Novel materials for photonic applications.

Abstract

This work involves the design, synthesis, and formulation of organic second-order nonlinear optical and photorefractive materials. The second-order nonlinear optical work is divided into two sections. The first section focuses on the design and synthesis of high glass transition temperature aromatic polyesters for high temperature nonlinear optical applications. The polyesters are based on azo dye derivatives of resorcinol and 3,3'-ethylenedioxydiphenol. These diphenols could be polymerized with 5-t-butylisophthaloyl dichloride using mild solution or interfacial polycondensation procedures. The incorporation of the t-butyl groups in the polymer backbone resulted in a significant increase in glass transition temperature and more importantly solubility. The ethylene linkage present in the 3,3'-ethylenedioxydiphenol had the effect of lowering the glass transition temperature while providing a small increase in solubility. The resulting polymers were soluble in common organic solvents and had glass transition temperatures ranging from 89°C to 171°C. These polymers will be characterized for their second-order nonlinear optical properties in the near future. The second section on nonlinear optical materials focuses on the synthesis and characterization of a model compound for future self-assembling nonlinear optical molecules and polymers. The synthesis of dispiro[indane-2,3'-piperazine-6',2''-indane]-2',5'-dione via the direct thermolysis and dimerization of methyl-2-amino-indan-2-oate hydrochloride was accomplished. The crystal structure of this compound showed the necessary hydrogen bonding needed for the construction of an anisotropic, noncentrosymmetric second-order nonlinear optical material. The photorefractive work involved the formulation of guest-host polymer composites that demonstrated the photorefractive effect. The polymer composites are composed of poly(N-vinylcarbazole), 2,4,7-trinitrofluorenone and a second-order nonlinear optical azo dye. The composites and could be processed into thick films suitable for photorefractive measurements by plasticizing with N-ethylcarbazole. These materials could be electric-field poled at room temperature and showed high diffraction efficiencies ranging from 1% to 5%. The photoisomerization of the azo dyes to produce a competing diffraction signal was found to be polarization sensitive. Thus, the photorefractive effect could be isolated and studied independently by selecting the appropriate polarization. The photoisomerization can be avoided altogether by tailoring the azo dyes so that their absorbance is minimal at the frequency of the laser light. It was possible to perform asymmetric two-beam coupling when the photoisomerization was minimal.