Effect of group velocity dispersion on supercontinuum generation and filamentation in transparent solids

Abstract

We experimentally investigate the spectral extent and spectral profile of the supercontinuum (SC) generated in transparent solids: barium fluoride, calcium fluoride, and fused silica upon irradiation by intense femtosecond-long pulses of 800, 1,380, and 2,200 nm light. These wavelengths correspond to the normal and anomalous group velocity dispersion (GVD) regimes in fused silica calcium fluoride and barium fluoride. We observe an isolated (anti-Stokes) wing on the blue side most prominently in fused silica but also in CaF2. The SC conversion efficiency is measured for the long wavelengths used in our experiments. We also present results on filamentation in BaF2 in the anomalous GVD regime, including visualization of focusing–refocusing events within the crystal; the size of a single filament is also determined. The 15-photon absorption cross section in BaF2 is deduced to be 6.5 × 10−190 cm30 W−15 s−1.