Near-diffraction-limited high power cw Nd:YAG laser using the spherical aberration of laser rods

In this work we propose a simple configuration with a single Nd:YAG oscillator which is very promising, we already obtained 215 W cw output power with a M² factor of M²=1.3/1.5 The optical to optical efficiency is 10.4%. The experiments were made with a "classical" cavity, based on two Nd:YAG rods with divergent lenses compensating for the thermal lensing and a polarization rotator compensating for the bifocusing. The resonator has a maximum M of approximately 6. At the limit of stability zone, we obtained a stable beam with 215 W cw output power with an M of 1.3/1.5. The total optical pump power was 2080 W. The optical-to-optical efficiency is 10.4 %.