Efficient two-photon-induced fluorescence in a new organic crystal

Results are presented on the two-photon absorption and fluorescence properties of a new molecular crystal based on (E)-(E)-4-(p-N,N-dimethylaniline)-1-cyano-1-di(ethoxy)phosphinoylbuta-1,3-diene (DCP). This material shows a two-photon-induced fluorescence when excited in the infrared, in powder similar to 6 times that obtained from a [2-[2-[4-dimethylaminophenyl]ethenyl]-6-methyl-4H-pyron-4-ylidene]propanedinitrile powder excited at 1.064 mu m, and similar to 50 times that of a 1-cm-long Rhodamine 640 solution (2 mM in methanol). Pulsed photoacoustic spectroscopy has been used to characterize the two-photon absorption band of the crystalline state. A high two-photon absorption coefficient, beta = 15 cm/GW, is reported, and an energy-conversion yield of 2.0% (incoherent fluorescence) was obtained in a DCP monocrystal in a single-pass beam configuration. Finally, a correlation is shown between the polarization of the excitation radiation and the crystalline structure of the material. (C) 1998 Optical Society of America.