Special Spin-Orbit Angular Momentum Interaction In The Near-Field Light Field

Angular momentum is an important degree of freedom for light.It can be divided into spin angular momentum(SAM)and orbital angular momentum(OAM).These two kinds of angular momentum can be coupled and transformed with each other,namely the so-called spin-orbit angular momentum interaction.Angular momentum has become a research hotspot in the field of optics.It has been widely researched and applied in the fields of high-speed optical communication,particle manipulation,holographic imaging,quantum optics,and new materials.Through previous research,it was found that under free space conditions,a left-handed circularly polarized beam focused by a lens can produce an orbital angular momentum beam with a+1 order phase vortex topology charge,and a right-handed circularly polarized beam focused by a lens orbital angular momentum beams with-1 order phase vortex topological charge can be generated.However,under near-field conditions,through verification,we can find that the mutual conversion between spin angular momentum and orbital angular momentum can produce some special phenomena,that is,there are regions with opposite topological charges in the near field.This phenomenon is called It is a special spin-orbit angular momentum interaction.This thesis mainly studies the special spin-orbit angular momentum interaction in the near-field light field.The research content includes the following two aspects:In the simulation part,first simulate and calculate the surface plasmon polaritons(SPP)light field excited by a circularly polarized incident beam with vortex phase.The phase difference of the E_xand E_ycomponents of the scattered field is always?/2 or-?/2,indicating that the central area of the scattering field is purely left-handed or right-handed.Secondly,the force of the particles in the vicinity of the surface field after the focus of the vortex light is calculated.The results show that the direction of the torque generated by the particles will be reversed at a certain position,which will cause the movement direction of the particles to change.Since the photo-rotation effect of the particles can reflect the spin-orbit angular momentum interaction,the simulation results can theoretically predict the existence of specific spin-orbit interactions in the near-field light field.In the experimental part,first,the stability of metal particles captured by SPP optical tweezers was improved by changing the solution carrier.This research helps to solve an urgent problem in the field of SPP optical tweezers and even optical tweezers:how to reduce the optical capture of Brownian motion The effect is to improve the capture stability of metal particles.Secondly,the phase adjustment is used to realize the movement of the focused light spot.This technology realizes the two-dimensional movement of the captured metal particles on the horizontal plane through the phase adjustment,so it can be used to realize high-precision,non-contact optical scanning imaging technology and optical manipulation,near-field scanning imaging,and research on the interaction between light and atoms play an important role.Finally,a coaxial double-beam optical tweezer experiment is designed,and it is expected that the specific spin orbit angular momentum will be transformed through experiments.