Fig. 3

Build-up of mode-locking. a B-field dependent Kerr signal at t = −15 ps for six scans taken at different times after depolarization of the nuclear spin polarization (difference between each scan is 15 s). An increase in offset or decrease in amplitude is a measure for mode-locking. b, c Extracted offset and amplitude of the oscillations in B from the fit in (a). Data are shown for different pump powers and a fixed probe power of 10 µW. The characteristic offset build-up time or amplitude decay time is pump power independent and is extracted from the fit to be 25 s