Study On The Propagation Properties Of Special-Correlation Twisted Beams

With the gradual deepening of laser research and the rapid development of laser applications,various light fields with novel spatial distributions have been proposed:Bessel beam without diffraction transmission,Airy beam with transverse self-acceleration,vortex beam with helical phase,and non-Gaussian correlated beams with various exotic optical properties(such as self-focusing,self-shaping,self-splitting,and self-steering).These new light fields exhibit various unique physical phenomena and effects,which are beneficial for people to discover new physical properties and propose new theories.Through the regulation of multiple degrees of freedom such as amplitude,phase,coherence structure,and polarization structure,the angular momentum and polarization state of spatially structured light fields can be further revealed.And this is a research hot-spot in the field of optics.For coherent light fields propagating in free space,various optical phenomena depend on the adjustment of phase and amplitude of the light waves.Among them,the complex phase structure of spatially structured light fields not only provides new degrees of freedom for various new observations and new applications,but also poses new challenges for the generation,regulation and transmission of light fields.How to overcome the effects of medium inhomogeneity,beam anisotropy and various aberrations,and achieve precise control of beam characteristics is a major topic in optical-field research.How to expand the basic research of novel spatial light fields and explore light fields with richer spatial distribution is also one of the key issues to be solved in this field.At present,due to the modulation of complex phase structures,rapid development has been made in the research of light fields.Such as:self-focusing beam with high-order phase,self-twisted beam with asymmetric quadratic phase,self-tilting beam with linear phase light field and airy-like beam with cubic phase.The extended research from inseparable phase control to separable phase has further promoted the experimental verification of these complex spatially structured light fields.It has good application value in the fields of particle manipulation,laser micromachining,information transmission and repair,and spin-selective imaging.And it also provides an effective scientific tool for research in other fields.In this dissertation,we mainly study the modulation of partially coherent light wave with complex coherent distribution and introduce a novel spatial light field with unique correlation distributions.Furthermore,we explore the adjustment to the vector beam due to the spatial phase.Considering the complex optical systems that partially coherent beams may encounter under realistic transmission conditions,we analyze the optical characteristics of partially coherent light propagation with various phase modulation in various environments,including free space,strongly non-local nonlinear media(SNNM),mixed media,and focusing systems.The trapping properties of Rayleigh particles by partially coherent light with complex coherence function are also analyzed.The dissertation is divided into six chapters.Chapter 1 presents the background and development of electromagnetic beams and singular beams both in coherent and partially coherent fields.In addition,we introduce the theories and methods in our work:unified theory of polarization and coherence;construction theory of partially coherent beam;ray transfer matrix and generalized diffraction integral;ocean turbulence power spectrum;transmission matrix of strong non-local nonlinear medium;theoretical model of optical radiation force;orbital angular momentum model of partially coherent beam.Chapter 2 investigates the twisted rectangular multi-Gaussian Schell-model(TRMGSM)beams’optical characteristics propagating in free space and ocean turbulence respectively.Firstly,the analytical expression of TRMGSM beams paraxially propagating is derived.According to the derived expression,degree of coherence and intensity distribution of TRMGSM beams traveling through ocean turbulence and free space are numerically simulated.The rotational properties of beams’ spectral density and coherence distribution under different medium propagation are analyzed in detail.Finally,the influence of twisted strength and ocean turbulence parameters setting on spectral density and coherent distribution are discussed.Chapter 3 studies the statistical properties of twisted Gaussian Shell-model array beams in vector dimension.Firstly,a free-space paraxially propagating theoretical formula for electromagnetic twisted Gaussian Schell-model array(EM TGSMA)beams is presented.We analyze the evolution process and twist effect of the transverse spectral distribution,degree of coherence and degree of polarization in detail.Finally,the evolution of on-axis degree of polarization with various twisted strength settings is discussed.Chapter 4 introduces a new class of Sinc-correlation twisted Shell-model beams.The theoretical model of this kind of twisted Sinc-correlation Schell-model(TSCSM)beam is given and its orbital angular momentum distribution is analyzed.Then the cross spectral density function of the TSCSM beam passing through the ABCD optical system at any output surface is derived.The distribution of transverse degree of coherence and light intensity of TSCSM beam passing through a thin-lens focusing system is simulated.The effects of twisted strength,spot size and coherence length on the twist effect of spectral density and coherence distribution are analyzed in detail.Finally,the regulation of the initial parameter setting on the self-splitting phenomenon of light intensity distribution is discussed.Chapter 5 studies the propagating characteristics of off-axis Gaussian Shell-model beams in strongly non-local nonlinear(SNNM)media and the application of optical trapping.The spectral density of the off-axis Gaussian Shell-model beam propagating in the SNNM medium is given.Furthermore,the off-axis trajectory of the propagating light intensity is quantitatively analyzed,revealing the regulation of the off-axis properties of spot by linear factors,wavelengths and propagation media.Next,the orbital angular momentum distribution of the off-axis beam is analyzed.Finally,we analyze the gradient force and scattering force of the beam under the Rayleigh approximation,and discuss the optical trapping of particles under different refractive indices.The effects of linear factor and coherence length on its capture range and stability are also given.Chapter 6 gives the main conclusions and innovations of this thesis.Besides,the plans for future work are also discussed.