The two major thermooptical influences on a frequency-doubled Nd:YAG laser by an intracavity Ba
2Na(NbO
3)
5crystal are discussed and theoretically examined. The absorption of λ106- and

m power by the crystal is shown to lead to the formulation of a thermally induced lens and diffraction loss due to the aspherical distortion. Equations for each are formulated. The effects of the lens and diffraction loss to the performance of the laser are illustrated. The modification to the laser resonator due to the inclusion of these effects is discussed.