Design Of Fiber Coupling System For High Brightness Semiconductor Laser Pump Source

Due to the influence of the material and structure of semiconductor lasers,they have many advantages over other lasers,and their fiber-coupled modules play the role of pump source in fiber lasers or solid-state lasers.The gain medium of fiber laser or solid-state laser has an impact on the absorption rate and brightness of the pump light,the higher the brightness of the pump light source,the higher the absorption rate of the gain medium,effectively improve the output power of the fiber laser or solid-state laser,and reduce the volume of the laser machine,so it is of great significance to study the high-brightness semiconductor laser pumped source fiber coupling module.This paper uses beam shaping,incoherent beam combination and fiber coupling as the theoretical basis,uses different semiconductor lasers as the light source,and designs different beam shaping methods and beam combining methods according to the optical characteristics of different semiconductor lasers to achieve high-efficiency and high-brightness laser output.The main research content of this paper can be divided into the following three aspects:(1)With high power single tube as the light source,the vertical arrangement in the space,compared with the ladder arrangement,can effectively avoid the height error of heat sink processing and lead to larger distance between light spots.The opposite group of lasers are interlaced with each other,and the high density arrangement of the fast axis beam is realized by the reflection of the 45°mirror.In the slow axis direction,the light beam is superimposed in the slow axis direction by increasing the heat sink,and then folding polarization beam combination is adopted,which doubles the optical power and reduces the width of the whole system.The results show that the difference between the data and the theory is within the controllable error range.The fiber with a coupling core diameter of100μm and a numerical aperture of 0.22 can achieve high brightness output.(2)A compact beam shaping system is proposed to balance the beam quality of the fast and slow axes of the mini-bar array semiconductor laser.A new stepped prism and two30°right Angle prisms were designed to fill the dark region in the fast axis direction.A compact high brightness fiber coupling system was designed by using a polarization beam synthesizer to compress the light width of the slow axis.The output luminance is as high as22.832MW/(cm ~2·sr)when the fiber is coupled into 100μm/0.22NA fiber,which is more advantageous than that of the existing fiber coupled module composed of mini-bar.(3)In order to further explore higher power semiconductor laser and achieve high brightness laser output,the stack array composed of cm-bar is used as the light source.in order to solve the problem that the slow axis collimation is difficult due to the relatively small duty in cm-bar,a BTS beam conversion mirror is designed to realize the fast and slow axis beam conversion,improve the transmission characteristics of the slow axis beam and reduce the slow axis divergence Angle.Then a folding polarization-splitting prism is used to reduce the light width and improve the quality of the slow axis beam.Because the beam is not uniform,it is directly coupled into the multi-mode fiber through the focusing lens,resulting in serious power loss.In order to reduce the power loss,the orthogonal Powell prism is designed to homogenize the beam,which can change the shape of the beam and narrow the dark area of the beam to form a tight beam.Compared with the beam coupling without the orthogonal Bowwell prism,the optical conversion efficiency is increased by7.7%and the brightness is increased by1MW/(cm ~2·sr).