The interplay between magnetic and electric degrees of freedom in magnetoelectric crystals significantly influences their optical properties. In particular, low-symmetry magnetoelectric materials can differentiate between counter-propagating light beams, and in extreme cases, they may be transparent in one direction while absorbing in the opposite. This effect relies on the comparable dipole oscillator strengths of magnetic and electric transitions and has been primarily explored in weakly electric dipole-active magnon excitations within the far-infrared and microwave spectral ranges.

To extend these phenomena into the visible and near-infrared spectral regions for potential applications, the candidate will investigate the optical transmission spectra of antiferromagnetic magnetoelectric crystals. The goal is to identify narrow, transparent resonances localized at 3d metal ions, which, when coupled with magnons of the antiferromagnetic phase, may exhibit non-reciprocal absorption. Additionally, these resonances may appear in photoluminescence spectra, providing experimental access to the splitting and shift of magnon resonances in the visible and near-infrared range.

The candidate will characterize the optical transmission of various magnetoelectric crystals, including rare-earth iron borates and transition-metal phosphorus trichalcogenides, to identify weak resonances in their magnetically ordered phase. Furthermore, they will examine the magnetic field dependence of absorption and photoluminescence signals. To interpret the results, optical spectra will be correlated with data obtained via time-resolved THz spectroscopy. Part of the experimental work of the candidate will be conducted in collaboration with industrial (Semilab) and international (TU Wien) partners.