Beam Shift Effects Of Polarized Vortex Beams

Light will be reflected and refracted at the interface of two different media.As for the actual beam,its cross section is always limited.The incident light contains a series of plane waves with different wavevectors.On the interface,the centroid of the reflected and refracted beam relative to the incident beam center will produce spatial shifts.The secondary beams(reflected and refracted beams)with traditional optical law predicted results will also produce angular deviations at the same time.These phenomena are collectively referred to as beam shift effects.With respect to the plane of incidence,the in-plane shift is called Goos-H(?)nchen(GH)spatial shift,and the out-of-plane shift is Imbert-Fedorov(IF)spatial shift,and similar angular shifts.Beam shift effects exist widely in optical systems.It is of great theoretical and practical value to study the effects of beam shift.In recent years,people have been interested in the beam shift effects with angular momentum.By using the nonlinear effect of the medium,the beam shift effects can be adjusted more flexibly.Polarized vortex beams,which carry both orbital and spin angular momentum,have become a hot research object in the fields of spin photonics and topological photonics,and have a wide range of applications in particle manipulation,quantum information coding,super resolution microscopic imaging and other fields.In this thesis,we mainly study the beam shift effects of the secondary beams generated by the incident polarized Laguerre-Gaussian beam to two different interfaces,including GH spatial shift,IF spatial shift and the corresponding angular shifts.At the same time,considering the effect of nonlinear medium on beam shift,a new method of orbit and spin angular momentum photon regulation can be established,which has important practical significance in all-optical switch,frequency conversion,quantum communication and other aspects.The main research contents of this thesis are as follows.Firstly,based on the Fourier transform theory,we numerically simulate the spatial and angular shift effects of beams under total and partial reflection conditions.Taking Gaussian beam and Laguerre-Gaussian beam as examples,the relationship between incident angle and shifts is given,and the numerical simulation results are in good agreement with the theoretical calculation.At the same time,the intensity distribution of the cross-section of the secondary beams is analyzed,and the basic characteristics of beam shift effects are presented intuitively in real space and wave-vector space respectively.Secondly,we investigate the linear beam shift effects of polarized Laguerre-Gaussian beams,and analyze the effects of wavelength,incident angle and relative refractive index on the results.Moreover,we focus on the relationship between spin angular momentum and orbital angular momentum and shifts.Among them,spin angular momentum mainly affects IF spatial shifts in the case of total reflection and partial reflection,while orbital angular momentum significantly affects the value and sign of GH spatial shift and IF spatial shift in the case of partial reflection,as well as the magnitude and direction of the corresponding angular shifts.Finally,on the basis of the above results,the nonlinear beam shift effects of polarized vortex beams are further discussed,and the influence of incident angle and light intensity on the results is analyzed.In the case of total reflection,with the increase of incident angle,the GH spatial shift decreases sharply at first and then gradually becomes stable,while the IF spatial shift increases slightly,but the change is not obvious.At the same time,the IF spatial shift increases slightly,but the change is not obvious.When the intensity of incident light increases,GH spatial shift decreases gradually,while IF spatial shift increases accordingly.In addition,the nonlinear beam shift effects under partial reflection are simulated,and the method of calculating the refractive index of the nonlinear medium is emphatically explored.In the case of partial reflection,the small change of the relative refractive index does not have a significant effect,and the shifts of the reflected and refracted beam only shows a slight change with the increase of the light intensity.