Gain-through-filtering enables tuneable frequency comb generation in passive optical resonators

TL;DR

This paper introduces a novel gain-through-filtering technique for generating tunable optical frequency combs in passive resonators, enabling frequency agility without complex dispersion engineering, demonstrated experimentally in fiber resonators.

Contribution

The paper presents a new method for OFC generation using gain-through-filtering, allowing tunable repetition rates without specialized dispersion engineering in passive resonators.

Findings

Successful experimental demonstration in fiber resonators.

Achieved tunable frequency combs with simple spectral filtering.

Pioneered a technique that simplifies OFC generation in passive resonators.

Abstract

Optical frequency combs (OFCs), consisting of a set of phase locked equally spaced laser frequency lines, have enabled a great leap in precision spectroscopy and metrology since seminal works of H\"ansch et al. . Nowadays, OFCs are cornerstones of a wealth of further applications ranging from chemistry and biology to astrophysics and including molecular fingerprinting and LIDARs among others. Driven passive optical resonators constitute the ideal platform for OFCs generation in terms of compactness and low energy footprint. We propose here a new technique for generation of OFCs with tuneable repetition rate in externally driven optical resonators based on the gain-through-filtering process, a simple and elegant method, due to an asymmetric spectral filtering on one side of the pump wave. We demonstrate a proof-of-concept experimental result in a fibre resonator, pioneering a new technique that does not require specific engineering of the resonator dispersion to generate frequency agile OFCs.