Spatial distribution of two-photon-excited fluorescence in scattering media

Spatial distribution of two-photon-excited fluorescence (TPF) for dye benea th the surface of a highly scattering medium was investigated dth picosecon d laser pulses at 1064 nm. The active scattering media consisted of a suspe nsion of polystyrene particles in a solution of Rhodamine 590 Tetrafluorobo rate dye. With the increase of scattering strength of the medium, the locat ion of the maximum TPF intensity was found to move closer to the surface aw ay from the focal region; the intensity of TPF was not confined to the foca l region as in the case of nonscattering medium but was more evenly distrib uted. The spatial resolution of nonlinear optical microscopy for probing a scattering medium is degraded. Taking into account the scattering of the me dium qualitatively explains the observed TPF spatial distribution. (C) 1999 Optical Society of America.