Slow axis collimation lens with variable curvature radius for semiconductor laser bars

•A design method of SAC with variable curvature radius is proposed.•Divergence angle of 6 mrad is obtained by the SAC with low refraction index.•Resorting to FEM, the designed SAC is feasible to be fabricated and applied.

Based on Snell's law and the constant phase in the front of optical field, a design method of the slow axis collimation lens with variable curvature radius is proposed for semiconductor laser bars. Variable radius of the collimator is designed by the transmission angle, and it is demonstrated that the collimator has good beam collimation ability by material with low refractive index. Resorting to the design thought of finite element method, the surface of the collimator has been divided, and it is feasible to be fabricated. This method is applied as an example in collimation of a 976 nm semiconductor laser bar. 6 mrad divergence angle of collimated beam at slow axis is realized by the designed collimation lens with refraction index of 1.51.