Laser-diode-seeded operation of a femtosecond optical parametric amplifierwith MgO : LiNbO3 and generation of 5-cycle pulses near 3 mu m

A high-power traveling-wave optical parametric amplifier based on MgO:LiNbO 3 that is capable of producing extremely short pulses in the 3-mu m spectra l range when pumped by a femtosecond Ti:sapphire amplifier near 800 nm has been developed. With seeding by 1-ns pulses from a low-power Q-switched mic rolaser, we demonstrate idler tunability between 3.1 and 3.9 mu m at >10-mu J pulse energy and <200-fs pulse duration. The maximum internal conversion efficiency is 40% for a single pass. The extremely high gain factors achie ved permit a more compact solution for the seed source, and we also report on successful seeding with a pulsed laser diode in the femtosecond regime, achieving 5-mu J pulse energy and 130-fs pulse duration near 3.5 pm. We hav e produced nearly transform-limited 50-fs, 2-mu J pulses near 3 mu m with a 1-mm-thick MgO:LiNbO3 sample by adding a second pass and employing sub-30- fs pumping. (C) 1999 Optical Society of America [S0740-3224(99)02709-5].