Off-axis ellipsoid focus method for a direct kilowatt-class laser diode stack for material processing

Abstract

An off-axis ellipsoid focus system is designed to focus rectangular beams that are emitted by a direct high-power laser diode (LD) stack for material processing. This off-axis ellipsoid focus method can be applied to LD stacks with different spot sizes. Compared to other focusing methods, only this focus system designed an ellipsoid mirror to simultaneously focus the fast and slow axis laser beams in the same focal plane. The detailed process of the theoretical derivation is shown in this paper, and the corresponding formula is summarized finally. The focus system and light path are simulated by ZEMAX software, and the corresponding experiment is also performed. The spot size of the LD stack is 42 mm × 10 mm (fast axis × slow axis). This rectangular spot is focused into an ellipse spot whose size is 1.5 mm × 3.0 mm, with a 300-mm focal length. This focus system can be directly used for material processing.