Tunable high-Q tapered silica microcylinder filter

We propose and demonstrate a tunable optical filter based on a tapered silica microcylinder, whose diam- eter is gradually varied along its longitudinal axis. The tapered microcylinder comprises a slowly varying transition zone fabricated through the fiber drawing technique. Given the tapered diameter of the micro- cylinder, the resonant wavelengths can be tuned by displacing the tapered microcylinder. This tunable filter exhibits a high Q-factor （-106） and a large tuning range （〉1 free spectral range （FSR））.