Study On The Transmission Characteristics Of Polarized Light Near The Sea Surface

There has been a growing demand for applications such as airborne laser communication,underwater detection and imaging with the continuous exploitation and utilization of marine resources.However,the complexity of the marine environment could result in the absorption and scattering of laser beams,which has a bad influence on the performance of many underwater applications and has limited their development.Polarization light is widely used in many fields such as underwater wireless communication and imaging as it contains more information than simple irradiance.However,the wide application of polarization light also benefits from the results of study on transmission characteristics of that in the medium,and transmission characteristics of that in different medium show different variation rules.Based on the above background,in the thesis,the atmosphere-seawater model is established considering the actual marine environment,and transmission characteristics of polarized light near the sea surface have been studied.The main contents and results are as follows(1)The transmittance and polarization degree of laser beams in monodisperse medium mentioned in the public literature are simulated based on vector Monte Carlo(MC)method and Mie scattering theory,which lays a theoretical foundation for study on the transmission characteristics of polarized light near the sea surface.(2)Based on the above,considering the multi-particle distribution of medium,the effect of parameters such as sea fog visibility and distance on spatial and temporal characteristics is studied.And through statistical calculations of polarization angle(?)and ellipticity(?)of photons,the polarization changes of linearly and circularly polarized light transmitted a distance of 100m in the sea fog are analyzed in detail.Considering that the layered structure of foam particles on the sea surface is different from that of solid particles,the effect of parameters of the foam layer on the scattering and transmission characteristics is analyzed,the result shows that the geometric mean deviation(?)of the particle size distribution(PSD)has a larger effect on the scattering characteristics and the effect of the bubble void fraction(fa)on polarization has little difference as it is greater than 0.5(3)The inhomogeneous seawater model is established based on the depth distribution of chlorophyll concentration,and the effect of parameters such as seawater types and receiving aperture on transmission characteristics is studied using a layered MC algorithm,the polarization evolution of different incident lights is also analyzed.The result shows the polarization degree of photons at the central area of the receiving spot is higher than that at the edge area and the type of seawater has a great influence on the laser transmssion.(4)Transmission model of polarized light at the irregular sea surface is established based on fluctuations of sea surface induced by wind speed,polarization characteristics of laser beams passing through the atmosphere-seawater system are studied,the result shows that the depolarization effect of linearly polarized light is stronger than that of circularly polarized light.And the effect of sea surface parameters(wind speed,PSD of the foam layer)and depth on the effective spot size and temporal distribution of laser is analyzed in detail.In the thesis,the spatial,temporal,and polarization characteristics of polarized light near the sea surface are studied,these results have important reference value for reducing the influence of multiple scattered photons in practical applications and the development of airborne laser communication,underwater detection and imaging technology.