Femtosecond filamentation in sapphire with diffractive lenses

In this paper, we demonstrate novel properties in the phenomenology of supercontinuum generation in sapphire with diffractive lenses and provide a complete spatial, spectral, and temporal characterization of the so-generated pulses. Filamentformationinside thesampleis analyzedandrelatedto the measured spectra, findingthat clipping of the filament results in blueshifted spectra. For comparison, filament formation with refractive lenses is also examined, and the roles of diffraction and extension of the focusing region are inspected. The tunability achieved in the anti-Stokes side of the spectrum is also extended to the ultraviolet by frequency mixing with infrared femtosecond pulses. ? 2013 Optical Society of America.