Nonlinear optical characteristics of MBE-grown phthalocyanine thin films

Summary form only given. We have developed the molecular beam epitaxial (MBE) growth technique for phthalocyanines on alkali halide single crystals, and found out that there are two typical epitaxial structures of 2-dimensional square lattices which are oriented uni- or bi-directionally. Anisotropical nature of the optical third harmonic genaration (THG, X/sup (3)/) is found to be closely correlated with this square lattice symmetry (4mm). In this report, we present the first observation of the spectral dependence of anisotropy of X/sup (3)/ of epitaxially grown vanadyl phthalocyanine films. It is revealed that the variation of the anisotropy of X/sup (3)/ is a result of the dispersion of the complex ratio 3/sub X 1221/ X 1111/. The re is a sharp two-photon resonance in X/sup (3)/ that may be attributed to the presence of a second exciton state of the square lattice system. Enhancement of X/sup (3)/ is achieved in the single-crystalline vanadyl phthalocyanine film by one order.