Propagation Of Laser Beams In Uniaxial Crystals Orthogonal To The Optical Axis

Anisotropic medium in linear optical and non-linear optical fields had a wide range of applications, such as:produce polarized light and optical harmonic, make optical sum frequency and difference frequency, realize the optical parametric amplification and oscillation, etc. Therefore, the study of the laser beams in anisotropic uniaxial crystals in transmission characteristics is of important theoretical and practical significance.This paper made a study of propagation that Hermite-sinusoidal-Gaussian laser beams propagated in the uniaxial crystal orthogonal to the optical axis, and the main work are as follows:Firstly,there expounded on the research background, satus and significance, that the beams propagating in uniaxial crystal. A brief summary for the relevant concept of crystal and optical properties were given, and it also presented the paraxial vectorial theory of the propagation of beams in uniaxial crystal orthogonal to the optical axis. Accordingly ordinary ray and extraordinary rays’propagating in uniaxial crystal orthogonal to the optical axis which slow amplitude expression was summarized.Secondly,based on the paraxial vectorial theory of the propagation of beams in uniaxial anisotropic media, the analytical formulas for a Cosine-Gaussian beam propagating in uniaxial crystals orthogonal to the optical axis are derived. And some numerical simulations were preformed to study the influence of the anisotropy on the polarization properties of the Cosine-Gaussian beams. The results show that the field distribution of the beam polarized along the x-direction derives a y component. With the increase of the transmission distance z, peak of initial optical field in a relatively short period increased gradually, beyond a certain range and reduce gradually; And in the x direction dispersion, the side-lobe diffraction are increasing, its original polarization properties will no longer keep. In addition, as the cosine-Gaussian beams in anisotropic uniaxial crystals perpendicular to the optical axis, a Gaussian--like, hollow, or nearly flat field distribution can be obtained on a specific section when appropriate parameters are selected, and then beam shaping can be realized.Then, the propagation of Sinh-Squared-Gaussian Beams has been investigated and the analytic solutions have been obtained by means of an angular spectrum technique in uniaxially anisotropic crystals orthogonal to the optical axis. The propagation properties of the polarized components which originate from Sinh-Squared-Gaussian Beams are discussed with numerical method in crystals. The results show that the polarization properties cannot remain the same during propagation due to effects of anisotropic crystals. the field distribution of the beam polarized along the x-direction derives a y component. Along with the increase of the transmission distance, the polarized amplitude of the extraordinary ray along the x axis and the z axis were reduced, intensity also decreased. In addition, the propagation of the Sinh-Squared-Gaussian beams in anisotropic uniaxial crystals orthogonal to the optical axis can be influenced by parameter β, and different β bring about different intensity distribution.The last of the full text the main conclusion was summarized and the direction of further research was put forward.