Bandwidth scaling and spectral flatness enhancement of optical frequency combs from phase modulated continuous-wave lasers using cascaded four-wave mixing

TL;DR

This paper presents a cascaded four-wave mixing method to significantly increase the bandwidth and spectral flatness of optical frequency combs generated from phase-modulated continuous-wave lasers, achieving record flatness and pulse generation.

Contribution

The authors introduce a novel cascaded four-wave mixing technique that enhances bandwidth and spectral flatness of frequency combs from CW lasers, with experimental demonstration of record flatness and pulse formation.

Findings

Achieved a 10 GHz frequency comb with over 100 lines within a 10-dB bandwidth.

Record 75 lines within 1-dB flatness.

Bandwidth increased by a factor of five through cascaded four-wave mixing.

Abstract

We introduce a new cascaded four-wave mixing technique which scales up the bandwidth of frequency combs generated by phase modulation of a continuous wave laser while simultaneously enhancing the spectral flatness. As a result we demonstrate a 10 GHz frequency comb with over 100 lines in a 10-dB bandwidth in which a record 75 lines are within a flatness of 1-dB. The cascaded four-wave mixing process increases the bandwidth of the initial comb generated by modulation of a CW laser by a factor of five. The broadband comb has approximately quadratic spectral phase, which is compensated upon propagation in single mode fiber, resulting in a 10 GHz train of 940 fs pulses