Design,Fabrication And Optical Properties Of Graphene-Noble Metal Composite Array Structures

As optoelectronic technology continues to develop toward miniaturization and integration,the diffraction limit in traditional optics has become a bottleneck,which restricts the development of technology in this field.Surface plasmon polariton(SPP)is usually a collective oscillating wave of free electrons excited by light on metal or semiconductor surfaces.It has the characteristics of super-diffraction and local electromagnetic energy density enhancement.It is expected to be widely used in many fields such as super-resolution imaging,infrared detection,biosensor and so on.However,the SPP modulation performance of a single metal structure device is relatively limited.The 2D material such as graphene has good optical and electrical modulation properties.The metal micro-nano optical antenna based on graphene can regulate more parameters of SPP on the sub-wavelength scale.The design of the composite antenna structure can obtain new optical physical properties at near-field and far-field.In this paper,a plasma optical antenna was constructed with the metal-graphene composite structure,which has the excellent photoelectric control characteristics.Then,the conversion mechanism of electromagnetic energy under different interference states of SPP was investigated.Then the electromagnetic energy conversion and the influence on the energy band structure of graphene under the corresponding SPP interference states was studied,and the photoconductivity regulation of the of composite optical antenna was obtained.The main research contents of this paper include the following parts:1.Firstly,the mechanism of SPP generation on metal-dielectric surface is explained by formula deduction.The two different polarization states(TM polarization and TE polarization)of the excitation light were studied respectively.The wave equation and dispersion relation of SPP under different polarization states were derived by Maxwell equations,Helmholtz equation and boundary conditions of electromagnetic field.Similarly,the transmission mechanism of SPP was derived on graphene.2.Secondly,according to the mechanism of SPP generation and interference,the metal-graphene composite structure was designed.The equivalent circuit model of the composited structure was explored;different geometrical structures of metal antenna correspond to different circuit parameters.The spacing between the adjacent metal antenna pairs and the material characteristics of graphene how to tune its resonance wavelength was analyzed.Study the electric field distribution of SPP generated by excitation light of single metal antenna-graphene composite structure,and then the metal-graphene composite optical antenna array with different SPP interference fields was constructed.The mechanism of electromagnetic energy conversion and the regulation of graphene photoconductivity under different SPP interference states were investigated.3.The structure of "cross" metal-graphene composite antenna which produces SPP interference pattern by simulation design,and the modulation of SPP interference pattern by excitation light of different polarization states was explored.A metal-graphene composite optical antenna array samples was fabricated by microfabrication method,and the samples were characterized and tested to explore the morphology and optical characteristics of the samples.Scattering near-field optical microscopy(s-SNOM)is used to image the sample in the near-field.The interference patterns of SPP waves produced by the composite structure under the irradiation of exciting light were detected.