Postweld-shift-induced fiber alignment shifts in laser-welded laser module packages: experiments and simulations

The fiber alignment shifts induced by the postweld shift (PWS) in laser-welded transistor outline (TO)-Can-type laser module packages were studied experimentally and numerically. The PWS-induced fiber alignment shifts were quantitatively determined by four geometrical parameters, namely: 1) the lateral shift (r); 2) the position angle (α); 3) the swing angle (θ); and 4) the tilt angle (ψ). The measured coupling powers in laser module packages before welding, after welding, and after a welding compensation clearly confirmed with the measured fiber alignment shifts determined by the dominant parameters of the r and α that the fiber shifts due to the PWS could be realigned back closer to their original optimum position after applying a welding compensation, and, hence, the coupling power loss due to the PWS could be regained. A coupled thermal-elastoplasticity model of finite-element-method (FEM) analysis was performed to evaluate the effects of PWS on fiber alignment shifts in laser module packages. The measured fiber alignment shifts determined by the dominant parameters of the r and α were in good agreement with the numerical calculation of the FEM analysis. In this study, the combination of the experimental and numerical results have significantly provided a practical design guideline for fabricating reliable laser-welded TO-Can-type laser module packages with a high yield and high performance for use in low-cost lightwave transmission systems.