EFFICIENT 2-PHOTON-INDUCED FLUORESCENCE IN A NEW ORGANIC-CRYSTAL

Results are presented on the two-photon absorption and fluorescence pr operties of a new molecular crystal based on ine)-1-cyano-1-di(ethoxy) phosphinoylbuta-1,3-diene (DCP). This material shows a two-photon-indu ced fluorescence when excited in the infrared, in powder similar to 6 times that obtained from a enyl]-6-methyl-4H-pyron-4-ylidene]propanedi nitrile 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 photoaco ustic spectroscopy has been used to characterize the two-photon absorp tion band of the crystalline state. A high two-photon absorption coeff icient, beta = 15 cm/GW, is reported, and an energy-conversion yield o f 2.0% (incoherent fluorescence) was obtained in a DCP monocrystal in a single-pass beam configuration. Finally, a correlation is shown betw een the polarization of the excitation radiation and the crystalline s tructure of the material. (C) 1998 Optical Society of America.