Research On The Generation Of Special Vortex Light Field And Its Application In Imaging

Vortices are common phenomena that widely exist in nature.From quantum vortex in liquid nitrogen to ocean circulation and typhoon vortex,and even to vortex galaxy in the Milky Way,vortex not only exists in macroscopic world,but also in structured optical fields.Such a beam with helical phase wavefront and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics,and is widely used in optical micro-particle manipulation,super-resolution imaging and light-matter interactions.In order to further broaden the application field of vortex beams and reveal more micro and macro physical essence,the flexible regulation of the amplitude,phase,and polarization of the vortex beams has become a research hotspot in recent years.This thesis mainly studies the generation and regulation of special vortex optical field and the application of vortex in edge enhancement.Firstly,introducing the axicon phase into the vortex beam,we can convert the vortex beam into perfect vortex beam whose radius is not affected by topological charges.Based on this theory,we report on a novel concentric beam named concentric perfect Poincaré beam,which contains three different categories of polarization structured fields in the concentric ring mode.These three polarization states can be represented by fundamental Poincaré sphere,high-order Poincaré sphere,and hybrid Poincaré sphere.A convenient and universally applicable experimental scheme is designed to generate the beam simultaneously,which verifies the feasibility of the scheme.This method effectively overcomes the shortcomings of the single mode of perfect vortex beams,enriches the mode distribution of the perfect vortex beams,and broadens the potential application of the perfect vortex beams in the fields of micro-manipulation and optical communication.Secondly,starting from the integral definition of the topological charge of the vortex beam,we decompose the integral region of the definition by the additivity of the integral.And the arbitrary control of the phase distribution can be achieved by controlling the integral region of the topological charge,thereby realizing noncanonical vortex beam with controllable phase distribution.However,since the radius of vortex beam is related to the topological charge,arbitrary controllable phase distribution will cause the beam to have an irregular shape.Therefore,in order to maintain the ring structure of the vortex beam,the vortex beam can be transformed into a perfect vortex beam to solve the above problems.Based on the above,the expression of the noncanonical perfect vortex beam is theoretically analyzed,and noncanonical scalar perfect vortex beam with controllable phase distribution and noncanonical vector perfect vortex beam with controllable azimuthal polarization variation rate are experimentally generated.This technology provides a new structure of vortex optical field for applications such as beam shaping and optical manipulation.Finally,based on Hilbert transform,we propose a Bessel-like composite vortex filter to perform high-contrast anisotropic edge enhancement with shadow-effect-free and low background noise.By suppressing the side lobes of the system point spread function,the background noise that affects the image quality can be reduced,thereby effectively improving the image contrast.By maintaining the radial symmetry of the filtering process,the shadow effect can be completely eliminated,thereby making the edges clearer and improving the image resolution.By introducing a weighting factor between two opposite vortex filter,the power of edge enhancement becomes controllable.Compared with previous anisotropic filters,numerical simulations and experimental results prove that the proposed filter achieves higher contrast edge enhancement for both phase-contrast and amplitude-contrast objects.