Photonic bandgap materials: design, fabrication, and characterization

Subramania, Ganapathi
Major Professor
Kai-Ming Ho
Gary Tuttle
Committee Member
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Physics and Astronomy
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Physics and Astronomy

The last few decades have seen a tremendous explosion in the area of new synthetic materials. As we begin to better understand the nature of the atomic and molecular bonds it has been possible to systematically search for materials with specific properties thanks to the availability of powerful supercomputers. Due to significant advances in materials synthesis a rich variety of artificial materials whose mechanical, chemical, electronic and optical properties can be suitably tailored can now be produced. Some of the materials (plastics, synthetic fibers, ceramics, alloys etc.) can replace or substitute traditional materials; some others have managed to create new applications themselves (semiconductors, superconductors, optical fibers etc.). Over the last decade there has been a growing interest in a new material called "photonic bandgap structures" which can manipulate light in an extraordinary way opening up new possibilities in the area of optics and optoelectronics, eventually paving the way for optical computing. Proof of principle structures that demonstrates the expected property has been successfully fabricated for low frequency electromagnetic waves. However, making photonic bandgap structures that can operate at visible frequency is quite challenging. This is because photonic bandgap material are essentially periodic dielectric structures where the periodicity is on the order of the wavelength of light. The goal of this dissertation is to develop a technique for the fabrication inverse FCC photonic crystals that can operate at the visible and near infrared frequencies. The technique essentially focuses on employing self organizing systems such as monodisperse colloidal systems of polystyrene microspheres as a basis for forming periodic structure at submicron dimensions. The main aspects are first to show that the experimental procedure for fabrication developed in this dissertation actually has the desired structural property. Demonstration of structural properties is done by means of optical microscopy and scanning electron microscopy. The other aspect is to demonstrate that the photonic structure so produced indeed shows effects due to photonic bandgap. Optical spectroscopy of the samples is used to show that these samples indeed show the pseudogap that has been theoretically predicted for photonic crystals made with the materials used.