Nonlinear flourescence through intermolecular energy transfer and resolution increase in flourescence miscrocopy

: Schönle A., Hänninen P., Hell S.

: 1999

Annalen der Physik

: Annalen der Physik (Leipzig)

: 8

: 2

: 115

: 133

: 19

: 0003-3804

: http://api.elsevier.com/content/abstract/scopus_id:0032715660

We investigate a novel concept to efficiently generate multiphoton induced fluorescence from organic molecules. The concept is based on frustrating the energy transfer between a fluorescent donor and one or more acceptors in conjugated molecule. The nonlinearity is not based on higher order molecular susceptibilities but entirely on their linear properties. Therefore, in contrast to nonresonant multiphoton absorption, this method does not require high local intensities. Likewise, the production of visible fluorescence does not require an infrared excitation wavelength. Hence, when applied to scanning microscopy this property is predicted to increase spatial resolution. Instead of the ∼10 GW/cm required in non-resonant multiphoton excitation, focal intensities of ∼10 MW/cm are expected to produce an equally strong nonlinear signal. The predicted resolution is up to 30% greater than that of an ideal confocal microscope operating at the same fluorescence wavelength. The resolution improvement over non-resonant two-photon absorption microscopes is about two-fold in all directions.