Quite a lot of factors will make effects on beam pointing stability of an optical system, Among them, the element tolerance is one of the most important and common factors. In some large laser systems, it will make final micro beams spot on the image plane deviate obviously. So it is essential for us to achieve effective and accurate analysis theoretically on element tolerance. In order to make the analysis of beam pointing stability convenient and theoretical, we consider transmission of a single chief ray rather than beams approximately to stand for the whole spot deviation. According to optical matrix, we also simplify this complex process of light transmission to multiplication of many matrices. So that we can set up element tolerance model, namely having mathematical expression to illustrate spot deviation in an optical system with element tolerance. In this way, we can realize quantitative analysis of beam pointing stability theoretically. In second half of the paper, we design an experiment to get the spot deviation in a multipass optical system caused by element tolerance, then we adjust the tolerance step by step and compare the results with the datum got from tolerance model, finally prove the correction of tolerance model successfully.
In the high-power laser system, the stray light which is generated by the surface’s residual reflection of optical elements and the multi-pass transmission in the system will lead to temperature increase in part of the system, the optical elements deformation and damage, distortion of wave-front and change of the beam’s divergence angle, which seriously influence the beam’s quality and propagation properties and damage the components in the system. So, it is very important to use the relevant software to analyze the stray light rigorously because the reliability and precision of the software is the guarantee of reliable results. Through two types of software we performed the simulation of the stray light in the system, including ghost’s distribution in the case of different states of rotating defocusing, beam’s pointing. Simultaneously, the impact of processing and assembling errors is analyzed in details. We built a specialized experiment to verify the reliability of results of the software and the related parameters of system are conveniently measured with the device.