We present a continuous-wave, pump-resonant, singly-resonant optical parametric oscillator based on periodically poled lithium niobate in a linear dual-cavity design which is applied for photoacoustic trace gas detection between 2.35 and 3.75 μm. Pumped by a Nd:YAG laser at 1064 nm a single-frequency output power of 2 x 100 mW is achieved. The frequency tuning qualities of the OPO allow to scan gas absorption structures. An ethane detection limit of 110 ppt is achieved. Sensitivity, tuning qualities and compact design make this OPO an ideal laser source in a transportable photoacoustic spectrometer.
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