Theory Of Optical Resonances Of Rotational Symmetry Nanostructures And Its Applications

The surface plasmon and enhanced electromagnetic field characteristics of metal nanostructures is widely used in supersurfaces,holographic display,ultra-sensitive biosensing,and virus molecular detection.Although researchers have conducted in-depth research on the surface plasmon resonance of metal nanostructures,various metal nanostructures with special properties have been designed and manufactured.However,there is still no unified rules about the surface plasmon resonance modes of metal nanostructures.Establishing a uniform rule of plasmon resonance on the surface plasmon resonance of metal nanostructures is an important scientific problem to be solved in the field of nanophotonics.It can provide basis theory for the design of nanofunctional devices and is of great significance for the development of micronanophotonics.How to classify metal nanostructures is the basis of establishing a uniform rules of the surface plasmon resonance mode.According to the point group theory,all two-dimensional structures have rotational symmetry characteristic and can be divided into different point groups according to the order of their principal axes of rotational symmetry.Therefore,this article attempts to reveal the corresponding relationship between the rotation characteristics and the surface plasmon resonance mode based on the rotational symmetry characteristics of metal nanostructures,and establish the two-dimensional metal nanostructure optical resonance rule.In this paper,we used Mie scattering theory to implement the electromagnetic multipole expansion of nanostructures scattering field.Based on the selection rules in vector field,the optical resonance law of rotationally symmetric metal nanostructures is proposed.It pointed out that under the irradiation of plane waves in the vertical direction,the high-order optical resonance modes of nanostructures can be directly derived from the corresponding irreducible representation of point group multipoles and the spherical harmonic function without the need of complicated numerical simulation calculations.The establishment of this theory provides a basis theory for designing and manufacturing nanostructures with specific high-order optical resonance modes.This article also validates the above theory from an experimental perspective.C_nh point group metal nanostructures were fabricated using focused ion beam etching technology,and their optical resonance rules were experimentally measured and numerically simulated.It was found that the first high-order resonance mode was in full consistent with above theory.In addition,the influence of the destruction of the symmetry of the nanostructure on the resonance mode was also verified.It was found that the emergence or disappearance of a resonance mode has a direct relationship with the rotation symmetry of the nanostructure,and further verified that the rotation symmetry of the nanostructure has a constraints of higher-order optical resonance effect on the nanostructure.This paper also explores the application of rotationally symmetric nanostructures in manipulating photoluminescence of two-dimensional materials and optical encryption.We used C_?point group aluminum nanodisks enhances the photoluminescence of single-layer molybdenum disulfide by more than ten times.We used three-dimensional non-rotationally symmetrical nanostructures and used its circular dichroism under left-right circularly polarized light to encrypt plasmonic color patterns,this provides a new solution for plasmonic color printing in document authentication and anti-counterfeiting.