Abstract: A method comprises non-destructive contact-free physical characterization of a sample by repeated excitations of the surface of a sample with a sequence of pulses comprising at least one pump pulse by a first “pump” laser followed by a succession of L temporarily offset pulses by a second “probe” laser, and the analysis of the beam emitted by the surface of the sample by an activated photodetector, for the acquisition of signals delivered by the photodetectors during constant time windows.