title: Whispering-gallery mode micro-kylix resonators.
abstract: Owing to their ability to confine electromagnetic energy in ultrasmall dielectric volumes, micro-disk, ring and toroid resonators hold interest for both specific applications and fundamental investigations. Generally, contributions from various loss channels within these devices lead to limited spectral windows (Q-bands) where highest mode Q-factors manifest. Here we describe a strategy for tuning Q-bands using a new class of micro-resonators, named micro-kylix resonators, in which engineered stress within an initially flat disk results in either concave or convex devices. To shift the Q-band by 60 nm towards short wavelengths in flat micro-disks a 50% diameter reduction is required, which causes severe radiative losses suppressing Q's. With a micro-kylix, we achieve similar tuning and even higher Q's by two orders of magnitude smaller diameter modification (0.4%). The phenomenon relies on geometry-induced smart interplay between modified dispersions of material absorption and radiative loss-related Q-factors. Micro-kylix devices can provide new functionalities and novel technological solutions for photonics and micro-resonator physics.
authors.affiliation: Advanced Photonics & Photovoltaics, Fondazione Bruno Kessler - irst, via Sommarive 18, Povo, Trento, Italy. ghulinyan@fbk.eu
authors.forename: Mher
authors.initials: M
authors.lastname: Ghulinyan
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pitanti
authors.forename: Georg
authors.initials: G
authors.lastname: Pucker
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Pavesi
mesh_terms: D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D055096:Optical Devices; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D014732:Vibration