Nonreciprocal magnetic-field-induced second harmonic generation of exciton polaritons in ZnSe

TL;DR

This paper demonstrates the first experimental observation of nonreciprocal second harmonic generation in semiconductor crystals, specifically in ZnSe exciton-polaritons under a magnetic field, revealing interference effects and symmetry considerations.

Contribution

It reports the first observation of nonreciprocal SHG in semiconductor crystals and develops phenomenological and microscopic models for the effect.

Findings

Nonreciprocal SHG intensity depends on magnetic field direction.

Interference of crystallographic and magnetic SHG signals explains the effect.

First experimental evidence of nonreciprocal SHG in exciton-polaritons.

Abstract

We report on the optical second harmonic generation (SHG) on the 1S exciton-polariton resonance in bulk ZnSe that is subject to an external magnetic field applied perpendicular to the light wave vector $\mathbf k$ (Voigt geometry). For the symmetry allowed geometry with the $\mathbf{k}\parallel[111]$ crystal axes, the nonreciprocal dependence of the SHG intensity on the magnetic field direction is found. It is explained by an interference of the crystallographic and magnetic-field-induced SHG signals. Relative phases of these signals are evaluated from the rotational anisotropy diagrams. Phenomenological and microscopic models of the effect are developed. To the best of our knowledge, this is the first experimental observation of the nonreciprocal SHG in semiconductor crystals, and the first one for exciton-polaritons.