Ultrafast insulator-to-metal phase transition as a switch to measure the spectrogram of a supercontinuum light pulse

摘要

In this letter we demonstrate the possibility to determine the temporal andspectral structure (spectrogram) of a complex light pulse exploiting theultrafast switching character of a non-thermal photo-induced phase transition.As a proof, we use a VO2 multi-film, undergoing an ultrafast insulator-to-metalphase transition when excited by femtosecond near-infrared laser pulses. Theabrupt variation of the multi-film optical properties, over a broadinfrared/visible frequency range, is exploited to determine, in-situ and in asimple way, the spectrogram of a supercontinuum pulse produced by a photoniccrystal fiber. The determination of the structure of the pulse is mandatory todevelop new pump-probe experiments with frequency resolution over a broadspectral range (700-1100 nm).