Abstract: A heterojunction-type laser is constructed with two closely spaced p-n junctions. Ohmic contacts are provided on both sides of the p-n junctions so that the voltages across the junctions can be individually controlled. By controlling the ratio of the voltages, the carrier distribution in the lasing active layer is controlled. This in turn controls the direction of the output beam of the laser in accordance with the ratio of the voltages, providing a laser beam which can be scanned without requiring mechanical means.

Abstract: A method is provided for selectively doping a compound semiconductor such as GaAs in situ by molecular beam epitaxy. The surface of the GaAs is coated with a thin layer of As by exposing it to an arsenic flux within a molecular beam epitaxy chamber. Selected areas of the surface are irradiated with a laser beam or a beam of photons, electrons, or ions in order to desorb As and form a mask of As on the surface. Dopant material such as tin is then deposited over the surface and As mask. The semiconductor is then heated to desorb the As mask while leaving the dopant in the unmasked areas. An epitaxial layer of GaAs is then grown over the surface by molecular beam epitaxy.

Abstract: A composite is produced by placing a reinforcement between foils of a superplastic metal alloy to provide stack. The stack is then heated to a temperature at which the metal alloy exhibits its superplastic properties, and pressure is applied to the heated stack. This causes the foils to flow around the reinforcement and diffusion bond together in the solid state. A structural composite is thus formed comprising a reinforcement dispersed throughout a matrix of superplastic metal alloy.

Abstract: Disclosed is a surface acoustic wave interferometer, including a substrate on which are disposed a first reflector and a second reflector so as to define a multimode resonant cavity therebetween. A third reflector is positioned on the substrate so that a single mode resonant cavity is defined between the second and third reflectors. An input transducer generates surface acoustic waves in the single mode cavity, while an output transducer detects the interference between surface acoustic waves in the multimode and single mode cavities. A base is rigidly affixed to the substrate in the region of the single mode cavity so that a force applied to the substrate will alter the surface acoustic wave propagation characteristics within the multimode cavity.

Abstract: A method is provided for drawing ions out of the glassy phase of a ceramic in order to improve its high temperature strength and to reduce its dielectric loss. The ceramic is heated to a high temperature to increase the mobility of the ions within the glassy phase. An electric field is then applied across the ceramic to draw the ions to the surfaces of the ceramic where they can be removed by grinding.

Abstract: Disclosed is a hybrid Schottky barrier focal plane, which includes a transparent semiconducting detector substrate of a first conductivity, with an array of detector groups disposed on the detector substrate, each group including a plurality of Schottky barrier detectors. An output contact is provided on the detector substrate for each of the detector groups. A field effect transistor for each detector includes a source region of a second conductivity type in the detector substrate and connected to the detector, a drain region of the second conductivity type in the detector substrate over the source and drain regions for controlling the connection between the source region and the drain region. An array of output contacts are disposed on a semiconducting multiplexer substrate, which also includes a charge coupled circuit for converting parallel signals from the input contacts to a serial output signal.

Abstract: Disclosed is a surface acoustic wave filter based on a ferroelectric crystal having a plurality of ordered domains of alternating polarity. An output interdigital transducer, with at least one pair of electrodes, is deposited on a surface of the crystal so that each of the electrode pairs corresponds to one of the ordered domains, and an input interdigital transducer is oriented on the surface to direct a surface acoustic wave toward the output transducer. In addition, sources of both positive and negative electrical potential may be provided, with a switch for each output electrode pair to selectably apply either the positive or the negative potential to that pair.

Abstract: Si.sub.3 N.sub.4 ceramics having a glassy phase densification aid are heated while their surface is in contact with SiO.sub.2. The SiO.sub.2 forms one side of a diffusion couple and draws the glassy phase out of the ceramic. The SiO.sub.2 can be provided by heating the ceramic in air to form an SiO.sub.2 scale by the oxidation of Si.sub.3 N.sub.4, or by imbedding the ceramic in SiO.sub.2 powder. Surface pits, if any, formed during oxidation, are removed by grinding.

