Stochastic Frequency Fluctuation Super-Resolution Imaging

Methods in super-resolution microscopy are critical for a variety of research endeavors. The inherent nonlinearity of photon correlation functions can be used to spatially distinguish identical optical emitters beyond the diffraction limit. For example, this is achieved in Super-Resolution Optical Fluctuation Imaging (SOFI), which relies on uncorrelated intensity fluctuations for emitter discrimination. We propose a complementary concept based on spectral correlation functions that localizes emitters based on emission frequency fluctuations. Our theoretical and computational analyses show that spatially resolving time-domain spectral correlation functions in the image plane provides up to a twofold improvement in resolution for two emitters with uncorrelated stochastic spectral fluctuations. We further propose an implementation called Spectral Fluctuation Super-Resolution (SFSR), which combines interferometry and spatiotemporal photon-correlation measurements to resolve spectral correlations. This method works for non-blinking emitters and stochastic spectral fluctuations with arbitrary temporal statistics, suggesting its utility in super-resolving quantum emitters at low temperatures, where spectral diffusion is often more pronounced than emitter blinking.