Polarization-Dependent Whispering Gallery Modes (WGMs) in Microspheres

Dielectric microspheres are optical structures that exhibit resonant properties, meaning they can be used to select very narrow wavelengths of an incoming light beam's spectrum for further manipulation and processing. The optical resonances of a microsphere are frequently called morphology dependent resonances (MDRs) or whispering gallery modes (WGMs). Innovators at NASA's Glenn Research Center have developed a method of separating low-level modes propagating in an optical fiber through the use of WGMs in spherical resonators. The unusually high quality factors (Q-factors) that can be achieved by side coupling of light into the dielectric spheres allow for measurement sensitivities that may far exceed those of more conventional sensors. Whispering gallery modes’ high sensitivity to environmental conditions and their small size make them good candidates for a wide range of sensors.