Abstract: A foreshortened log periodic antenna comprising variously configured dipole elements and a tapered feedline is further size reduced with an improved configuration of the dipole with the lowest resonant frequency. By substantially increasing the thickness of that dipole, the overall length of the already size-reduced dipole is further decreased by 8% to 10%.

Abstract: A technique for measuring the unknown subsurface temperature T of a bulk transparent medium such as sea water by focussing a high intensity pulsed laser beam in a first direction into the water to a predetermined depth D, producing stimulated Brillouin scattering (SBS) in a second direction opposite to the first direction and generating from the SBS stimulated Raman scattering (SRS) in the second direction, analyzing the spectra of the SRS and determining therefrom the temperature T. The depth D is is selected to insure that the entire SBS pulse is in the water.

Abstract: A technique for measuring the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water by splitting a pulsed laser beam having a high intensity into two sub-beams, one of which is a probe beam directed into the medium. The intensity of the output beam pulses exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering within the medium and to produce therefrom a phase-conjugate beam which propagates along the path of the first sub-beam but in the opposite direction. The second sub-beam combines with the PC beam and the combined beams mix at the cathode of a photodetector thereby producing a heterodyne frequency proportional to the temperature T.sub.s. Converts the heterodyne frequency into a temperature value yields the desired unknown T.sub.s.

Abstract: A technique for measuring the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water by generating a continuous (cw) laser beam and pulsed laser beam both having the same wavelength, with the intensity of the pulsed laser beam exceeding the intensity required to produce stimulated Brillouin scattering in the water. By directing the pulsed laser beam into the water, it causes a return phase-conjugate beam to emanate therefrom. The return phase-conjugate beam and the pulsed laser beam are separated, and the phase-conjugate beam and the cw beam are mixed together thereby producing a heterodyne frequency proportional to the temperature T.sub.s. By converting the heterodyne frequency into a temperature value, yields the desired unknown T.sub.s.

Abstract: A method of remotely measuring the diffuse attenuation coefficient K of ocean water from an airborne platform such as an aircraft. By directing a pulsed laser beam having a wavelength .lambda..sub.0 from the platform into the water, the beam interacts therewith to produce inelastic Brillouin backscatter signals at the wavelength .lambda..sub.1, where .lambda..sub.1 .noteq..lambda..sub.0. The desired backscatter propagate generally oppositely to the direction of propagation of the pulsed laser beam so that the backscatter can be received and collected at the platform. The upwelling optical energy includes the desired backscatter signals, which are separated out from the remainder of the upwelling optical energy. The separated backscatter signals are converted to equivalent electrical signals and periodically analyzed to generate therefrom the diffuse attenuation coefficient of the ocean water at the .lambda..sub.1 wavelength at periodic depths beneath the water surface.

Abstract: Apparatus is disclosed for remotely measuring the diffuse attenuation coefficient K of ocean water from a platform such as an aircraft flying over the ocean. A pulsed laser beam is directed as a probe beam from the aircraft into the water to produce therein Brillouin backscattering signals which emanate back up through the water to the aircraft. An optical receiver in the aircraft receives and processes those backscattered signals. A very narrow optical bandpass filter passes the Brillouin signals to a photodetector, a digitizer and a data processor, the latter being programmed to compute the diffuse attenuation coefficient at predetermined depths and at the Brillouin wavelength. Measurements of the diffuse attenuation coefficient at various depths is accomplished by sampling and digitizing the Brillouin signals at predetermined intervals, each interval corresponding to a depth beneath the surface of the water.

Abstract: To remotely measure the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water, a laser beam having a high power or intensity is split into two parts, a probe beam and a reference beam. The probe beam is directed into a sample of ocean water, and the reference beam into a reference sample of water having a known temperature T.sub.r. The intensities of the two beams, which exceed a predetermined threshold are sufficient to cause stimulated Brillouin scattering (SBS) within the two samples and produce therefrom two phase-conjugate beams. The two phase-conjugate beams are mixed to produce a heterodyne frequency that is proportional to the difference in temperature T.sub.s and T.sub.r. The frequency difference is converted into a temperature value equal to the value of T.sub.s.

Abstract: Apparatus for measuring the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water comprises a pulsed laser having a high intensity (power per unit area) output beam split into two sub-beams, one of which is a probe beam directed into the ocean water. The intensity of the output beam pulses exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering within the medium and to produce therefrom a phase-conjugate beam which propagates along the path of the first sub-beam but in the opposite direction. The second sub-beam is reflected by a mirror to and combines with the PC beam and the combined beams are mixed at the cathode of a photodetector which produces a heterodyne frequency that is proportional to the temperature T.sub.s. A frequency measuring instrument converts the heterodyne frequency into a temperature value equal to T.sub.s.

Abstract: Apparatus is disclosed for remotely sensing the unknown subsurface temperature T.sub.s of a bulk transparent medium, such as ocean water, using a cw laser beam and a pulsed laser beam. In one embodiment the cw output of a continuous laser is split into two sub-beams. An optical amplifier periodically amplifies the first such sub-beam thereby generating an intense pulsed laser beam having a plurality of pulses with the same wavelength as the cw laser beam. The intensity level of the pulses is sufficient to produce stimulated Brillouin scattering when focussed into the ocean water. The pulsed laser beam is directed into the water thereby generating an intense return phase-conjugate beam propagating along the path of the pulsed laser beam but in the opposite direction thereto. The phase-conjugate beam and the second sub-beam are mixed at the cathode of a photodetector to produce a heterodyne frequency proportional to the temperature T.sub.s.

