Open AccessThe effects of inter-cavity separation on optical coupling in dielectric bispheres
Author(s) -
Shashaanka Ashili,
Vasily N. Astratov,
E. Charles H. Sykes
Publication year - 2006
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.14.009460
Subject(s) - whispering gallery wave , spheres , optics , physics , excited state , fano resonance , coupling (piping) , resonance (particle physics) , dielectric , integrating sphere , scattering , whispering gallery , light scattering , radiative transfer , atomic physics , resonator , materials science , optoelectronics , astronomy , plasmon , metallurgy
The optical coupling between two size-mismatched spheres was studied by using one sphere as a local source of light with whispering gallery modes (WGMs) and detecting the intensity of the light scattered by a second sphere playing the part of a receiver of electromagnetic energy. We developed techniques to control inter-cavity gap sizes between microspheres with ~30nm accuracy. We demonstrate high efficiencies (up to 0.2-0.3) of coupling between two separated cavities with strongly detuned eigenstates. At small separations (<1 microm) between the spheres, the mechanism of coupling is interpreted in terms of the Fano resonance between discrete level (true WGMs excited in a source sphere) and a continuum of "quasi"-WGMs with distorted shape which can be induced in the receiving sphere. At larger separations the spectra detected from the receiving sphere originate from scattering of the radiative modes.