The Design And Study On V-shaped Nanoantenna Based On Surface Plasmons

Traditionally,the lens realizes beam shaping by consecutive refraction of rays on curved surface.While with the development of integrated optics,traditional lens has restrictions like large volume as well as poor performance,making it encounters unprecedented challenge in the application of micro-nano optical system.Metallic nanoantenna structure can couple free light wave and produce surface plasmon polaritons(hereinafter refers to SPPs).The wavefront shape could be adjusted by controlling the SPPs,and then comprehensive regulation of the optical field can be realized in an ultra planar area.Optical distortion,astigmatism as well as coma are meanwhile prevented.The V-shaped nanoantenna is one of the various kinds of surface plasmons nanoantenna structures.By virtue of its good properties of ultrathinness,double resonance effect,whole phase position adjustment,and distortionlessness,the V-shaped nanoantenna becomes a good choice to design ultrathin planar focal lens.First,an ultrathin planar lens able to realize beam focusing is designed in this paper based on V-shaped nanoantennas.Second,countermeasures are proposed to the problems of lens on focusing properties.Third,the planar focal lens is adjusted on the basis of super oscillation theory,making it possible to realize super resolution focusing in the far field and relevant experimental preparations and optical testings are done.The research contents and relative achievement are as follows:1.The optical property researches of V-shaped nanoantenna structure are carried out.On one hand,the resonance pattern of V-shaped antenna is analyzed and the finite different time domain(FDTD)is applied to calculate the phase distribution and amplitude response to be produced when the scattered light penetrates through the antenna.On the other hand,some methods to design planar focal lens by V-shaped nanoantenna arrays are introduced and several ultrathin planar focal lens with different focal lengths,different arrangements,and different applications are designed accordingly methods.By simulation,these planar lens structures based on V-shaped nanoantenna arrays are capable to realize high efficiency focusing.2.The focusing property related researches of planar focal lens based on V-shaped nanoantenna arrays are carried out.To improve the focusing property of surface plasmons(SPs)planar focal lens,a metal-insulator-metal(MIM)structure is introduced this paper,which is composed of V-shaped nanoantenna arrays at the top,gold film at the bottom,and the Si medium between.This design is optimized by the separation distance between the two layers of metal structures and the thickness of metal film at the bottom,making the original SPs waves transmitting respectively on the two metal layers produce resonance coupling enhancement under a certain condition.Therefore,the focal light intensity of MIM structure lens improved 1.5 times larger than before.Additionally,a method which can effectively improve the resolution of planar focal lens is mentioned,namely,to place the planar focal lens into the mediums with refractive indexes greater than that of air.By comparison and analysis of the focuses in mediums with different refractive indexes,the method of oil immersion is easyier and more feasible.This method can not only dramatically improve the resolution of focal lens,but it also increases its focal length.At last,the author also analyzes the focal properties of planar lens based on the V-shaped nanoantennas in this paper,including focal properties in broadband wave and oblique focusing.3.A way to design super oscillatory lens(SOL)based on the V-shaped nanoantenna arrays is proposed.On the basis of super oscillatory theory,a lens structure able to realize super resolution focusing in the far field is designed by shielding of phase position.By optimization,a phase position of ? is added to the 8th to 17 th ring of V-shaped nanoantenna of the lens,the lens can realize a focal effect which is 0.89 times larger than the diffraction limit at 34?m.To verify the super resolution,the author also probes into the ways to prepare V-shaped nanoantenna arrays.In the research,electron beam lithography(EBL)combined with micro processing technique is applied to prepare the SOL structure.In the end,optical testing platform is set up to the optical field distribution test.There is no much difference between the testing results and simulating ones,which verifies correctness of the design and its principles.The above works have the potential to promote the applications of V-shaped nanoantennas in laser direct writing,optical integration,super resolution image,telescoping,high-density integration and so on.