Abstract
We demonstrate off-axis spectral beam combining applied to a 980 nm high power broad area diode laser bar. The experiments yielded 9 W of optical power at 30 A of operating current and the measured M2 values of the combined beam from 12 emitters were 1.9 and 6.4 for the fast and the slow axis, respectively. The slow axis beam quality was 5-6 times better than the value obtained from a single emitter in free running mode. A high brightness of 79 MW/cm2-str was achieved using this configuration. To our knowledge, this is the highest brightness level ever achieved from a broad area diode laser bar.
Highlights
High power broad area diode laser bars are interesting devices for a range of specific industrial applications such as, e.g., cutting/marking of certain artificial materials [1] or cladding pumping of fibre amplifiers [2]
We demonstrate off-axis spectral beam combining applied to a 980 nm high power broad area diode laser bar
The slow axis beam quality was 5-6 times better than the value obtained from a single emitter in free running mode
Summary
High power broad area diode laser bars are interesting devices for a range of specific industrial applications such as, e.g., cutting/marking of certain artificial materials [1] or cladding pumping of fibre amplifiers [2]. Several research groups have used different approaches for improving the beam quality and spatial brightness of high power diode laser bar systems One such approach applied on a broad area laser array is using an external cavity providing off-axis feedback to all the emitters in the array [4]. In 2006, Jensen et al, [10] applied off-axis spectral beam combining to a segmented broad area laser diode and achieved a beam quality improvement of a factor of 3.4 compared to a single free running segment. We applied off-axis feedback to 12 broad area emitters, which resulted in a 5-6 fold improvement in the beam quality along the slow axis of the output beam compared to a free running single emitter on the same laser bar. A 34 fold improvement was observed resulting in a brightness of 79 MW/cm2-str which to our knowledge is the highest obtained brightness for a broad area diode laser bar
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