Optical properties of novel structures of colloidal crystals
Mittleman, Daniel M.
Doctor of Philosophy
Photonic crystals are materials having a periodicity in their refractive index. This results in the inhibition of select frequencies of light from propagating within the crystal causing the formation of a gap in the photonic band structure. Analogous to semiconductors, the presence of a photonic band gap makes these materials tremendously promising for a new revolution in the technology industry. Their periodic nature make them ideal for two-dimensional lithographic fabrication. However self assembly methods with colloids offer the most promising route to fabricating three-dimensional structures, so as to affect the confinement of light in all directions. The work presented in this thesis strives to advance the understanding of colloidal crystals to ultimately facilitate the construction of real, working, commercial devices. We probe the optical properties of such colloidal crystals and describe techniques to engineer them into novel structures, such as crystals of hollow spherical shells, to enhance the performance of the photonic band gap. We examine novel architectures like colloidal photonic superlattices to generate propagation modes within the band gap and show that such structures can be fabricated to have uses as filters and optical resonators. We investigate incorporating colloidal crystal structures into organic light-emitting devices to improve device performance by spatially modifying the light output. Finally, as it is critical to fabricate high quality devices approaching the accuracy obtained by lithography, we conduct a systematic and quantitative study of the nature of defects in these colloidal crystals and correlate structural defects during fabrication to altered optical properties.