Thermal Characteristics And Reliability Analysis Of High-power Photonic Crystal Laser Bar

Semiconductor lasers have a wide range of applications in solid-state,fiber laser pump sources,industrial processing,LIDAR,optical communications,medical aesthetics and other applications because of their small size,high efficiency,wide wavelength range coverage and high reliability.In order to further broaden the application field of semiconductor lasers and continuously improve the output power of lasers,semiconductor lasers have developed from single emitter to multiple emitters of the bar.With the increase of laser bar output power,a large amount of waste heat will be generated,resulting in junction temperature increase,excitation wavelength redshift,threshold current increase,electro-optical conversion efficiency reduction,mode instability and reliability reduction,which seriously restrict the further improvement of laser bar performance.The photonic crystal laser bar has the advantages of a small vertical divergence angle,high power density and high threshold of optical damage against cavity surface catastrophe,and is widely concerned.In this thesis,a combination of numerical simulation and experimental verification analysis is used to simulate and test the steady-state and transient thermal characteristics of a highpower low-dispersion-angle photonic crystal laser bar,and the effects of the bar structure and other parameters on its thermal and optoelectronic characteristics are investigated in detail,which is of theoretical guidance to improve the performance and reliability of the photonic crystal laser bar.The research contents and innovative work of this paper are as follows:1.Based on the basic theory of thermal properties,a flow-solid coupled conjugate heat transfer model of a microchannel water-cooled photonic crystal laser bar is established using finite element analysis(FEM)and computational fluid dynamics(CFD)numerical simulation methods.The steady-state thermal characteristics,including junction temperature and temperature field distribution,of the photonic crystal laser bar are simulated under continuous operating conditions.The simulated junction temperature of the photonic crystal laser bar is 55.47 °C and the thermal resistance is 0.48 K/W under continuous operation at 120 A.The measured thermal resistance is 57.00 °C and 0.50 K/W.The simulated results are in good agreement with the experimental results.2.The transient thermal behavior of a photonic crystal laser bar is simulated under continuous and quasi-continuous operating conditions.The factors affecting thermal crosstalk are investigated,and it is pointed out that thermal crosstalk leads to inhomogeneous temperature distribution of the bar,and the independent emitter method is used to investigate the causes of thermal crosstalk.The parabolic temperature distribution of the bar with high middle and low edges is experimentally verified by testing the spatial spectra of the bar.3.Theoretically and experimentally,the effects of structural parameters such as cavity length,strip width,number of emitters and filling factor on the thermal resistance variation,thermal crosstalk and temperature distribution of a photonic crystal laser bar are investigated.This paper provides design guidelines for the selection of bar width,number of emitters and cavity length under different application conditions,so as to obtain a bar with lower thermal resistance,higher temperature uniformity and output power.4.Based on the optimized design of photonic crystal laser bar,we successfully developed a 200 μm bar width,2.5 mm cavity length photonic crystal laser bar with a continuous output power of 203.2 W@250 A and a maximum electro-optical conversion efficiency of 63.48%;a 100 μm bar width,1.5 mm cavity length photonic crystal laser bar with a maximum electro-optical conversion efficiency of 69.28% and a continuous.The output power reaches 100.5 W@100 A.5.The single-tube failure mechanism of photonic crystal lasers was studied,and high-temperature and variable-current accelerated aging tests were conducted to deduce the activation energy of the device 0.23 e V and the acceleration factor index 5.77,and the average lifetime of 20 °C at 10 A was deduced to be 4287.69 h.And with the help of microscopic observation and push-pull test,the failure causes were analyzed and the cavity surface COD was found to be the main cause of device failure,and relevant improvement suggestions were put forward.