Quantum Walk Comb in a Fast Gain Laser

TL;DR

This paper introduces a Quantum Walk Laser in synthetic frequency space using a modulated semiconductor laser, producing a broadband, stable frequency comb with potential for various photonic applications.

Contribution

It demonstrates a novel quantum walk laser device that stabilizes in a broadband frequency comb thanks to fast-gain nonlinearity, advancing photonic synthetic lattice technologies.

Findings

Produces a low-noise, broadband frequency comb up to 100 cm$^{-1}$ bandwidth

The device's behavior is well predicted by theoretical models

Offers a new platform for tunable, stable frequency comb generation

Abstract

Synthetic lattices in photonics enable the exploration of light states in new dimensions, transcending phenomena common only to physical space. We propose and demonstrate a Quantum Walk Laser in synthetic frequency space formed by externally modulating a ring-shaped semiconductor laser with ultrafast recovery times. In this device, the initially ballistic quantum walk does not dissipate into low supermode states of the synthetic lattice; instead, thanks to the fast-gain nonlinearity of our quantum cascade laser active material, the state stabilizes in a broad frequency comb, unlocking the full potential of the lattice. This device produces a low-noise, nearly-flat broadband comb (reaching 100 cm$^{-1}$ bandwidth), well predicted by our models. The proposed Quantum Walk Laser offers a promising platform to generate broadband, tunable and stable frequency combs.