Generation And Propagation Of The Partially Coherent Beams From Theory To Experiment,And Study Of Tightly Focused Properties Of It

Completely coherent and completely incoherent beams don’t exist in the nature, and partially coherent beams are exposed everywhere. In many fields, it shows that decreasing the coherence of beam is to make the energy of the beam more homogeneous, which in inertial confinement fusion by laser and material thermal processing by laser beam etc is more useful than high coherent beam. Besides, decreasing the coherence of beam propagating in the turbulent atmosphere can dramatically reduce the scintillation factor and beam wander, so we can get more high quality by this way, which is significant in atmospheric laser communication.Object of this thesis is the partially coherent beams, and the partially coherent beams include two kinds. The first kind is the partially coherent beam with special correlation function(non-Gaussian). Here, we present the correlation function being cosine-Gaussian function with rectangular symmetry and multi-Gaussian function. Other kind is the partially coherent beam with conventional correlation function(Gaussian). In this thesis, we study the generation and propagation of the partially coherent beam with special correlation function from theory to experiment. In addition, we discuss the tightly focused properties of the partially coherent beam with conventional correlation function through a high numerical aperture thin lens at the focal plane.In chapter 1, we mainly introduce the background and processing of partially coherent beam with conventional correlation function and partially coherent beam with special correlation function.In chapter 2, it presents basic theory knowledge. We introduce basic theory of partially coherence including mutual coherence function and cross spectral density function. And then, we narrate the basic theory and approaches of laser propagation. The propagation theory of completely coherent beam does not apply to the partially coherent beam, so we give the propagation theory of partially coherent beam. At last, we represent the content of the tightly focused.In chapter 3, for the partially coherent beams with special correlation functions, we propose cosine-Gaussian-correlated Schell-model beams with rectangular symmetry and generalized multi-Gaussian correlated Schell-model beam in the theory field. Besides, we study the properties of propagation in the free space, and the effect of the ini tial parameters of the beams on the properties of propagation.In chapter 4, these beams proposed in chapter 3 have been carried out in the experiment, and our experimental results verify theoretical predictions.In chapter 5, we obtain the formulas of the propagation of a linearly polarized, partially coherent anomalous hollow beam with conventional correlation function through a high numerical aperture thin lens, and we study the properties of the beam in the focal plane, including the degree of polarization, the intensity distribution, and the degree of coherence. In addition, we talk about the effect of the parameters of the beam itself and thin lens on the properties of the tightly focused.In chapter 6, the conclusion of this thesis is drawn and some prospects are illustrated.