Novel Setup For Time-Resolved Fluorescence Microscopy

Time-resolved fluorescence is a direct measure for excited states lifetimes, decay channels and corresponding rates. Hitherto, investigations on systems exhibiting fluorescence lifetimes below approximately 10 ps have been restricted to ensemble measurement. Ensemble measurements bear the disadvantage of averaging sample inhomogeneities and complex distributions. However, the latter problem,can be circumvented by single-molecule experiments, without the restriction to special, typically simple systems that can be prepare with very high homogeneity. Time-resolved single-molecule microscopy is especially powerful as it allows one to probe the spatial, temporal and spectral inhomogeneities. At present, its most common implementation, the scanning confocal time correlated single photon counting (TCSPC), is limited to a time resolution of 20 ps. In the wide-field epifluorescence microscopy temporal resolution is achieved by the use of intensified CCD cameras, the fastest of which reach resolution of 80 ps. Here we present a Kerr-gated microscope setup capable of collecting diffraction limited 2D fluorescence images with approximately 100 fs time resolution. The concept is based on the insertion of an optical Kerr gate into a standard wide-field microscope. In addition to the considerably improved temporal resolution, the wide-field design will allow simultaneous tracking of several molecules or nanoparticles and ultrafast fluorescence lifetime imaging of doped and heterogeneous surfaces. Preliminary measurements to demonstrate the performance of the setup are presented.