High Power Laser System Based On Space Combination

Laser beam combining technique is one of the hotspots in the field of laser research,which is a kind of effective mean to greatly enhance the laser output power and radiation brightness by combining multibeam lasers into single beam.In this paper,the experimental and engineering studies of high power laser fiber coupled transmission technology and spatial incoherent beam combining technique were carried out,and fiber transmission combining laser with 10 kW level output was achieved.The main research contents are as follows:Starting from the numerical aperture of optical fiber and coupling formula,based on the design principle of optical coupling system with a large aperture,a high power fiber combiner semiconductor laser beam has been developed by choosing four mirrors transmission structure with the advantages of simple stucture and convenient installation.It meets the technical requirements of 500 W level 976 nm laser beams fiber combining transmission.The refractive index multimode step-index quartz fiber was used as the transmission fiber whose core diameter is 440 ?m and numerical aperture is 0.22.Besides,on the basis of the theoretical analysis of bending fiber,the relationship between the bending degree of fiber and the transmission power loss was studied.This experiment proves that the power loss resulting from the transmission in bending fiber could be reduced by controlling the bending radius of optical fiber over 50 cm.Based on the theoretical analysis,the laser beam combiner was redesign by adopting a combining approach of spatial beam combining technique and incoherent beam combining technique.This kind of spatial incoherent beam combiner consists of two independent parts:beam expander collimation and beam focusing.By us:ing the simulation and optimization software,we confimed the parameters of collimating lens group,and designed three kinds of beam focusing lens with focal length of 400 mm,500 mm,600 mm.Moreover,a simulation analysis diagram of the beam power distribution on its cross section with different beam combination focal length were obtained.On this basis,the structure and packaging of the beam combiner were carried out.Starting from the frame of the laser beam combining system,the four subsystems of power distribution system,laser drive power supply integrated system,water cooling system and digital control system were designed respectively.The laser beam combiner with 10 kW level output was developed basing on spatial beam combining technique and incoherent beam combining technique,and sinlge beam of high power laser output transmission in fiber with a certain depth of focus was achieved.The power of combining laser could be altered by adjusting the driving current of laser and the number of combining beams,in this process,the quality of the combining beam laser was not affected and the loss rate of optical power of combiner is less than 2%.In addition,the laser focal length,focal depth and waist could be confirmed by selecting different beam focusing lens group according to the actual requirement and the output power of combiner could be enhanced by increasing input powers of beams.Through experimental measurement,the wavelength of output laser is 976 nm,its maximum output power is 10552 W,and the power instability is less than 2%.