چكيده به لاتين
In the last decade, we have witnessed a significant increase in the output power of fiber lasers up to several kilowatts. Powerful fiber lasers are vulnerable to nonlinear effects due to the large length of fiber that leads to the large length of the nonlinear environment and the very small cross-sectional area of the brain that causes high power density. The results of these effects can lead to the production of new frequencies, the expansion of the optical spectrum, the creation of backlight and the destruction of the quality of the beam. However, the simplest way to increase the nonlinear threshold is to enlarge the median area. Fiber with a large media area will perform multi-mode. Therefore, the high average power and large media area cause a new effect called media instability, which severely limits the output power of systems and fiber amplifiers. When the output power reaches a certain threshold, the transverse instability of the modem manifests itself as rapid oscillations of the output beam from the order of milliseconds. As power increases, the output beam behaves erratically and loses its quality. The widespread scientific and economic impact of the effect of modal instability on high-power fiber-optic laser systems has led to a serious study of the experimental and theoretical effects of this effect. Most importantly, controlling or eliminating this limiting phenomenon has become a major challenge for researchers and scientists. In their studies, they theoretically proposed ways to increase the median instability threshold that were consistent with experimental results.
In this project, by understanding the physics of the phenomenon of media instability by solving the heat transfer equation and finding the nonlinear pairing coefficient and modeling it, the factors affecting the instability of the medium have been investigated.
