Ghost Images In The High-power Laser Device For Analysis

As a high-power laser system, the multi-pass amplifier has special request in stray light analysis and control. In order to avoid the ghost's focusing on some key elements of the system, it is necessary to make a general ghost simulation in the overall laser system, figuring out their locations, carried energy as well as the effect upon the optical elements, etc.The technical integration line (TIL), which is the full scale prototype for Shengguang-Ⅲ laser facility (SG-Ⅲ), will contain a neodymium glass laser system with more than 70 large (40-100 cm) optical components. Reflections from these surfaces (so-called ghost reflections) are numerous and extensive computation has been required to track them in the TIL optical system. The tremendous number of ghost paths also requires a visualization method that allows overlapping ghosts on optics, and then sums them up to illustrate its potential damage on critical surfaces. Therefore, how to make an effective identification and visualization of multi-order "ghost" has been a major part of the optical design effort.In our analysis, we present a novel method to make analysis on the ghosts, i.e. combining the paraxial ray tracing and real ray tracing. The data structure of Binary Tree is also presented to store the intermediate dada. For some specific structure, such as tilt, de-center or pinhole, we add the corresponding codes to well describe them.This paper takes some of the "dangerous surfaces" as example, simulating the energy distribution graph on it by tracing numerous real rays. According to the shape of ghost energy graph and its corresponding optical structure, suggestions are made to effectively mitigate the damage on the studied optical surfaces. This analytical result is in good accordance with that in practice. It is proven that such an analytical method has provided a detailed reference for mitigation of ghost caused damage.