Research On The Statistical Optical Properties Of The Light Waves Scattered From A Semi-hard Boundary Medium

When a light wave is incident on a non-uniform medium,part of the light wave will disperse in all directions.This phenomenon is called light wave scattering.So far,great progress has been made in the study of the light wave scattering.On the one hand,researchers expand the incident light wave from plane light wave to various common light waves,such as the polychromatic wave,the spherical wave,the partially coherent light,the pulsed light,etc;On the other hand,researchers extend scattering media to a variety of media,such as the deterministic medium,the multi particle medum,the hollow medium,the quasi-uniform random medium and so on.Light wave scattering has attracted the attention of researchers because of its rich physical properties and great development potential in optical communication and imaging.What is particularly interesting in the study of light wave scattering is the influence of the change of the boundary refractive index of scattering medium on the statistical characteristics of scattered light field.The discontinuity of the boundary refractive index of scattering medium will have an important impact on the electromagnetic scattering.Semi-hard boundary medium is a new scattering medium recently proposed,which has the characteristics of constant central refractive index and adjustable boundary refractive index.Up to now,there are few studies on the scattering of light waves through semi-hard boundary medium.In this context,this paper studies the scattering law of various types of light waves through semi-hard boundary medium within the first-order Born approximation,and focuses on the influence of the change of boundary refractive index of scattering media on the statistical characteristics of scattered light field.The main research is as follows:(1)The scattering of plane light wave through semi-hard boundary medium and multi-Gaussian Schell model medium is studied and compared in detail.Under the condition of the first-order Born approximation,the expression of the spectral density of the light field after the plane light wave is scattered by the two media is derived.The effects of the summation index,effective radius and coherence length of the two scattering media on the spectral density distribution of the scattered light field are analyzed.The results show that the spectral density of the scattered light field is closely related to the relevant parameters of the scattering medium.It is worth noting that the spectrum scattered by the semi-hard boundary medium shows multiple interference fringes,while the spectrum scattered by the multi-Gaussian distribution medium does not show interference fringes.The results of this research work are expected to provide a theoretical basis for the inversion of the structural information of scattering media.(2)The scattering research of semi-hard boundary medium is extended from plane light wave to partially correlated light with special spatial correlation structure,and the scattering of generalized multi-Gaussian correlated partially coherent light through semi-hard boundary medium is studied.Under the condition of the first-order Born approximation,the analytical expression of the spectral density of the scattered light field of the beam scattered by the semi-hard boundary medium is derived.The effects of the summation index and effective radius of the semi-hard boundary medium,the light source radius,coherence length and beam order of the generalized multi-Gaussian correlation partially coherent light on the spectral density distribution of the scattered light field are analyzed in detail.The results show that the spectral density of the scattered light field decreases monotonically with the increase of the scattering angle.When the relevant parameters of the light source and medium change,the attenuation rate will change.The numerical results provide an important reference for the development of scattering theory.(3)The scattering characteristics of the semi-hard boundary medium are extended from the steady-state beam to the pulsed beam,and the scattering of the cosine Gaussian correlation Schell model pulsed light through the semi-hard boundary medium is studied.Under the condition of the first-order Born approximation,the analytical expressions of the spectral density and temporal coherence of the scattered light field are derived.The cosine order and pulse width of the beam are analyzed in detail,The effects of the time coherence length,the summation index of the scattering medium and the change of the effective radius on the time coherence and spectral density distribution of the scattered light field.The results show that the spectral density of the scattered light field decreases monotonically with the increase of the scattering angle,and the temporal coherence of the scattered light field changes in a oscillatory distribution with the time difference.The results obtained will enrich the scattering theory of pulsed beams and provide reference significance for deriving the structural information of semi-hard boundary medium.