To control thermo-optic (T-O) coefficient of polymer materials, hybrid polymer system with inorganic nanoparticles
was examined. Polymer materials have high T-O coefficient but low refractive index. On the other hand, inorganic
materials have low T-O coefficient but high refractive index. Then surface treated inorganic nanoparticles were dispersed
into epoxy polymers. By increasing inorganic nanoparticle contents, refractive index of hybrid polymer changed and its
T-O coefficient decreased.
An unparalleled range of photonic nanocomposites has been developed utilizing surface engineering over preformed nanoparticles. These nanocomposites cover a number of organic polymers as host materials. By controlling a loading level of inorganic nanoparticles (e.g., nano-TiO2) within a polymer host, important optical parameters including the refractive index (n) can be varied over 50~100 % with respect to the corresponding polymer matrix. This refractive index control capability enables a large refractive index contrast (Dn) that is a very significant requirement for fabrication of microphotonic devices such as photonic crystals. High levels of nanoparticle dispersion within a polymer host can be achieved even at loading levels up to 60 wt% to assure low scattering, i.e., transparent coated films in the infrared and visible light regions for photonic crystal applications. This paper presents nano-engineered polymer-based photonic crystal materials and processes to make them. Use of very uniform nanoparticles preformed by laser-driven chemical reaction is vital for successful fabrication of optical-class composite films and described here. Major benefits out of the current approach are discussed including (a) high Δn, (b) easy-to-fabricate 'hetero-interface', a minimal unit of periodic photonic crystal structures, and (c) significant economical benefit.