Conductively Cooled 1 kW—QCW Diode Laser Stacks Enabling Simple Fiber Coupling

Abstract

A new mini-bar design densely packed with 13 emitters in a 1.6 mm aperture has been developed. These mini-bars deliver >200 W output. With a very low divergence of 95% power enclosed in 25° they are suitable for fast axis collimation (FAC) lenses with large working distance. The mini-bars are mounted on compact CuW carriers, which are further integrated into a custom stack assembly where they are conductively cooled from both sides. This completely AuSn soldered stack consists of only coefficient of thermal expansion matched materials and was 100 times temperature cycled from -40°C to 85°C, without any change in the PUI characteristic, the spectrum and the far field. The beam propagation factor M 2 of a 12-layer stack is ?130 in the vertical direction (after FAC) and ?210 in the lateral direction. Thus, the stack can be coupled to a 1.2 mm multi-mode fiber (M 2 = 260) with a coupling efficiency of 90% using only low-cost lenses.