Grating Hot Model Calculation In The Coherent Coupling Technique

With the rapid development of laser technology, lasers are more and more widely applied in the scientific, military, medical, industrial etc, and the research on lasers characteristics are increasingly in-depth. As early as the70s of last century to create high-power lasers have become an important direction, and many countries are actively developing high-power laser products. Thermal effect is a main factor of restricting thigh-power laser development, which make laser gain medium suffer from thermal deformation. Because of high power of the laser, lens and other optical component inside the cavity also occur deformation and loss, which would influence greatly output power and beam quality. In order to acquire high power and high quality laser output, beam combination with volume Bragg grating is a main direction at present.In this paper, firstly, a systematic exposition on the development process of Bragg Grating is presented. Its working principle and classification are described in detail. Secondly, based on Kogelnik’s theory of coupled waves, the wavelength selectivity and angular selectivity of volume Bragg gratings were discussed. Heat deposition and superficial thermal deformation of volume Bragg grating caused by the strong diffraction intensity of high power laser are analyzed. Besides, the effect on grating refractive index and cycle are discussed. In the end, temperature and thermal deformation distribution of volume Bragg grating was simulated by COMSOL Multiphysics in the different fixed ways, cooling modes and beam diameter, then the simulation results were compared and analyzed.