Spectrally resolved linewidth enhancement factor of a semiconductor frequency comb

TL;DR

This paper introduces a novel phase-sensitive method to directly measure the spectrally resolved linewidth enhancement factor in semiconductor laser frequency combs, verified through simulations and demonstrated experimentally on a quantum cascade laser.

Contribution

It presents a new modulation technique for direct spectral LEF measurement in laser combs, advancing understanding of comb dynamics.

Findings

Successful experimental measurement of spectral LEF in a quantum cascade laser

Verification of the technique through Maxwell-Bloch simulations

Potential for improved control of semiconductor laser frequency combs

Abstract

The linewidth enhancement factor (LEF) has recently moved into the spotlight of research on frequency comb generation in semiconductor lasers. Here we present a novel modulation experiment, which enables the direct measurement of the spectrally resolved LEF in a laser frequency comb. By utilizing a phase-sensitive technique, we are able to extract the LEF for each comb mode. We first investigate and verify this universally applicable technique using Maxwell-Bloch simulations and then present the experimental demonstration on a quantum cascade laser frequency comb.