Photonic Crystals, Wave Localization and Applications

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We propose to elucidate novel effects in photonic and phononic crystals with an eye to practical applications. The novelty of photonic crystals arises from their ability to coherently trap photons in unique ways and their enabling of strong coupling between light and matter. We propose to demonstrate the efficacy of photonic crystals for high-efficiency solar energy harvesting in thin-films and for medical diagnostics through novel optical bio-sensors.***We propose to develop thin-film photonic crystal architectures for solar light trapping and absorption in next generation photovoltaics. Our effort will focus on the computational design and modeling (both wave optics and electronics) and close collaboration with experimental groups. The underlying physics of our enhanced light trapping and solar absorption is through the coupling of sunlight to slow-light modes of the photonic crystal that propagate in directions transverse to the thin-film surface. This corresponds to a spectral range where the photonic density of states is enhanced relative to that of a homogeneous material. The ultimate aim of this research is the realization of a thin (10 micron) silicon solar cell with power conversion efficiency above 30%. ***A related topic is acoustic wave trapping and absorption in thin phononic crystals sheets. We propose to study the role of parallel-to-interface refraction and slow-sound modes in suitably designed, periodically-modulated, elastic materials to achieve broad-band sound absorption for the purpose of sound-proofing. This involves phononic band structure optimization and finite-difference time-domain simulations of sound passing from air into thin phononic crystal sheets.***We propose to extend our study of lab-in-a-photonic-crystal biosensors for medical diagnostics to realistic 3D architectures amenable to low-cost fabrication. The spectral fingerprinting and logical discrimination of multiple disease-markers is facilitated by the interaction of multiple resonance modes within a photonic band gap. Our aim is to work closely with leading experimental groups with expertise in fabrication of nano-pillar photonic crystals, knowledge in micro-fluidics and experience in functionalizing dielectric surfaces with biologically relevant molecules.***We propose to design and characterize new materials capable of realizing exciton-polariton coherence and long-lifetime, equilibrium Bose-Einstein condensation at room temperature. We will study the nature of quantum many-body correlations resulting from interactions in the excitonic Bose condensate such as bi-exciton Feshbach resonances. We will elucidate the nature of laser-like light emission as the condensate decays radiatively. In the case of attractive exciton-polariton interactions, we will explore the possibility of “Schrodinger Cat” and other macroscopic quantum superposition states made possible by the protective environment of the photonic band gap.**