A Fiber-Endface, Fabry–Perot Vapor Microsensor Fabricated by Multiphoton Polymerization

A Fabry-Perot micro-optical sensing resonator fabricated by direct laser writing on the endface of a standard telecom fiber is demonstrated. This endface optical fiber sensing probe has been tested for tracing the vapors of common organic solvents. The device operates in the spectral region lying between 1440 and 1660 nm, while the spectra recorded in reflection mode correlate to the refractive index changes due to the different vapors trapped inside the microcavity. The performance of the device operation with respect to the reflecting surface porosity of the fabricated microstructure is presented, while the sensing of ethanol traces down to 4 ppm concentrations was achieved.