Single-molecule excitation-emission spectroscopy at room temperature based on a common-path interferometer

Single molecule (SM) emission spectroscopy [1] has proven to be a powerful, non-invasive tool in life science, materials science, and photophysics. The vast majorities of SM detection techniques are based on fixed-wavelength excitation of individual molecules combined with dispersed detection of emission. These methods mainly provide information on the relaxed environment of the photo-excited molecules. Attempts at reintroducing molecular ground-state information by recording fluorescence excitation spectra have been made both by the tunable narrow-band excitation approach and by interferometry [2]. Here, we introduce a new interferometric approach capable of simultaneously acquiring the complete spectral information of SMs, involving both their ground and excited states, by recording a 2D Excitation-Emission Map (EEM).