Simultaneous generation of Raman-assisted Soliton Microcombs and Tunable Multi-chromatic Raman Microlasers in Single Monolithic Thin-film Lithium Niobate Microrings

TL;DR

This paper demonstrates a monolithic lithium niobate microring platform capable of generating tunable Raman-assisted soliton microcombs and multi-chromatic Raman microlasers, advancing integrated broadband coherent light sources for various applications.

Contribution

The study introduces a novel dispersion-engineered LNOI microring with all waves of the same polarization, enabling simultaneous generation of soliton microcombs and multi-chromatic Raman lasers with efficient tuning.

Findings

Achieved a record-low pump threshold for Raman-assisted soliton combs.

Generated multi-chromatic Raman lasing at multiple wavelengths within a single device.

Demonstrated efficient wavelength tuning through pump wavelength adjustment.

Abstract

High-performance integrated broadband coherent light sources are essential for advanced applications in high-bandwidth data processing and chip-scale metrology, yet remain challenging. In this study, we demonstrate a monolithic Z-cut lithium niobate on insulator (LNOI) microring platform that enables simultaneous generation of tunable multi-chromatic microlasers and Raman-assisted soliton microcombs. Exploiting the strong Raman activity and high second-order nonlinearity of LNOI, we engineered a dispersion-optimized microring with a loaded Q factor of 3.86X10^6, facilitating on-chip efficient broadband coherent light source. A novel phase-matching configuration with all the waves of the same ordinary polarization was realized for the first time in this platform, feasibly enabling modal-phase matched Raman-quadratic nonlinear processes that extend lasing signals into the visible spectrum. Under continuous-wave laser pumping at 3.73 mW in the telecom band, we achieved a Raman-assisted soliton comb centered at 1624.49 nm with record-low pump threshold on the LNOI platform. Concurrently, multi-chromatic Raman lasing outputs were observed at ~1700, ~813, and ~535 nm within the same microring. The system exhibited efficient wavelength tuning of these multi-chromatic laser signals through a 5 nm shift in pump wavelength. This work represents a significant advance in integrated photonics for versatile optical signal generation.