Abstract: A technique in which one or more phase conjugation cells, such as stimulated Brillouin scattering cells, are controlled by use of a seed beam injected into the cells. When a laser beam is focused into a phase conjugation cell, a reflected phase conjugated beam is produced. The seed beam is injected at the same frequency and in the same direction as the expected phase conjugated beam, and is adjusted to control the phase and other characteristics of the phase conjugated beam. In multiple cell arrays, seed beams are employed to ensure phase coherency of multiple beams. For lower energy applications, use of the seed beam allows a phase conjugation cell to be operated with incident beams of lower energy than would be needed without the seed beam.

Abstract: A structural improvement to the feedback (i.e., output) mirror of an unstable optical resonator. The improvement may comprise either a step-like projection (either convex or concave) on the internal surface of the feedback mirror, or a change in curvature of the internal surface of the mirror. Each of these improvements actually constitutes a discontinuity in the internal surface of the mirror, with the curvature of the mirror on either side (i.e., around) the improvement remaining the same. The improvement cancels the interfering edge waves at the geometric source point of the resonator, thereby minimizing the effect of edge diffraction, and results in yielding more "geometric" modes having relatively uniform intensity profiles and large differences in feedback ratios between the dominant and higher-order modes.

Abstract: An unstable optical resonator with self-imaging aperture having at least two reflecting surfaces and a primary outcoupling aperture in optical alignment with each other. In the resonator the result of a single round-trip propagation is to image the primary aperture at its own plane. The self-imaging condition is met when a pass through the resonator, starting at the outcoupling aperture, produces an infinite Fresnel number.