Ultracompact Intrinsic Micro Air-Cavity Fiber Mach–Zehnder Interferometer

Abstract—A compact intrinsic fiber Mach–Zehnder interferom-eter (MZI) is proposed and experimentally demonstrated by in-corporating a micro air-cavity ablated by femtosecond laser irra-diation. A short cavity of length 10 m along the single-mode fiber core provided two optical paths: one propagating through the air and the other guided along the ring-shaped silica cladding. A spectral analysis confirmed MZI in a good agreement with exper-imental results. Temperature-dependent spectral shifts were mea-sured and analyzed. Index Terms—All-fiber device, interference filter, laser microma-chining, Mach–Zehnder interferometer (MZI). I