MEASUREMENT OF 2-PHOTON ABSORPTION CROSS-SECTION OF DYE MOLECULES DOPED IN THIN-FILMS OF POLYMETHYLMETHACRYLATE

Two-photon absorption cross sections of two dye molecules, doped in th in films of polymethylmethacrylate, are measured by comparing fluoresc ence intensities induced by single- and two-photon excitations. Ratio of the single- and two-photon absorption cross sections is related to the ratio of the single- and two-photon pumped fluorescence intensitie s. Using this sensitive and background-free detection technique, dispe rsion of the nonlinearity is measured over a wavelength range of 700-8 00 nm. (C) 1997 American Institute of Physics.