Trw Limited

USA As Represented by Secretary of the Navy

Donald C Winter

Robert King

Robert E Brooks

David B Hall

William L Shackleford

A system for automatically aligning a high power laser. The optical train the high power laser includes an unstable resonator cavity, a two axis, gimballed turning mirror and a extraction mirror. The autoalignment system utilizes a HeNe laser to propagate an alignment beam coaxial with, and prealigned with, the high power beam. The reference beam traverses the same optical path as the main, high power beam, propagating through all of the relay optics of the laser train. This allows angular deviations in the pointing direction of the main beam to be inferred from the angularity of the reference beam. At the downstream end of the laser train, the extraction mirror functions as an optical interface, pointing the main beam in the preferred output direction and extracting the reference beam by means of a central passageway through the extraction mirror. The extracted reference beam is directed on a path incident to a null angle sensor. The angularity of the extracted reference beam is detected by the null angle sensor. Any angular displacement results in a corresponding error signal. The error signals are translated by alignment system servo electronics into correcting tilt adjustments to the gimballed turning mirror, realigning the main beam as well as the coaxial reference beam.

Autoalignment system for high power laser

A modulator for a laser such as a chemical or electrically excited laser radiating in the region between approximately 2 and approximately 5 microns. The modulator consists of a transparent ferroelectric ceramic of the type known as PLZT. Such a polycrystal is disposed in the laser cavity. An electric voltage is applied to the crystal for causing it to exhibit optical birefringence, thus spoiling the Q of the laser cavity. Further, means is disposed in the laser cavity for linearly polarizing the radiation such as one or more Brewster windows transparent to the radiation. The crystal is cooled by fluid means such as a gas transparent to the radiation. Further, the crystal is mounted by means having an acoustic impedance substantially matching that of the crystal so that mechanical stress waves set up in the crystal are not reflected back into the crystal.

Near infrared laser modulator

A novel hologram functioning as a multiple lenslet array of high density in which the lenslets have selected small spacings and relatively long focal lengths is disposed in a holographic data recording system to provide an object beam along a selected axis. Using the holographic lens array, a data hologram may be recorded with improved uniformity between data points, efficiency, hologram illumination, and with minimization of data beam blockage. In preparing the novel hologram, a coherent object beam may be used to define a plurality of sources for simultaneous recording of a plurality of lenslets. The lenslets of a refractive precursor array defined by a commercially available fly's eye lens may be illuminated simultaneously, and selected size, shape, spacing and f- number characteristics for the lenslets may be achieved by concurrent optical transformation of the individual beamlets before recording. The precursor array may advantageously be immersed in a surrounding fluid of controllable refractivity, to substantially increase the effective focal length at the precursor lenses, and enable a substantially larger area of each lenslet to be used.

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Manhattan Beach, CA, United States of America

Donald C Winter