Selective Excitation and Probing of Axial Modes in a Microcylindrical Resonator for Robust Filter

We experimentally investigate selective excitation and probing of localized axial modes in a microcylindrical resonator using two tapered fibers. The channel dropping properties of such a resonator are characterized and discussed, which are shown to depend on the excitation and probing structures. More importantly, the tunability in both drop efficiency and bandwidth can be achieved by vertically moving the add-drop fiber while keeping it in contact with the surface of the microcylinder. In contrast to tuning methods reported to date, such a physical contact combined with the significantly large axial distance between the two nearby nodes of mode function exhibited by our resonator allows for a fine, controlled, and stable tuning, making a robust and dynamic all-fiber device that may intrigue unique potential in sensors, microlasers, and add-drop filters applications.