Abstract: A shape memory wire latch mechanism for releasably connecting two separable structural members. The latch mechanism utilizes the unique material properties of shape memory alloys as a means for releasing the structural members. The latch mechanism includes a pair of mating latch elements and a shape memory wire mounted on one of the latch elements. The mating latch elements attach to the two structural members and, when engaged, latch the structural members together. The shape memory wire disengages the latch elements when heated above its transition temperature, thus allowing the structural members to separate. The latch mechanism is particularly useful for securely stowing collapsible antennas and solar panels in a launch vehicle and then providing safe and reliable deployment of the antennas and solar panels once in space.

Abstract: Apparatus and a related method for detecting signal photons of a selected wavelength using ionization induced by collisions between atomic or molecular particles. Signal photons raise the energy level of a proportion of particles introduced into a detection chamber to a selected metastable state. Optionally, a pump laser assists in raising the energy level of the particles to a metastable state close to the ionization continuum. Collisions between particles in the selected metastable state and particles of the buffer gas cause ionization of the metastable particles, and a measurable electrical current is obtained, without the need for strong electric fields for ionization, or the need for strong optical fields for photoionization. In a variant form of the invention, a second substance is admitted into the detection chamber.

Abstract: A multistage pulse tube cooler in which a portion of the heat from each successively lower-temperature pulse tube cooler is rejected to a heat sink other than the preceding higher-temperature pulse tube cooler, thus substantially improving the overall efficiency of the multistage cooler. Multistage pulse tube coolers of the prior art reject all the heat from each successively lower-temperature pulse tube cooler to the preceding higher-temperature pulse tube cooler, thus imposing a large cooling load on the higher-temperature pulse tube coolers which considerably reduces the overall efficiency of the cooler.

Abstract: Device coherency and optical-mode stability are obtained in light sources having large apertures and output powers, by using an important property of arrays of antiguides or negative-index waveguides. One embodiment of the invention is a power amplifier into which a light beam is input from a master oscillator. The input beam is introduced into one or more waveguides of an array, and leaks into successive adjacent waveguides, forming a fan-out pattern as it progresses along the array. The antiguides have an interelement spacing that is selected to produce a resonance effect, as a result of which light is coherently coupled to all waveguides in the array. The structure also provides lateral mode control and assures mode stability of the output. In the amplifier embodiment of the invention, the end faces of the array are antireflective coated and light makes only a single pass through the structure.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or tetraalkylester of an aromatic tetracarboxylic acid, (b) an aromatic diamine, and (c) an end cap compound. The ratio of (a), (b), and (c) is chosen so that upon heating the mixtures, low molecular weight prepolymers are formed, the prepolymers having only one end cap radical and being suitable for chain extension and crosslinking to form high molecular weight, thermally stable polyimides. Upon heating, the prepolymers form polyimide resins, which can have T.sub.g in excess of 600.degree. F. and superior physical properties.

Abstract: In a process for reducing the sulfur and ash contents of coal, coal is sequentially contacted with fused alkali metal caustic, wash water, and acid. Contacting the coal with the caustic produces water-soluble compounds. Sufficient wash water is used to reduce the temperature of the caustic treated coal and dissolve the bulk of the water-soluble compounds before the water-soluble compounds convert to water-insoluble compounds that precipitate on the caustic-treated coal. Caustic removed from the coal by the water is recovered as anhydrous caustic for again contacting coal.

Abstract: A semiconductor laser array of antiguides having a large number of antiguide elements to provide relatively high optical power output with a high degree of coherence and array mode discrimination. The antiguide elements are grouped into array cells that are separated by interarray regions having a width and refractive index selected to produce a resonance condition in the 0.degree.-phase-shift array mode. Each array cell is also designed to operate in the resonant condition, and losses in the interarray regions discriminate against modes other than the 0.degree.-phase-shift mode. The entire group of cells operates as a high-power, coherent ensemble, without the degradation of mode discrimination and beam quality usually associated with large numbers of waveguide elements.

