Imperfectly spherical whispering gallery mode resonators to provide surface-enhanced spectroscopic signals.
NASAs Jet Propulsion Laboratory has developed a robust spectroscopic sensor and method for sensitive detection and chemical analysis of organic and molecular compounds. The field of surface-enhanced Raman spectroscopy (SERS) has grown considerably since the discovery that a Raman signal can be greatly enhanced for molecules absorbed on special metallic nanostructures and particles. Conventional SERS methods involve coupling to a plasmonic mechanism, which requires physical contact between the whispering gallery mode resonator (WGMR) and the optics of the spectrometer. JPLs novel silica sphere WGMRs enable a nonplasmonic approach to SERS that offers a number of advantages over the conventional methods: the active substrate is chemically inert, thermally stable, and simple to fabricate.