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arXiv · 2512.09388

Twisted light from topological chiral exceptional points in a nanolaser array

Kaiwen Ji·Melissa Hedir·Qi Zhong·Ramy El-Ganainy·Alejandro M. Yacomotti·Li Ge
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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.

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Kaiwen Ji, Melissa Hedir, Qi Zhong, Ramy El-Ganainy, Alejandro M. Yacomotti, Li Ge. 2025-12-10. Twisted light from topological chiral exceptional points in a nanolaser array. https://arxiv.org/abs/2512.09388

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