Whispering mode micro-resonator

Apparatus comprising at least one element providing for cavitation of electromagnetic energy with cavitation being primarily dependent upon whispering gallery modes in accordance with which modal path is defined within a body of high refractive index for such energy relative to refractive index of surrounding ambient at an interface between such body and ambient, such path being polygonal and of at least three sides with retention being primarily due to incidence of cavitating wave energy at or below the critical angle defined at such interface

• Characterized in that the said element, at least over a region corresponding with a substantial portion of such cavitation path, has a dimension of a maximum of .lambda./2n.sub.eff as measured in a direction normal to the plane of the path, in which .lambda. is the wavelength of cavitating energy as measured in a vacuum and n.sub.eff is the actual refractive index for such cavitating energy, such value accounting both for variation in bulk index for the medium of the body and for such variation on such bulk index as is introduced due to constraining surfaces, and in which such interface is of refractive index contrast for cavitating energy which is numerically equal to at least 1.5, such value yielded by the fraction n.sub.eff /n.sub.s in which n.sub.eff is the effective refractive index for cavitating energy within the said body and n.sub.s is the refractive index for such energy outside the defining interface of such body.