Properties And Applications Of Transverse Spin Angular Momentum Of Optical Fields

In recent years,the transverse spin of light field has been found to be a novel field phenomenon,which is different from the previous cognition.The light field not only carries the spin angular momentum along the propagation direction but also the transverse spin angular momentum perpendicular to the propagation direction.In other words,when a nanoparticle is located in a field with transverse spin characteristics,it will rotate in the transverse direction under the action of torque caused by transverse spin momentum,which provides a new degree of freedom for optical micro-manipulation.In addition,because of the transverse spin locking,the circular polarization dipole will generate a unidirectional propagation pattern in the waveguide.Besides,the transverse spin of the light field can also be applied to the field of quantum optical communication and optical metasurface.In this dissertation,the transverse spin characteristics of the optical field in three aspects are studied,and the specific contents are as follows:The transverse spin characteristics of the tightly focused vector vortex beam are studied,and the Laguerre-Gaussian beam is used as the light source.By using the dipole approximation model,the optical force and the transverse spin moment of gold nanoparticles in the tightly focused field are calculated,and the motion state of gold nanoparticles is deduced by analysis and calculation.Various factors such as topological charge,particle radius,the refractive index of particles on the transverse spin are considered.The total transverse spin is found the number of topological charge is zero.The transverse spin effect produced in waveguide is studied.In order to realize the research purpose,in this dissertation,we first calculate the distribution of the light field near the strip waveguide and the slit waveguide,and calculate the optical force and the spin moment of gold nanoparticles near the waveguide by the dipole approximation model,and then the motion state of the particles near the waveguide is obtained.Finally,we investigate the influence of the geometrical structure of the slit waveguide on the optical force and the spin moment,calculate the slit width,the influence of the height and width of the silicon medium on the pattern field distribution and the force and torque of the gold nanoparticles.This dissertation studies the phenomenon that the circular polarization dipole generated by the transverse spin of the light field stimulates the single guide mode in the waveguide.First,we use the quantum spin Hall effect of photon and the near field interference theory to explain the physical nature of this unidirectional excitation phenomenon,and prove by numerical simulation that the dipole point source can excite the single guide mode in waveguide.Then we use the rice scattering theory to select the appropriate dielectric constant and size of the medium ball as the scattering body,it is proved that the scattering of the medium ball can induce the unidirectional excitation phenomenon,and whether or not the input TM mode in the waveguide can produce this phenomenon,In addition,the direction of beam propagation can be controlled by adjusting the direction of the circular polarization of the light field.Finally,in order to apply this phenomenon to life,we design an optical micro-device which can control the direction of beam propagation.