Generalized Circuit Theory Description And Application Of Plasmon Micro-structure

Metal nanostructures offer the possibility of controlling nanoscale light,and have many possible applications,such as nano-antennas,nanoscale waveguides,and metamaterials,which are based on the capability of local strong electromagnetic field in nanostructures.Metal surface plasmon resonance is the collective oscillation of conduction electrons in nanoparticles,which can greatly enhance the local electromagnetic field.However,at present,most researches on plasmons are based on numerical simulation methods.This method is used as a means of numerical experiments,but it cannot analytically give the specific connection between the parameters,such as the relationship between geometrical parameters and resonant frequencies.In this paper,we introduce the fundamental properties of plasmon resonance and its resonance around the theme of plasmon resonance.According to the nature of the plasmon resonance,the resonance frequency will change significantly with the shape,size,and surrounding medium of the nanostructure.It is easy to model them equivalently using a lumped circuit in the form of a resistor,inductor and capacitor(RLC)element.A circuit with distributed inductance and capacitance elements can capture most of the physical quantities in Maxwell’s equations.This circuit model provides a good solution and can reveal physics that may be hidden in an accurate analysis solution.In this paper,firstly,the “circuitization” process of the rectangular metal nanorod plasma is introduced in detail.Under light excitation,charge is accumulated on the surface of the metal nanostructure to generate potential energy;at the same time,the kinetic energy of the electron motion can be generated by dynamic inductance;and the current movement generates a magnetic field that can be represented by a Faraday inductance.Under quasi-static conditions,combined with Ohm’s law,we analyzed analytical equations that describe the resonant frequency characteristics.We also use microwave studios to build models and conducted numerical simulations.Comparing the results of numerical simulations with our analysis results,we find that they can be well matched.This illustrates the accuracy of our theory and the effectiveness of our circuit model.Later,we extended the model to L-shaped nanorods.Although the L-shaped nanorod plasmon resonance has been solved,it is different from our explanation.Although there are subtle differences in values,only the slight changes in capacitance and inductance.The main characteristics ofrectangular nanorod plasmon resonance can be well maintained,and we have also tested rectangular nanoresonators with different sizes,shapes and peripheral media.It further proves the validity of our deduced expression.Secondly,we extend the previous theoretical derivation to single-layer structured graphene.Since graphene has metal-like properties,single-layered nanostructured graphene can still be conveniently passed through the form of inductance(L)and capacitance(C).The total circuit components are analogized.Under quasi-static conditions,combined with Ohm’s law,we analyzed analytical formulas for the resonant frequency of monolayer structured graphene plasmon resonance.We conducte a numerical simulation of the simulation and compare the results of the numerical simulation with the results obtained from our analysis.We found that they have a high degree of matching,which further illustrats the accuracy of our theory and the effectiveness of the circuit model.The formula can accurately determine the variation of the resonance frequency of the graphene plasmon with the surrounding medium,its own geometry and fermi energy,which provides convenience for the modulation of the graphene plasmon resonator.Finally,using the characteristics of plasmon resonance coupling and local magnetic field enhancement,we designed a segmented near-field optical antenna with uniform magnetic field enhancement.The antenna is mainly composed of two parts: the base and the metal structure.The base material we use is MgF2.The metal structure is composed of two cavities inside and outside,and each cavity arm is segmented.The segmented type can realize the inverse of the internal and external cavities.The energy flow is moved to achieve uniform enhancement of the magnetic field in the inner cavity region.