Mid-infrared femtosecond optical parametric amplification in potassium niobate

We generated synchronized sub-200-fs pulses between 3 and 4.4 mm at a 1-kHz repetition rate by pumping a KNbO(3) optical parametric amplifier with a femtosecond Ti:sapphire regenerative amplifier and seeding it by narrow-band quasi-cw radiation. Output idler energies as high as 7 microJ at 4 microm are reported from this extremely simple single-stage device, which correspond to amplification factors as high as 3 x 10(5) and a conversion efficiency of 15.