Broad-band picosecond radiation may be produced by sending trains of pulses, or single pulses, from mode-locked high-power lasers through amorphous solids, liquids, and liquid mixtures. The broad-band picosecond radiation that results is useful, for example, in absorption spectroscopy of short-lived species. Broad-band picosecond light sources have been developed and used extensively by Rentzepis and co-workers. Pure H2O and pure D2O were employed to produce the broad-band picosecond continuum, which was considered to arise primarily from self-phase modulation in the pure liquids.
M. J. Colles and G. E. Walrafen, "Broad-band Picosecond Light Source," Appl. Spectrosc. 30, 463-465 (1976)