# Experimental demonstration of asymmetric diffraction based on a passive parity-time-symmetric acoustic grating

## TL;DR

This paper experimentally demonstrates asymmetric diffraction in a passive parity-time-symmetric acoustic grating, showing enhanced diffraction and potential for advanced acoustic wave control in non-Hermitian systems.

## Contribution

It introduces a novel passive PT-symmetric acoustic grating with improved diffraction capabilities and eliminates previous design disturbances, enabling asymmetric diffraction observation.

## Key findings

- Enhanced diffraction ability in passive PT-symmetric grating
- Observation of asymmetric diffraction with balanced refractive index modulation
- Elimination of first-order disturbances in diffraction patterns

## Abstract

Passive parity-time-symmetric medium provides a feasible scheme to investigate non-Hermitian systems experimentally. Here, we design a passive PT-symmetric acoustic grating with a period equal to exact PT-symmetric medium. This treatment enhances the diffraction ability of a passive PT-symmetric grating with more compact modulation. Above all, it eliminates the first-order disturbance of previous design in diffraction grating. Additional cavities and small leaked holes on top plate in a 2D waveguide are used to construct a parity-time-symmetric potential. The combining between additional cavities and leaked holes makes it possible to modulate the real and imaginary parts of refractive index simultaneously. When the real and imaginary parts of refractive index are balanced in modulation, asymmetric diffraction can be observed between a pair of oblique incident waves. This demonstration provides a feasible way to construct passive parity-time-symmetric acoustic medium. It opens new possibilities for further investigation of acoustic wave control in non-Hermitian systems.

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Source: https://tomesphere.com/paper/1904.12692