We report on a simple, compact continuous-wave 456-nm laser by intracavity frequency doubling of an end-pumped Nd:GdVO4 laser on the 4 F3/2 → 4 I9/2 transition. A 5-mm-long, 0.2-at % Nd:GdVO4bulk...

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A long distance, distributed gas sensing using the micro-nano fiber evanescent wave (FEW) quartz enhanced photoacoustic spectroscopy technique was demonstrated. Such a sensor scheme has the advantages of higher detection sensitivity, distributed gas sensing ability, lower cost, and a simpler fabrication procedure compared to conventional FEW gas sensors using a photonic crystal fiber or a tapered fiber with chemical sputtering. A 3 km single mode fiber with multiple tapers and an erbium doped fiber amplifier with an output optical power of 700 mW were employed to perform long distance, distributed gas measurements.