The goal of this project is to conduct analytical, numerical, and experimental research on the resonant leaky modes associated with periodic refractive-index lattices such as gratings and photonic crystals. As shown by numerous simulations, single-layer subwavelength periodic leaky-mode waveguide films with binary profiles can be applied to fashion optical elements that provide a remarkably broad variety of tailored spectral characteristics. These sparse elements with one-dimensional periodicity can function as new types of narrow-line bandpass filters, polarized wideband reflectors, polarizers, polarization-independent elements, and as wideband antireflectors. The project addresses fabrication and characterization of new device concepts based on these structures with the main objectives as follows: 1. Develop an analytical model for resonance elements with weakly modulated asymmetric profiles to elucidate the detailed resonance physics and leaky-mode interactions in this limit. 2. Numerically quantify spectral enhancements realized by addition of homogeneous layers. 3. Numerically characterize the resonant leaky-mode photonic band structure. 4. Numerically quantify resonant leaky-mode spatial field distributions to clarify the leaky-mode interaction dynamics. 5. Fabricate and test resonant elements using silicon-on-insulator wafers.
Intellectual merit: This project provides new, creative directions in photonic device research by addressing fundamental phenomena for subwavelength leaky-mode resonant device technologies. The preliminary results indicate that a new class of optical elements is possible and explain how pertinent devices might be implemented. The associated physical properties are explained in terms of the photonic band structure and its relation to the structural symmetry of the elements. The interaction dynamics of the leaky modes at resonance contribute to sculpting the diverse spectral bands observed by numerical simulations. The leaky-mode spectral placement, their spectral density, and their levels of interaction are shown to be fundamentally important in understanding device operation. These ideas merit further theoretical and experimental research and development as proposed.
Broader impacts: Single-layer leaky-mode elements can have functionality somewhat comparable to multilayer homogeneous thin-film elements. Traditional thin optical films are applied to design and fabricate elements with diverse spectral features which are widely used in optical systems. The guided-mode resonance elements of interest in this proposal possess analogous spectral versatility but are governed by different physics. Thus, new possibilities in function and applications can be envisioned that may provide complementary capability with the field of thin-film optics. Finally, the project will benefit graduate and undergraduate education and enhance the experience of numerous high school students and teachers attending summer programs in engineering.