Abstract: Disclosed is a multiple-quantum-layer detector for responding to photons having a predetermined amount of energy. The detector includes a purality of parallel layers of a first semiconducting material having a first conduction band energy level, with a plurality of layers of a second semiconducting material parallel to the first layers and having a second conduction band energy level differing from the first conduction band energy level by no more than the predetermined energy. The second layers alternate with the first to establish a plurality of parallel heterojunctions. First and second electrodes are provided for applying an electric potential across the alternating layers.

Abstract: Disclosed is an electromagnetic acoustic transducer for use with electrically conductive objects. The transducer includes an electromagnet for establishing a static magnetic field directed into the object in a first region and directed out of the object in a second region. A meander coil for inducing eddy currents in the object when an alternating current is applied to the coil includes a first serpentine printed circuit on a first side of a printed circuit board and a second serpentine printed circuit on a second side of the board. The source and the coil are so oriented that the vector product of the field and the eddy currents produces an instantaneous force field in the object which is periodically alternately oriented.

Abstract: A meter and a method are provided for measuring the composition and flow rate of a coal slurry and other similar mixtures. The meter is a waveguide through which the mixture flows. Microwaves are propagated in the waveguide from a transmitter probe. A detector probe spaced from the transmitter probe receives signals from the microwaves. Those signals are processed to determine a characteristic frequency of the waveguide or the wavelength of the propagating microwave, which are related to the composition of the mixture within the waveguide. A second transmitter and detector pair determines these properties for another portion of the waveguide. Differences in the frequencies resulting from inhomogenuities in the mixture are cross correlated to determine the flow rate of the mixture.

Abstract: An imaging charge coupled device (CCD) is provided which has a support on the non-illuminated, circuit side of a CCD channel layer. The other side of the CCD channel layer (the semiconductor side) is epitaxially joined to an absorber layer of semiconductor which is epitaxially joined to a window layer. This structure is fabricated by growing the epitaxial semiconductor layers (window, absorber, and channel) on a semiconductor substrate, fabricating a CCD circuit on the channel layer, mounting the channel layer to a support, and finally etching off the substrate.

Abstract: An apparatus for generating acoustic waves of wavelength .lambda. in an electrically conductive object includes an electromagnetic acoustic transducer, with a source of magnetic flux for producing a magnetic field in the object, a first periodic coil within the field, and a second periodic coil within the field and offset from the first coil by .lambda./4. A first port of a four port hybrid is connected to the first coil and a second port is connected to the second coil, with a 90.degree. phase delay element interposed between the first port and the first coil. A signal generator provides an input signal at a frequency corresponding to .lambda., with a transmitter for applying the signal to either a third or a fourth port of the hybrid to generate a unidirectional wave in one of two opposite directions. An apparatus for detecting acoustic waves includes a first receiver connected to the third port and a second receiver connected to the fourth port.

Abstract: Disclosed is a logic circuit with a plurality of AND logic elements, each including a plurality of Schottky diodes with each cathode connected to a logic input and the anodes connected in common to establish an AND output. A diode pull up FET is provided for each AND output, with the source connected to the AND output, the gate connected to the source, and the drain connected to a source of positive bias potential. An OR logic element includes a plurality of Schottky diodes with each anode connected to one of the AND outputs and the cathodes connected in common to establish an OR output, while a diode pull down FET has its drain connected to the OR output, with the gate connected to the source and the source connected to a source of negative bias potential. A level shifting diode is placed between the OR output and the pull down FET. An output FET is connected through its gate to the drain of the diode pull down FET, with the source connected to ground and the drain providing a logic output from the circuit.

