Abstract: This invention relates to a laser amplifier system for amplifying a diverged laser beam to very high power levels, at constant flux density, over a very long optical path folded into a compact arrangement consisting of two rows of amplifier segments of progressively increasing diameter, the wide separation between each segment along the optical path being utilized to increase the self-oscillation of the system as a whole. The invention can also utilize only one row of amplifier segments with one or two rows of passive reflectors replacing the other row of amplifier segments, without changing its basic character. The invention is useful in thermonuclear reaction studies and optics studies.