Optical detection of electron spin dynamics driven by fast variations of a magnetic field: a simple method to measure [Formula: see text] , [Formula: see text] , and [Formula: see text] in semiconductors

We develop a simple method for measuring the electron spin relaxation times [Formula: see text] , [Formula: see text] and [Formula: see text] in semiconductors and demonstrate its exemplary application to n-type GaAs. Using an abrupt variation of the magnetic field acting on electron spins, we detect the spin evolution by measuring the Faraday rotation of a short laser pulse. Depending on the magnetic field orientation, this allows us to measure either the longitudinal spin relaxation time [Formula: see text] or the inhomogeneous transverse spin dephasing time [Formula: see text] . In order to determine the homogeneous spin coherence time [Formula: see text] , we apply a pulse of an oscillating radiofrequency (rf) field resonant with the Larmor frequency and detect the subsequent decay of the spin precession. The amplitude of the rf-driven spin precession is significantly enhanced upon additional optical pumping along the magnetic field.