Research On Transmittance Enhancement Of Hollow Conical Metal Waveguide Via Dielectric Microsphere

In this dissertation,a new method is proposed to improve the transmittance of a hollow conical metal waveguide(HCMW)by embedding dielectric microsphere(DM),and based on the theory of metal optical waveguide and the theory of surface plasmon,the optical field transmission characteristics of the HCMW are studied systematically by finite difference time domain(FDTD)method.It is found that compared with the case without DM,the optical field transmission law of the HCMW embedded with DM is fundamentally changed,and the optical field transmittance of the tip aperture can be greatly enhanced.Analysis and comparison show that on the inner wall of the HCMW embedded with DM,the effective excitation and propagation of surface plasmon polaritons(SPPs)are realized.This is completely different from the case without DM that higher-order transmission mode of the optical field gradually evolve into lower order transmission mode,and in the tip region,the fundamental mode cut off and the remainning optical energy attenuation radiation through the aperture.Then,based on the SPPs dispersion relation and the standing wave conditions of SPPs resonance,the dissertation discusses how to achieve the resonance excitation and effective compression of SPPs on the inner wall of the HCMW.At the end of the paper,the effects of the important parameters such as microsphere radius,incident wavelength of optical field,numerical aperture of coupling lens and microsphere dielectric constant on the transmittance enhancement of the HCMW embedded with DM are systematically studied,and achieved the maximum enhancement of the optical field transmittance of 49.4 times through parameter optimization.The research of the transmittance enhancement of HCMW has important theoretical significance for exploring new integrated and miniature nano-optical devices,and has a good application prospect in the fields of ultra-high resolution imaging,surface plasmon waveguide and surface plasmon resonance imaging,etc.