High-average-power harmonic generation has been limited in the past by the average-power capabilities of the fundamental frequency source. The power densities required for efficient harmonic generation could be reached only by focusing the fundamental in the nonlinear medium. This approach gives rise to large transverse temperature gradients which disrupt phase matching and is inherently not scalable to large apertures. Recent work1 at LLNL has indicated that solid-state lasers may be capable of very high average power. At these high average powers, focusing the beam will result in optical damage to the nonlinear medium.