Highly Efficient Optical Add-Drop Filter With an Angle-Polished Fiber Coupler
Abstract
Microbubble whispering-gallery resonators have shown great promise in fiber-optic communications because of their low confinement loss and hollow cores, which allow for facile stress-based tunability. Usually, the transmission spectrum of taper-coupled microbubbles contains closely spaced modes due to the relatively large radii and oblate geometry of microbubbles. In this letter, we develop an optical add-drop filter using a microbubble coupled to fiber taper and angle-polished fiber waveguides. Because of the extra degree of freedom in the angle of its polish surface, the angle-polished fiber can be used for the discriminatory excitation of certain radial-order modes in the optical microcavity, reducing the high modal density and enhancing add-drop selectivity. Our robust and tunable add-drop filter demonstrated a drop efficiency of 85.9% and quality factor of 2 x 10^7, corresponding to a linewidth of 9.68 MHz. As a proof of concept, the drop frequency was tuned using internal aerostatic pressure at a rate of 7.3 +/- 0.2 GHz/bar with no diminishing effects on the add-drop filter performance.
- Publication:
-
IEEE Photonics Technology Letters
- Pub Date:
- January 2020
- DOI:
- 10.1109/LPT.2019.2957266
- arXiv:
- arXiv:1906.00024
- Bibcode:
- 2020IPTL...32...71D
- Keywords:
-
- Physics - Applied Physics;
- Physics - Optics
- E-Print:
- 12 pages, 5 figures