Optical Dark States And Their Modulation On The Transmission Properties Of Subwavelength Waveguide

Metal-dielectric-metal(MDM) plasmonic waveguiding structure shave been extensively studied over the past years. They are nano-photonic systems with broad potential applications for their ability of overcoming the diffraction limit, confining and transporting electromagnetic fields purposefully in nanoscale dimensions. As plasmonic structures offer significant manipulations of light in the nanometric scale, enabling deep subwavelength confinement of light, they may support many analogous coherent phenomena in atomic system, such as Fano resonance and electromagnetically induced transparency. In this thesis, with both theoretical and numerical approaches, we study using optical bright states and dark states to control the waveguiding properties in plamonic waveguiding systems.First of all, effects of optical bright, especially dark states and their mutual action on the transmission spectrum of MDM waveguides are analyzed systematically. It is shown that different number of dark states and their interaction have great effects on the transmission spectrum, forming interesting plamonon induced transparency(PIT).Temporal coupled mode theory is used to investigated the wave-manipulation characteristics of MDM waveguides for the orthogonal modes and non-orthogonal modes in lossless multimode cavities. The presence of orthogonal modes creates interesting transport properties which cannot be obtained in normal resonator systems. When difference of the orthogonal modes is below a definite threshold, the system is all pass, i.e., the modes are invisible for the bus waveguide. We validate the theoretical results by comparing them with finite-element-method simulations and obtaining excellent agreement between the two.Based on the coupled mode theory and the transfer matrix approach, we investigate the interaction between the Bragg gap resulting from the multiple Bragg reflection and the polariton gap caused by the localized resonances, in a periodic MDM waveguides with cascaded resonators. When the Bragg gap associated with the period and the polariton gap related with the hybridized modes in a unit cell are partially(or fully) overlapped, a mini-band would be arise, where the plasmonic wave can travel through the structure in an otherwise stop-band. These are referred to as multi-PIT phenomena.The results in this thesis may provide certain guiding significance for novel subwavelength coherent waveguide device. They can be used to build filters, routers, and adder-subtracter, etc., based on the structure of the MDM.