Abstract
We report performance optimization of hollow-core photonic bandgap fiber (HC-PBF) photothermal (PT) gas sensors. The PT phase modulation efficiency of a filled HC-PBF (HC-1550-02) is found independent of the pump modulation frequency for up to , but starts to drop quickly to 10% of the maximum value at a couple of megahertz. With a 1.1 m long HC-PBF gas cell with angle-cleaved single-mode fiber/HC-PBF joints to reduce reflection and a modified Sagnac interferometer with balanced detection for phase demodulation, a noise equivalent concentration of is achieved with a 1 s time constant, and it goes down to with 145 s integration time. The system has good long-term stability and exhibits signal fluctuations of over a period.
© 2017 Optical Society of America
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