Optical frequency comb generation from a monolithic microresonator

TL;DR

This paper introduces a novel method for generating optical frequency combs using a monolithic microresonator and Kerr nonlinearity, achieving broad, stable combs without external spectral broadening.

Contribution

It demonstrates the first generation of optical frequency combs from a monolithic microresonator via Kerr nonlinearity, bypassing traditional mode-locking techniques.

Findings

Generated a 70 THz wide comb span around 1550 nm

Achieved mode spacing uniformity within 7.3×10^(-18)

Overcame passive cavity dispersion with cascaded parametric interactions

Abstract

Optical frequency combs provide equidistant frequency markers in the infrared, visible and ultra-violet and can link an unknown optical frequency to a radio or microwave frequency reference. Since their inception frequency combs have triggered major advances in optical frequency metrology and precision measurements and in applications such as broadband laser-based gas sensing8 and molecular fingerprinting. Early work generated frequency combs by intra-cavity phase modulation while to date frequency combs are generated utilizing the comb-like mode structure of mode-locked lasers, whose repetition rate and carrier envelope phase can be stabilized. Here, we report an entirely novel approach in which equally spaced frequency markers are generated from a continuous wave (CW) pump laser of a known frequency interacting with the modes of a monolithic high-Q microresonator13 via the Kerr nonlinearity. The intrinsically broadband nature of parametric gain enables the generation of discrete comb modes over a 500 nm wide span (ca. 70 THz) around 1550 nm without relying on any external spectral broadening. Optical-heterodyne-based measurements reveal that cascaded parametric interactions give rise to an optical frequency comb, overcoming passive cavity dispersion. The uniformity of the mode spacing has been verified to within a relative experimental precision of 7.3*10(-18).