Objective  High reliability becomes very important for the application of high-power laser diodes, and lifetime prediction is the primary aspect of reliability assessment of high-power laser diodes. Accelerated degradation test is a test method to accelerate the degradation process in the laboratory in accordance with the degradation model, which can obtain statistically significant lifetime prediction in a short time. With the advancement of device technology and its reliability, single-stress accelerated degradation test faces problems such as long test time, high cost, and excessive stress application in the degradation mechanism. Therefore, it is necessary to propose an accelerated degradation test for lifetime prediction of highly reliable and long-lived devices. For this purpose, a double-stress cross-step accelerated degradation technological method is designed in this paper.

  Methods  A double-stress cross-step accelerated degradation test is proposed. Aging test platform for high-power laser diodes was built (Fig.5). The device (Fig.4) was subjected to 1600 h accelerated degradation test, and the accelerated degradation data of optical output power under different stress conditions were collected (Tab.1). Performance degradation model was established to analyze the data with the accelerated model to obtain the lifetime prediction values, and the accuracy of the model was tested for significance (Tab.5).

  Results and Discussions   The overall scheme of high-power laser diodes lifetime prediction (Fig.1) has three main steps of bringing degradation data into the model, fitting the lifetime probability density distribution function, and checking accuracy. The double-stress cross-step accelerated degradation test sets the temperature and current as the stress conditions, and the two stress conditions are cross-stepped to form a total of four different stress conditions (Fig.2) as A 22 ℃, 1.4 A, B 42 ℃, 1.4 A, C 42 ℃, 1.8 A, and D 62 ℃, 1.8 A, respec-tively. The performance degradation model is built according to the YamaKoshi equation and the laser optical output power failure threshold is set. The acceleration model is established according to the generalized Irene model, and the degradation track of the optical output power during the accelerated degradation test is expressed as a segmentation function. After the estimation of the model conversion parameters, the lifetime prediction results were obtained and the parameter errors were compared (Tab.5), and they were all below 10%, which verified the accuracy of the model.

  Conclusions  The accelerated degradation test of 12 830 nm F-mount single-emitter device was conducted for 1600 h using four different current-temperature double-stress conditions in cross-step by self-designed experimental platform. The MTTF of the device is 5 811 h. The accelerated test method used in this paper saves at least 57.7% of the test time compared with the conventional single-stress constant accelerated lifetime test method, and has the advantages of less sample size and more flexibility in stress conditions. The method has been experimentally validated to provide statistically significant results for device lifetime prediction with experimental cost savings for different high-power laser diodes.