Nonlinear absorption properties of some 1,4,8,11,15,18,22,25-octaalkylphthalocyanines and their metallated derivatives

Abstract

The third-order nonlinear optical properties of a series of 15 unmetallated and metallated 1,4,8,11,15,18,22,25-octaalkylphthalocyanines have been investigated. The palladium-metallated compound is the strongest nonlinear absorber of the series, but, due to its comparatively high linear absorption coefficient, it exhibits a relatively low ratio of excited- to ground-state absorption cross-sections (κ) when compared to the other compounds. The highest values for κ were found for derivatives metallated with indium and lead. The nickel-metallated compounds are the weakest nonlinear absorbers, indicating that they are unsuitable as potential materials for practical passive optical limiters. Phenomenologically, the data for κ and the saturation energy density (F_sat) were found to follow trends dependent upon the linear absorption coefficient. This may have some implications for the design of phthalocyanines for nonlinear optical applications.