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Combining optics and microfluidics to create a portable optofluidic photonic crystal (PhC) biosensor is an approach with promising applications in the fields of counter-terrorism, agricultural sciences, and health sciences. Presented here are fabrication processes of a gallium nitride (GaN)-based PhC biosensor with a resonance-enhanced fluorescence detection mechanism that shows potential for meeting the single molecule detection requirements of these application areas. GaN is being targeted as the photonic crystal slab material for two main reasons: its transparency in the visible spectral range, within which the excitation and emission wavelengths of the commercial fluorescent-labeling dyes fall, and its intrinsic thermal stability which provides an increased flexibility of operating in different environments. Optical modeling efforts indicate a 25-fold enhancement of the fluorescent emission in this portable fluorescentbased PhC biosensor.

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Large-scale two dimensional ordering of silica nanospheres on GaN substrates was fabricated using spin-coating and observed using Matlab-based Nomarski image processing, which was developed to calculate the surface coverage of 2D and 3D ordering of silica nanospheres on GaN substrates. Optimal spin coating condition and SDS concentration were investigated with Nomarski image processing and an SEM. The details on spin coating process parameters or SDS concentration vs. surface coverage of silica nanospheres on GaN substrate are discussed, along with a theoretical exploration of the effects of nanosphere patterning on photonic crystals fabricated using this method.

Nanophotonics, specifically photonic crystals (PhCs), offer unique optical bandgap engineering possibilities that has driven the emergence of a variety of device platforms, including: beam splitters, nano-cavity resonators, lasers, fibers, waveguides and highly sensitive optofluidic biosensor devices. The design and fabrication of accurate lattice parameters for a PhC is very important to achieving the desired operating bandgap. The inclusion of tunability in thin film PhCs not only offers a means of adjusting for fabrication errors but also a mechanism to increase device functionality as well as providing a wider range of operating wavelengths. Nitride thin films, specifically Aluminum Nitride (AlN) and Gallium Nitride (GaN), are being used as PhC slab materials by our group due to their desirable optical properties at visible wavelengths and high chemical and thermal stability under harsh conditions. The inherent piezoelectric properties of these materials offer a means of direct tuning of PhC lattice parameters through piezoelectric deformation. This thesis presents the results of research aimed at actively tuning the bandgap of PhCs fabricated in piezoelectric AlN thin films. Theoretical investigations of the bandgap tuning of ‗as-drawn' and deformed 1and 2-D PhC lattice structures using coupled results from PhC optical behavioral modeling and finite element mechanical simulations are discussed. The results of experimental characterization of the optical and mechanical (i.e. tuning) properties of micro to nanoscale PhC lattice structures fabricated in Si and AlN using e-beam and optical lithography and reactive ion etching are presented. Experimental data is then used to explore the bandwidth tuning capability of large-area periodic nanophotonic structures. iii Acknowledgements I would like to express my sincere thanks to Dr. Jeremy Dawson, my research advisor and committee chairperson who has been a constant source of motivation and support throughout my research work. I would also like to thank him for helping me to develop wide range of skills in design, fabrication as well as in characterization processes. I bestow my sincere thanks to my committee members Dr. Lawrence Hornak and Dr. Dimitris Korakakis for their time, valuable suggestions and support throughout my research experience. I would like to acknowledge Dr. Kolin Brown for his assistance and guidance in the clean room. I would like to express my special thanks to Sridhar Kuchibhatla and Henry Andagana for their constant support and informative discussions. I would also like to thank Swetha Sanju Koduri, Bashar Hamza and Anand Kadiyala for their support throughout my work. Most importantly, I would like to thank my father, Y.V. Padmanabham and my mother, Sridevi for their unconditional love and support without which nothing would have been possible in my life. I would also like to thank my elder sister Swapna for her love and care towards me all these years. Last but not least, I would like to thank my fiancé, Naveen Kantamneni for his love, emoti...