A spatially-fed high-power amplifier comprises one or more shaped reflectors to reflect an initial wavefront, and an active array amplifier to amplify the reflected wavefront to generate a high-power planar wavefront. The shaped reflectors provide the reflected wavefront with substantially uniform amplitude when incident on the active array amplifier. The initial wavefront may be a substantially spherical wavefront, and the shaped reflectors may compensate for any amplitude taper of the initial wavefront to provide the reflected wavefront with substantially uniform amplitude components for incident on the active array amplifier. In some embodiments, the shaped reflectors may also contour the illumination to fit the shape of the active array amplifier to help minimize spillover.