Design of non-linear optical films by Langmuir-Blodgett technique

Abstract

Publisher Summary This chapter discusses the application of Langmuir-Blodgett technique in designing non-linear optical films. The Langmuir-Blodgett (LB) technique provides a unique method of fabricating organic thin films with noncentrosymmetric molecular orientation. Using the LB technique, one expects to obtain three types of noncentrosymmetric LB films: hetero Y-type, X-type, and Z-type films. In addition, the film thickness is controllable at molecular level, within several nm, by the number of deposited monomolecular layers. The refractive index of the LB films can be also controlled by incorporating heavy metal ions as a counter ion into the films. These features are advantageous for the application to nonlinear optical devices, in particular, nonlinear optical waveguides. The first issue of the construction of noncentrosymmetric LB films with highly efficient optical nonlinearity is how one overcomes the difficulty in realizing a high-degree orientational order of polar molecules, which possess high hetero Y- molecular hyperpolarizability, in the noncentrosymmetric LB films. The chapter also presents a molecular design for the construction of noncentrosymmetric LB films with high degree of molecular orientation and a novel technique to improve the orientational order of polar molecules in LB films using the molecular mixing between homologous amphiphiles. Further, the optical nonlinearity in the pyrazine LB films and the application of the pyrazine LB films to a frequency-doubling waveguide device is also presented. The optical nonlinearity in the pyrazine LB films and the application of the pyrazine LB films to a frequency-doubling waveguide device is also demonstrated.