Design Of Beam Shaping System For Fiber-Coupled Output Semiconductor Lasers

Semiconductor lasers have tremendous advantages in terms of reliability,lifetime,and power consumption.It has been widely used in various fields such as laser cutting,welding,and medical treatment.However,it has a large difference in the divergence angle between horizontal and vertical directions,and the luminous width varies,which will lead to an uneven distribution of the emitted laser light intensity.To solve the above problem,it is usually necessary to collimate the laser source in the fast and slow axes first,and then perform secondary shaping and beam combining on the collimated beam.In the process of shaping and combining laser beams,it is necessary not only to improve the beam quality,power and brightness of the output beam,but also to pursue efficient,simple and compact optical components to reduce the application cost and the size of the laser module.Therefore,the proposed efficient and implementable beam shaping system scheme is of great significance and application value for the development of high brightness and high power fiber-coupled output semiconductor laser modules.By investigating and analyzing the status of fiber-coupled output semiconductor lasers at home and abroad,a compact beam shaping system with polarization plane multiplexing and a simple beam shaping system with one-mirror beam compression and self-polarization are designed with practical applications.The light sources of both systems are laser stacked arrays composed of multiple centimeter bar stacks,and wavelength combining,polarization combining and spatial combining techniques are used to increase the output power of the fiber coupled system to obtain high power and high brightness output light.The main work is specified as follows:(1)A compact beam shaping system with polarization plane multiplexing was designed.By studying the conventional polarization prisms,it is found that the utilization rate of the polarization plane is not high when the collimated beam passes through the polarization prism,and considering the expensive cost of the polarization plane coating,a step prism with multiple polarization planes is designed,which can not only polarize and combine the two sets of P and S polarization states of the laser,but also fill the dark area in the fast axis direction by the total reflection of the stepped ramp.The laser source composed of a stack of centimeter bars is first collimated in the fast and slow axes,then the collimated light passes through the designed polarization surface multiplexed step prisms,then three rotating prisms and a set of slow-axis beam expanders are used to further improve the beam quality and homogenize the spot area,and finally coupled into the 200μm/0.22NA fiber through an aspheric focusing lens.The system was simulated in optical software,and the results showed that the opticalto-optical conversion efficiency of the system was 85.8%.(2)A simple beam shaping system with one-mirror beam compression and selfpolarization was designed.Through the study of beam shaping,it is found that in the laser stacked array output beam to eliminate the fast axis direction of the luminescent dark area,the use of a large number of different angles stacked flat glass or tiny step reflector,in addition to the beam quality homogenization need to "cut-rotate-rearrange",which will cause uneven distribution of the edge spot.To this end,we propose a beam shaping scheme that combines a diamond prism stacked offset beam and a diamond prism pair of misaligned reflections to jointly fill the luminous dark region,and combines beam self-polarization to homogenize the beam quality.Further,in order to improve the output power of fiber coupling,the wavelength of the collimated light source is combined first,and then the designed one-mirror beam compression and selfpolarization structure is used to realize the compression of the light-emitting dark area in the fast-axis direction and the self-polarization of the light-emitting dark area in the slow-axis direction,and the remaining light-emitting dark area in the fast-axis direction is filled by the misaligned reflection of the rhombic prism,and finally coupled into the 200μm/0.22NA fiber through the aspheric lens focus.The output power of 1161W was obtained in the optical software simulation,and the optical-to-optical conversion efficiency of the system reached 90.7%.