Third-order nonlinear optical properties of phthalocyanines in solution and in polystyrene films

Abstract

Degenerate four-wave mixing (DFNM) measurements of third-order nonlinear optical (NLO) coefficients of metal-free, Cu, Pt, Pb and Pi octal 2-ethylhexyloxy) phthalocyanines (MPc's) were done with 20 ps duration laser pulses under resonant conditions at 532 nm in polystyrene films and under nonresonant conditions at 1064 nm in chloroform solutions. The NLO coefficients chi(xxxx)((3)) show saturation with increasing incident intensity and no strong dependence on the central metal atom of the MPc below the saturation intensity. Optical delays of the probe-pulse up to 3 ns show an acoustic phonon response in both the polystyrene films and the chloroform solutions. An intensity-dependent absorption coefficient was measured by a pump/probe experiment and used in a simple model to qualitatively account for the saturation of chi((3)) measured by DFWM.