Broadly tunable mid-infrared femtosecond pulses directly generated by an optical parametric amplifier

We introduce an optical parametric amplifier, pumped by an amplified femtosecond Yb:KGW laser, which directly generates broadly tunable mid-infrared (MIR) pulses, covering the whole vibrational spectrum from 3 to 10 pm. The avoidance of the traditional difference-frequency generation stage to access the MIR range simplifies the setup while enabling high conversion efficiencies. The two-stage design employs in the second stage either periodically poled lithium niobate, optimized for the CH/OH stretching region (3-5 pm) or LiGaS2, which allows extending the tunability to the fingerprint region (up to 10 pm). We anticipate applications of this versatile source to ultrafast vibrational spectroscopy and infrared microscopy. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement