Lopsided optical diffraction in loop electromagnetically induced grating

TL;DR

This paper presents a theoretical scheme for creating a lopsided optical diffraction grating in a cold Rubidium-87 atomic ensemble using non-Hermitian optical structures and loop-phase modulation, enabling precise control of asymmetric optical responses.

Contribution

It introduces a novel non-Hermitian optical scheme with switchable $ ext{PT}$ and $ ext{APT}$ symmetry for asymmetric diffraction control in atomic ensembles.

Findings

Realization of lopsided optical diffraction in a cold atomic ensemble.

Robustness of $ ext{PT}$ and $ ext{APT}$ symmetry to coupling field amplitudes.

Observation of nontrivial diffraction phenomena like single-order and asymmetric diffraction.

Abstract

We propose a theoretical scheme in a cold Rubidium-87 ($^{87}$Rb) atomic ensemble with a non-Hermitian optical structure, in which a lopsided optical diffraction grating can be realized just with the combination of single spatially periodic modulation and loop-phase.~Parity-time ($\mathcal{PT}$) symmetric and parity-time antisymmetric ($\mathcal{APT}$) modulation can be switched by adjusting different relative phases of the applied beams. Both $\mathcal{PT}$ symmetry and $\mathcal{PT}$ antisymmetry in our system are robust to the amplitudes of coupling fields, which allows optical response to be modulated precisely without symmetry breaking. Our scheme shows some nontrivial optical properties, such as lopsided diffraction, single-order diffraction, asymmetric Dammam-like diffraction, etc. Our work will benefit the development of versatile non-Hermitian/asymmetric optical devices.