# Unidirectional and controllable higher-order diffraction by a Rydberg electromagnetically induced grating

## TL;DR

This paper introduces a novel Rydberg electromagnetically induced grating that enables unidirectional and higher-order diffraction of a probe beam, advancing quantum device implementations with cold Rydberg atoms.

## Contribution

It proposes a new scheme combining position-dependent two-photon detuning and standing-wave modulation to achieve controllable unidirectional and higher-order diffraction.

## Key findings

- Perfect unidirectional diffraction grating achieved.
- Higher-order diffraction increases with van der Waals interaction.
- Dispersion modulation enables controllable diffraction patterns.

## Abstract

A method for diffracting the weak probe beam into unidirectional and higher-order directions is proposed via a novel Rydberg electromagnetically induced grating, providing a new way for the implementations of quantum devices with cold Rydberg atoms. The proposed scheme utilizes a suitable and position-dependent adjustment to the two-photon detuning besides the modulation of the standing-wave coupling field, bringing a in-phase modulation which can change the parity of the dispersion. We observe that when the modulation amplitude is appropriate, a perfect unidirectional diffraction grating can be realized. In addition, due to the mutual effect between the van der Waals (vdWs) interaction and the atom-field interaction length that deeply improves the dispersion of the medium, the probe energy can be counter-intuitively transferred into higher-order diffractions as increasing the vdWs interaction, leading to the realization of a controllable higher-order diffraction grating via strong blockade.