The PIs propose to develop a new class of nanoparticle sensors based on ultrahigh quality factor (Q) optical micro-resonators on a silicon wafer to achieve not only ultra-sensitive detection but also molecule-specific identification and measurement of nanoparticles and molecules in air and in liquid environments at single particle resolution. The merit of this new technique lies in enhancing Raman and Rayleigh scattering and integrating them in an ultrahigh-Q Whispering Gallery mode (WGM) micro resonator to achieve multi-function sensors. On one hand, Rayleigh scattering in resonators leads to self-referencing mode-splitting, which can be utilized to detect and measure nanoparticles (e.g., size) down to several nm in size. On the other hand, Raman scattering, which is greatly enhanced by several orders of magnitude in an ultrahigh-Q microresonator, provides identification of molecules/particles through recognition of their spectral fingerprints of molecular vibrations. By integrating mode-splitting and microresonator-enhanced Raman spectroscopy, they can achieve a multifunction sensing unit capable of ultra-sensitive real-time, in-situ detection, identification and measurement of single nanoparticles.
