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?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%.