Direct Observation of Exceptional Points in Photonic Crystal by Cross-Polarization Imaging in Momentum Space

Viet Anh Nguyen; Viet Hoang Le; Loïc Malgrey; Eirini Sarelli; Dang-Khue Luu; Ha Linh Chu; Cong Quang Tong; Vu Dinh Lam; Christian Seassal; Quynh Le-Van; Hai Son Nguyen

arXiv · 2309.01712

Direct Observation of Exceptional Points in Photonic Crystal by Cross-Polarization Imaging in Momentum Space

Viet Anh Nguyen·Viet Hoang Le·Loïc Malgrey·Eirini Sarelli·Dang-Khue Luu·Ha Linh Chu·Cong Quang Tong·Vu Dinh Lam·Christian Seassal·Quynh Le-Van·Hai Son Nguyen

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Abstract

This study explores exceptional points (EPs) in photonic crystals (PhCs) and introduces a novel method for their single-shot observation. Exceptional points are spectral singularities found in non-Hermitian systems, such as leaky PhC slabs. However, directly observing EPs in PhC systems using regular reflectivity spectroscopy is a considerable challenge due to interference between guided resonances and background signals. In this work, we present a simple, nondestructive technique that employs crossed polarizations to directly observe EPs in momentum-resolved resonant scattering. This approach effectively suppresses the background signal, enabling exclusive probing of the guided resonances where EPs manifest. Our results demonstrate the formation of EPs in both energy-momentum mapping and isofrequency imaging. All experimental findings align seamlessly with numerical simulations and analytical models. Our approach holds great potential as a robust tool for studying non-Hermitian physics in PhC platform.

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Viet Anh Nguyen, Viet Hoang Le, Loïc Malgrey, Eirini Sarelli, Dang-Khue Luu, Ha Linh Chu, Cong Quang Tong, Vu Dinh Lam, Christian Seassal, Quynh Le-Van, Hai Son Nguyen. 2023-09-04. Direct Observation of Exceptional Points in Photonic Crystal by Cross-Polarization Imaging in Momentum Space. https://arxiv.org/abs/2309.01712

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