Research And Simulation Of High Beam Quality Semiconductor Laser Bar Spectral Beam Combining System

In recent years,high-power diode lasers have gradually become an excellent high power laser source thanks to its advantages such as small vollume,high power,long lifespan and high efficiency.However,the commonly used high power diode laser arrays have very poor beam quality,typically hundreds or even thousands of diffraction limits.One of the most effective ways to improve the beam quality is spectral beam combining.Based on the above,the main contents of this paper are as follows:(1)The theoretical model of high-power wide-band semiconductor laser is discussed.Some important theoretical results are summarized and the theoretical basis is provided for modeling.Then the principle of external cavity-grating spectral beam combining system is analyzed in detail and the typical combination is described.The defects of the beam system and various existing improvements are discussed.(2)The important components of the spectral beam combining system(mainly beam shaping components)is designed,simulated and analyzed.Firstly,the collimating effects of two kinds of fast axis collimating microlenses are compared and the influence of the fitting error is also analyzed.Then,the causes and application limitations of the collimation effect of the slow axis collimating microlens are analyzed.Finally,the beam rotating components are analyzed and optimized,and the advantages and disadvantages of various beam rotating components are compared.(3)Simulation and combining and feedback quality analysis of the mini-bar and the standard 1cm-bar respectively using a typical spectral beam combining structure.Slow axis M~2 of the mini-bar beam is about 20.09,and fast axis M~2 is about 1.039.The combination is then extended to two high-power mini-stack modules,resulting in a high-brightness output of 3.08×10~4W/cm~2/sr.Subsequently,the cause of feedback failure of the standard1cm-bar using typical spectral beam combining system is analyzed.In addition,the feedback failure of the system caused by the adjustment error of the conversion lens is analyzed,and it is found that the micron-level adjustment error may cause the optical feedback to completely fail.(4)The design,simulation and analysis of four new methods of improving beam quality and feedback effects are carried out,target on the standard 1cm bar beam combining system.By each method,the beam quality is close to that of a single emitter and the feedback effect is good.Besides,advantages and disadvantages of these four methods are compared and discussed.Using the telescope spectral width compression structure,the combined beam of19 emitters with a line width of 7.8125 nm is obtained.