Two-photon and three-photon absorption in dinaphthoporphycenes

We present our results from the detailed investigations of both metal free-base and metal substituted dinaphthoporphycenes using the Z-scan technique with picosecond pulses. The compounds exhibited singular nonlinear absorption properties because of their molecular structure allowing us to access the two-photon and three-photon absorption states with different peak intensities when excited at the wavelength of 800 nm. This type of behaviour is explained using the unique energy level configuration of porphycene molecules. The orders of magnitude of both two-photon absorption and effective three-photon absorption coefficients and cross-sections were estimated along with sign and magnitude of the third order nonlinearity.