Propagation Of Multi-Gaussian Schell-model Beams In Random Media

Professor Wolf has proposed the unified theory of coherence and polarization in 2003, in which it pointed out that the spectral degree of coherence and polarization are two closely related optical characteristics in statistical optics. The cross-spectral density matrix can be applied to determine the properties of beams propagating through different media. Once the theory has been raised, it has gained worldwide attention and brought about much research concerning it, as well as the applications in tracking, remote sensing and optical sensing, etc.The multi-Gaussian Schell-model beam is a new type of beam proposed recently, which has aroused much attention from researchers. Its optical intensity has the property "Gaussian in the origin, flat in the far field" and its degree of coherence is the sum of that of several Gaussian Schel-modell functions. In this paper, we discuss the propagation properties of multi-Gaussian Schell-model beams in random media, based on the unified theory of coherence and polarization.The power spectrum of the oceanic turbulence mainly relies on the fluctuation of temperature and salinity while that of the atmospheric turbulence depends on the spectral index and the refractive-index structure parameter. In this paper, we particularly select these two media and study the propagation properties of multi-Gaussian Schell-model beams in oceanic and atmospheric turbulence.The dissertation is divided into four chapters, as follows:In Chapter 1, we introduce the research background of this paper including the unified theory of coherence and polarization; basic properties and study advances concerning multi-Gaussian Schell-model beams; the model for the power spectrum characterizing oceanic fluctuations; the model for the power spectrum characterizing non-Kolmogorov atmospheric fluctuations. Through obtaining the relative background knowledge, we could have a general perception and understanding of the research work.In Chapter 2, the cross-spectral density function of the propagation of multi-Gaussian Schell-model beams in oceanic turbulence is deduced. Through selecting appropriate parameters, we numerically study the behaviors of the spectral density and the spectral degree of coherence of such beams. The results also indicate that with the propagation distance increasing, the multi-Gaussian Schell-model beams begin to generate flat intensity profiles and the strength of the oceanic fluctuation will exert different effect on the optical spectra at various distances.In Chapter 3, we derive the cross-spectral density function of the multi-Gaussian Schell-model beams propagating in atmospheric turbulence. Similarly, through selecting appropriate coefficients, numerical simulations show that the spectral density and the spectral degree of coherence of the beams propagating in atmospheric turbulence. We also find out the influence of the atmospheric fluctuation on the optical intensity at different distances.In Chapter 4, we conclude the work we’ve done and point out the innovative points, furthermore propose the plan for future study.