Abstract: A process for depositing a high temperature stress and oxidation resistant coating on a silicon nitride- or silicon carbide-based substrate body. A gas mixture is passed over the substrate at about 900.degree.-1500.degree. C. and about 1 torr to about ambient pressure. The gas mixture includes one or more halide vapors with other suitable reactant gases. The partial pressure ratios, flow rates, and process times are sufficient to deposit a continuous, fully dense, adherent coating. The halide and other reactant gases are gradually varied during deposition so that the coating is a graded coating of at least two layers. Each layer is a graded layer changing in composition from the material over which it is deposited to the material of the layer and further to the material, if any, deposited thereon, so that no clearly defined compositional interfaces exist.

Abstract: A system for measuring the frequency response of an electrooptic device, such as an optical detector, includes an optical amplifier for generating an optical white noise spectrum that is delivered to the detector. In a first embodiment, an optical amplifier or a luminescent fiber amplifier generates a white noise signal due to spontaneous-spontaneous beat noise emission, while a second embodiment utilizes the signal-spontaneous and spontaneous-spontaneous beat noise emissions generated by an optical amplifier driven by a laser source. The frequency response of the detector is determined from a measurement of the detected noise signal wherein any roll-off in the response must be due to the detector since the originally generated noise spectrum is flat.

Abstract: A method for identifying and determining the concentration of nitrous oxide in a gas containing nitrous oxide, oxygen and nitrogen is disclosed. A negative voltage is applied across a set of electrodes separated by an electrolyte wall. The voltage is of such a magnitude to produce an electric current which is on a plateau. The current is measured initially using air or oxygen as a test gas. After this reading is taken the gas containing nitrous oxide in oxygen and air is measured for its current and the concentration of nitrous oxide is determined using the two measured currents. The negative voltage can be applied at two different magnitudes to have two currents measured. Nitrous oxide containing mixtures would yield equivalent current readings.

Abstract: A new and improved microfocus radiography system incorporating a novel x-ray collimating device for eliminating shadow anomalies caused by secondary radiation from materials within the path of x-rays emitting from an x-ray source. The improved system includes a body defining an opening through which primary radiation may pass from a focal spot x-ray source toward a sample, an x-ray window covering the distal end of the opening, x-ray detection means, and an internal collimator to suppress secondary radiation. The window is penetrable by primary radiation passing through the opening with negligible generation of secondary radiation. The collimator defines an aperture and is disposed along the path of the radiation between said focal spot and said window so as to attenuate any passing primary radiation not directly striking the x-ray window. The collimator is formed from a material having a low vapor pressure at temperatures and pressures at which the system is operated.

Abstract: An optical serial-to-parallel converter constructed from at least two optical shift registers connected in cascade, each optical shift register having a 1.times.2 optical switch connected to its output. Each optical shift register in the sequence is optically coupled to the next sequential optical shift register through one output of said 1.times.2 optical switch to the input port of the next sequential optical shift register. The input port of the first optical shift register serves as the input to the optical serial-to-parallel converter, receiving a series of optical pulses. The output ports of each of said third optical switches serve as the output ports of the optical serial-to-parallel converter. The optical shift registers are controlled by two clocks, operating at the same rate, but each out of phase with the other.

Abstract: A method of producing crack free ceramic parts having large cross-sections is disclosed. An initial mixture of ceramic powder containing a binder and from 0.1 v/o to 10 v/o of whiskers or fibers which are made of carbon, graphite or high temperature melting or decomposition point organic polymers. The mixture is either injection molded or slip cast to form a shaped article. The shaped article is heated in a nitrogen atmosphere to a temperature of 450.degree. C. and then in an atmosphere of air at a temperature of 450.degree. C. to 600.degree. C. to completely remove the binder. The resulting binderless shaped article is then heated at 800.degree. C. for a period of time sufficient to completely remove the whiskers or fibers from the shaped articles. The article is then encapsulated in glass and hot isostatically pressed at a pressure of 30,000 psi to densify the article to approximately 99% of theoretical. The resulting article has a complex geometry and a large cross-section but without detrimental cracks.

Abstract: A microscratch-test method for measuring adhesion between a first material and a second material adhered to one another at an interface and forming an article. The method involves polishing a planar surface of the article generally normal to the interface and exposing the interface and the first and second materials. A static load of predetermined mass is applied to a starting point on the first or second material in a direction generally normal to the planar surface, using a load means of a third material harder than the first and second materials. The load means is moved across the planar surface from the starting point in a straight line generally toward and across the interface at an angle relative to the interface of between 90.degree. and about 20.degree.. These steps are repeated, varying the mass. The starting point for each repetition is spaced apart from other starting points but is approximately equidistant with other starting points from the interface.

