Optical Vectorial Effect Of The Strongly Nonlocal Nonlinear Medium

The different optical effects of the interaction of photons carrying various information with the medium have led to a series of technological innovations and promoted the development of science and technology.The interaction between light and matter has always been a hot research topic,whose scientific research results promote the progress of modern optics continuously.The research on the interaction between light and matter is mainly focused on the scalar optical field with uniform polarization distribution,without considering the influence of the state of polarization(SoP)as an important parameter of light waves on the light field regulation.With the further study of complex optical field,the interaction between the vector light field with spatially-variant SoP and the medium has gradually attracted people's attention and has been widely used in different fields such as focal field control,optical micromachining,optical micromanipulation,and optical information transmission.In addition,strongly nonlocal nonlinear medium(SNNM)and parity-time(PT)symmetrical optical systems have unique and charming optical properties,a series of new phenomena and effects have been obtained in recent theoretical and experimental research.This thesis intends to explore the optical vectorial effect of the SNNM,which can be divided into the following four contents:1.The propagation dynamics of azimuthally polarization state variable vector optical light field with vortex phase in SNNM are studied by coupled nonlocal nonlinear Schrodinger equations(NNLSE).According to the analytical solution solved by the moment method,the root mean square beam width of VVOF oscillates periodically with propagation distance in SNNM Numerical results obtained by the split-step finite-difference method indicate that VVOF as well as the distribution of SoP in the field cross-section always evolves reciprocally with cycles of stretch and shrink in the SNNM.The final evolution is affected by the relationship between incident power Pin and Pcr which in full agreement with analytical results.The dynamics of interaction between the singular points of polarization and vortex during propagation in the SNNM leads to novel phenomena.When the topological charge number of the polarization is equal to that of the vortex,the singular point in the beam center is annihilated and the energy can accumulate in the beam center due to the self-focus effect.Furthermore,if the topological charge number of the polarization is not equal to that of the vortex,the linear-circular polarization conversion occurs in the beam center or the periphery of VVOF depending on the different topological charge numbers of the vortex and polarization,due to the coherent superposition of the different polarization components during propagation in a SNNM.The VVOF rotates along the propagation axis in a SNNM because of the existence of the vortex.The underlying physics for the linear-circular polarization conversion and its conversion efficiency in a VVOF during propagation in a SNNM are discussed in detail.2.Propagation of a VVOF with both fractional order of polarization topological charge m and fractional order of vortex topological charge n with spatially-variant SoP in a SNNM is studied by NNLSE.The optical field always evolves reciprocally with a cycle of stretch and shrink in SNNM with dark stripes form at z=t?zp(t denotes an integer number),as a result from the coherent superposition of the vortices with different order topological charges and weighting coefficients.In particular,the conversions between linear and circular polarization components occur during propagation.The evolutions of the Stokes parameters of the fractional order VVOF(FO-VVOF)during propagating in a SNNM show that the spatial distributions of different polarization components are closely related to the topological charges,the initial powers and the propagation distances,which can be explained that the FO-VVOF can be regarded as a superposition of two different fractional order vortices with orthogonal circular polarization components3.The vectorial effect of the optical field with spatially-variant SoP in the propagation of strongly nonlocal nonlinear PT(SNN-PT)symmetrical optical system is discussed.We analyzed the propagation dynamics of the SoP of the scalar field(such as Gaussian beam)and VVOF before the PT symmetry breaking.It is interesting to note that the periodic variation within the same distance increases as the refractive index coefficient increases of the optical field in an SNN-PT symmetric optical system.4.Two simple and economical measuring devices are designed based on the evolution of VVOF in SNNM:(1)A distance detection system that can sensitive measure the change in the size of the SNNM,and it can detect the laser power changes by improving.(2)A system generates orthogonal circular(linear)polarized light at the same time.The ring spacing distribution of the orthogonal circular(linear)polarization controlled by changing the Pin and the topological charge.