OSE Seminars
High Power All-Fiber Lasers at the Air Force Research Laboratory (AFRL)
Presented by Dr. Angel Flores, the AFRL Laser Division
For industrial and directed energy (DE) applications, fiber lasers have the advantages of reduced size, weight, and power consumption compared with their bulk solid-state and chemical counterparts. However, while multimode fiber lasers with powers as high as 100kW are now commercially available, these have poor beam quality. They are suitable for material processing but not DE applications, which require fiber lasers with near diffraction limited beam quality, and are much more challenging to build.
As such, to scale overall power and brightness, researchers have pursued multiple beam combining techniques; with spectral beam combining (SBC) and coherent beam combining (CBC) being the most prevalent architectures. Specifically, for efficient beam combining narrow optical linewidths are preferred for both architectures. Thus, to further scale the power of beam combinable fiber amplifiers, we have theoretically and experimentally investigated pseudo random bit sequence (PRBS) phase modulation. Consequently, we have demonstrated kW class fiber amplifiers at significantly reduced optical linewidths. In this work, we present results from two ~1.5 kW Yb-doped fiber amplifiers with comparable optical efficiencies and linewidths. Furthermore, five pseudo random modulated kW-class fiber amplifiers were coherently combined with a diffractive optical element (DOE). Overall, an output of power of ~5 kW and 82% combining efficiency was attained and multi-kW beam combining of pseudo random modulated fiber amplifiers was demonstrated for the first time.
11:00 am, Thursday, March 28, 2019
PAIS-2540, PAIS
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