Intrinsic Fabry-Pérot Interferometer Based on Concave Well on Fiber End

miniature fiber-optic Fabry-Pérot cavity interferometerA miniature fiber-optic Fabry-Pérot cavity interferometer is presented. The interferometer is fabricated at the fiber tip by wet chemical etching using hydrofluoric acid. A concave well is created on the fiber end face. Interference happens between the reflections from the fiber core and the end of the cladding. We demonstrate applications of the interferometric sensor for temperature and gas refractive index sensing.