Broadband deep-ultraviolet femtosecond pulse generation by third-order nonlinear optical processes in thin media

Intense sub-300-nm deep-ultraviolet (DUV) ultrashort pulses are very important for photochemistry, photobiology, ultrafast spectroscopy and laser processing of materials. The generation of sub-20-fs DUV radiation is a challenging task and a topic of intense research. Previously used techniques include four-wave mixing (FWM) of amplified femtosecond pulses with different frequencies in gaseous media, from FWM in a gas filament [1] to chirped FWM in complex dual hollow-fiber systems [2], as well as direct upconversion of few-cycle femtosecond pulses in gas targets [3]. In general, these methods can produce broadband DUV pulses in the microjoule range but require complicated and/or large setups and involve the handling of gases.