Study on Asymmetric Diffraction of Acoustic Parity-Time-Symmetric Gratings Using Rigorous Coupled-Wave Analysis

TL;DR

This paper develops a rigorous coupled-wave analysis method to study asymmetric diffraction in acoustic PT-symmetric gratings, revealing how modulation approaches influence diffraction and sound energy distribution.

Contribution

Introduces a novel RCWA-based analysis for acoustic PT-symmetric gratings with two modulation strategies, advancing understanding of asymmetric diffraction behaviors.

Findings

Diffraction vanishing points depend on modulation amplitude and approach.

Sound energy can be enhanced or weakened at Bragg angles.

Asymmetric diffraction varies with incident angles and modulation ratios.

Abstract

In PT-symmetric gratings, asymmetric diffraction can be generated by modulating the ratio between imaginary and real refractive indices. In this paper, a rigorous coupled-wave analysis (RCWA) has been developed to analyze the diffraction properties of acoustic PT-symmetric gratings with two kinds of modulating approaches, including modulating the effective modulus and the effective density. Asymmetric diffraction with both Bragg incident angles and perpendicular incident angles is discussed by using the RCWA method. Results show that the modulation ratio for the diffraction vanishing point changes with the modulation amplitude differently for two kinds of modulating approaches. Moreover, the sound energy will be weaken or be enhanced at Bragg incident angles depending on the sign of incident angles and the modulation ratio.