# Topological Microlaser with A non-Hermitian Topological Bulk

## TL;DR

This paper demonstrates a topological microlaser with a well-defined non-Hermitian bulk topology in a 1D resonator array, experimentally linking non-Hermitian topological theory with laser applications.

## Contribution

It introduces a 1D topological laser with a non-Hermitian bulk topology, modeled as a 2D non-Hermitian Chern insulator via synthetic dimensions, and experimentally verifies its properties.

## Key findings

- Successful experimental realization of topological edge-mode lasing.
- Clear identification of non-Hermitian bulk topology in the laser system.
- Establishment of a link between 1D resonator arrays and 2D non-Hermitian topological models.

## Abstract

Bulk-edge correspondence, with quantized bulk topology leading to protected edge states, is a hallmark of topological states of matter and has been experimentally observed in electronic, atomic, photonic, and many other systems. While bulk-edge correspondence has been extensively studied in Hermitian systems, a non-Hermitian bulk could drastically modify the Hermitian topological band theory due to the interplay between non-Hermiticity and topology; and its effect on bulk-edge correspondence is still an ongoing pursuit. Importantly, including non-Hermicity can significantly expand the horizon of topological states of matter and lead to a plethora of unique properties and device applications, an example of which is a topological laser. However, the bulk topology, and thereby the bulk-edge correspondence, in existing topological edge-mode lasers is not well defined. Here, we propose and experimentally probe topological edge-mode lasing with a well-defined non-Hermitian bulk topology in a one-dimensional (1D) array of coupled ring resonators. By modeling the Hamiltonian with an additional degree of freedom (referred to as synthetic dimension), our 1D structure is equivalent to a 2D non-Hermitian Chern insulator with precise mapping. Our work may open a new pathway for probing non-Hermitian topological effects and exploring non-Hermitian topological device applications.

---
Source: https://tomesphere.com/paper/2303.00114