Enhancement of Third-Order Optical Nonlinearities of Soluble Vanadyl Phthalocyanines in Doped Polymer Films

The third-order optical susceptibilities χ1111 (3)(-3ω; ω, ω, ω)s of a soluble vanadyl phthalocyanine derivative ((t-Bu)1.1VOPc) are studied for thin films and doped polymethylmathacrylate films by optical third-harmonic generation measurements at wavelengths of 1543 nm and 1907 nm. The χ(3) values are enhanced by a factor of 2-7 at resonant and nonresonant wavelengths, concurrent with an absorption change induced by exposure to solvent vapor. The red-shifted phase (phase II), obtained by the treatment, has larger χ(3) values than the as-prepared phase (phase I). The enhancement of third-order optical nonlinear susceptibilities in phthalocyanine thin films is discussed in terms of electronic transition and molecular packing.