Abstract: A laser system for producing pulsed, longitudinal mode optical energy over a widely tunable range of wavelengths. The system includes an optical cavity and a solid-state gain medium. The optical cavity comprises first, second, and third optical element means. The first optical element means reflects energy received along a first reflective optical axis and directs the energy toward the second optical element means, which diffracts the optical energy into at least two orders of interference. The energy diffracted according to a first order of interference is reflected back toward the second optical element means by a third optical element means, thereby creating a resonant optical cavity. Another portion of the optical energy diffracted by the second optical element means is produced as an output beam.

Abstract: In aiming a neutral particle beam cross hair sights are first lined up relative to a target, and then the beam is lined up with the cross hair sights. Blocking means is disposed in a particle beam so as to absorb, scatter and/or otherwise remove particles from the beam and thereby create a downstream shadow of predetermined size and shape in the beam. Shadow detecting means is disposed in the beam downstream of the blocking means and senses the particles and emits steering signals systematically related to the extent to which the shadow detecting means is in the shadow of the blocking means. Aligning means lines up the blocking means and the shadow means in a desired direction relative to the target. The steering signals are thus systematically related to the direction of the beam relative to the desired direction. The steering signal from the sensing means is used to direct the neutral particle beam to hit the target.