Research On The Generation And Control Technology Of Fractional Vector Light Field

With the development of optical technology,it has been found that light has natural advantage as a carrier of information and energy,thus the modulation of optical field is also very important.Traditional modulation of optical field mainly focuses on the amplitude and phase,except the polarization of beams.Due to the polarization plays a crucial role in nature attribute,the propagation characteristics of light,and the interaction between light and matter,it has gradually evolved into a new research hotspot recently.This article focuses on the generation and control of fractional vector beams with multiple dark gaps.Firstly,this article proposes a method for generating the fractional ellipse perfect vector beams(EPVBs)by superposition of a pair of orthogonal polarized ellipse perfect optical vortices(EPOVs).This method is based on the traditional perfect optical vortex(POV)beam and perfect vector beam(PVB),combining the concept of fractional optical vortex beam,we transform the topological charge into fraction to further realize the shape change from circle to ellipse by stretching the Cartesian coordinates.At the same time,we also design a new spiral phase plate to replace the traditional fractional spiral phase plate,which includes several angular sectors where the phase grows from 0 to π,so more fractional radial dark gaps can be generated,and fractional EPVBs with multiple fractional dark gaps are obtained.Secondly,this article studies a method for generating the fractional ellipse perfect vector beams(F-EPVBs)and the fractional rectangle perfect vector beams(F-RPVBs)based on the holographic beam shaping technique.Different from the traditional research method,this method is realized by point-by-point integration,and the ellipse or rectangle perfect vector beams are obtained by coaxial superposition of the two scalar ellipse or rectangle perfect optical vortex beams.Meanwhile,due to the intensity and phase of the scalar beams are distributed along the two-dimensional curve path,we compare it with the traditional spiral phase plate,and study the characteristics of its phase distribution,further transform the phase distribution on the curve path into multiple fractional phase segments which from 0 to π,so that more fractional dark gaps can be obtained.Thirdly,in this article,a method of the tunable fractional vector curvilinear beams(VCBs)with nonuniform distribution of fractional dark gaps is designed.This method is based on the vector optical field generator(VOFG)system,which produces two orthogonal polarized scalar curvilinear beams(SCBs)as the components of the base vector,and finally coaxial superposition.We also design a new annular phase distribution with several loops of 0 to π,in order to generate more fractional radial dark gaps.By varying the phase variation rate,the phase distribution becomes nonuniform,and the positions of the dark gaps are changed accordingly.Using the different parameters of the curves,more curvilinear beams with different shapes can be obtained.By using a phase-only computer-generated hologram(CGH),the two orthogonal polarized SCBs with the opposite topological charges are modulated,in order to perform the beam conversion,and the experimental results coincide with the theoretics.Finally,in this article,the extinction theory of the dark gaps of the fractional optical vortex is analyzed,and based on this theory,the phase discontinuity on the spiral phase plate of the fractional POV is further extended from the radial direction to the angular direction,so that the POV beam of the complete monocyclic structure can be transformed into the multiple-ring perfect optical vortex(MR-POV)beam of the polycyclic structure.In the experiment,we transform it into the multiple-ring perfect vector beam(MR-PVB)with vector characteristics by using the Q-plate.And the experimental results show that the distinction between ring and ring is obvious,the distribution of the polarization states is related to the parameter q of the Q-plate.