This application relates to optical resonators, and more specifically, to optical whispering-gallery-mode resonators.
A dielectric sphere may be used to form an optical whispering-gallery-mode resonator which supports a special set of resonator modes known as xe2x80x9cwhispering gallery modesxe2x80x9d. These modes represent optical fields confined in an interior region close to the surface of the sphere around its equator due to the total internal reflection at the sphere boundary. Microspheres with diameters on the order of 10xcx9c102 microns have been used to form compact optical resonators. Such resonators have a resonator dimension much larger than the wavelength of light so that the optical loss due to the finite curvature of the resonators can be small. The primary sources for optical loss include optical absorption in the dielectric material and optical scattering due to the inhomogeneity of the sphere (e.g., irregularities on the sphere surface). As a result, a high quality factor, Q, may be achieved in such resonators. Some microspheres with sub-millimeter dimensions have been demonstrated to exhibit very high quality factors for light waves, exceeding 109 for quartz microspheres. Hence, optical energy, once coupled into a whispering gallery mode, can circulate at or near the sphere equator with a long photon life time.
Whispering-gallery-mode resonators may use resonator geometries based on spheres. Since the whispering gallery modes essentially exist near the equator of a sphere, a resonator may not be necessarily a whole sphere but a portion of the sphere near the equator that is sufficiently large to support the whispering gallery modes. Hence, rings, disks and other geometries formed from a proper section of a sphere may be used. Such resonators are still spherical and their whispering gallery modes are essentially identical to such modes of the respective whole spheres.
This application includes non-spherical whispering-gallery-mode resonators and their applications. In one embodiment, a spheroidal cavity is used to generate a true finesse on the order of 104, a free spectral range of the order of few nanometers, and a quality-factor Qxcx9c1xc3x97107. Devices based on such a spheroidal cavity are also disclosed.