Design And Characterization Of Subwavelength Optoelectronic Devices Based On Graphene SPPs

With the rapid development of opto-electronic integrated circuits,surface plasmon polaritons(SPPs)has shown great application potential,and has become the focus of scholars’ research.Surface plasmon polaritons wave has good local restriction and can be used to design sub-wavelength photoelectric devices,which is more beneficial to the integration of photovoltaic system.At present,the research on SPPs is mainly based on the precious metals represented by gold and silver.However,due to the decoherence and limited response band range of metal SPPs,its practical application in optical devices is greatly limited,and its working frequency band is difficult to cover Mid-infrared.In this context,more and more scholars have turned their attention to graphene,a typical two-dimensional material.The metal-like properties of graphene enable it to excite SPPs,and graphene SPPs has excellent photoelectric properties such as ultra-wide frequency band response,which are superior to metal SPPs,making it be widely used in optical applications.At present,there have been a lot of studies on graphene SPPs in optics,but the application research in Mid-infrared is still very lacking,and the improvement of device performance has reached a bottleneck.Based on this,this paper mainly focuses on the study of high-performance optoelectronic devices based on graphene SPPs,with applications ranging from near infrared to Mid-infrared.New structure devices are designed and systematically analyzed theoretically.The performance of the device is greatly improved compared with previous research.The specific work contents of this paper are as follows:1.Based on the knowledge of electromagnetic field,the basic principle of graphene SPPs is theoretically analyzed through formula derivation.On this basis,the graphene SPPs is compared with the metal SPPs.Compared with the traditional metal SPPs,graphene has obvious advantages,including low loss and wide working frequency band.Its applicability and advantages in the design of photoelectric devices are studied.The COMSOL simulation methods of graphene surface plasmon optoelectronic devices are determined by reviewing literatures,including structure design,material selection,parameter setting,device structure modeling,etc.2.The transmission characteristics of graphene SPPs in Mid-infrared band are studied.On this basis,the dielectric-graphene-substrate-dielectric heterojunction waveguide structure is designed,and the transmission characteristics of graphene SPPs in this structure are studied.COMSOL software is used to conduct modeling and simulation verification of the designed structure,and the results are compared with the theoretical values.It shows that it has excellent performance in modulation of optical transmission length in Mid-infrared band.In addition,the phase modulation characteristics of the dielectric-graphene-dielectric heterojunction are studied,and it is confirmed that the structure can achieve continuous tunable phase shift at multiple wavelengths.3.A hybrid triangular prism waveguide with an incident wavelength of 1550 nm is designed.The principle of the hybrid waveguide is to couple the traditional silicon waveguide mode with the silver surface plasmon mode,and the performance parameters of the hybrid waveguide are greatly improved compared with the traditional waveguide.The advantages of the waveguide are small device size,small effective mode area and long optical transmission length.After designing the device structure and selecting the appropriate material,the RF module of COMSOL Multiphysics software is used for modeling and simulation.The device performance is optimized by changing various parameters of the device,and the desired effect is finally obtained.In addition,based on the hybrid waveguide,a waveguide integrated electro-optic modulator is designed.The performance of the modulator is very superior,which is greatly improved compared with previous designs.4.A Mid-infrared band stop filter is designed.The application of graphene SPPs in Mid-infrared optoelectronic devices is studied by taking the filter as an example.The narrowband band stop filter is based on the periodic structure of graphene nanoribbons.The Fermi level of graphene is changed by the applied voltage,and then changes the refractive index of graphene itself.Finally,the effective refractive index of the whole device is affected to achieve the regulation of optical transmission characteristics.COMSOL software is used for the modeling and simulation of the periodic structure.The performance of the filter is optimized by adjusting the structural parameters of the nanoribbon,and the center frequency is blue shifted or red shifted by adjusting the applied voltage.Compared with other Mid-infrared filters,the performance of this filter is greatly improved,including the center frequency can reach a wide range of tunability,very narrow 3d B bandwidth,and good robustness.