Abstract: A method of compensating for the angular coupling of optical fibers to a tilted facet optoelectronic component involves a precise calculation of the coupling angle with respect to the active layer of the component and with respect to the side walls of the package in which the component is to be mounted. With these angles computed, the tilted facet component is positioned on a carrier at an offset to the perpendicular such that input/output fibers can exit the component package perpendicularly to its sidewalls. The component is secured to the carrier by a solder having a high melting point such that subsequent soldering of parts to the carrier will not affect the component positioning. A localized cooling method then allows the sequential alignment and soldering of one optical fiber at a time to the offset tilted facet component, while previously aligned and soldered optical fibers are held fixed.

Abstract: A method for optically coupling multiple single-mode optical fibers to a single packaged optoelectronic array device uses a single graded index lens to magnify the images of the active semi-conductor elements and to expand the spacing between their light beams. These separated magnified light beams then coupled to an associated array of uptapered optical fibers. Simultaneous alignment is possible because the location of the semiconductor array beams can be known with high precision relative to the central beam in the array. A lens with known magnification is first positioned relative to the central beam. Alignment to this central beam automatically aligns other optical fibers held collectively in a fixture engineered with the geometry set by the known magnification of the lens. The coupling of single-mode optical fiber to two-dimensional semiconductor surface arrays utilizes the projected and magnified beams of the array which replicate the precise placement of the array elements.

Abstract: A method of generating high power optical signals in the 1-100 GHz frequency range uses a frequency modulated semiconductor laser and an interferometer. This method is especially useful for microwave carrier frequency optical communications, distribution of microwave frequency local oscillator signals, and the generation of sinusoidal optical modulation at frequencies that cannot be reached by direct modulation in semiconductor lasers or with external module lasers.

Abstract: The invention features a theft resistant security system for motor vehicles. The system has receptacle with a coupling coil. A SAW (surface acoustical wave) device associated with the receptacle for relative movement thereto is also provided. The SAW device has a code and its own coupling coil for interaction with the receptacle coupling coil. A testing mechanism is connected to the receptacle for determining whether the code of the SAW device is valid for operation of the motor vehicle. Problems of crosstalk and wave reflection may produce spurious code pulses in systems of this type. The invention provides techniques for eliminating or reducing these unwanted pulses.

Abstract: An optical transmission system includes a power splitter for dividing an RF input signal into a plurality of intermediate signals each assigned to a respective one of a plurality of parallel optic links. Each link optically transmits its respective intermediate RF signal over a respective fiber line before being detected at a receiver end. The detected signals are combined by an RF power combiner into an output signal having an enhanced signal to noise ratio that is better by 10 log n dB over that of a single link, where n is the number of parallel links. In order to permit operation at arbitrarily high frequencies, a pilot tone delay equalization circuit is coupled to each link at the receiver end for equalizing the delay variations between the various fiber paths.

Abstract: The I.sub.2 bound exciton in cadmium sulfide (bound to a neutral donor) is a very efficient radiator, providing low switching energy and fast switching times for an ON and OFF optical bistable device, desirable for all-optical signal processing applications. The optical bistable device for light at a given wavelength includes a Fabry-Perot cavity having a pair of opposed mirrored surfaces. A direct bandgap semiconductor, such as CuCl, CdSe, CdS, and GaAs having a bound exciton, is located within the cavity. The cavity is tuned near resonance of the light. The bound exciton has a coefficient of absorption tuned near resonance. A light beam of varying intensity is applied from without the cavity to one of the surfaces. The semiconductor has both an index of refraction and a coefficient of absorption that vary with the magnitude of applied light. Thus, light applied thereto passes through the device either substantially unimpeded or impeded, dependent upon its magnitude.

Abstract: A method of fabricating a semiconductor heterostructure includes the growth of a quantum well active region that is highly lattice-mismatched relative to a substrate. A buffer layer having a thickness above a critical value is grown on the substrate whereby the stress due to a lattice constant mismatch between the buffer layer and substrate is relieved through the formation of misfit dislocations. A strained superlattice structure is grown on the buffer layer in order to terminate any upwardly-propagating dislocations. An unstrained barrier layer is subsequently grown on the superlattice structure. The fabrication method concludes with the growth of a quantum well structure on the unstrained layer wherein a lattice constant mismatch between the quantum well structure and the unstrained barrier layer is smaller than the lattice constant mismatch between the quantum well structure and the substrate.

