Study On The Propagation Properties Of Laser Beams In Gradient-Index Medium

With the continuous development of the gradient index optical theory and the optical design theory, the gradient-index medium has broad prospects for the application in the laser disc systems, the optical communication, the laser illumination devices, the optical sensing technology, the network detection, and the fiber fusion. Therefore, it has the important value in the theory and practice to systematically study the propagation properties of laser beams in gradient Index medium.This thesis mainly studies the transmission characteristics of the laser light beams in the gradient index medium.Firstly, there is a brief review of the development history in the transformation of the laser beams and optics of the gradient index, and an introduction to their research status at home and abroad. The section of the theory introduces the research methods, the radial gradient index medium and the beam mathematics - physical model in the transformation of the laser beams.Secondly, there is a study of the propagation properties of cosine-Gaussian beams in the gradient index medium. By using the generalized Huygens - Fresnel diffraction integral, the transmission analytical expression of cosine Gaussian beams in the gradient index medium is deduced. And further through the numerical calculation and analysis, the influence on the propagation properties from the medium gradient refractive index coefficient and the modulation parameters is discussed. The results show that when cosine-Gaussian beams propagate in Gradient-Index medium, the intensity distribution on the axis varies periodically, and the change period is inversely proportional to the gradient refractive index. The transverse intensity distribution is affected largely by the gradient-index coefficient and the modulation parameters. It is unstable to the Cosine-Gaussian beam in the transmission, but the shape of Cosine-Gaussian beam can be changed by adjusting appropriate parameter in some spatial position, such as the flat-topped beam, which can be obtained.Finally, the thesis studies on the propagation properties of the flattened Gaussian beams in the gradient index media. By using the generalized Huygens - Fresnel diffraction integral, the transmission analytical expression of flattened Gaussian beams in gradient index medium is deduced. The results show that when flattened Gaussian beams propagate in Gradient-Index medium, the intensity distribution on the axis varies periodically. Its change period is decided on the gradient-index parameter of medium, but has nothing with the beam order. The transverse intensity distribution of the peak on the axis is affected largely by the gradient-index coefficient and the beam order. The maximum of transversal intensity increases with the increase of the gradient refractive index coefficient.