N. Hodgson et H. Weber, INFLUENCE OF SPHERICAL-ABERRATION OF THE ACTIVE MEDIUM ON THE PERFORMANCE OF ND-YAG LASERS, IEEE journal of quantum electronics, 29(9), 1993, pp. 2497-2507
In general, the temperature distribution in Nd:YAG laser rods deviates
from a parabolic functional form due to the temperature dependence of
thermal conductivity and the inhomogeneity of pumping light distribut
ions. An analytical expression is derived which relates the resulting
radially dependent refractive power to the shape of the pumping light
distribution. To first order, the refractive power has a parabolic rad
ial dependence and this spherical aberration considerably affects the
laser's output characteristics. The performance of both stable and uns
table resonators is investigated theoretically by numerically solving
the Fresnel-integrals, including the amplification, the refractive pow
er and the aberration of the rod. High output power and good beam qual
ity cannot be achieved simultaneously when aberration is present. Expe
riments for both resonator types were performed with a pulsed Nd:YAG l
aser capable of a maximum output of 320 watts of average power.