Abstract: A method of optically coupling an optoelectronic device having a photoactive element to an uptapered single-mode optical fiber which connects said optoelectronic device to an external device includes securing a graded index lens to a substrate carrier within a housing at a distance calculated to provide a known magnification of a light beam emanating from said element, and further includes mechanically positioning and actively aligning the fiber to said magnified light beam to achieve optimal optical coupling to said optoelectronic device. The location of a plurality of reference marks and surfaces are determined such that the photoactive element, the lens and the uptapered end of the single-mode optical fiber may be positioned with respect to these references for precise optical coupling using an active alignment for final adjustments. The reference surfaces include a pedestal for the laser and a plurality of stops for the lens integrally formed with the substrate.

Abstract: A process is disclosed for purifying scandium from an acid solution containing scandium and various impurities. The process involves mixing the acid solution with a chelating resin in the hydrogen form to from a slurry and packing the slurry in a short ion exchange column. The ion exchange column is rinsed with a mineral acid and the scandium is removed by passing diglycolic acid through the column. The diglycolic acid containing scandium is then passed through a chelating resin in the H form. When the scandium concentration in the effluent from the chelating resin reaches a preselected level the effluent of digylcolic acid and scandium is collected. Collection is stopped when the scandium concentration in the eluent falls below a preselected level. This collected eluent is passed through a strong cation exchange column where the scandium is collected.

Abstract: A hybrid optical Y-junction device includes a 1.times.N optical fiber coupler connected to N waveguide structures fabricated on a single substrate. When the waveguide structure is a semiconductor optical amplifier, the hybrid Y-junction device is operable as either a modulator or lossless power divider. A nonblocking optical switch is constructed by coupling M.times.1 optical fiber couplers to the outputs of the waveguide structures in the hybrid Y-junction. The switch is also effective as a wavelength division multiplexer when periodic gratings are integrated into the waveguide amplifiers.

Abstract: An inductively coupled RF plasma generator and method. The plasma generator includes a body having a conduit having a gas inlet and an outlet. Induction structure surrounding the conduit inductively excites the gas, generating a plasma which leaves the conduit outlet as a tail flame. An electrically insulating chimney is positioned at the outlet so that the chimney surrounds the tail flame and no electrical path to ground exists between the outlet and the chimney means. A grounded electrode is positioned downstream of the plasma and sufficiently near the outlet to provide an electrical path to ground from the tail flame shorter than other available paths to ground. The method for generating a plasma utilizing the inductively coupled RF plasma generator involves inductively exciting the gas to generate a plasma which leaves the outlet as a tail flame. The tail flame is surrounded by a chimney so that no path to ground exists between the outlet and the chimney.

Abstract: A new, simplified method of fabricating optically transparent fluoride glasses containing ZrF.sub.4 and/or HfF.sub.4 has been developed which relies on a high vacuum pre-treatment for surface dehydration, melting in a rigorously inert argon atmosphere, and incorporation of a nonvolatile metallic oxidant in the melt such as InF.sub.3 and SnF.sub.4. Previous method for making these glasses have relied on either addition of ammonium bifluoride into the batch materials, or melting in an oxidizing atmosphere (so-called reactive atmosphere processing or RAP); both of these latter techniques have significant drawbacks.

Abstract: A method for preparing a highly aligned thick film of superconducting bismuth strontium calcium copper oxide ceramic material to improve its critical current density. A film about 5-200 .mu.m thick of bismuth strontium calcium copper oxide is deposited on a suitable substrate. The ratios of Bi:(Sr, Ca):Cu in the film are about 2:3:2 to 2:4:3. A laser beam is translated over the deposited film at a rate of about 0.2-15 cm/hr while the film is held at a temperature of about 500.degree.-950.degree. C. The beam is about 0.01-0.50 cm wide along the direction of translation, and provides about 0.2-10W of optical power to the film. The temperature and the beam translation rate, width, and optical power are selected to permit zone melting and resolidification of the film to form the highly aligned thick film of superconducting bismuth strontium calcium copper oxide ceramic material. The J.sub.c may, if desired, be further improved by annealing the resolidified film at about 900.degree.-965.degree. C.