Tunable Fano-like resonance enabled by coupling a microsphere with a fiber Mach-Zehnder interferometer

We demonstrate a simple scheme to achieve Fano-like resonance by coupling a microsphere resonator with a fiber Mach-Zehnder interferometer (FMZI), which includes a tapered microfiber in one pathway to evanescently couple with the microsphere. In this system, Fano-like asymmetric lineshapes could be converted into different types by introducing an extra phase shift in the FMZI. In addition, the sharpness of the Fano-like lineshapes could be controlled by changing the coupling strength between the microsphere and the microfiber. This Fano-like resonance with advantages of fiber integration, tunable lineshape, and ease of operation may have great potential in optical signal processing and sensing.