s m and w i u2192 w i m the same optimum point on the contour can be reached by allowing l u2192 l m the minimum input beam area and crystal length are limited by the damage threshold of either the crystal antireflection coating or the crystal itself whichever is lower all input beams with larger area are equivalent in performance we have neglected absorption in our discussion of conversion efficiency because if the absorption is weak the efficiency shown in fig4 is reduced slightly due to energy loss but the overall shape of the curve is not changed significantly due to thermal dephasing consequently the effects of absorption on the system performance can be estimated simply by reducing by appropriate amounts the fundamental and second harmonic output intensities predicted using equation 3 however a potentially more serious consequence of even weak absorption is the deposition of heat in the crystal which can induce focusing variations due to small changes in the local refractive index the contribution of crystal heating to the overall dephasing can be estimated by u03b4 t u03b2 t u03b4tl 8 where u03b2 t is the thermal sensitivity of the crystal the temperature difference between the center of the crystal and the nearest side of the crystal assumed to be a distance w i 2 from the crystal center is u03b4t w i w s u03b1 l p av 8k p av is.