Mid-infrared pulsed nanosecond difference frequency generation of oxide LGN crystal up to 5.7 µm

We demonstrate the tunable difference frequency generation (DFG) of an oxide (LGN) crystal pumped by near-infrared lasers with nanosecond pulses for the first time to our knowledge. The type I and II phase-matching conditions of DFG were calculated in the mid-infrared region. With the processed LGN crystals, tunable lasers in the wavelength range from 4.4 to 5.7 µm and 4.56 to 5.6 µm were achieved under type II and I phase-matching conditions, respectively, with the maximum output energy of 13.1 µJ, which agreed well with the theoretical calculation. This work provides the kind of promising mid-infrared nonlinear crystals for the pumping of nanosecond pulsed lasers as well as a tunable mid-infrared laser source at a wavelength over 5 µm in further photonic applications.