Twisted light from topological chiral exceptional points in a nanolaser array

TL;DR

This paper demonstrates a nanolaser array that generates twisted light with orbital angular momentum by exploiting topological chiral exceptional points in a non-Hermitian photonic system, enabling controllable structured light emission.

Contribution

It introduces a novel topological nanolaser array design that utilizes non-Hermitian physics to produce and control orbital angular momentum in laser emission.

Findings

Realization of a topological nanolaser array with orbital angular momentum output.

Experimental demonstration of unidirectional energy flow at a chiral exceptional point.

Controlled tuning of laser phase and angular momentum via gain/loss contrast.

Abstract

We propose and experimentally demonstrate an orbital angular momentum (OAM) nanolaser array arranged in a ring geometry on an InP-based photonic crystal membrane. The device realizes a non-Hermitian extension of the Rice-Mele model, featuring alternating coupling strengths and imaginary on-site detunings. This configuration supports a symmetry-protected zero mode stabilized by non-Hermitian particle-hole symmetry, which enforces a uniform $\pi/2$ phase shift between adjacent nanolasers, establishing a coherent phase winding around the array. By adjusting the gain/loss contrast in a parity-time (PT)-like pumping scheme, the system can be tuned to a chiral exceptional point, where energy flows unidirectionally between nanocavities despite their reciprocal coupling. This symmetry-enforced, directional tunneling leads to far-field emission carrying non-zero OAM, providing a direct signature of the phase-structured lasing mode. Our results demonstrate a robust and scalable strategy for engineering compact, phase-locked laser arrays with controllable angular momentum output, and open new avenues for structured light generation in integrated photonic platforms.