Nozaki-Bekki optical solitons

TL;DR

This paper introduces Nozaki-Bekki solitons, a new type of stable, self-formed optical soliton in ring semiconductor lasers, achieved without external pumping, with potential for integrated frequency comb applications.

Contribution

It demonstrates the first experimental realization of Nozaki-Bekki solitons in a ring laser, combining theory and experiments to reveal their properties and formation mechanisms.

Findings

Nozaki-Bekki solitons are structurally stable in ring lasers.

Spontaneous formation of solitons with bias tuning eliminates external pump.

Multisoliton states and soliton crystals are observed.

Abstract

Recent years witnessed rapid progress of chip-scale integrated optical frequency comb sources. Among them, two classes are particularly significant -- semiconductor Fabry-Per\'{o}t lasers and passive ring Kerr microresonators. Here, we merge the two technologies in a ring semiconductor laser and demonstrate a new paradigm for free-running soliton formation, called Nozaki-Bekki soliton. These dissipative waveforms emerge in a family of traveling localized dark pulses, known within the famed complex Ginzburg-Landau equation. We show that Nozaki-Bekki solitons are structurally-stable in a ring laser and form spontaneously with tuning of the laser bias -- eliminating the need for an external optical pump. By combining conclusive experimental findings and a complementary elaborate theoretical model, we reveal the salient characteristics of these solitons and provide a guideline for their generation. Beyond the fundamental soliton circulating inside the ring laser, we demonstrate multisoliton states as well, verifying their localized nature and offering an insight into formation of soliton crystals. Our results consolidate a monolithic electrically-driven platform for direct soliton generation and open a door for a new research field at the junction of laser multimode dynamics and Kerr parametric processes.