Abstract

Picojoule colliding-pulse mode-locked pulses are amplified in four Bethune dye cells (sulforhodamine 640) and dispersion precompensated in a grating-telescope pulse shaper, typically to 200 pulses of ~100 fs duration. They pump a two-stage parametric generator of beta-barium borate (BBO). The large effective nonlinearity and angular sensitivity of BBO permit efficient conversion to 800 nm pulses, conserving the bandwidth of the pump. A collimated beam (2 mm diameter) passes the BBO crystals (7 and 5 mm length), which is cut at 20.3° for type I phase matching. The spatial separation (30 cm) and anti parallel orientation of the optical axes suppress noncollinear phase matching. Signal and idler frequencies at 830 nm and 2450 nm are generated with an overall energy conversion efficiency of 10%. This value is expected to increase closer to degeneracy. The signal can be precompensated to 150 fs: We use it for white-light generation in a 1 cm water cell and short-pulse amplification in titanium-doped sapphire. The idler provides interesting perspectives for saturation molecular spectroscopy around 3 μm with increased time resolution.

© 1990 Optical Society of America