Abstract: At least 1 mole % SiO.sub.2 and 1/2 mole % Sc.sub.2 O.sub.3 are used as a densification aid to provide a polyphase silicon nitride ceramic having high creep strength. The composition is within the Si.sub.3 N.sub.4 - Si.sub.2 N.sub.2 O tie line, the Si.sub.3 N.sub.4 - Sc.sub.2 Si.sub.2 O.sub.7 tie line, and the Sc.sub.2 Si.sub.2 O.sub.7 - Si.sub.2 N.sub.2 O tie line in the ternary phase diagram for the Si.sub.3 N.sub.4, SiO.sub.2, Sc.sub.2 O.sub.3 system. The phases in the sintered ceramic are Sc.sub.2 Si.sub.2 O.sub.7, and Si.sub.3 N.sub.2 O, and at least 50 mole % Si.sub.3 N.sub.4.

Abstract: Disclosed is an acoustic transducer which includes a pressure tight vessel with a window in the vessel which is transparent to acoustic wave energy. A gas is disposed within the vessel, while an electromechanical transducer is located within the vessel at an antinode for a resonant wave of the gas. A port communicates with the interior of the vessel, with a pressure control coupled to the port and to a source of the gas for controlling the pressure of the fluid within the vessel.

Abstract: A broadband electromagnetic acoustic transducer is disclosed for use with an electrically conductive object. The transducer includes a source of magnetic flux for establishing a static magnetic field in the object and an electrical conductor for inducing eddy currents in the object when an alternating current is applied to the conductor. The magnetic field and the conductor are oriented so that the vector product of the magnetic field and the eddy currents produces an instantaneous force field in the object which is periodically alternately directed with a logarithmic periodicity. The source of magnetic flux may be provided by a plurality of alternately oriented magnets aligned along a propagation direction. Alternatively, the conductor may be a serpentine conductor with a plurality of parallel elements which are perpendicular to a propagation direction, the ratio of adjacent spacings between the elements being constant.

Abstract: A monolithic microwave amplifier fabricated on a GaAs substrate utilizes MESFETs to provide both gain and impedance matching. The source of a first MESFET is connected to an input terminal of the amplifier and its drain is connected to an interstage matching network. The gate of a second MESFET is connected to the output of the interstage matching network and its source is connected to the output terminal of the amplifier. Suitable voltages are applied to the MESFETs to bias the devices appropriately. The gate of the first MESFET and the drain of the second MESFET are connected in common with the grounds of the amplifier's input and output ports. In a second embodiment, additional gain is obtained by providing a third MESFET with a common source connection between the first and second MESFETs.

Abstract: Disclosed is an integrated dual gate switch which is fabricated on a semi-insulating GaAs substrate. A metallic input line is deposited on the substrate and coupled to an ion implanted n-type region in the substrate through a first ohmic contact. A metallic output line is spaced from the input line and coupled through a second ohmic contact to the n-type region. A first metallic gate is deposited on the substrate between the input and output lines, while a second metallic gate is deposited between the first gate and the output line. A first capacitive coupling between the input line and the first gate includes a first metallic conductor deposited on the substrate and overlapping portions of the input line and first gate, and a first dielectric layer between the first gate and the first conductor. A similar second capacitive coupling between the output line and the second gate includes a second metallic conductor and a second dielectric layer.

Abstract: Disclosed is a method for determining the dispersion of a surface acoustic wave in an object, including the steps of generating a broadband acoustic wave in a surface of the object, detecting the wave at first location on the surface, and detecting the wave at a second location on the surface. Fourier transforms of the first and second detected waves are calculated, then the change in phase .DELTA..phi.(f) of the frequency component f of the detected wave, between the first and second locations, is computed from the phase components of the quotient of the two transforms. The dispersion of the wave in the surface is given by the formulav(f)=(2.pi.f .DELTA.l/.DELTA..phi.(f))In a pulse-echo version of the method, the wave is generated and detected at the first location, and generated and detected at the second location, the dispersion then being according to the formulav(f)=4.pi.f .DELTA.l/.DELTA..phi.(f)).