FIber Nonlinear rEsonator for ultra-stable optical frequency COMBs

Objective

The project FINECOMB (FIber Nonlinear rEsonator for ultra-stable optical frequency COMBs) aims to stabilize the repetition rate and phase of an optical frequency comb generated with a coherently driven fiber resonator, to develop this technology for high-resolution metrology applications. Optical frequency combs are coherent light sources emitting a broad spectrum of discrete and evenly spaced narrow frequency lines, corresponding in the time domain to a train of optical pulses with a regular repetition rate. They are widely used as optical references and have driven major advances in fields such as high-resolution spectroscopy, optical referencing of atomic clocks, astronomy, and high-capacity optical communications. Nonlinear fiber resonators, typically composed of tens of meters of optical fiber looped back on itself, can generate such frequency combs through the emergence of cavity solitons: non-deforming pulses of light that circulate indefinitely within the resonator when coherently driven by an external continuous-wave laser. By releasing energy at each round trip, a regular pulse train is obtained at the cavity output, generating an optical frequency comb. However, these devices are very sensitive to mechanical vibrations and thermal fluctuations, leading to noisy comb at the output and limiting their use in applications. The aim of FINECOMB is to build an ultra-stable optical frequency comb source based on a nonlinear fiber resonator. It will investigate the noise dynamics of the generated combs and develop solutions to achieve a low-noise frequency comb, with metrological applications as the ultimate goal. The focus will be on transferring the stability of an optical reference to the comb generated by the fiber cavity.