Optical Excitation and Probing of Antiferromagnetic Modes with Nonuniform-in-depth Distribution in Birefringent Antiferromagnetic Crystals

Optical pump-probe setups are commonly used for excitation and investigation of the spin dynamics in various types of magnetic materials. Usually spatially homogeneous excitation is considered, but here the authors describe the optical excitation of the $n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}f\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}m$ terahertz spin dynamics that are due to the intrinsic anisotropic properties of a weakly ferromagnetic material. They furthermore present an approach for probing and restoring the spatial distribution inside a magnetic crystal, which allows one to properly interpret the experimental results and obtain the complete picture of nonuniform terahertz spin dynamics.