title: Mechanical tuning of whispering gallery modes over a 0.5 THz tuning range with MHz resolution in a silica microsphere at cryogenic temperatures.
abstract: We experimentally demonstrate the mechanical tuning of whispering gallery modes in a 40 μm diameter silica microsphere at 10K, over a tuning range of 450 GHz and with a resolution less than 10 MHz. This is achieved by mechanically stretching the stems of a double-stemmed silica microsphere with a commercially available piezo-driven nano-positioner. The large tuning range is made possible by the millimeter long slip-stick motion of the nano-positioner. The ultrafine tuning resolution, corresponding to sub-picometer changes in the sphere diameter, is enabled by the use of relatively long and thin fiber stems, which reduces the effective Poisson ratio of the combined sphere-stem system to approximately 0.0005. The mechanical tuning demonstrated here removes a major obstacle for the use of ultrahigh Q-factor silica microspheres in cavity QED studies of solid state systems and, in particular, cavity QED studies of nitrogen vacancy centers in diamond.
authors.affiliation: Department of Physics and Oregon Center for Optics, University of Oregon, Eugene, Oregon 97403, USA. kdinyari@uoregon.edu
authors.forename: Khodadad N
authors.initials: KN
authors.lastname: Dinyari
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Barbour
authors.forename: D Andrew
authors.initials: DA
authors.lastname: Golter
authors.forename: Hailin
authors.initials: H
authors.lastname: Wang