750 nm laser based on an BaGa₄Se₇ optical parametric oscillator

The red edge effect of plants is extensively utilized in vegetation remote sensing, particularly by applying hyperspectral LiDAR (HSL) technology. This technology effectively captures spectral information from targets together with range measurements by processing recorded waveforms in the red-edge spectral bands. Despite its widespread use, there is still potential for enhancing the tuning accuracy and the energy output of each channel. What we believe to be a novel nonlinear crystal, BaGa₄Se₇ (BGSe), has been employed to achieve laser output in the red edge spectral band with a wide tuning range and high tuning precision for the first time. Successful generation of laser radiation at 1512 nm was achieved, with an angular tuning resolution of 35.9 nm/°. When the pump light energy was 17.81 mJ, the energy of the 1512 nm near-infrared laser was 3.210 mJ, with a slope efficiency of 31.2% and an optical-to-optical conversion efficiency (pump to signal) of 18.0%. Subsequent pumping of the second harmonic generation crystal KTiOPO₄ (KTP) with the 1512 nm laser output from the BGSe optical parametric oscillator (OPO) facilitated the generation of 756 nm red light laser output. Angle tuning of the BGSe OPO eventually enabled the tunable output of the red edge spectral laser ranging from 701 nm to 780 nm with output energy of approximately 2 mJ, which is several orders of magnitude higher than traditional supercontinuum laser source solution. Such improvement becomes a solid cornerstone for long-range HSL applications.