Abstract

Visible light pulses shorter than 10 fs are required in several advanced ultrafast spectroscopy experiments. Optical parametric amplifiers (OPAs) pumped by the second harmonic (SH) of a Ti.Sapphire laser provide such pulses, but with durations limited by the narrow phase matching bandwidths. Gale et al. [1] discovered a peculiar property of ß-barium borate (BBO) for optical parametric amplification, when pumped at 400 nm: using noncollinear phase matching with a pump-signal angle of 3.7°, the phase matching angle becomes independent of wavelength over most of the visible. Recently, this property was exploited to build noncollinear OPAs tunable across the visible, generating sub-20 fs pulses [2, 3].

© 1998 IEEE