Nonlinear delayed fluorescence in confocal scanning microscopy. Point-spread-function analysis.

Generation of the signal beam in the confocal scanning fluorescence microscopy by means of nonlinear delayed fluorescence phenomenon based on triplet-triplet annihilation is proposed. From the point of view of the spatial resolution of three-dimensional confocal imaging the superiority of the phenomenon proposed over the classical two-photon fluorescence is demonstrated. This is done in terms of axial and lateral point spread functions computed for the assumed model of nonlinearity.