A self-starting bi-chromatic LiNbO3 soliton microcomb

TL;DR

This paper demonstrates a self-starting soliton microcomb in lithium niobate resonators, leveraging its nonlinear and electro-optic properties for advanced optical applications.

Contribution

It introduces a monolithic lithium niobate microcomb with self-starting soliton mode locking and bi-directional switching, enabling multifunctional optical control.

Findings

Self-starting soliton mode locking achieved.

Observation of second-harmonic generation in the spectrum.

Determination of lithium niobate's Raman shock time constant.

Abstract

For its many useful properties, including second and third-order optical nonlinearity as well as electro-optic control, lithium niobate is considered an important potential microcomb material. Here, a soliton microcomb is demonstrated in a monolithic high-Q lithium niobate resonator. Besides the demonstration of soliton mode locking, the photorefractive effect enables mode locking to self-start and soliton switching to occur bi-directionally. Second-harmonic generation of the soliton spectrum is also observed, an essential step for comb self-referencing. The Raman shock time constant of lithium niobate is also determined by measurement of soliton self-frequency-shift. Besides the considerable technical simplification provided by a self-starting soliton system, these demonstrations, together with the electro-optic and piezoelectric properties of lithium niobate, open the door to a multi-functional microcomb providing f-2f generation and fast electrical control of optical frequency and repetition rate, all of which are critical in applications including time keeping, frequency synthesis/division, spectroscopy and signal generation.