Fiber-coupled diode modules have various applications in material processing and fiber laser pumping because of their high efficiency and high reliability. Commercial fiber-coupled diode modules using spatial beam combining and polarization beam combining cannot be employed in high-brightness applications, for example metal cutting, which demands a laser power exceeding 1 kW with a BPP of a few mm*mrad. Dense wavelength beam combining (DWBC) technology showed the possibility of further scaling-up the output power of fiber-coupled diode modules while maintaining the same beam quality that allows for fiber-coupled diode modules to be used in high-brightness applications. The efficiency, reliability, and brightness of fiber-coupled diode modules can be improved by using single emitters instead of laser diode bars as power sources in DWBC. Two types of high-brightness 100 µm/0.22 NA 2 kW fiber-coupled diode modules employing single-emitter-based DWBC technology, which have a wavelength range from 953 to 991 nm with 50% efficiency and a narrower wavelength range with 48% efficiency respectively, were developed for material processing and Raman fiber amplifier pumping. Furthermore, we combined 15 high-brightness 100 μm/0.22 NA 1.4 kW fiber-coupled diode modules into a 600 μm/0.22 NA fiber, achieving more than 22 kW at the output.
High brightness, high efficiency laser sources become more and more promising in diode laser applications for fiber laser pumping and materials processing. Dense wavelength beam combining (DWBC) technology has great advantages over other beam combining technologies as the brightness is significantly improved. However, the brightness and efficiency of DWBC technology based on laser diode bars are naturally limited by the laser source due to smile effect and low polarization ratio. By employing single emitter based DWBC technology and optimizing the optical design, a laser diode module capable of delivering above 600 W at 976 nm in a 0.22 NA 100/120 fiber is developed and 48% power conversion efficiency is achieved. The maximal power conversion efficiency, 51%, is reached at 400 W output. The intrinsic wavelength stabilization of DWBC technology allows the use of the module for efficiently pumping.
The paper reports on the design and development of an innovative high power and high brightness laser diode module that is capable of delivering more than 350 W at 976 nm in a standard 0.2 NA 50/125 fiber and 95% of power is in 0.15 NA. This module combines Everbright's multi-emitter modules assembled with 50 μm ridge width 976 nm laser diode chips through dense wavelength beam combining (DWBC) and polarization combining. The intrinsic wavelength stabilization of DWBC technology allows the use of the module for efficiently pumping Yb-doped fiber lasers.
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