| The field of photonics hopes to harness light to supercede in performance many of the functions carried out by electronics. To accomplish this, the flow of light can be controlled by means of a photonic band gap (PBG) the same way electronic band gaps can control the flow of electrons. PBGs, through the coherent backscattering of radiation, create frequency ranges in which light propagation is forbidden. A PBG is created when a wave propagates through a periodic array of materials with sufficient refractive index (n ) contrast (n1/n 2) where the dimensionality of the periodicity defines the dimensionality of the PBG. The n contrast required to open a PBG increases as the dimensionality increases. Currently, only inorganic materials have a sufficiently high n to open a complete 3-D PBG.; The goal of this project is to fabricate a polymeric material with a complete 3-D PBG, to bring the tailorable physical, electrical, and optical properties of polymeric materials to 3-D PBG materials. The first step was to develop a polymer with a sufficiently high n. Because of its conjugated nature and the presence of a heavy sulfur atom in its repeat unit, poly(thiophene) (PT) is predicted to have one of the highest polymeric refractive indices with n = 3.9 at 700 nm1, but the reported n value for PT is 1.4 at 633 nm.2 This discrepancy is because the potential needed to electrosynthesize PT, the only method available to synthesize thick and high quality PT films, is higher than its degradation potential. It was found that by polymerizing thiophene with an optimized monomer concentration, proton trap concentration, and reaction temperature in a strong aprotic Lewis acid solvent, the polymerization potential could be reduced below the degradation potential of PT. The resultant PT film had a maximum n of 3.36, which is sufficiently high to open a 3-D PBG.; Photonic templates were then constructed using a combination of Colvin's method3 with monodisperse spheres and mechanical annealing. High n PT was used to infiltrate the templates, and the templates were removed, leaving a polymeric inverse opal with the possibility of a complete 3-D PBG. |
