Third harmonic generation of soluble vanadyl-phthalocyanine doped in polymer film

The third-order optical susceptibilities of PMMA thin films doped with soluble vanadyl-phthalocyanine derivatives ((t-Bu)_nVOPc) were studied by Maker fringe method. We intended to control the molecular packing of VOPc in PMMA in order to improve third-order optical susceptibility (χ⁽³⁾). For this purpose we selected soluble _nVOPc derivatives and obtained a packing structure similar to the phase II of VOPc thin film. Packing control of the phthalocyanine molecules was carried out by exposing PMMA films to organic solvent vapour. PMMA thin films doped with (t-Bu)₄VOPc, (t-Bu)_1.45VOPc and (t-Bu)_1.44 VOPc were treated with dichloroethane vapour in a desiccator at room temperature. The intensity of THG are in the order of (t-Bu)_1.45VOfc/PMMA>(t-Bu)_1.44 VOPc/PMMA>VOPc(t-Bu)₄VOPc/PMMA. This means that the hyperpolarisability of (t-Bu)_nVOPc molecule depends upon a number of tert-butyl radicals. The third-order optical susceptibility (χ⁽³⁾) was estimated for (t-Bu)_1.45VOPc/PMMA. Its value was about 7×10^-12 esu. This technique is useful to make optical waveguide