Measurement with subpicosecond resolution of the frequency sweep of an ultraviolet supercontinuum.

It has been reported in the literature that when high-power subpicosecond pulses are focused into high-pressure gases such as H2 or Ar, supercontinuum generation occurs. The present authors have measured with subpicosecond resolution the frequency sweep of the spectrum of the energetic UV supercontinuum beam that emerges from a high-pressure Ar cell when high-power subpicosecond UV (308-nm) pulses are focused into the cell, using a novel method based on time-resolved absorption spectroscopy. The experimental procedure is described, and the results are shown. The technique, which utilizes TlCl photodissociation, has also revealed some interesting features of the photodissociation process itself.