On last year’s SPIE conference, BWT has launched a pump source in weight around 500g, which was locked at 976nm, output 420W from a 135μm diameter and NA 0.22 fiber. In order to meet the need of higher output power pumping of fiber lasers, BWT has achieved 650W output from a 135μm diameter and NA0.22 fiber with a diode laser locked at 969nm and 982nm based on dense spatial beam combination (DSBC) and wavelength beam combination. In the absorption spectrum of Yb3+ ions, 969nm and 982nm have lower absorption coefficients than 976nm,. The active fiber with the same doping concentration will produce less heat accumulation per unit length, which has an obvious effect on improving the TMI threshold (transverse mode instability) and increasing the single-mode fiber laser power. With the enhancement of pump source brightness and the improvement of active fiber doping process and wave-guide structure, the power of single mode fiber laser directly pumped by diode laser is expected to exceed 10kW in the future.
BWT introduced the idea of dense spatial beam combination(DSBC) and proved it experimentally with kW level pump source. Currently, the output power of single emitters has reached 15W~30W@BPP≈5-12mm·mrad with electro-optical efficiency<60%. This makes it possible for the high-power pump source with optical fiber output to maintain high brightness, small volume, and light weight. With commercial available chips, BWT achieved 420W output locked at 976nm from a fiber of 135μm core diameter and NA0.22, and mass of ≈500g. Also 1000W output at 976nm (or 915nm) from a 220μm core diameter 0.22NA fiber is obtained and mass of ≈400g. In the future, with increasing diode chip brightness and electro-optical efficiency, the pump source with high power and mass ratio will have an important role in small size and high power fiber lasers, which will become an active driver for defence and industrial applications.
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