Abstract
Light propagation effects can strongly influence the excitation and the detection of laser-induced
magnetization dynamics. We investigated experimentally and analytically the effects of
crystallographic linear birefringence on the excitation and detection of ultrafast magnetization
dynamics in the rare-earth orthoferrites (Sm 0.5 Pr 0.5 )FeO 3 and (Sm 0.55 Tb 0.45 )FeO 3 , which
possess weak and strong linear birefringence, respectively. Our finding is that the effect of linear
birefringence on the result of a magneto-optical pump-probe experiment strongly depends on the
mechanism of excitation. When magnetization dynamics, probed by means of the Faraday effect, is
excited via a rapid, heat-induced phase transition, the measured rotation of the probe pulse
polarization is strongly suppressed due to the birefringence. This contrasts with the situation for
magnetization dynamics induced by the ultrafast inverse Faraday effect, where the corresponding
probe polarization rotation values were larger in the orthoferrite with strong linear birefringence.
We show that this striking difference results from an interplay between the polarization
transformations experienced by pump and probe pulses in the birefringent medium.
