High efficiency high brightness spectral beam combination based on an ultra-broad area laser diode stack

Abstract

We demonstrate what we believe to be for the first time a high efficiency, high brightness laser source by external cavity spectral beam combination (SBC) in the fast axis based on the 1000 µm ultra-broad area laser diode (UBALD). Regarding the slow axis beam quality of UBALD, we propose a feedback model of the slow axis angle energy distribution in the oscillation process. By adding a structure with a filtering effect in the external cavity, both theory and experiment show that the beam quality of the slow axis can be effectively improved. With a 25-emitter UBALD stack, an SBC maximum CW output power reaches up to 730.6 W with an electro-optical efficiency of 63.7%. The SBC spectrum consists of 25 discrete peaks with a central wavelength of ∼967 nm and an overall spectrum width of 27.2 nm. The beam quality M2 values along the fast and slow axes are measured to be 5.2 and 22.8 at an output power of 623.4 W, corresponding to a brightness as high as 562.3 MW/(cm2•sr).