Thermal lensing measurements in line-focus end-pumped neodymium yttrium aluminium garnet using holographic lateral shearing interferometry

Thermal leasing in compact neodymium yttrium aluminium garnet slabs and rods end pumped with a beam brought to a line focus has been measured using holographic lateral shearing interferometry. This powerful technique enabled us to directly measure thermal lenses with focal lengths in the range 0.02-12 m with an accuracy of 12% and good spatial resolution. It was found that the line focused pump beam resulted in severe astigmatic thermal lensing. The measured thermal lens strongly deviated from the ideal parabolic profile along both axes, introducing an important additional consideration for laser-diode end-pumped laser resonator design. The degree of longitudinal heat flow was found to strongly influence thermal lens power. It is anticipated that results obtained from the measurement technique presented here will enable optimal design of high-power end-pumped solid-state laser cavities.