Abstract

High-gain direct-drive laser fusion requires a uniform spherical pellet implosion. This in turn requires that the focal profile of each driving beam be sufficiently uniform and controlled. Several methods for producing uniform beams have been proposed. One promising technique, echelon-free induced spatial incoherence (ISI), consists of propagating a broadband spatially incoherent beam through an entire laser system.¹ A commercially available broadband multi-spatial mode KrF discharge oscillator, which uniformly illuminates a small aperture, is used as the source of incoherent light. To minimize the effects of long-wavelength amplifier gain nonuniformities, the spatial Fourier transform of the input aperture is image relayed through the amplifier chain. If the total phase distortion suffered by the beam as it propagates through the optical system is small enough, the final focusing lens will produce a high-fidelity image of the input aperture on the target.

© 1991 Optical Society of America