Mid-infrared interferometry with non-adiabatic tapered ZBLAN optical fiber.

This work illustrates, to the best of our knowledge, the first non-adiabatic tapered single-mode zirconium fluoride optical fiber sensor in the mid-infrared spectral range. It is designed and fabricated via pulling and heating technique. A waist diameter d = 25 µm with no visible crystallization is achieved, overcoming the typical fluoride glass challenges associated with crystallization, narrow temperature fabrication window, and low glass transition temperature. The performance of the non-adiabatic tapered optical fiber is theoretically and experimentally investigated, demonstrating its high potential for a wide range of sensing applications in the mid-infrared spectral range.