522 W average power, spectrally beam-combined fiber laser with near-diffraction-limited beam quality.

We report a three-channel, spectrally beam-combined (SBC), 1 mum fiber laser that produces 522 W of average power with near-diffraction-limited (M2 ~ 1.2) beam quality. The laser features a SBC power combining efficiency of 93%, versatile master-oscillator, power-amplifier fiber channels with up to 260 W of narrow-band, polarized, and near-diffraction-limited output that is tunable over nearly the entire 1 micro m Yb(3+) gain bandwidth, and excellent prospects for significant power scaling. To our knowledge, these results represent the highest beam quality and average power achieved to date for a beam-combined fiber laser system.

60-W green output by frequency doubling of a polarized Yb-doped fiber laser.

The frequency doubling of a 110-W linearly polarized diffraction-limited Yb-doped fiber oscillator power amplifier (FOPA) has generated 60-W near-diffraction-limited (M2 < or = 1.33) linearly polarized green output. The FOPA produces as much as 2.4 kW of peak power and less than 20-pm linewidth at a 10-MHz repetition rate and 5-ns pulse duration without the onset of nonlinear effects. With two lithium triborate crystals at noncritical phase matching, a maximum of 54.5% doubling efficiency has been demonstrated. The overall electrical efficiency to the green portion of the spectrum is 10%.