Measurement of nonlinear temporal phase shifts using spectral Foucault technique

Temporal phase shifts induced by cross-phase modulation are directly characterised with a spectral equivalent of the Foucault technique used to spatially resolve wavefronts. The temporal phase induced by a high power pulsed pump on a monochromatic probe is converted to a temporal intensity modulation via spectral filtering. A measurement of the modulated instantaneous power of the filtered signal allows direct determination of the time-resolved nonlinear phase shift. An experimental demonstration is performed on a highly nonlinear fibre.