Studies On Propagation Properties Of Multi-gaussian Correlated Partially Coherent Beams In Turbulent Ocean

Though the coherence of partially coherent beams is low,they display remarkable advantages in many areas due to their unique properties,e.g.,inertial confinement fusion,optical communication etc.The correlation function of the traditional partially coherent beams is only limited to Gaussian function.With the development of technology and the needs of production,the performance of partially coherent beams is put forward higher requirements.Recent research discusses the sufficient condition for devising physically genuine correlation functions of scalar partially coherent beams and extends the method to the random electromagnetic fields.In mathematics,as long as the specific conditions are satisfied,various kinds of special correlation functions can be constructed.With this method,a great number of special correlated partially coherent beams are introduced in theory and laboratory.Some related researches have also been carried out.It is found that these beams present intriguing and novel characteristics on propagation,for instance,self-focusing effect,self-shaping effect,flat-topped beam profile and ring-shaped beam profile and so on,which are useful in optical communication,optical trapping and optical imaging.On the other hand,beam propagation is always an important research topic.Study of the beam propagation lays the solid theoretical foundation for us to deeply understand the light phenomenon and the interaction between light beams and matter,and eventually helps us control and utilize the light fields.With the development of ocean optical communication,sensing and optical imaging,it is significant to investigate the statistical properties of beams propagating through turbulent ocean in detail.In this context,we investigate the propagation of electromagnetic multi-Gaussian Schell-model(EM MGSM)beams with astigmatic aberration and rectangular fractional multi-Gaussian Schell-model(FMGSM)beams in turbulent ocean respectively,and then discuss the behavior of the statistical properties under different situations.The thesis consists of four chapters,specific chapters are arranged as follows:Chapter I is the introduction.To begin,we start with the background and current situation from three aspects:partially coherent beams and stochastic electromagnetic beams,special correlated partially coherent beams,propagation in turbulent ocean,and then we point out the purpose and significance of the research.Then,the theoretical basis and fundamental methods mainly used in the thesis are introduced,including cross-spectral density(CSD)function and CSD matrix,extended Huygens-Fresnel principle and models of turbulent ocean.In chapter 2,an analytical expression for the elements of the CSD matrix of EM MGSM beams with astigmatic aberration propagating through the turbulent ocean is derived.We investigate the statistical characteristics of the beams on propagation in great detail and mainly discuss the influence of astigmatism on the spectral density and spectral degree of polarization on propagation.It is found that,due to astigmatism,the circular symmetry of such beams suffers a certain degree of damage in the near field through turbulent ocean.Meanwhile,astigmatism also destroys the attractive far-field flat profiles in free space.In addition,astigmatism and oceanic turbulence both have certain effects on the spectral degree of polarization.In chapter 3,we investigate the propagation properties of rectangular FMGSM beams through the turbulent ocean.Based on the mathematical integral,the the analytical formula for the CSD function of the rectangular FMGSM beams propagating in oceanic turbulence is derived.The statistical properties incorporating the spectral density and the spectral degree of coherence of the beams on propagation are discussed and investigated.It is found that the beams maintain rectangular-shaped cusped profile in weak turbulence just as in free space,whereas in strong turbulence or in the propagation plane far enough,the beams profile would be destroyed little by little,turning out to be Gaussian profile eventually.Moreover,the beams with smaller coherence length exhibit more obvious rectangular outline.In addition,the spectral density and the spectral degree of coherence are both affected by various turbulence parameters and strong turbulence always gives rise to the decrease of these statistical propertiesChapter 4 summarizes the main research work and innovations of the thesis and puts forward the next research plan.