Study On Laser Beams Propagating Through Uniaxial Crystals

Crystal elements (such as optical polarizer, optical compensation and optical switch) played an important role in the realization of optoelectronic devices and the generation and applications of nonlinear optical phenomena. Therefore, the study of beams had important theoretical and practical significance in the anisotropic propagation properties of uniaxial crystals media. However, when the issue of propagation beams in the crystal was studied, the vector properties of light field in the practical applications could not be ignored due to crystal birefringence was essential for the propagation of light. This article analyzed the effects of uniaxial anisotropy on polarization properties and symmetry properties of the laser beams. The main works in this thesis are summarized as follows:1.A brief summary for the relevant concept and classification of crystal was given, and the vector property of the beam in a uniaxial crystal propagation was studied. Through the method of angular spectrum, summarize the analytical expression of the propagation of ordinary light and extraordinary light in the crystal media, and obtain the vector propagation model of paraxial approximation. On above basis, this article described the properties of ordinary light and extraordinary light in the crystal media.2.Based on the paraxial vectorial theory of the propagation of beam along the optical axis in uniaxially anisotropic media,the analytical propagation function of circular flattened Gaussian beams in uniaxially anisotropic crystal is derived. And some numerical simulations were preformed to study the effect of anisotropic media on the x-polarization properties and symmetry properties of the circular flattened Gaussian beams. The results showed that light intensity distribution was no longer maintained circular symmetry, and the light intensity decreased with increasing of the propagation distance z. During the propagation of circular flattened Gaussian beams in crystal media, the light intensity changed by increasing of the propagation distance z, and its strength and shape related with n_e/n_o( n_o and n_e are the ordinary and extraordinary refractive indexes, respectively)due to the anisotropy of crystals.3.Based on the paraxial vectorial theory of the propagation of beam perpendicular to the optical axis in uniaxially anisotropic media,the analytical propagation function of elliptical Gaussian beams perpendicular to the optical axis in uniaxially anisotropic crystal is derived. And some numerical simulations were analyzed and preformed to study the effect of anisotropic media on the x-polarization properties and symmetry properties of elliptical Gaussian beams. The results showed that during the propagation of elliptical Gaussian beams in crystal media, elliptical Gaussian beams increased with increasing of the propagation distance z, its lightfields diffused in the xy plane the same during peak gradually decreased on account of the anisotropy of crystals. Owing to ordinary light and extraordinary light had different diffraction lengths in the anisotropic crystals;, it led that elliptical Gaussian beams could have remained symmetry Polarized field in the crystal Ex Distribution. Elliptical Gaussian beams in the diffraction would induce y-polarized field components, and Ey strenthed with increasing of the propagation distance z.Finally, the full-text was summarized and the future research was expected.