Correction of spherical and azimuthal aberrations in radially polarized beams from strongly pumped laser rods

Spherical aberration of heavily pumped Nd:YAG rods was corrected by use of spherical relay optics selected to add conjugate amounts of aberration. Wavefront measurements showed elimination of spherical aberration. Correction of spherical aberration allowed 250 W of power to be generated in a radially polarized, birefringence-free oscillator (60% more power than without correction). Scale-up of wavefront maintenance was demonstrated in a two-rod amplifier module (6.3 kW electrical pump power). Radial polarization and spherical aberration correction together eliminated the main aberrations in uniformly pumped rod-based lasers. Rotating adjacent pump chambers substantially reduced the multifold aberrations induced by nonuniformity of the azimuthal pumps. DeltaM2 in the radially polarized beam was 0.3 and 1.4 with and without aberration correction, respectively, in each two-pump chamber module. Analysis predicts further improvements when higher-order aberration correction is applied.