Abstract

Flashlamp-induced aberrations potentially limit the beam quality and fill a factor of solid state laser systems. We have measured pump-induced beam steering vs time and aperture position in the largest Nova disk amplifiers, the 31.5- and 46-cm amplifiers, with ~1-μrad sensitivity at 1052 nm. The measurements show two distinct components: a large steering near (and toward) the disk edges and a weaker steering throughout the aperture in the plane of incidence of the Brewster angle disks. The experiments suggest that the edge steering is caused by the edge cladding which is heated by amplified spontaneous emission, locally distorting the disk, while the central-aperture steering is caused by disk bending resulting from differences in flashlamp illumination of the disk faces. Calculations agree well with the amplitude and position dependence of the edge steering, and they show that face-to-face illumination differences can account for the central-steering magnitudes and directions. The implied steering of the Nova output beam (74-cm beam diam) produced by the final two amplifier stages (five 31.5-cm and four 46-cm amplifiers) is inconsequential over most of the aperture (less than ±10 μrad), but the edge steering results in a 5% loss of useful beam area.

© 1988 Optical Society of America