Broadband generation produced in Raman-active crystals by two- and three-color femtosecond laser pulses

We observe broadband generation by non-collinearly focusing two- or three-color ultrashort laser pulses into Raman-active crystals.~ The generated spectrum extends from infrared to ultraviolet, and consists of discrete spatially-separated Raman sidebands. Up to 20 sidebands are observed when two-color fs-laser pulses interact with PbWO4 crystal.~ Similar generation is observed in diamond.~ By applying the third probe beam, about 50 sidebands are generated through the Raman-resonant four wave mixing.~ By looking at the coherent Stokes and anti-Stokes signal with delayed probe pulse, we can see that multiple Raman levels are excited by the short (50 fs) pulses used.~ Combining the multiple generated sidebands may prove to be a way to synthesize subfemtosecond pulses.