High Power Semiconductor Laser Shaping And Design Of Fiber Coupling System

Compared with other lasers,semiconductor lasers have been widely used in recent years because of their small size,long lifetime,high electro-optical conversion efficiency and high reliability.However,due to the characteristics of the active layer structure of semiconductor lasers,the symmetry of the output beams in the two-dimensional direction is very poor,and the divergence angle and emission width in the fast and slow axis direction are quite different,which results in a large difference in the quality of the fast and slow axis beams,which limits the direct application of semiconductor lasers.Therefore,it is of great significance to develop an efficient beam shaping system to homogenize the beam quality for fiber coupling.The high brightness and high beam quality laser output from the fiber is of great significance.The fiber coupling module has been gradually applied to industrial processing,laser pumping,biomedicine,fiber communication and other aspects.In this paper,a compact beam shaping system is designed to improve the power of the fiber coupling design system by using polarization beam combining and wavelength beam combining technology,and to obtain high power laser output.The main research of this paper is to investigate and analyze the reported research methods of fiber coupling output semiconductor lasers using mini-bar stacked arrays in the fast-axis direction as light source,and to improve the power of the system by using polarization beam combining and wavelength beam combining technology.The content can be divided into the following aspects.(1)In this paper,the beam alignment,beam shaping and beam combination techniques of semiconductor lasers are discussed,and the methods of collimation,beam shaping and beam combination are introduced.(2)In this paper,the light source of the optical fiber coupling system is a semiconductor laser stack consisting of mini-bars.By means of compression and rotation rearrangement,the hollow trapezoid prism and parallel quadrilateral flat plate compressed beam prism are designed to reduce the width and improve the beam quality.Then the fast and slow axis beam quality is homogenized by rotating rearrangement with right angle prism,and the stack array consisting of eight mini-bars is coupled.The core diameter is 200 micron and the numerical aperture is 0.22.(3)In order to further simplify the beam shaping system,a trapezoidal prism is designed,which is composed of five quadrilateral prisms.By using the total internal reflection of the beam,the laser beam emitted from the semiconductor laser stack array is evenly compressed in the fast axis direction,so as to improve the beam quality.(4)In order to improve the output power of fiber coupling and improve the previous beam combining technology,a step polarization combiner is designed,which combines the polarization combiner and beam shaping to achieve beam shaping and double the power atthe same time.In order to obtain high power fiber coupling output,wavelength combining and polarization combining are combined.Eight groups of semiconductor laser stacks(wavelength 808,880,938 and 980 nm,respectively)are used to combine wavelength and polarization combining first.With the same beam quality,the power is increased by 8 times.The output energy is 2253.5W,and the optical-to-optical conversion efficiency is 88%.