# Non-Hermitian spectral changes in the scattering of partially coherent radiation by periodic structures

## TL;DR

This paper investigates how partially coherent light interacts with PT-symmetric non-Hermitian periodic structures, revealing unique spectral diffraction effects influenced by gain and loss properties.

## Contribution

It introduces a statistical optics analysis of partially coherent radiation scattering in PT-symmetric media, highlighting spectral changes due to non-Hermitian properties.

## Key findings

- Spectral density profiles depend on gain/loss characteristics.
- Unexpected contrasting diffraction patterns emerge compared to Hermitian structures.
- Light fluctuations influence spectrum changes and angular divergence.

## Abstract

The physical aspects of partially coherent radiation interacting with deterministic non-Hermitian periodic materials remain largely unexplored in the statistical optics literature. Here, we consider the scattering of partially coherent radiation by a deterministic periodic medium, symmetric under the simultaneous transformations of parity inversion and time reversal, that is, a parity-time (PT)-symmetric periodic medium. Taking into account light fluctuations, one is able to describe the spectrum changes on propagation and the influence of the coherence-driven angular divergence effect. The far-field spectral density profile is found to depend crucially on the loss/gain properties of the material, giving rise to unexpected and contrasting spectral diffraction profiles when compared to the Hermitian ones.