Research On High Brightness Semiconductor Laser Beam Combining Technolog

High brightness,high power laser diode fiber coupling module has many advantages compared with other types of lasers,such as high efficiency,good reliability,stable performance,small size,and long life.It is widely used in laser material processing,laser information processing,laser biology and medicine,laser printing,communications,laser chemistry,laser detection,and national defense security applications.And it also has stimulated the research on improving its reliability,output power and other performance.Incoherent beam combining technology based on single emitters or line arrays is the primary method used in practical applications.Compared with the beam combining with bars and arrays,beam combination of multiple single-emitter laser diodes has a relatively dispersed heat source and better heat dissipation.And there is no"smile"effect,so it can provide laser output with better beam quality,and it has lower cost without complex and expensive micro lens arrays.Therefore,designing and development of the fiber coupling module based on single emitters using beam combining have great significance.In this paper,several fiber coupling modules based on single laser diodes using space and polarization beam combining have be designed or confirmed experimentally.In order to obtain a module with more coupling efficiency and higher brightness output,it is crucial to coupling more single emitters into the fiber with smaller core diameter or NA,through designing different optical systems.The main contents and results of this paper are as follows:1.A fiber coupling module with laser diode emitters face-to-face arrangement is designed and simulated,in order to reduce the optical path difference of the beams emitted from laser diodes at different spatial positions and weaken the influence of the rest divergence angle after collimating on the size and shape of the beam spot.The spatial combining of reflected beams is realized by stacking two thin mirrors.The simulation results show that compared with the emitters linear arrangement module,this module can significantly reduce the influence of rest divergence angle and the optical path difference between beams.Using the same optical system,the size of the beam spot before the focusing lens is 0.52 mm×2.6 mm reduced to 0.38 mm×2.4 mm,the output power from 105μm/NA0.22 fiber is increased from 7.9 W to8.169 W.2.In order to increase the number of coupling emitters,it is proposed to expand the typical one-dimensional space beam combining on fast axis to the two-dimensional on fast axis and slow axis.Two modules are proposed from the two directions of using optical elements and using two emitters.For the former,a module with double-row on slow axis using beam guide mirror is proposed.And through calculating by the fiber coupling condition,the maximum number of coupling emitters in the fiber with a core diameter of 105μm and NA 0.22 is 26.In the configuration of the same laser diode and optical elements,this module has 11additional emitters compared with the module of limit stacking on fast axis,the power is increased by 67%and the coupling efficiency only reduced by 3%.For the latter,a bifocal lens is designed to collimate the fast and slow axis simultaneously.The bifocal lens array is used to collimate the laser diode source with two emitters to realize double-row on slow axis.The module is coupled into 105μm/NA0.22 fiber to obtain55 W output power and 92%coupling efficiency.3.A multi-emitter fiber-coupling laser diode module is simulated and tested.This module contains four 9-emitters spatial beam combining sub-modules.Emitters are collimated by micro lens group,and then reflected by mirrors group.Then,the large size mirror carries out the spatial beam combining of the two dimensions of the fast axis and the slow axis.In addition,it also combines polarization beam combining,which can scale the power without damaging the beam quality.Finally,the experimental module can be coupled into the 105μm/NA0.22 fiber with the power output of 177.7 W and the brightness of 13.5 MW/(cm~2·str).4.In order to further optimize the space beam combining design on two-dimensional,a fiber coupling module based on fast and slow axis conversion filling(FSCF)spatial beam combining is designed.In the configuration of the same laser diode and optical elements,compared with the limit stacking on fast axis module and limit stacking on fast and slow axis module,the simulation results show that the FSCF module can increase the space utilization rate by 33.57%compared with the former,and 7.2%compared with the latter.And the output power is increased by nearly 80%compared with the former,and about 9%compared with the latter,when the coupling efficiency is only reduced by 1%.