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

TL;DR

This paper introduces a novel, nondestructive method using cross-polarization imaging to directly observe exceptional points in photonic crystals, overcoming previous challenges in spectral singularity detection.

Contribution

The study presents a simple, effective technique for directly visualizing exceptional points in momentum space of photonic crystals, validated by experiments and simulations.

Findings

Successful direct observation of EPs in momentum-resolved scattering

Alignment of experimental results with numerical simulations

Enhanced ability to study non-Hermitian physics in PhCs

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.