Supercontinuum from a few-cycle filament in argon: Characterization and UV spectroscopic application

摘要

Focusing few-cycle pulses with duration 6 - 12 fs at 800 nm with moderate energy (0.25 - 0.35 mJ) into atmospheric-pressure argon gives rise to filamentation (self-focusing) and a supercontinuum with a very broad pedestal, extending in the UV to 200 - 250 nm respectively. Apart from the very broad spectrum, this supercontinuum has other remarkable features as well, like absence of conical emission, no contribution from third harmonic, intrinsically shorter duration than the incoming pulse and spectral conversion efficiency that is on the level of 0.01 - 0.001. The application of the supercontinuum as a simple source of short UV pump pulses of tunable wavelength for transient spectroscopy is demonstrated.