Compact and robust common-path scheme for fourth harmonic generation of deep UV ultrashort laser pulses

Ultrashort pulses in the deep-UV region around 200 nm have important applications in laser spectroscopy and Free-Electron laser technology [1,2]. Such pulses can be obtained using Ti:Sapphire laser followed by a fourth harmonic generation (FHG). In this case due to phase matching limitations of the available nonlinear crystals the fourth harmonic (FH) can only be generated in a three-step setup starting with second harmonic generation (SHG), followed by third harmonic generation (THG) realized by sum frequency mixing (SF) of SH and fundamental pulses, and then a final FHG stage based on sum frequency mixing of third harmonic (TH) and fundamental pulses.