Research On Beam Regulation Based On Artificial Microstructured Materials

Vortex beams are beams with orbital angular momentum.Because of their special spiral phase structure,they are widely used in the capture of small particles and atoms,classical and quantum communication technologies,optical imaging and biomedicine.Since Allen discovered that vortex beams carry orbital angular momentum,people’s enthusiasm for the research of orbital angular momentum beams has rapidly increased,and they have quickly entered the research frenzy.In order to be able to generate vortex beams and meet the application of vortex beams,people have designed optics to generate vortex beams in different bands Commonly used are:spiral phase plate,spatial optical modulator,computational hologram,hypersurface and artificial surface.A series of methods such as plasmon structure.Based on the study of transform optics and artificial surface plasmon structure,two structures are also designed to generate vortex beams.The research is as follows:First of all,This paper designs a flat spiral phase plate based on the method of transform optics.The traditional spiral phase plate is a stepped type,the refractive index of the dielectric material is constant,but the height along the azimuth direction gradually increases.The flat spiral phase plate is designed on the basis of the traditional spiral phase plate.Coordinate transformation is used to change the traditional spiral phase plate to a spiral phase plate whose height along the azimuth direction is kept constant,but the refractive index gradually increases.This paper uses theoretical analysis and numerical simulation to verify whether the flat spiral phase plate can achieve the effect of the traditional spiral phase plate.The height of the spiral phase plate and the topology of the generated orbital angular momentum beam are adjusted by changing the refractive index of the dielectric material.Dutch.Numerical simulations show that the orbital angular momentum beam generated by the flat spiral phase plate is the same as the traditional spiral phase plate.Generally,in order to meet the needs of practical applications,flat spiral phase plates can also be stacked to obtain orbital angular momentum beams with different topological charges.Secondly,This article designs a metal spiral antenna with a chiral structure based on an artificial surface plasmon structure,that is,the thread structure is etched on the surface of a metal cylinder to achieve vortex beam radiation in the terahertz spectrum.The vortex light can be adjusted by changing the structural parameters of the antenna.Spiral antennas generate vortex beams through electrical dipole excitation.Through numerical simulation and theoretical analysis,the vortex beam can be adjusted by changing the antenna’s thread depth,antenna length,and the position of the electrical dipole excitation.Changing the structural parameters of the helical antenna makes the antenna more restrained from electromagnetic waves,which makes it easier to obtain a better vortex beam.