This book discusses advances in research and applications of plasmonics. Chapter One examines the plasmonic interaction in enhanced luminescent down shifting layers for photovoltaic devices. Chapter Two presents a short review on a variety of coherent optical interactions in plasmonic nanostructures that are akin to certain quantum physics originally discovered in condensed-matter and electronic systems. Chapter Three reviews atomic-phase-coherence assisted surface plasmon resonance and negative optical parameters in multilevel media.