Abstract
Laser spectroscopy outperforms electrochemical and semiconductor gas sensors in selectivity and environmental survivability. However, the performance of the state-of-the-art laser sensors is still insufficient for many high precision applications. Here, we report mode-phase-difference photothermal spectroscopy with a dual-mode anti-resonant hollow-core optical fiber and demonstrate all-fiber gas (acetylene) detection down to ppt (parts-per-trillion) and <1% instability over a period of 3 hours. An anti-resonant hollow-core fiber could be designed to transmit light signals over a broad wavelength range from visible to infrared, covering molecular absorption lines of many important gases. This would enable multi-component gas detection with a single sensing element and pave the way for ultra-precision gas sensing for medical, environmental and industrial applications.
Highlights
Laser spectroscopy outperforms electrochemical and semiconductor gas sensors in selectivity and environmental survivability
The sensitivity of laser absorption spectroscopy (LAS) depends on absorption path length and line strength that is weak in the near infrared (NIR) and much stronger in the mid-infrared (MIR)
A modulated pump laser beam propagating in a dual-mode hollowcore optical fiber (HCF) is absorbed by trace molecules in the hollow-core, which heats up the gas and perturbs the refractive index (RI) distribution
Summary
Laser spectroscopy outperforms electrochemical and semiconductor gas sensors in selectivity and environmental survivability. We report mode-phasedifference photothermal spectroscopy with a dual-mode anti-resonant hollow-core optical fiber and demonstrate all-fiber gas (acetylene) detection down to ppt (parts-per-trillion) and
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