Theoretical Studies On Surface Plasmons In Near-field Lithography And Micro-nano Waveguide

Surface plasmon (SPs) for the special spatial distribution, resonant characteristics and nonlinear effects has been employed in many fields. On the basis of numerical simulation, SPs application in near-field lithography and micro-nano waveguide is studied in this thesis.Keeping the resolution of near field lithography far beyond the diffraction limit, a periodic metal-insulator-metal shaped mask capable of light transmission enhancement in the lithographic channels is designed to produce uniform field intensity distributions at the channel exits with fine contrast and small interspace between them. It is found that the transmission efficiency can be enhanced by a metal nanostrip placed right above the channel. The strip is also convenient to reduce the distance between the lithographic patterns based on decreasing interspace of channels. As the interspace is decreased, the intensity of interference field between the channels at the output side is increased at the cost of field intensity contrast adjacent to the exit. A way of reducing the interference intensity is proposed by etching a groove in the mask between the channels at the output side. In the case, both the field intensity and distribution at the exit are kept off influence, while the groove position and its parameters are suitable. The interference intensity depends on the groove location, depth and width; we find that an optimal location of the groove etched is the centre of adjacent channels. Our researches are advances of exploring near-field lithography with small distance of lithographic patterns and fine contrast besides the high resolution.Control of incident light wave propagating in a "⊥" shaped MIM waveguide is studied by a groove etched in the wall of the horizontal channel. The light transmission depends on the parameters of groove and waveguide. Some of the novel phenomenon such as the sawtooth distribution of light intensity at the exit with the changing position of groove and lower metal film is observed and explained. The-results are good for developing the miniaturized photonic devices with the function of filter, light path and intensity control.The optical effects of two sliver nanosphere chains are studied. The results show that, changing the sphere size, the dimer number and the interspace of them, the resonant multipole oscillation, especially the resonance-coupled quadrupole oscillation in the chains plays an important role in the control of SPs resonance and position of near field enhancement. In the case of resonance, the polarized electronic current in the chains is investigated and we find that the electrons distribution in the penultimate dimer is similar as that of the resonant dipole case, thereby, the resonant dipole spectrum together with the maximal localized field enhancement is produced in where. The studies can provide a guideline for SPs application in optical waveguide, optical sensor and surface enhanced spectrum analysis etc.