Solid state lasers for fusion experiments must reliably deliver maximum power to small (approximately .5 mm) targets from stand-off focal distances of 1 m or more. This requirement places stringent limits upon the optical quality of the several major components -- amplifiers, Faraday isolators, spatial filters -- in each amplifier train. Residual static aberrations in optical components are transferred to the beam as it traverses the optical amplifier chain. Although individual components are typically less than λ/20 for components less than 10 cm clear aperture; and less than λ/10 for components less than 20 cm clear aperture; the large number of such components in optical series results in a wavefront error that may exceed one wave for modern solid state lasers. For pulse operation, the focal spot is additionally broadened by intensity dependent nonlinearities. Specific examples of the performance of large aperture components will be presented within the context of the Argus and Shiva laser systems, which are presently operational at Lawrence Livermore National Laboratory. Design requirements upon the larger aperture Nova laser components, up to 74 cm in clear aperture, will also be discussed; these pose a significant challenge to the optical industry.
W. W. Simmons,
"Aberrations And Focusability In Large Solid-State Laser Systems", Proc. SPIE 0293, Wavefront Distortions in Power Optics, (30 December 1981); doi: 10.1117/12.932325; https://doi.org/10.1117/12.932325