Photonic bandgap materials are periodic structures that exclude electromagnetic field propagation over frequency intervals known as bandgaps. These materials exhibit remarkable wave dispersion and have found use in many applications that require control over dynamic electromagnetic fields, as their properties can be tailored by design. The two principal objectives of this thesis are the development of a liquid crystal-based microwave photonic bandgap device whose bandgap could be tuned during operation and the design and implementation of a spectral transmission-line modeling method for band structure calculations. The description of computational methods comprises an overview of the implemented numerical routines, a derivation of the spectral properties of the transmission-line modeling method in periodic domains, and the development of an efficient sparse matrix eigenvalue algorithm that formed the basis of the spectral transmission-line modeling method. The discussion of experimental methods considers the use of liquid crystals in microwave applications and details the design and fabrication of several devices. These include a series of modified twisted nematic cells that were used to evaluate liquid crystal alignment and switching, a patch resonator that was used to measure liquid crystal permittivity, and the liquid crystal photonic bandgap device itself. Numerical experiments showed that the spectral transmission-line modeling method is accurate and substantially faster and less memory intensive than the reference plane wave method for problems of high dielectric contrast or rapidly varying spatial detail. Physical experiments successfully realized a microwave photonic bandgap structure whose bandgap could be continuously tuned with a bias voltage. The very good agreement between simulated and measured results validate the computational and experimental methods used, particularly the resonance-based technique for permittivity measurement. This work's results may be applied to many applications, including microwave filters, negative group velocity/negative refraction materials, and microwave permittivity measurement of liquid crystals.

Photonic cavities are able to confine light to a volume of the order of wavelength of light and this ability can be described in terms of the cavity’s quality factor, which in turn, is proportional to the confinement time in units of optical period. This property of the photonic cavities have been found to be very useful in cavity quantum electrodynamics, for e.g., controlling emission from strongly coupled single photon sources like quantum dots. The smallest possible mode volume attainable by a dielectric cavity, however, poses a limit to the degree of coupling and therefore to the Purcell effect. As metal nanoparticles with plasmonic properties can have mode volumes far below the diffraction limit of light, these can be used to achieve stronger coupling, but the lossy nature of the metals can result in extremely poor quality factors. Hence a hybrid approach, where a high-quality dielectric cavity is combined with a low-quality metal nanoparticle, is being actively pursued. Such structures have been shown to have the potential to preserve the best of both worlds. This thesis describes the design, fabrication and characterization of hybrid plasmonic – photonic nanobeam cavities. Experimentally, we were able to achieve a quality factor of 1200 with the hybrid approach, which suggests that the results are promising for future single photon emission studies. It was found that modeling the behaviour (resonant frequencies, quality factors) of these hybrid cavities with conventional computation methods like FDTD can be tedious, for e.g., a comprehensive study of the electromagnetic fields inside a hybrid photonic nanobeam cavity has been found to take up to 48 hours with FDTD. Hence, we also present an alternate method of analysis using perturbation theory, showing good agreement with FDTD. / Graduate

No description available.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: FDTD; Linear interpolation; MEMS; NEMS; Photonic crystals; Wavelength conversion; Frequency conversion; Doppler. Includes bibliographical references (leaves 107-114).

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains xi, 99 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 80-83).

Thesis (Ph.D.) - University of St Andrews, August 2007.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xii, 142 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 138-142).

Thesis (Ph.D.) - University of St Andrews, November 2009. / Restricted until 2nd November 2011.

Artificial opals are self-assembled face centered cubic (fcc) structures of  spherically shaped beads, which interesting applications as photonic band gap materials. Inverse opals are photonic crystals consisting of fcc paced voids of a low refractive index material imbedded in a high refractive index material. Such structures has been used to enhance the photocatalytic effect of different materials and motivates further studies to improve the deposition process of the opal templates and their inversion. We state the fabrication method to design and model metal oxide inverse opals. We have successfully created alumina and alumina-titania inverse opals. With the help of simulations, we engineered inverse opals with self-assembly and atomic layer deposition.

Optoelectronic devices operating in the mid-infrared spectral region are attracting increasing attention due to potential applications in a wide range of disciplines. For example, mid-infrared photodetectors play a key role in thermophotovoltaic (TPV) energy conversion, whereby a photovoltaic device is used to extract electrical power from heat radiation. This technology is attractive for waste heat harvesting and clean energy production in several different environments. Similarly, mid-infrared light sources are particularly useful for biochemical sensing and spectroscopy, where the distinctive absorption features of many molecular species of interest can be exploited for their sensitive identification and detection. Both devices are investigated in this thesis work. In the area of TPV energy conversion, I have studied the use of intersubband transitions in semiconductor quantum cascade structures as a means to overcome the fundamental limitations of existing TPV devices using mature InP-based technology. Very efficient coverage of the incident radiation spectrum and optimal current matching can be achieved using multiple quantum-cascade structures monolithically integrated with a p-n junction, by taking advantage of their intrinsic cascading scheme, spectral agility, and design flexibility. Numerical simulations indicate that this approach can effectively double the present state-of-the-art in TPV output electrical power. In the area of mid-infrared light sources, my work has focused on developing efficient light emitters based on tensilely strained Germanium nanomembranes (Ge NMs). These ultrathin (a few ten nanometers) single-crystal membranes are good candidates for the development of CMOS-compatible Group-IV light sources, by virtue of their ability to sustain large strain levels and in the process become direct-bandgap materials. My research efforts have concentrated on the development of optical cavities based on Ge NMs that can satisfy the mechanical flexibility requirement of this materials platform. In particular, photonic-crystal (PhC) cavities in the form of disconnected dielectric-column arrays have been designed and fabricated based on a novel membrane assembly method, producing clear cavity-mode features in NM photoluminescence spectra. / 2016-08-17T00:00:00Z