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Based on Nanometer Ball and a Strip Waveguide Surface Plasma Structure Design Research

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Tutor: LiZhiQuan
School: Yanshan University
Course: Detection Technology and Automation
Keywords: surface plasmon,the finite difference time domain method,nanospheres,strip waveg
CLC: O53
Type: Master's thesis
Year:  2012
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The surface plasmons (SPs) is a cluster effect of the vibration of the free electrons atthe medium interface. With the great development of nanophotonics and microprocessingtechnology, domestic and foreign experts have strong interest in the study of SPs effect.Experts have found the generation mechanism of SPs: Only in the precious metals (gold,silver or aluminum) which have higher resonance frequency and lower collision frequency,meanwhile we use specific structure to match the incident wave and the wave vector ofSPs, so that the energy of light waves and energy of free electrons can be coupled to passand the collective momentum of the free electrons increases, we can produce the SPsphenomenon.Because the SPs phenomenon is mostly happening in precious metals and the opticalproperties of the metal and free electrons are closely connected, to study the opticalproperties of the metal is to study the electromagnetic fields generated by the interactionof the free electrons in the metal and light waves as well as scattering, absorption,reflection and other phenomena. So this paper begins with the optical characteristics of theSPs and analyzes the differences between plasma and SPs, especially analyzing theinternal and surface optical properties of the metal. We also investigate the absorption andscattering properties of the metal for the incident. Using the Maxwell equation combinedwith the rate equation, We establish an electronic Drude model to deduce the resonantfrequency of the metal free electrons, the dielectric power factor and quality factor and soon.Due to the enhanced near-field localization properties of the SPs, we first establishthe gold nanosphere system, and use the finite difference time domain (FDTD) method forthe distribution of the simulated local field and the frequency spectrum of the changinglocal characteristics caused by the incident angle changes. Secondly, we extend thelocalization properties to the semiboundless strip waveguide surface plasmon embeddedwith grating and plate strip waveguide surface with gold film to generate SPs. This systemmainly researches for the SPs phenomenon excited by the grating coupling, simulates collective electron oscillation phenomenon, and draws the conclusion that the SPs vibratemore strongly at the edge of the gold film and that the propagation distance can attain themicron level. And it also verifies the law of the transmission rate and efficiency of thetransmitted light through changing the metal film thickness and incident angle.
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