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.