chemical composition of this material can be precisely set during the fabrication process, leading to an extra degree of freedom for tailoring the optical and mechanical properties of photonic chips. Silicon-rich silicon nitride waveguides are appealing for nonlinear optics, because they have a higher nonlinear Kerr coefficient and refractive index than what is possible with stoichiometric silicon nitride. This is a direct consequence of the increased silicon content. However, silicon-rich silicon nitride waveguides typically display higher absorption losses. In this Letter, we report low-loss ($\sim 0.4\mathrm{dB}/\mathrm{cm}$) silicon-rich silicon nitride waveguides. The structures feature high optical confinement and can be engineered with low anomalous dispersion. We find an optimum silicon composition that, through an annealing process, overcomes optical losses associated to N-H bonds in the telecom band. Based on this technology, we successfully fabricate microresonators with mean quality factors ($Q$) $\sim 0.8\times {10}^6$ in the C and L bands. Broadband coherent microresonator frequency combs are generated in this platform, indicating its potential for efficient Kerr nonlinear optics.

© 2019 Optical Society of America

Impact of the precursor gas ratio on dispersion engineering of broadband silicon nitride microresonator frequency combs

Gregory Moille, Daron Westly, Gregory Simelgor, and Kartik Srinivasan
Opt. Lett. 46(23) 5970-5973 (2021)

Linear and nonlinear characterization of low-stress high-confinement silicon-rich nitride waveguides

Clemens J. Krückel, Attila Fülöp, Thomas Klintberg, Jörgen Bengtsson, Peter A. Andrekson, and Víctor Torres-Company
Opt. Express 23(20) 25827-25837 (2015)

High-Q Si₃N₄ microresonators based on a subtractive processing for Kerr nonlinear optics

Zhichao Ye, Krishna Twayana, Peter A. Andrekson, and Victor Torres-Company
Opt. Express 27(24) 35719-35727 (2019)

Thermo-optic coefficient of PECVD silicon-rich silicon nitride

Natale G. Pruiti, Charalambos Klitis, Christopher Gough, Stuart May, and Marc Sorel
Opt. Lett. 45(22) 6242-6245 (2020)

Demonstration of the DC-Kerr effect in silicon-rich nitride

Alex Friedman, Hani Nejadriahi, Rajat Sharma, and Yeshaiahu Fainman
Opt. Lett. 46(17) 4236-4239 (2021)