The Optical Properties Of Light Waves On Scattering From Several New Types Of Random Media

When a light wave is incident on an inhomogeneous medium,it deviates from its origin path and is scattered in all directions,which is known as light wave scattering.When the incident light wave is scattered by different types of media,the statistical optical properties of the scattered field are different,and these differences are closely related to the structural properties of media.In other words,the structural information of media can be obtained from the knowledge of the scattered field,which has great significance to the situations where structural information of objects cannot be detected directly.Therefore,the exploration of scattering from different kinds of media is a major focus in the theory of light scattering,and these studies have potential applications in the fields like target detection,remote sensing,medical diagnosis and so on.By 2010,most of the research in light scattering has concentrated on traditional scatterer models such as deterministic media and quasi-homogeneous media.Although traditional scatterer models have good representativeness and mathematical convenience,they still have some limitations and cannot take some specific structural properties into account.In order to solve the limitations of traditional scatterer models,researchers have proposed some new types of scatterer models such as anisotropic media,semisoft media and hollow media.Afcter that,more and more efforts are devoted to the scattering from new types of media.On the other hand,the fast development of modern medium manufacturing techniques and 3D printing techniques makes it possible to experimentally produce a medium with a particular correlation function.Since media parameters have important influences on the modulation of the scattered field,researchers began trying to produce the desired scattered intensity patterns by designing random media with prescribed correlation functions,and they have successfully realized square,rectangular,ring-like,frame-like,asymmetric structured,lattice-structured scattered intensity patterns.In this dissertation,we study the scattering of plane waves or partially coherent beams from new types of random scatterers including semisoft random media,hollow random media and random dispersive media within the accuracy of the first-order Born approximation.We also explore to obtain concentric rings-like intensity profiles in the scattered field by designing the scattering media.The dissertation is arranged as follows:Chapter 1 is the introduction,which has two parts.Firstly,the research background and the status of light wave scattering are given.By analyzing the history and trend of the research,the motivation and significance of this dissertation are presented clearly.Then,the theoretical bases and methods used in the content are stated as follows:weak scattering theory of scalar light waves,weak scattering theory of vector light waves and traditional scatterer models.Chapter 2 investigates the statistical optical properties of light waves on scattering from semisoft random media.Firstly,the spectral density,spectral degree of coherence and spectral degree of polarization of the far-zone scattered field generated by scattering of plane waves from semisoft media are studied,and the influences of the boundary hardness,correlation length and effective radius of media on the scattered field are discussed in detail.Then,we further consider the scattering of partially coherent beams from semisoft random media and a multi-Gaussian Schell-model beam is taken as an example.in the process of numerical-simulations.The proportion of the scatterer role and that of the beam role in the modulation of the scattered field are investigated emphatically.Chapter 3 studies the spectral changes of vector light waves on scattering from hollow random media.We obtain the scattered spectrum expression from the cross-spectral density matrix of the scattered field.The difference between the scattered spectrum and the incident spectrum,and the changes of the scattered spectrum as scattering angle increases are analyzed by numerical simulation results.Besides,the influences of the shell thinness,the outer and inner correlation lengths of the medium and the polarization of the incident light wave on the scattered spectral shifts are discussed in detail.Chapter 4 proposes a new type of random dispersive media and studies the scattering of stochastic electromagnetic beams from this type of media.Firstly,we take the dependence of random media on the frequency of the incident light wave into consideration,and propose the correlation function of scattering potential of random dispersive media.Then,based on the generalized Stokes parameters,we obtain the spectral density,spectral degree of coherence and spectral degree of polarization of the far-zone scattered field generated by scattering of stochastic electromagnetic beams from random dispersive media.Finally,we take a vector Gaussian Schell-model beam as an example of stochastic electromagnetic beams and assume that the deperdence mentioned above take the form of Gaussian function.Under these assumptions,the influences of the central wavelengths of spectral distributions of correlation length and effective radius of the medium,the beam size,the correlation width and anisotropy of the beam on the scattered field are analyzed in the situations of medium-led modulation and beam-led modulation.Chapter 5 designs a class of random media with novel correlation functions to scatter light waves producing concentric rings-like intensity profiles in the far field.Firstly,the relations among the spectral density of the scattered field,the correlation function of scattering potential of random media and the non-negative defniteness function of random media are derived.Then,according to the expected scattered intensity patterns,we design the non-negative defniteness function of random media and further obtain the correlation function of random media.Finally,the numerical simulations demonstrate that the designed random media can scatter light waves producing concentric rings-like intensity patterns in the far field.Chapter 6 gives the main conclusions and innovations of this dissertation.Besides,the plans for future work are also presented.