A three-wavelength narrow-linewidth mid-infrared optical parametric oscillator based on secondary-pumping tandem MgO:PPLN double crystals

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This study demonstrates a mid-infrared narrow-linewidth tandem optical parametric oscillator (TOPO) based on dual MgO: PPLN crystals.A secondary-pumping technique with a periodically poled MgO:PPLN crystal is employed to achieve threewavelength mid-infrared laser outputs at 2.70, 3.45, and 4.25 μm.A 1064 nm ytterbium-doped fiber laser is employed as the pump source, with a single laser output sequentially pumping two MgO:PPLN crystals which have period lengths of 30.44 and 31.89μm, respectively.The synchronous three-wavelength mid-infrared laser output is achieved through two optical parametric oscillation (OPO) processes and one TOPO process.The processes are as follows: 1.06 μm → 1.53 μm + 3.45 μm; 1.06 μm → 1.75 μm + 2.70 μm; 1.53 μm → 2.40 μm + 4.25 μm.The linewidth of the signal light is compressed using a 1 mm thick Fabry-Perot (F-P) etalon, reducing the linewidths of 2.70, 3.45, and 4.25 μm from 3.03, 7.83, and 1.20 nm to 0.32, 0.60, and 0.55 nm, respectively.The associated output powers are 0.681, 1.342, and 0.098 W.