Second Harmonic Enhancement Based On Antiferromagnetic/Graphene Material System

Graphene monolayer is a two-dimensional,nonporous special semiconductor material with unique optical,electrical,and chemical properties,particularly the ability to support surface plasm on polaritons?SSP?in the terahertz?THz?and infrared frequency ranges.Compared with the surface plasmon polaritons excited by metal,the SPP of Graphene can make its propagation length longer and electromagnetic field constraint better by changing the external magnetic field,and its optical properties are continuously adjustable in the THz band.Therefore Graphene is widely used in optical devices.The resonance frequency of the antiferromagnetic material?AF?is located in the THz band,which is different from the optical nonlinearity of ordinary materials.The magneto-optical nonlinearity of AF materials comes from the nonlinear response of magnetization to electromagnetic waves in maxwell's equations.The study on the magneto-optical nonlinearity of AF materials is conducive to the development of THz devices in future detection and communication.Due to the strong absorption near the resonance frequency of AF material,the power of the laser is required to be very high,so many optical nonlinear effects of AF material are difficult to be effectively utilized.Due to the special zero-bandgap structure and carrier relaxation performance of Graphene,the particle number of Graphene is reversed under electromagnetic wave excitation,and the electromagnetic wave generated by interband carrier transition recombination is just within the THz range,which can generate and amplify the electromagnetic wave,so that the SPP of Graphene is highly localized.The development of Graphene has provided an effective method for improving the nonlinear optical output of AF materials and realizing controllable operation at the same time.This paper mainly explores the physical mechanism of the enhancement of the nonlinear optical effect of AF material based on the optical properties of the SPP excitated of Graphene in THz frequency range.Using the classical electromagnetic theory and the method of transmission matrix,the generation and enhancement effect of the second harmonic?SH?in AF/Graphene sandwich structure and one-dimensional AF/Graphene photonics crystal structure under Faraday coordinates is theoretically studied from the aspects of structure design and component selection.The following conclusions are meaningful:1.This paper proposes a method to enhance SH generation by embedding Graphene into SiO₂/MnF₂/ZnF₂ sandwich structure.In Faraday coordinates,the influence of Graphene on SH generation in SiO₂/MnF₂/Graphene/ZnF₂ sandwich structure is discussed when the external magnetic field is perpendicular to the surface of AF and the incident wave is TE wave.The numerical simulation results show that the SH output of SiO₂/MnF₂/Graphene/ZnF₂ sandwich structure is significantly improved:compared with SiO₂/MnF₂/ZnF₂ sandwich structure,the SH output on the upper and lower surface of the structure significantly improve one or two orders.The influence of Graphene Fermi energy level and external magnetic field on SH generation intensity and output frequency is analyzed theoretically,so as to achieve the purpose of regulating SH output by adjusting gate voltage or external magnetic field.2.The second harmonic generation of?SiO₂/MnF₂/Graphene?^N/ZrO₂ photonic crystal in Faraday coordinates was further investigated.The results show that when the incident wave is TE wave,compared with AF photonic crystal without Graphene,the SH output can improve about two or three orders;compared with the sandwich result,the SH output can improve one or two orders.The intensity and frequency of SH output can be further regulated by changing the Fermi energy level of Graphene and external magnetic field.By discussing the effects of Graphene position,dielectric and cyclic layers on SH generation,an optimal structure to enhance SH output is proposed,which also provides another possible way to regulate SH output.