Thermal Characteristics Of Quasi-Continuous-Wave Conduction-Cooled High Power Semiconductor Laser Arrays

High-power semiconductor lasers(HPSLs)are widely used in pumping fiber and solid lasers,medical scientific research,material processing,aerospace,etc.because of their high electro-optical conversion efficiency,high reliability,small size,light weight and long lifetime.With the increase in output power,thermal management is one of the critical bottlenecks affecting the optical-electrical performance and reliability of HPSLs.In this paper,thermal characteristics of QCW conduction-cooled semiconductor laser arrays and HPSLs side-pumped Nd:YAG laser has been analyzed systematically.Firstly,finite element method(FEM)is used to study the thermal performance of 2 bar QCW conduction-cooled semiconductor laser arrays with different packaging structures and chip parameters.The structure parameters of G-Stack semiconductor laser array are presented and optimized.High power semiconductor laser arrays with superior performance have been fabricated and characterized.Secondly,thermal characteristics of QCW conduction-cooled semiconductor laser arrays under different working conditions is analyzed,by numerical simulation and experimental analysis.Thermal characteristics of a kW-level conduction cooled semiconductor laser array is analyzed based on numerical simulations and experiments.Transient thermal characteristics has been studied using finite element method.There is significant “thermal crosstalk” behavior among the semiconductor laser bars with pulse width greater than 250μs.It shows thermal resistances along horizontal and vertical directions are 64.7% and 35.3%,respectively,indicating that heat mainly dissipates along horizontal direction.74.9% of thermal resistance along horizontal direction and 66.5% of thermal resistance along vertical direction originate from CuW layer,which shows that CuW is the most significant factor restricting heat dissipation efficiency.Based on accumulated average temperature method,the simulated temperature differences are 2.13,1.47,0.75℃ at the repetition frequencies of 20 Hz,30Hz and 40 Hz compared with that at the frequency of 50 Hz.Average junction temperature rises at different repetition frequency have been measured using spectral method,and the temperature differences at the repetition frequencies of 20 Hz,30Hz and 40 Hz are 2.33,1.56,0.78℃,respectively.The average error is less than 6.85% between experiment results and numerical simulation.It shows that the simulated transient thermal resistance agrees well with the experimental result.Finally,the thermal power density inside the Nd:YAG laser crystal rod side-pumped by QCW conduction-cooled semiconductor laser array laser is analyzed.The influence of the spectrum profiles of HPSLs on the absorption efficiency of laser crystal rods is studied in detail.The temperature distribution in the Nd:YAG crystal side-pumped by the semiconductor laser with Gaussian beam distribution has been analyzed.The influences of the number of arrays,the beam waist radius and the crystal rod radius on the maximum temperature inside the laser crystal were analyzed,which provided the theoretical guidance for the design of diode-pumped solid-state lasers.