Second harmonic generation in multilayer langmuir - Blodgett films of blue transparent organic polymers

Multilayer Langmuir - Blodgett (LB) films were fabricated with two blue transparent nonlinear optical polymers in which the orientation of the nonlinear optical chromophore in one polymer is reversed with respect to the other. The intensity of the frequency-doubled light generated in these multilayers increases quadratically, with the increasing number of bilayers indicating that the macroscopic optical nonlinearity, χ⁽²⁾, of the bilayer is a linear sum of the macroscopic optical nonlinearities of the individual monolayer. Also, multilayer LB films of each blue transparent polymer were made by alternate deposition with a spacer polymer, poly(tert-butyl methacrylate). The intensity of the frequency-doubled light generated by these multilayer films was approximately 4 times smaller than that generated by multilayer films of two blue transparent polymers with the same number of layers, indicating that the use of another nonlinear optical active polymer in the place of passive poly(tert-butyl methacrylate) polymer leads to considerable improvement in the frequency-doubling efficiency. Multilayer LB films of these polymers show a great potential for achieving a practical level of performance.