Selective excitation of axial modes in a high-Q microcylindrical resonator for controlled and robust coupling.

We investigate selective excitation of localized axial modes in a high-Q microcylindrical resonator experimentally, numerically, and theoretically. The resonator is fabricated using a standard fusion splicer, and the characteristic resonance spectra are acquired by using a tapered fiber coupled at different positions along the microcylinder. The spatial and spectral mode properties are analyzed with our numerical and theoretical model, which are in good agreement with the experimental results. Moreover, controlled and robust coupling is experimentally demonstrated by vertically moving the resonator while keeping it in contact with the tapered fiber. Our microcylindrical resonator combines clean and nearly equidistant spectra, a high quality factor up to 3.1×10(7), a large mode volume, and a more favorable frequency spacing of ∼3.91  GHz, offering unique potential in sensors, microlasers, optical filters, group delay lines, and especially some applied fields that require tuning.