Title

Resonant leaky-mode spectral-band engineering and device applications

Date of Completion

January 2006

Keywords

Engineering, Electronics and Electrical|Physics, Optics

Degree

Ph.D.

Abstract

This dissertation addresses electromagnetic analysis and design of waveguide-grating devices based on the guided-mode resonance (GMR) effect. The resonance occurs when the incident light is coupled to a leaky waveguide mode through one or more periodically modulated layers. The characteristics of the devices are shaped by the number of resonances, as well as their spectral linewidths and locations. ^ Numerical tools used to study the diffraction and dispersion properties of one-dimensional and two-dimensional dielectric periodic layers are introduced. The main diffraction characteristics and dispersion properties of dielectric waveguide gratings are discussed and plotted. Two representations of dispersion results, one using real frequency and complex propagation constant, the other using complex frequency and real propagation constant, are discussed. It is shown that dispersion results in complex frequency provide clear band gaps and connect well to the diffraction properties of these elements. One-dimensional metallic-dielectric gratings are also studied with rigorous numerical formulation and an approximate model. After presenting the resonance locations in a normalized mode diagram, the leaky modes that support resonance are revealed. ^ The waveguide grating is studied analytically with a simplified version of the rigorous coupled-wave analysis as well as coupled-mode analysis. While the former locates the resonance and explain the degeneracy caused by the symmetry of the modulation profile, the latter analysis provides clear physical insights into the resonance effects. The coupled-mode analysis explicitly shows the connection between the diffraction properties and the dispersion characteristics of the resonant photonic-crystal lattices under study. This analytical model is also applied to metallic-dielectric gratings that support leaky-mode resonance. ^ The application of interacting GMRs for leaky-band spectral engineering is presented. As shown by numerous simulations, single-layer GMR elements with binary profiles can be applied to fashion optical elements that provide a remarkably broad variety of tailored spectral characteristics. It is shown that these sparse elements with 1D periodicity can function as narrow-line bandpass filters, polarized wideband reflectors, polarizers, polarization-independent elements, and as wideband anti-reflectors. ^

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