Plasmonic Metallic Nano Gratings

摘要

In this study the finite-difference time-domain method based software MEEP and Lumerical are used in simulated research The optical properties and applications of surface plasmon (SP) on both ring and chirped metallic gratings are discussed through the result of simulation and theoretical analysis At first the plasmonic Archimedean spiral modes on concentric metallic ring gratings are generated by placing the ring grating under a silver nanorod to extract the orbital angular momentum of spiral surface plasmon (SSP) mode on the nanorod and transform it into orbital motion of SP on the grating Different topological charge of SSP can generate different type of Archimedean spiral mode It should be noted that the proposed structure and excitation can be used to shape the near-field pattern with special symmetry But if the SSP mode coupled onto a straight Ag grating the θ-directional velocity of SP cannot be maintained The spiral pattern will disappear Although the Archimedean spiral pattern cannot be generated it still can be used in switch or circular polarization detection devices Next the generation of convergent beam by surface plasmon locked Smith-Purcell radiation (SPR) is investigated SPR is a kind of radiation containing a frequency band when an electron bunch passing through a periodic metal grating Recently it has been found that SPR can be locked and enhanced at some emission wavelength and angle by excitation of SP on the metal substrate Here an insulator-metal-insulator (IMI) substrate structure is composed of with chirped gratings on the substrate The chirped gratings are designed such that a convergent beam containing a single wavelength is formed directly above the gratings when an electron bunch passes beneath the substrate And the IMI structure gives another way to change the locked wavelength without change the period of grating This work offers potential applications in the fields of optical beam steering holography cryptography and light source

獎項日期	2017 12月 27
原文	English
監督員	Yung-Chiang Lan (Supervisor)