Third-order nonlinear optical susceptibilities of the Langmuir–Blodgett films of octa-substituted metallophthalocyanines

Abstract

The third-order susceptibilities χ(3)(−3ω:ω,ω,ω) of Langmuir–Blodgett films of a series of octasubstituted metallophthalocyanines have been measured by third-harmonic generation experiments at 1.064 and 1.904 μm. For the latter excitation wavelength a marked enhancement of the nonlinearity for the cobalt-containing compound has been found, and χ(3) values are one order of magnitude larger than for the other systems. The effect has been associated to the role of two-photon allowed metal (possibly d−d) transitions in the cobalt derivative.