Analysis Of Ghosts In The High Power Laser System

When light inputs the surface of optical elements, there is reflection as well as refraction, so ghost light come into being, its focus is called ghost image. In high power laser systems, they can become so strong to damage optical elements, air may be ionized, resulting in the quality of light going bad. Therefore, it is rather important to locate the ghost image and intensity of ghost image quantitatively.1. The formula of the propagation of Gassian-Beam in the co-axial optical system with aperture stop is deduced, and formula of the spot of parallel light and spherical light wave with finite beam width in the co-axial optical system is present.2. In the off-axial optical system , formula of the spot of parallel light and spherical light wave with finite beam width is given. Then formula of the size and intensity of ghost image is present.3.The method of "mirror imaging" is introduced to deal with the optical system . that is, all elements are imaged to axis of one element, then ghost images are imaged to the original multi-axial optical system.4.A Visual C++ programme is programmed to calculate ghost image in high power laser system with a number of elements. The programme not only calculates the location ghost images, but also calculates the size and intensity of ghost images.These may contribute to the design of high power laser systems as SG-III.