Photonic Damascene Process for Integrated High-Q Microresonator Based Nonlinear Photonics

TL;DR

This paper introduces a novel photonic Damascene process for fabricating high-Q silicon nitride microresonators, enabling reliable, high-performance nonlinear photonic devices with broad applications in frequency comb generation.

Contribution

The paper presents a new fabrication method that improves stress control and crack prevention in high-Q SiN microresonators, achieving near-unity yield and high optical quality factors.

Findings

Achieved optical Q factors of 3.7×10^6 in microresonators.

Demonstrated single dissipative Kerr soliton frequency combs.

Developed a fabrication process applicable to various material platforms.

Abstract

High confinement, integrated silicon nitride (SiN) waveguides have recently emerged as attractive platform for on-chip nonlinear optical devices. The fabrication of high-Q SiN microresonators with anomalous group velocity dispersion (GVD) has enabled broadband nonlinear optical frequency comb generation. Such frequency combs have been successfully applied in coherent communication and ultrashort pulse generation. However, the reliable fabrication of high confinement waveguides from stoichiometric, high stress SiN remains challenging. Here we present a novel photonic Damascene fabrication process enabling the use of substrate topography for stress control and thin film crack prevention. With close to unity sample yield we fabricate microresonators with $1.35\,\mu\mathrm{m}$ thick waveguides and optical Q factors of $3.7\times10^{6}$ and demonstrate single temporal dissipative Kerr soliton (DKS) based coherent optical frequency comb generation. Our newly developed process is interesting also for other material platforms, photonic integration and mid infrared Kerr comb generation.