Lifetime Prediction And Reliable Research On High Power Laser Diode Under Double-stress Cross-step Accelerated Degradation Test

Laser diodes were widely used in various fields,including communication,processing,medical,consumer electronics,and national defense,due to their high electro-optical conversion efficiency,easy modulation,long service life,small size,and integrability.As the laser technology continued to develop,all-solid-state and fiber laser systems require increasingly reliable high power laser diodes.These devices not only need to meet performance requirements but also require a long working life in harsh environments.Life prediction was the primary step in the reliability assessment of high power laser diodes.However,the current level of laser device or equipment design and manufacturing had been greatly improved,and their service life is increasingly longer,making it difficult to obtain sufficient failure data for reliability testing in a short period.Therefore,researching a more efficient accelerated test method has significant guiding significance for process improvement and reliability enhancement of high power laser diodes.This thesis takes an 830 nm F-mount high power laser diode single-emitter as the research object,using the double-stress cross-step accelerated degradation test method,establishes a laser life prediction model,and extrapolates and predicts its average failure time through performance degradation data processing.In addition,this thesis also analyzes the failure mechanism of experimental devices.The main research contents and results of this thesis are as follows:1.Accelerated degradation tests can make up for the shortage of less failure data from long-life samples by recording performance degradation data.Based on reliability theory and acceleration theory,this paper proposes a temperature-current cross-step accelerated degradation test plan,establishes a power output degradation model based on the Yamakoshi equation,and gives its parameter estimation method,acceleration model parameter optimization plan,and significance testing process.2.A high power laser diode single-emitter degradation test platform was independently built,and 12 single-emitters were subjected to a total of 1600 hours of accelerated degradation tests under four different double-stress conditions: A [22°C,1.4A],B [42°C,1.4 A],C [42°C,1.8 A],and D [62°C,1.8 A],each for 400 hours.The power output degradation data were fitted to the performance degradation model.The parameter estimation results were used for statistical inference of the number of model parameters by fitting them into the generalized Aalen model,and the accelerated model was corrected and combined with the Weibull life distribution.The mean time to failure(MTTF)of the device under the rated working conditions [22°C,0.9 A] was extrapolated by using 80% power output degradation as the failure criterion.The test saved more than 57.7% of the test time compared to the traditional constant current accelerated life test.In addition,the accuracy of the life prediction model was tested using data from the first three double-stress conditions,and the error did not exceed10%.3.The internal failure mechanism of the device that fails within 200 hours of the accelerated test is studied.Scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and electroluminescence(EL)are used to observe the cavity surface and the inside of the active region.Its degradation data analysis shows that there are two main reasons for device failure: one is that the active region of the device works for a long time under high current conditions,which leads to the diffusion of defects,and the optical catastrophe damage of the bulk material is observed through EL images;the other is that the cavity surface is caused by cavity surface defects or Local pollution leads to thermal runaway under high temperature conditions,forming a positive feedback mechanism to burn the cavity surface,and the optical catastrophe damage of the cavity surface is observed through SEM images.From the analysis of device failure results,excessive current and temperature conditions will form an interaction,which will further affect the degradation of semiconductor lasers.Improving the optical catastrophe damage threshold of the cavity surface of the device and introducing fewer defects into the active region and the cavity surface in the process are the keys to improving the reliability of the device.