Side-polished fiber evanescent wave quartz-enhanced photoacoustic spectroscopy employing dielectric coatings for evanescent field enhancement.

ABSTRACT: We report an all-fiber laser gas analyzer (LGA) based on quartz-enhanced photoacoustic spectroscopy (QEPAS) that exploits strong evanescent wave (EW) enhancement using a dielectric coating on side-polished fiber. The dielectric coating increases the fraction of the evanescent field in air, significantly amplifying light-gas interaction within the polished region. A single-mode fiber with a 17 mm polished section passes through two millimeter-scale resonator tubes and a custom quartz tuning fork (QTF) with 0.8 mm prong spacing. The optimized EW coupling efficiently generates photoacoustic waves that excite the QTF's fundamental flexural mode. Methane-nitrogen mixtures at 800 mbar were used to evaluate performance, achieving a detection limit of 2.5 ppmv for CH₄ with 300 ms integr

SUBMITTER: Twomey CF 

PROVIDER: S-EPMC12664072 | biostudies-literature | 2025 Dec

REPOSITORIES: biostudies-literature