The Research Of Coaxial Laser Diode Coupling Alignment And Post Welding Shift

There are two main factors affecting the quality of coaxial-type laser diode package:coupling alignment technique and laser welding technology. The core of coupling alignment is the platforms’ high-precision positioning and fast alignment automation. How to select the appropriate aligning platform has become the key to improve the coupling technique. Pulsed laser welding technique is commonly used in optoelectronic device packaging. But the existence of post welding shift will cause great loss of device coupling efficiency, reducing the device performance. To solve the problems above, four aspects of study are done as follows:1. Based on the coupling of semiconductor laser and single-mode fiber using ball lens, combined with the far field analysis of double heterostructure (DH) semiconductor laser, the relationship between coupling efficiency and alignment errors was given. The alignment error tolerance and alignment accuracy respectively corresponding to1dB and0.1dB excess loss were calculated. What’s more, Using Monte Carlo method, the coupling efficiency distribution with different alignment errors, which can estimate the device performance after packaging, was analyzed.2. According to special requirements, a clamp is designed which has the characteristics such as good centering accuracy, fast loading and unloading and appropriate retain force et al. With finite element method, the collet, which works as an important component in the clamp, was analyzed. The result proves that the collet’s structure design is effective.3. Based on APDL language, coaxial-type laser packaging model was established. Using thermal-structural coupled method, a three-dimensional finite element model for predicting the post welding shift is presented. The post welding shift were observed respectively when the welding energy of the three weld spot were unbalanced, the weld spot offsets were exist and welding defocusing amounts were unequal. It is concluded that the direction of post welding shift is toward the direction of larger combining energy.4. Coaxial-type laser diode welding system was set up. Using the system, laser welding packaging experiment is conducted. From the experiment, the characteristics of post welding shift were analyzed when welding hammer parameters varied. And the experiment results prove that the analysis of post welding shift’s direction by finite element method is correct.