Abstract

A series of polymers and copolymers were synthesized from benzidine and para substituted phenols by the horseradish peroxidase catalyzed reaction in dioxane. Third-order nonlinear optical susceptibility χ⁽³⁾ was measured for all these bioengineered polymers in a solution of dimethyl sulfoxide and methyl alcohol (in the ratio 4:1), using the technique of degenerate four-wave mixing. The source used for the measurements was a frequency doubled Nd:YAG laser giving 17-ps pulses. The vertically polarized output at 532 nm was split into three beams which are spatially and temporally overlapped in the sample contained in a cuvette of 1- or 2-mm light path. The χ⁽³⁾ values of polymers were obtained by comparison with a reference sample of CS₂. The molecular hyperpolarizability (γ) was obtained from the polymer solution measurements, and the macroscopic value χ⁽³⁾ for the pure polymer was calculated. χ⁽³⁾ values of polymers were in the range of 10^-9 to 10^-8 esu, three to four orders larger compared to the monomers. Relative magnitude of the electronic and orientation contributions to the nonlinearity were determined by changing the probe polarization from parallel to perpendicular orientation with respect to the pump beams. The phase-conjugate signal was also measured as a function of probe delay with respect to pump beams.

© 1991 Optical Society of America