Optical frequency combs significantly spanned to broad bandwidths by an optomechanical resonance

TL;DR

This paper introduces a novel method to generate broadband optomechanical frequency combs with over 10,000 lines by employing a self-organized nonlinear resonance mechanism, enabling stable and wide spectral coverage at low power.

Contribution

A new approach using dual-tone pumping to induce self-organized nonlinear resonance, significantly increasing comb line numbers and stability in optomechanical frequency combs.

Findings

Over 10,000 comb lines achieved with milliwatt pump power

Mechanical frequency locking ensures stable repetition rate

Broadband combs generated via nonlinear resonance mechanism

Abstract

Optical frequency comb, as a spectrum made of discrete and equally spaced spectral lines, is a light source with essential applications in modern technology. Cavity optomechanical systems were found to be a feasible candidate for realizing on-chip frequency comb with low repetition rate. However, it was difficult to increase the comb line numbers of this type of frequency combs because the mechanical oscillation amplitude of such system, which determines the frequency comb bandwidth, cannot quickly increase with pump laser power. Here, we develop a new approach to generate broadband optomechanical frequency comb by employing a different mechanism to enhance the mechanical oscillation. Two pump tones with their frequency difference matching the mechanical frequency will drive the system into a self-organized nonlinear resonance and thus tremendously transfer the energy to the mechanical resonator. As a result, more than $10000$ or even more comb lines become available under the pump laser power in the order of milliwatt. A unique feature of the self-organized resonance is the mechanical frequency locking so that, within a certain range of the frequency difference between two drive tones, the distance between comb teeth can be locked by the two drive tones and becomes independent of any change of pump power. This property guarantees a stable repetition rate of the generated frequency comb.