Continuously Tunable Fano Resonance Filter in a Fiber Taper Coupled Conical Microcavity

A conical microresonator with cone half-angle of ~10−5 rad is fabricated from a single mode fiber by a chemical etching method. Fano resonance with EIT-like spectrum is generated in a thin fiber taper coupled conical microcavity. Such the Fano spectrum can be used as the bandpass optical filter. Also, the central wavelength of the filter can be tuned continuously by displacing the fiber taper along the axis direction of the conical microcavity. The quality factor and extinction ratio of the optical filter could be up to 7×104 and 11.4dB. And the wavelength tunable coefficient is 0.22nm/mm.