Optical multistability in a compact microcavity enabled by near-exceptional coupling
Abstract
Multistability -- the emergence of multiple stable states under identical conditions -- is a hallmark of nonlinear complexity and an enabling mechanism for multilevel optical memory and photonic computing. Its realization in a compact footprint, however, is limited by intrinsically weak optical nonlinearities and the enlarged free spectral range that raises the multistability threshold. Here, we overcome this constraint by engineering a pair of spectrally close, ultra-high-Q resonances in a photonic crystal microcavity. Leveraging structural perturbations that deliberately introduce non-Hermitian coupling through a shared radiation channel, we drive the resonances toward an exceptional point with nearly degenerate wavelengths and balanced quality factors approaching . This configuration substantially enhances thermo-optical nonlinearity and produces pronounced tristability and hysteresis loops within a footprint of 20 {\mu}m at input powers below 240 {\mu}W. We further demonstrate proof-of-concept optical random-access memory through controlled switching among multistable states. These results establish a general strategy for nonlinear microcavities to achieve energy-efficient multistability for reconfigurable all-optical memories, logic, and neuromorphic processors.
Cite
@article{arxiv.2511.12037,
title = {Optical multistability in a compact microcavity enabled by near-exceptional coupling},
author = {Zhen Liu and Xuefan Yin and Andrey Bogdanov and Yujia Nie and Yi Zuo and Hongbin Li and Feifan Wang and Chao Peng},
journal= {arXiv preprint arXiv:2511.12037},
year = {2025}
}