Beam quality improvement by controlling thermal lens spherical aberration in an end-pumped Nd:YVO4 laser.

We present for the first time, to the best of our knowledge, the influence of spherical aberration on the beam quality of a single-stage laser amplifier. We set up an amplifier with a special structure to measure the spherical aberration distribution in the cavity. The output power of the oscillator was controlled, and the pump power of the amplifier was adjusted to improve the beam quality. The results show that there is an optimal amplifier pump power, which maximizes the output laser beam quality. In the presented experiment, an optimal laser beam was achieved with an output power of 10.54 W and beam quality of Mx2=1.54, My2=1.39 for a pump power of 9.33 W, oscillator output power of 9.2 W, and a beam quality of Mx2=2.10, My2=2.03.