Coherent Optical Effects In A Number Of Small-scale System

The research on mesoscopic physics, especially the physical effects on a small scale(such as nano, molecular scale) is highly significant not only for understanding basic problems in quantum physics, statistical physics and classical physics, but also for the technical innovation on novel electro-optical devices, quantum information process and miniaturized photonic circuits. This dissertation mainly focused on two kinds of small scale systems, then obtained the quantum coherent properties in the Bose-Einstein condensate (BEC) photoassociation system and the new generation mechanism of surface plasmons in metal nanostructures - electron bombardment, which are powerful support for the further studying on quantum effects on mesoscopic, especially on the electro-optical integrated circuit and plasmon-based quantum information process. Our key work and results are shown as follows.(1) In atomic BEC photoassociation system, we adopted an exactly solvable mean-field method to study this process by linearizing the bilinear atom-molecule coupling, and obtained the exact solutions of atomic and molecular fields, which allowed us to conveniently probe quantum dynamics and statistics properties of the system when the initial atomic state is classical coherent state and non-classical squeezed state respectively. The results are important for understanding both the quantum coherent property in this system and the formation of quantum control technique in atom-molecule system.(2) We provided a practical solution to the important problem of plasmon generation at designated locations in space, which is a major ingredient (still missing) in any realistic application of plasmonics. More specifically, we reported on highly-efficient generation of propagating plasmons by electron beams in planar films, planar dielectric cavities, metallic wires, and nanoparticle waveguides, and we obtained excitation yields as high as one plasmon per incoming electron over the visible and near-infrared range. Our results provided full support for the application of electron bombardment to excite propagating plasmons. (3) We systematically studied the generation of anapole plasmons in nanotorus structures by electron beams, which means that electron beams can efficiently excite not only propagating plasmons, but also localized surface plasmons in nanostructures. More further, this phenomenon is a restatement of microscopic electromagnetic property in mesoscopic scale, which will be very important for the research on chemistry and biology.Several studies above on optical coherence physics of a small scale, including the quantum statistical and dynamics properties in atomic BEC photoassociation process, novel method for exciting surface plasmons in nanostructure, not only lie a solid foundation for further studying on quantum effects on mesoscopic, but also are very valuable for application, especially the latter will be very significant for the technology of electro-optical conversion.