Location and width of morphology-dependent resonances in microspheres

A dielectric microsphere possesses natural modes of oscillation at characteristic frequencies, corresponding to specific size to wavelength ratios. These structure resonances are known to cause extremely large field intensities and have extremely high quality. We investigate here systematically the characteristic equation, defining the natural frequencies, as a function of the change in the asymptotic behavior of spherical Bessel functions which reveals the fact that there exists resonances with very narrow linewidth. This characteristic has very important implications to nonlinear optics.