Abstract: In a process for reducing the sulfur and ash contents of coal, coal is sequentially contacted with fused alkali metal caustic, water, carbonic acid, and a strong acid. Caustic removed from the coal by the water and the carbonic acid is recovered as anhydrous caustic for again contacting coal.

Abstract: An array of semiconductor laser diodes having parallel waveguide elements, of which each adjacent pair is coupled together by an X-shaped waveguide junction having a connecting waveguide in which lateral modes are formed as a result of merging of the pair of waveguide elements. The waveguide elements diverge again from the connecting waveguide at an angle great enough to ensure that there are high scattering and radiation losses near the point of divergence of the waveguide elements, for the fundamental mode in the connecting waveguide. If an adjacent pair of waveguide elements operate in phase, this excites the fundamental mode in the connecting waveguide, which is effectively suppressed by the losses that occur near the point of divergence from the connecting waveguide. The structure thereby discriminates against connecting waveguide in an in-phase mode, resulting in operation in the 180.degree.

Abstract: A semiconductor diode laser device, and a related method for its fabrication, the laser being of the type from which light is emitted in a direction perpendicular to planar layers forming the device. The laser includes an active layer and cladding layers formed on a supporting substrate, and a highly reflective semiconductor stack reflector formed on one of the cladding layers. The semiconductor stack reflector may be placed in contact with a heat sink and performs the multiple functions of electrical current conduction, heat removal and light reflection. A current confinement layer is formed laterally surrounding the semiconductor stack reflector, to provide one element of a back-biased junction that confines the current to the reflector region. A dielectric stack reflector is formed in a well in the substrate, and provides for light emission from the device.

Abstract: A composite structure of elastic and viscoelastic components in which dynamic loads are effectively damped by transmission through the viscoelastic components. The structure includes a continuous sandwich comprised either of a single elastic layer enclosed by two viscoelastic layers or of a single viscoelastic layer enclosed by two elastic layers such that the sandwich has little stiffness in any intended direction of loading, and two segmented elastic layers having stiffness in a desired loading direction. The segmented layers have alternating segments and gaps and are disposed one on each side of the viscoelastic layer in such a manner that the gaps of one segmented layer overlap the segments of the other segmented layer. Dynamic loads in the loading direction are transmitted back and forth from one segmented layer to the other, through the continuous sandwich layer containing the viscoelastic material, which thereby provides a high degree of damping.

Abstract: Apparatus, and a related method for its operation, for producing a high-power optical beam from a free-electron laser, at a high overall efficiency. Electrons are accelerated in an electron acceleration system producing bunches of electrons having a narrow energy spread but relatively long time spread. A bunch compression technique converts each bunch to one having a narrow time spread and relatively wide energy spread, suitable for injection into the gain region of a free-electron laser. After exit from the gain region, each electron bunch is further processed to restore it to the same energy-phase distribution as electrons produced by the acceleration system. The restored bunches of electrons are decelerated in the acceleration system, to conserve energy and increase the overall efficiency of the system.

Abstract: A two-dimensional integrated laser array having a plurality of surface-emitting laser arrays and a plurality of waveguides for optically coupling the individual laser arrays together. Each surface-emitting laser array includes a plurality of injection lasers which are evanescently coupled together in order to emit a single beam of light. The coupling provided by the waveguides causes the surface-emitting laser arrays to operate in phase and at the same wavelength as an external master oscillator. Therefore, the surface-emitting laser arrays generate coherent beams of light, which are combined and focused by a micro-lens. The output of the micro-lens is a single, coherent high-power optical beam which is emitted perpendicular to the two-dimensional integrated laser array.

