The Propagation And Application In Micro-displacement Measurement Of Beams With Particular Correlation Structure

Under the background of new era,in order to meet the demands of diversification optical field in various application scenarios,the new type of optical field modulation has gradually become a major research trend.In 2017,the National Natural Science Foundation of China(NSFC)listed the physics and application of the new type of optical field modulation as a major research plan,setting off a boom in optical field modulation in China.The optical field modulation aims to modulate the multi-dimensional,such as spatial domain,time domain and frequency domain,to produce new types of optical fields with special performances.Spatial coherence modulation is one of the means of the optical field modulation.Modulating the spatial correlation structure of beams can obtain beams with various peculiar propagation properties.For example,the intensities present flat-top,hollow,array and other special distributions,or show self-shaping,self-shifting,self-focusing,self-splitting,self-healing and other properties.These properties make the beams with particular spatial correlation structure have important application prospects in many fields such as beam shaping,optical communication,particle trapping,optical imaging,second harmonic generation and material processing.This paper focuses on the theoretical research of partially coherent beams with particular spatial correlation structure.The main content is to propose a class of non-uniformly correlated partially coherent array beams and to study their propagation properties.As well as selected a class of uniformly correlated partially coherent beams to achieve the Rayleigh limit overcoming and apply them to the micro-displacement measurement scene.Firstly,introduced the research backgrounds of the optical field modulation,partially coherent light,beams with particular spatial correlation structure and their propagation properties in atmospheric turbulence.As well as introduced the basic theoretical knowledge of partially coherent light,construction method of scalar and vector beams with particular spatial correlation structure and the propagations of partially coherent beams in free space and atmospheric turbulence.Then,proposed a class of non-uniformly correlated partially coherent beam model,Hermite non-uniformly correlated array beams.Based on the generalized Huygens-Fresnel principle,derived the expressions of cross spectral density and degree of coherence of the beam in the source plane and during the propagation process,and theoretically studied their propagation properties in free space and atmospheric turbulence.The results shown that such beams have multiple self-focusing properties and can form a controllable array distribution.The degradation of intensity and degree of coherence induced by turbulence can be effectively resisted by modulating the initial beam parameters(beam orders,shift parameters,array parameters and coherent length).Finally,by using a class of uniformly correlated partially coherent beams,complex Gaussian correlated beams as illumination source,studied the imaging process of four symmetrical pinholes through a 4-f system,derived the expression of intensity and simulated the intensity distribution in the detection plane.In addition,proposed an approach for optical displacement measurement by the beams.The results shown that modulating the correlation structure of complex Gaussian correlated beams can overcome the classical Rayleigh diffraction limit.The minimum resolution distance of the four symmetrical pinholes can reach at least 0.05 times of the Rayleigh diffraction limit.And such beams can be used to measure the displacements below the Rayleigh diffraction limit.