Mid-IR wavelength range (between 2 and 8 μm) offers perspective applications, such as minimally-invasive neurosurgery, gas sensing, or plastic and polymer processing. Maturity of high average power near-IR lasers is beneficial for powerful mid-IR generation by optical parametric conversion. We utilize in-house developed Yb:YAG thin-disk laser of 100 W average power at 77 kHz repetition rate, wavelength of 1030 nm, and about 2 ps pulse width for pumping of a ten-watt level picosecond mid-IR source. Seed beam is obtained by optical parametric generation in a double-pass 10 mm long PPLN crystal pumped by a part of the fundamental near-IR beam. Tunability of the signal wavelength between 1.46 μm and 1.95 μm was achieved with power of several tens of miliwatts. Main part of the fundamental beam pumps an optical parametric amplification stage, which includes a walk-off compensating pair of 10 mm long KTP crystals. We already demonstrated the OPA output signal and idler beam tunability between 1.70-1.95 μm and 2.18-2.62 μm, respectively. The signal and idler beams were amplified up to 8.5 W and 5 W, respectively, at 42 W pump without evidence of strong saturation. Thus, increase in signal and idler output power is expected for pump power increase.
High average power wavelength tunable picosecond mid-IR source based on parametric down-conversion is being
developed. The conversion system is pumped by a Yb:YAG thin-disk laser delivering 100 W of average power at
100 kHz repetition rate, 1030 nm wavelength, and 3 ps pulse width. First, part of the beam pumps an optical parametric
generator (OPG) consisting of a PPLN crystal. The generated wavelength is determined by PPLN’s poling period and
temperature. Signal beam covered wavelength range between 1.46 mμ and 1.95 mμ. The corresponding idler
wavelengths are 3.5 mμ and 2.18 mμ, respectively. Signal beam of about 20 mW was generated at 2 W pumping and
double pass arrangement of the OPG stage. The signal pulse energy is further boosted in an optical parametric amplifier
(OPA) consisting of two KTP crystals. The signal beam was amplified to 2 W at pumping of 38 W. The idler beam is
taken out of the OPA stage as well. Wavelength tuning by KTP crystals’ phase-matching angle change was achieved in
ranges and 1.7 - 1.95 μm and 2.18 - 2.62 mμ for signal and idler beam, respectively.