Ultrasensitive measurement of gas refractive index using an optical nanofiber coupler
2018
We report an
ultrasensitivegas refractive index (RI) sensor based on optical nanofiber couplers (ONCs). Theoretical analysis reveals that a dispersion turning point (DTP) exists when the diameter of the coupler is below 1000 nm. Leveraging this DTP, the gas RI sensitivity can be significantly improved to infinity. Then we experimentally demonstrate a DTP and achieve ultrahigh sensitivities of 46,470 nm/refractive index unit (RIU) and −45,550 nm/RIU around the DTP using an ONC with a diameter of 700 nm. More importantly, the unique twin dips/peaks interference characteristics around the DTP offers further enhancement on the sensitivity to 92,020 nm/RIU. The demonstrated sensor not only shows vast potential in
ultrasensitive
pressure sensing, acoustic sensing, gas sensing, and gas phase biomarker detection, but also provides a new tool for nonlinear optics, ultrafast optics,
quantum optics, and
ultracold atomoptics.
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