Generation of high beam quality, high-energy and broadband tunable mid-infrared pulse from a KTA optical parametric amplifier

National Basic Research Program of China [2011CB808101]; National Natural Science Foundation of China [61078037, 11127901, 11134010, 61205208, 11204328]We have demonstrated efficient generation of high beam quality, high-energy and broadband tunable femtosecond mid-infrared pulses using a three-stage collinear optical parametric amplifier (OPA). The white-light continuum (WLC) seeded OPA setup, based on KTA crystal in three stages and pumped by a femtosecond laser pulse at 800 nm, is capable of producing idler wavelength ranging from 2.4 mu m to 4.0 mu m with energy up to 82 mu J at 3.27 mu m, which corresponds to signal energy of 350 mu J at 1060 nm. The output pulse has excellent intensity distribution with measured beam quality factor M-2 similar to 1.1 for signal and M-2 similar to 1.7 for idler. To our knowledge, this is the best beam quality reported in 3-5 Lim femtosecond OPA until now. The achieved mid-infrared pulse also has a good energy stability with a fluctuation of 1.01% rms over half an hour. (C) 2016 Elsevier B.V. All rights reserved