Parametric Upconversion Driven By Vectorially Structured Light Fields

Paraxial light fields,as a class of electromagnetic waves obeying full-vector Maxwell theory,manifest vector nature via their states of polarization(So Ps),and the fields are broadly called vector light when the So Ps are spatially non-uniform.The feature of spatially non-uniform So P originates from intrinsic spin-orbit coupling(SOC)within the light field,therefore,vector light can be regarded as SOC states(or fields).In recent years,vector light with a custom spatial polarization structure has played an underpinning role in the science of structured light,which has become one of today's most active and rapidly expanding fields of photonics.For nonlinear optics,the SOC-mediated nonlinear polarization(NP)afforded by vector light introduce a host of vector nonlinear optical phenomena and rich functionalities that have no analog in scalar interactions.Specifically,it can,on the hand,significantly enhanced our ability to tailor nonlinear interactions;and on the other hand,provide also a feasible way to shape and control the spatial structure of light.In the present thesis,as the MA part of MA-Ph D in optics,parametric upconversion of vector light is taken as the platform to study the novel phenomena in the SOC-mediated second-order nonlinear interactions.First,we introduced concepts of photonic spin angular momentum,orbital angular momentum,and SOC states,respectively,and corresponding geometric descriptions.Special attention is given to the properties of vector cylindrical vector(CV)and full-Poincaré(FP)modes constructed by Laguerre-Gaussian beams,and associated methods for generation and characterization.On the basis of these toolkits,we started form type-II SHG pumped by vector light,where we theoretically studied the SOC-mediated parametric upconversion;then,we further considered a vector SHG in realized in a Sagnac nonlinear interferometer and analyzed the corresponding transition of vectorial spatial modes.Finally,we experimentally verified the theory by using a type-II SHG in a PPKTP crystal and a Sagnac nonlinear interferometer based on a type-I BBO crystal,respectively.