Abstract: A technique for correcting wavefront aberrations introduced by large primary optical elements in portions of the electromagnetic spectrum. The aberrations of the primary element are first transferred to a beacon beam and this aberrated beam is interfered with a reference beam in a holographic medium. These beams are then turned off and a beam from a distant object, containing the same aberrations, is allowed to diffract from the hologram. The diffracted beam from the hologram contains the image of the distant object with aberrations removed. Use of this technique permits the construction of large optical elements inexpensively, since surface tolerances of the elements can be substantially relaxed.

Abstract: Apparatus for multiplexing or demultiplexing multiple laser beams of different wavelength. In multiplexing, the outputs from multiple diode lasers are combined in such a manner as to produce a practically parallel set of beams for direction onto a diffraction grating. The latter component deflects each beam from its normal path by an angular amount determined from the wavelength of the incident light. The angles of incidence of the multiple beams are chosen to provide angles of diffraction that are practically identical for all wavelengths under consideration. In demultiplexing, similar apparatus includes a diffraction grating to provide angular dispersion of the multiple wavelengths, at least one lens to magnify the angular differences, and a set of detectors positioned in the paths of the dispersed beams of different wavelengths.

Abstract: Apparatus and a related method for control of the colinearity of multiple laser output beams in a wavelength-multiplexed optical communications system. Multiple lasers of different wavelengths formed into a single composite beam by means of a diffraction grating and other optical components are subject to loss in colinearity due to wavelength drift and mechanical alignment drift. The apparatus of one disclosed embodiment of the invention includes an alignment detector for the output beam and a set of tracer modulation detectors responsive to tracer modulation signals impressed on the individual laser beams. Misalignment detected in any one or more of the laser beams contained in the output beam is corrected by temperature control of the appropriate lasers.

Abstract: A diode laser having an acitve layer bounded by confinement layers and two end facets that include etched mirrors selected to form an unstable resonator with good transverse mode quality. Energy from the unstable resonator is coupled out of the device through a transmissive window in one of the facets, the window providing a relatively large flux area and permitting higher output powers without loss of mode quality. Since stripe geometry is not used to control mode quality, a large current-carrying area is available, which reduces the current density and also permits higher output powers and longer operating lives.

Abstract: A gas laser having a bandwidth which substantially exceeds the normal doppler bandwidth. To this end the lasing beam is made to propagate at an angle to the direction of flow of the stream of lasing gases. The gases should move at a supersonic speed so that the normal doppler bandwidth of the laser is shifted up or down in frequency by a predetermined amount. By utilizing two or more gas flows at different angles to each other, the normal amplification band of the laser medium can be shifted up and down in frequency by different amounts to obtain an overall bandwidth on the order of 1 - 2 gigahertz (ghz).