Laser-diode-seeded operation of a femtosecond optical parametric amplifier with MgO:LiNbO_3 and generation of 5-cycle pulses near 3 μm

A high-power traveling-wave optical parametric amplifier based on $\mathrm{MgO}:{\mathrm{LiNbO}}_3$ that is capable of producing extremely short pulses in the 3-µm spectral 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 microlaser, we demonstrate idler tunability between 3.1 and 3.9 µm at >10-µJ pulse energy and <200-fs pulse duration. The maximum internal conversion efficiency is 40% for a single pass. The extremely high gain factors achieved 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-µJ pulse energy and 130-fs pulse duration near 3.5 µm. We have produced nearly transform-limited 50-fs, 2-µJ pulses near 3 µm with a 1-mm-thick $\mathrm{MgO}:{\mathrm{LiNbO}}_3$ sample by adding a second pass and employing sub-30-fs pumping.