Optical limiting, degenerate four-wave mixing and transient absorption experiments have been performed on a neat liquid lead substituted phthalocyanine. The photophysical mechanisms responsible for the good optical limiting observed in other phthalocyanine solutions are maintained in this pure liquid despite its different peripheral substitution pattern. The liquid is shown to have excited state absorption cross sections that exceed those of the ground state through much of the visible spectrum. Hybrid absorptive/refractive nonlinear response is demonstrated to contribute to both the four-wave mixing and optical limiting response. The mechanism and states responsible are discussed.

Photoexcitation of a new pure liquid phthalocyanine gives both a strong nonlinear absorption and photoalectrical charge generation. The novel photoelectrical properties of the material lead to plasma formation, an additional limiting mechanism, at moderate fluences.

Systematic studies of the nonlinear optical properties of metallo-organic materials have led to the development of promising new phthalocyanine materials for optical limiting. Several heavy metal substituted phthalocyanines exhibit a strong nonlinear absorption that is useful for optical limiters in the visible. In fast optical systems, other mechanisms, such as the thermal refraction, contribute to the limiting. The spectral window for limiting can by modified by altering the molecular structure.

The wavelength dependence of the nonlinear absorption for lead tetrakis (cumyl-phenoxy) phthalocyanine (PbPc(CP)4) and lead octa (α-pentoxy) napthalocyanine (PbNc(α-PO)8) are reported. The ground state absorption and the reverse saturable absorption are substantially red shifted in PbNc (α-PO)8 as expected. Such control over the reverse saturable absorption is crucial to design optical limiting materials for specific wavelength ranges.

The third order nonlinear optical (NLO) response of metal free tetrakis(cumylphenoxy)-phthalocyanine, (H2Pc(CP)4) was investigated at 597 nm, near resonance with the strong Q band. The second hyperpolarizability, γ, and the figure of merit, χ(3)/α, measured with a 1.2 ps pulse. was approximately independent of concentration between a 4.6×10−4 M solution and a neat thin film. The decay of the nonlinear response, however, depended substantially on the concentration and physical state of the material.

This paper discusses the third-order nonlinear optical (NLO) properties of substituted phthalocyanines measured by time-resolved degenerate four-wave mixing at 1064 nm. The study explores optical pumping as a mechanism contributing to a large third-order optical nonlinearity in one member of this interesting class of NLO materials, PbPc(CP)4.

We have measured extremely large second hyperpolarizabilities〈γxxxx〉 in solutions of two recently prepared organic polymer semiconductor superlattices. These block copolymers are of alternating aromatic and quinoidal moieties and structurally differ by a side group substituent. The values observed are 1.6 × 10−29 esu for the parent copolymer (PBTBQ) and 3.7 × 10−30 esu for its acetoxy derivative (PBTABQ). The corresponding values of χ(3) are estimated to be 2.7 × 10−7 esu and 4.5 × 108 esu. The measurements, made by picosecond degenerate four wave mixing at 532 nm, showed that the dynamics of the larger χ(3) valued copolymer were faster than the 30 ps resolution of the instrument while the derivative exhibited a slower response. The large magnitude and rapid response of the cubic optical nonlinearities in these novel materials suggest theiT potential for further development and photonic device applications.