This article provides a method to combine multiple fiber lasers up to the 100 watt power level, and to electronically steer the combined output. The authors hold out hope of phasing up to kilowatt-class fiber lasers using the same basic approach. To coherently combine lasers emitted from multiple apertures a scientist must know, and control, the relative phase of the combined beams. An optical phased array, OPA, can steer a laser beam with no moving parts by simply changing phase of the combined beam emitted from multiple phase controlled apertures. An OPA can be space fed, where an external modulator changes phases, or each transmit or receive aperture can be phase modulated. Most of the discussion in my 2009 article, referenced in this article, is about space feed phased arrays, but this article focuses on phase modulation of multiple transmitters, which can allow steering of the combined laser beam. A previous work had measured phase of outgoing lasers by using feedback from reflections at the exit aperture. This work varies the effective amount allowed to reflect back so they can use a similar technique with higher power lasers, demonstrating up to 100 watts per laser. They demonstrate combining and steering 3 one hundred watt fiber lasers emitted from separate apertures. The technique is compatible with high power lasers using pseudo-random codes to reduce the effect of SBS.
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