Research On Heat Dissipation Technology Of Micro-channel Heat Sink For LD End-pumped Solid-state Laser

Due to the incomplete absorption of the medium,part of the pump power is transformed into waste heat that accumulates in the laser crystal,and the resulting thermal effect problem will directly lead to the degradation of the optical performance of the laser crystal.As solid-state lasers continue to develop in the direction of miniaturization,high output power and long-time operation,the thermal effect of laser crystals is becoming more and more prominent,and the current heat dissipation methods can no longer meet the demand for continuous and efficient heat dissipation of solid-state lasers.In order to quickly and efficiently export the waste heat generated by laser crystals and reduce their thermal effects,microchannel heat sink heat dissipation technology has been introduced.The current research on microchannel heat sink is mainly focused on the improvement of heat sink heat dissipation performance,mostly using parallel flow,low coolant flow performance,large pressure drop loss,and more complex internal structure,poor processability.In order to address the above problems,this paper carried out a study on microchannel heat sink thermal technology for LD end-pumped solid-state lasers,and confirmed the excellent thermal performance of microchannel heat sink and its important role in improving the performance parameters of solid-state lasers,the main research contents of this paper are as follows.1.Designed a simple structure of impinging flow based manifold sinusoidal microchannel heat sink with higher heat transfer efficiency,smaller pressure drop loss,and simpler processing.Through the theoretical analysis of the total thermal resistance and pressure drop loss of the heat sink,combined with the study of boundary layer theory and field synergy theory,to guide the structural design of the microchannel heat sink.2.Based on the finite element analysis method of heat-flow-solid coupling in Ansys-fluent,the effects of different coolant flow rates,laser crystal dissipation power,microchannel width,depth,shape and manifold structure on the fluid flow and heat transfer characteristics inside the microchannel heat sink are investigated,and a structure with the best overall performance is obtained by considering its process performance,which provides a theoretical basis for the optimization of the heat sink design scheme.The optimized heat sink is a sinusoidal microchannel structure with overlapping channels,the number of channels is 8,the length,width and depth of the microchannel is 30×0.4×2.5 mm3,and the total thermal resistance of the heat sink is Rtotal=0.247℃/W at f=0.6 ml/s.3.According to the optimized results,the microchannel heat sink was prepared and experimentally verified in the LD end-pumped solid-state laser,and the total heat sink resistance Rtotal=0.395℃/W at f=0.6 ml/s.Compared with the predesigned linear manifold microchannel heat sink and large channel heat sink,the total heat resistance was reduced by 11.5%and 44.2%,respectively,and the pressure drop loss was reduced by 3.3%compared with the large channel heat sink.This shows that the microchannel heat sink can effectively improve the heat dissipation of the laser crystal.At the pump power of 15W,the output beam quality of the laser with the optimized microchannel heat sink was significantly improved,and the light intensity distribution was also effectively improved.