Mercury thiogallate mid-infrared femtosecond optical parametric generator pumped at 125 µm by a Cr:forsterite regenerative amplifier

We demonstrate a novel traveling-wave-type optical parametric generator based on $1.25‐\mathit{\mu }\mathrm{m}$ pumping of ${\mathrm{HgGa}}_2{\mathrm{S}}_4$ that produces tunable, high-power, transform-limited $\propto 200‐\mathrm{fs}$ pulses in the mid-IR from 5 to $9 \mathit{\mu }\mathrm{m}$. Output idler energies on the microjoule level are obtained with maximum conversion efficiency of 11% for the amplifier stage, which is more than two times better than the results obtained with an analogous sample of the widely spread material ${\mathrm{AgGaS}}_2$.