Solvent effects on nonlinear absorption of meso-tetrakis methylpyridiniumyl porphyrin for picosecond pulse trains

As a typical category of two-photon absorption molecules, solvent effects on dynamical properties of porphyrin were studied for picosecond pulse trains in this work. The pulse train contains 20 subpulses of 70 picoseconds width at 532 nanometers, separated by 13 nanoseconds. According to the molecular energy level distributing, porphyrin was simplified as a generalized five-level model during the nonlinear optical process, and the two-step TPA is the main absorption tunnel. In the theoretical simulation, we used Crank–Nicholson numerical method to solve entangled equations of two-dimensional paraxial field and the rate equations. Interacting with picosecond pulse trains, meso-tetrakis (methylpyridiniumyl) porphyrin (TMPyP) in aqueous and in several organic solvents shows excellent optical limiting behaviors. Besides water, negatively charged sodium dodecylsulfate, protonic methyl, ethyl and propyl alcohols and aprotic acetonitrile were considered as the solvents. Our results show that TMPyP in water has the lowest energy transmittance, which is mainly due to the formatted hydrogen bonds of nitrogen atom in TMPyP to water.