Hollow Beams Through Uniaxial Crystals Transmission

:With the continuous development of laser application technology, laser has been widely used in military, medical treatment, scientific research, industrial, information and other fields. Especially in recent years, with the rapid development of laser communication technology, Uniaxial crystals has been widely used in various lasers and optoelectronic devices.Therefore, it has the important value in the theory and practice to study the propagation properties and diffraction of laser beams in uniaxial crystal. This thesis mainly will study propagation properties of hollow beams in the uniaxial crystals. The main work in this thesis are summarized as follows:1.A brief summary the anisotropic optical properties of uniaxial crystals, A detailed description paraxial vectorial theory of the propagation of beam along the optical axis and orththogonal to the optical axis in uniaxial crystals. And introduced methods of produce of hollow beams and application of hollow beams in this thesis.2.Based on the paraxial vectorial theory of the propagation beam in uniaxial crystals, we have obtained the propagation equations of beam in uniaxial crystal. By using these equations,numerical calculation examples have been presented to illustrate its propagation properties,the propagation of controllable dark-hollow beam in uniaxial crystal is studied.It shows that the distribution of intensity is greatly affected by controllable parameter ξ and the beam order N when the controllable dark-hollow beam propagates in uniaxial crystal. The larger controllable parameter ξ is, the bigger the dark region of beam is, and the smaller the intensity is. The size of the dark region of beam increases with the beam order N, but the intensity will decrease. With the increasing of the beam transformation distance, the central intensity will increase gradually, and the distribution of intensity does no longer keep the original nature of hollow.3.Use of the paraxial vectorial theory of the propagation of beam in uniaxial crystals,the propagation of annular flat-topped beams in uniaxial crystal orthogonal to the optical axis is studied, and the polarization field of amplitude expression has been derived. According to the numerical calculation results, propagation properties of the beam have been analyzed. It is shown that The anisotropy of crystal has an effect on intensity distribution of annular flat-topped beams. The beam in the positive uniaxial crystal in far field, with the increase of the ratio of extraordinary to ordinary refractive indices,the intensity decreases,the beam spread in the xy plane the smaller, the beam propagation Properties in negative uniaxial crystal of the opposite.with the increasing of the propagation distance z,the central intensity will increase gradually, and the distribution of intensity does not keep the original nature of hollow.Finally,the work of this paper are summarized.