Fiber Endface Fabry–Perot Microsensor With Distinct Response to Vapors of Different Chlorinated Organic Solvents

A Fabry-Perot optical sensing microresonator, fabricated by direct laser writing on the endface of a standard telecom fiber, is demonstrated as a microsensor for the specific detection of common chlorinated organic solvent vapors. The device operates within the 1550-nm spectral region, while the spectra recorded in the reflection mode correlate to the refractive index and absorption changes due to the different vapors trapped inside the microcavity. The operation of the microresonator sensing probe is explained in terms of standard physisorption and molecule packing mechanisms of organic vapors onto the porous sites of the photopolymerized reflection surface. The sensing of traces of three different chlorinated organic solvents vapors at concentrations down to 4 ppm and their discrimination through their spectral and temporal evolution is demonstrated and discussed, while the chlorinated volatile organic compound identification potential is also considered.