Thermal lens characterization of a side-pumped Nd:YVO4 laser

We present a diode side-pumped Nd:YVO4 laser emitting up to 11 W CW output power c axis polarized at 1064 nm in a bounce geometry. We employed a 2 x 4 x 12 mm(3), 6 degrees wedge, 1.1% Nd3+ doped slab crystal. We set up a compact 2-mirrors cavity design using a cylindrical high reflectivity mirror (curved in the tangential plane) and several plane output coupler. The optimum total internal reflection angle of the designed bounce geometry, leading to the maximum output power, was measured to be about 3.5 degrees. The overall length of the cavity ranges from 8 to 11 cm depending on the investigated configuration. As much as 11 W CW output power was obtained for approximately 26 W of absorbed pump power at 808 nm, with a slope efficiency up to 50% and a near diffraction limited output beam in the vertical direction. An overall M-2 < 3 was obtained at the maximum output power. We also present a focal thermal lens characterization of the cavity carried out by the combined study of the beam quality and beam transverse dimensions inside the cavity in two different experimental setup. The study was based on a first order dependence of the focal thermal length on the absorbed pump power model f(th) proportional to k/P-abs. Our results are in good agreement with the model and the experimental behaviour of the system confirmed the outcome of the focal thermal lens measurements.