Abstract: A deformation sensing device, and related method, for measuring overall deformation of a structural member subject to deformation by an actuator. The device includes a first sensor located in a region of influence of the actuator and a second sensor located outside but near to the region of influence of the actuator. The device takes a weighted average of output signals from the two sensors, using weighting factors that, in one embodiment, are applied either electronically and are selected either as proportional to the lengths of the member regions under the influence of the actuator and not under the influence of the actuator, or are selected to provide a desired transfer function between input to the actuator and output from the sensing device. In other embodiments, weighting of the output signals is obtained by using different surface areas for the sensors or by appropriately positioning two shear-mode sensors in relation to the region of influence of the actuator.

Abstract: A high-speed, high-resolution superconducting counting A/D converter providing greatly increased conversion speeds with a low device count. The superconducting counting A/D converter includes a double-junction SQUID quantizer and a bidirectional binary counter having n stages of grounded four-junction SQUID flip-flops, where n is the number of bits of accuracy of the counter. The quantizer continuously tracks an analog signal, generating up-count and down-count voltage pulses of the same polarity on two different output lines for increasing and decreasing values of the analog current, respectively. The bidirectional binary counter algebraically counts the voltage pulses, increasing the binary count when up-count pulses are received and decreasing the binary count when downcount pulses are received.

Abstract: A high-speed, high-resolution superconducting counting A/D converter providing greatly increased conversion speeds with a low device count. The superconducting counting A/D converter includes includes a double-junction SQUID quantizer and a bidirectional binary counter having n stages of floating four-junction SQUID flip-flops, where n is the number of bits of accuracy of the counter. The quantizer continuously tracks an analog signal, generating up-count and down-count voltage pulses of the same polarity on two different output lines for increasing and decreasing values of the analog current, respectively. The bidirectional binary counter algebraically counts the voltage pulses, increasing the binary count when up-count pulses are received and decreasing the binary count when down-count pulses are received. Several techniques for reading the contents of the bidirectional binary counter at the end of each sampling interval are also disclosed.

Abstract: Apparatus and a corresponding method, for removing the effect of phase aberrations introduced into an incident light wave by a large optical element, such as a large concave mirror. Rather than building additional precision into the mirror, phase correction is effected by first collimating and phase conjugating the incident beam after reflection from the mirror, then expanding the beam again to fill the mirror. After its second reflection from the large mirror, the light beam is practically free of phase errors, since the phase conjugated beam is subject to substantially the same phase aberrating conditions as the incident beam. The apparatus may be used to produce an aberration-free image of a distant object, or to produce an aberration-free collimated light beam from a diffraction-limited laser source.

Abstract: An intrusion-alarmed optical communication system in which two separate modal groups are launched into a single graded index transmission fiber. The system includes two light sources and a lens to focus the light sources into the transmission fiber. A spatial filter is used to selectively limit the angles of incidence of the light on the fiber, and operates in conjunction with the lens to launch light from one source at appropriate angles and points of excitation to excite higher-order modes in the fiber, and to launch light from the other source at appropriate angles and points of excitation to excite lower-order modes in the fiber.

Abstract: Apparatus and a corresponding method for controlling the attitude of a space vehicle during operation of its propulsion engines, without gimbaling of the engines. Two engines are differentially throttled, one above and one below a nominal thrust setting of the engines, in response to an error signal indicative of the difference between an actual attitude angle and a desired attitude angle. Three or four engines can be used to control attitude about two orthogonal axes, or a greater number of engines can be used for redundancy.

Abstract: A semiconductor laser array with features providing good beam quality at high powers, first by employing a laterally unguided diffraction region in which light from a set of waveguides is re-imaged in accordance with the Talbot effect and two arrays of waveguides may be used to provide a spatial filtering effect to select a desired array mode. This provides a laser array with increased power per unit solid angle, and with additional advantages of ability to scale the device up to larger arrays, ability to control the electrical excitation of the device for better optimization, and improved modal discrimination. A second aspect of the invention is the use of a resonance condition in an antiguide array, to produce a uniform near-field intensity pattern and improved coupling and device coherence.