  We demonstrate that the magneto-optic-Kerr effect with normal light incidence
can be used to obtain quantitative optical measurements of both components of
spin-orbit-induced torque (both the antidamping and effective-field components)
in heavy-metal/ferromagnet bilayers. This is achieved by analyzing the
quadratic Kerr effect as well as the polar Kerr effect. The two effects can be
distinguished by properly selecting the polarization of the incident light. We
use this all-optical technique to determine the spin-orbit torques generated by
a series of Pt/Permalloy samples, finding values in excellent agreement with
spin-torque ferromagnetic resonance measurements.