Abstract: To remotely measure the unknown subsurface temperature T.sub.s of a bulk transparent medium such as ocean water, a high intensity pulsed laser beam is split into two sub-beams, a probe beam and a reference beam. The probe beam is directed into a sample of ocean water of unknown temperature, and the reference beam into a reference sample of water having a known temperature T.sub.r. The irradiance of the two pulse beams exceeds a predetermined threshold sufficient to cause stimulated Brillouin scattering (SBS) within the two samples and produce therefrom two return phase-conjugate (PC) beams. A photodetector mixes the two PC beams and produces a heterodyne frequency that is proportional to the difference in temperatures T.sub.s and T.sub.r. A frequency measuring instrument converts the heterodyne frequency into a temperature value equal to T.sub.s.

Abstract: A linkage device connectable between adjacent ends of a tubular support member and payload member is adapted to rotate the payload member through approximately 180.degree. about the end of the support member between inoperative and operative positions by movement of an actuating rod longitudinally within the tubular member. The linkage device comprises first and second frames secured to adjacent ends of the members and four bars pivotally connected at opposite ends to corners of the frames, the first pair of bars extending within the frames and the second pair extending outside the frames. The actuating rod is connected to the first pair of bars and rotates them about their pivotal connection to the first frame when the rod is moved longitudinally within the tubular member. Both pairs of bars cause the payload member to rotate about the end of the support member through 180.degree. and into an operative position in longitudinal alignment with the support member.

Abstract: A winch having a torodially-shaped drum with an axis of rotation and at least one cable wound on the drum having a cable length extending from the drum parallel to and substantially equally spaced from said axis at all times during rotation of the winch. The drum has negatively-curved and positively-curved surfaces joined at a common edge, the cable being wound on the negatively-curved surface and directed therefrom over the positively-curved surface in a direction parallel to the drum axis. This drum is used advantageously with the mast system described in application Ser. No. 246,112.

Abstract: The etendue (throughput or area-solid angle product) of a high resolution interferometer is maintained at a substantially high level by use of a transparent chamber defined by a highly reflective internal surface, the chamber being located at the input to the interferometer. The chamber has an input aperture to admit light into the chamber and an output aperture or exit opening to pass light to the interferometer. By integrating the input light through multiple reflections thereof within the chamber until it exits to the interferometer, the etendue of the latter is substantially enhanced.

Abstract: The subsurface temperature of a body of water such as an ocean is measured remotely by directing a laser beam deeply into the water and analyzing the resultant Brillouin and Rayleigh backscatter components. Wavelength shifted Brillouin scatter is mixed with the unshifted Rayleigh scatter in a self-heterodyne manner for each volume element of illuminated water and the frequency of the heterodyne signal is measured. This produces the desired temperature-depth profile of the water.

Abstract: Subsurface waves in a body of water such as an ocean caused by a submarine are remotely nonacoustically detected by monitoring subsurface water temperatures using a laser. A pulsed laser beam is directed into the water to at least the depth of the thermocline and an analysis is made of the resultant Brillouin and Rayleigh backscatter components. Wavelength shifted Brillouin scatter is mixed with the unshifted Rayleigh scatter in a self-heterodyne manner for each volume element of illuminated water, and the frequency of the heterodyne signal is measured and converted into temperature. This produces the desired temperature-depth profile of the water enabling detection of internal waves generated by submarines.

Abstract: The efficiency of an optically pumped solid state laser is substantially improved with a controlled geometry fluorescent converter between the pump light source and the lasing medium. Fluorescent materials have the capability of absorbing broadband pumping radiation, shifting it in wavelength and re-emitting it in the absorption band of the selected solid state laser medium. Use of angular formations having the converter surface facing the laser medium reduces fluorescent light trapping within the converter due to internal reflection thereby greatly increasing the total light output of the converter and thus the efficiency of the laser.

Abstract: An adjustable optical mounting assembly, particularly suited for folding or periscope optics, provides for optical beam motion in three axes using a bearing having a spherical surface. This invention greatly simplifies the mount mechanism and operting procedure, reduces the size, and provides enhanced stability and lockability relative to comparable conventional devices.

Abstract: Improved gain control in a photomultiplier tube having a plurality of dynode stages is achieved through manual or automatic change of the bias voltage on at least one of the several dynodes between the anode and cathode of the tube. By such means, maximum tube gain change is obtained with a minimum of bias voltage swing.

Abstract: A crossed log-periodic dipole antenna having a unique feedline/boom structure providing improved antenna performance. The antenna is assembled from a pair of orthogonally displaced log-periodic antennas each having a pair of half-dipole structures, each structure having a half-dipole assembly and a central feed boom. The half-dipole assembly comprises a single sheet of conducting material formed to provide a central boom portion and a plurality of half-dipole elements projecting radially from opposite sides of the boom. The boom portion has a reduced thickness, a shape which complements that of the outer surface of the boom, and is press-fitted against and bonded to the boom exterior to form an integrated rigid unit. This configuration minimizes the force required to connect each half-dipole assembly with the adjacent boom, decreases the offset distance between the two dipole halves of each antenna, and reduces the electrical shadowing effect of the booms on the antennas.

Abstract: A system for rapidly scanning a remote field of regard with transmitter laser beams comprises an optical system having a focal plane, a plurality of lasers capable of being sequentially fired, and a like number of optical fibers coupled at one end to the respective laser outputs. The opposite fiber ends lie in the focal plane of the optical system and are aligned in the direction of the height of the field of regard. The beams move rapidly across the width of the field of regard simultaneously with sequential operation of the lasers, thus illuminating the entire area of interest in a minimum of time.