Mode-Locked Topological Insulator Laser Utilizing Synthetic Dimensions

TL;DR

This paper introduces a topological photonics-based laser system that uses synthetic dimensions to achieve robust mode-locking of multiple semiconductor lasers, resulting in stable, short pulses despite disorder.

Contribution

It presents a novel topological laser design utilizing synthetic frequency dimensions and Floquet edge states for robust, synchronized mode-locking of laser arrays.

Findings

Achieves mode-locking through topological edge states

Demonstrates robustness to disorder in laser arrays

Provides a proof-of-concept for topological laser synchronization

Abstract

We propose a system that exploits the fundamental features of topological photonics and synthetic dimensions to force many semiconductor laser resonators to synchronize, mutually lock, and under suitable modulation emit a train of transform-limited mode-locked pulses. These lasers exploit the Floquet topological edge states in a 1D array of ring resonators, which corresponds to a 2D topological system with one spatial dimension and one synthetic frequency dimension. We show that the lasing state of the multi-element laser system possesses the distinct characteristics of spatial topological edge states while exhibiting topologically protected transport. The topological synthetic-space edge mode imposes a constant-phase difference between the multi-frequency modes on the edges, and together with modulation of the individual elements forces the ensemble of resonators to mode-lock and emit short pulses, robust to disorder in the multi-resonator system. Our results offer a proof-of-concept mechanism to actively mode-lock a laser diode array of many lasing elements, which is otherwise extremely difficult due to the presence of many spatial modes of the array. The topological synthetic-space concepts proposed here offer an avenue to overcome this major technological challenge, and open new opportunities in laser physics.