Polarization-resolved measurement of forward volume spin waves by micro-focused Brillouin light scattering
Abstract
We show how the micro-focused BLS signal of forward volume spin waves is formed and why it remains observable despite symmetry-based "suppression" expectations. A reciprocity-theorem based model with vectorial diffraction-limited focusing identifies the nonnegligible longitudinal focal-field component as the key element responsible for BLS sensitivity in the forward volume geometry. We further demonstrate that full polarization analysis, implemented through polarizer-analyzer maps of coherently excited spin waves, provides information beyond the conventional crossed polarizer-analyzer readout. In a BiYIG thin film, the measured maps exhibit Stokes/anti-Stokes polarization asymmetries and nontrivial patterns that stem from quadratic magneto-optical coupling terms. Fitting the data with a model including Voigt and Cotton-Mouton contributions yields an effective Cotton-Mouton constant and shows that the quadratic response is comparable to the linear Voigt contribution.
Keywords
Cite
@article{arxiv.2602.15760,
title = {Polarization-resolved measurement of forward volume spin waves by micro-focused Brillouin light scattering},
author = {Krzysztof Szulc and Mengying Guo and Ondřej Wojewoda and Hongyu Wang and Dominik Pavelka and Jan Klíma and Jakub Krčma and Xiufeng Han and Qi Wang and Michal Urbánek},
journal= {arXiv preprint arXiv:2602.15760},
year = {2026}
}