Abstract: | The defect chalcopyrite crystal HgGa2S4 has been employed in a 1064‐nm pumped optical parametric oscillator operating at 100 Hz, to generate ~5 ns long idler pulses near 4 µm with energies as high as 6.1 mJ and average power of 610 mW. At crystal dimensions comparable to those available for the commercial AgGaS2 crystal, operation of the 1064‐nm pumped HgGa2S4 OPO is characterized by much lower pump threshold and higher conversion efficiency, with the most important consequence that such a device might become practical at pump levels sufficiently lower than the optical damage threshold. |