Theoretical and experimental studies of tunable ultraviolet-blue femtosecond pulses in a 405-nm pumped type I beta-BaB2O4 noncollinear optical parametric amplifier and cascading sum-frequency generation

Abstract

Femtosecond laser pulses that are tunable from 380 to 460 nm were directly generated from a 405-nm-pumped type I beta-BaB2O4 noncollinear optical parametric amplifier (NOPA). A white-light supercontinuum from a CaF2 plate excited by 810-nm pulses was seeded into the NOPA. A theoretical analysis showed that the near-UV-to-blue radiation generated is attributable to cascaded sum-frequency generation (SFG) of the output of the NOPA and the residual fundamental beam at 810 nm. One can tune the blue-UV light by either changing the orientation of the NOPA crystal or adjusting the angle between the pump and the seeding pulse. The optical conversion efficiency from the 405-nm pump to the tunable SFG radiation is more than 5%. (C) 2004 Optical Society of America.