New organic infiltrants for 2-D and 3-D photonic crystals

Photonic crystals have now started to make the transition from basic to applied research, with new materials systems and device results being published on a frequent basis. While a number of photonic crystals have been made using organic materials, the lack of high index organic materials has impeded their development. We have investigated several novel high index organic systems for use in both 2-D and 3-D photonic crystals. 2-D photonic crystal templates were made by a rapid multibeam interference method in the photoresist SU-8, using 532nm laser radiation. These samples, typically on glass, were then infiltrated by a number of methods including from solution and melt, as well through chemical vapor deposition. Solutions of a titanium precursor with a cured refractive index of 2.1 at 633nm were infiltrated and cured in the SU-8 structure, with the infiltrant deposited by both by spin coating and casting. The resulting structure was shown to preserve the six-fold symmetry of the initial photonic crystal and subsequent firing at high temperature effectively removed the SU-8 template. We have also explored the infiltration of nanoamorphous carbon into the photonic crystals using chemical vapor deposition. This material, which is essentially a carbon-silicon ceramic, has exceptional infrared optical properties with a refractive index > 2 for wavelengths beyond 2 μm. The SU-8 polymer template has been shown to survive the CVD deposition process and the resulting infiltrated structure also preserves the initial PC symmetry. A series of metal-like PCs with a full range of properties is enabled by the ability to dope the nanoamorphous carbon with metals that possess exceptional refractive indices in the infrared regions of interest. We have also investigated the potential for nonlinear optical devices based upon azobenzene copolymer infiltrated silicon PCs and demonstrate the excellent properties of this material with respect to all-optical effects.