Abstract: A tunable fiber grating comprises a temperature-sensitive body secured to a fiber having a fiber grating region for transmitting thermally-induced strain to the grating. The amount of strain and hence the degree of wavelength tuning are controlled by adjusting the temperature of the temperature-sensitive body, wherein the extent of adjustment is preferably pre-determined according to feedback from a wavelength detector. Large thermal strains obtainable with the present invention allow a wide range of wavelength tuning with a relatively small and convenient temperature change near ambient temperature. In a preferred embodiment, the temperature-sensitive body is cylindrical and comprised of a nickel-titanium alloy bonded to the grating. In alternative arrangements, the thermal strain effect can be amplified. An add/drop multiplexer employing the tunable gratings is also described.

Abstract: A novel non-mechanical optical fiber switch contains a magneto-optic element and a tubular magnet. The magneto-optic element is disposed within the field of the magnet but outside of the magnet bore. The beam of radiation from the switch input to the switch output passes through the axial bore of the magnet. The magnet contains magnetically anisotropic material, preferably a deformation-aged alloy having Fe, Cr and Co as major constituents. The switch is advantageously used in optical fiber communication systems.

Abstract: The present invention provides a method for metallizing a ceramic surface comprising a ferrite through a surface reduction treatment. A ceramic surface comprising a ferrite is heated. At least a portion of the ferrite is contacted with a gaseous reducing agent to create a metallic region by removing oxygen from the ferrite. The surface is cooled and, optionally, post-treated to enhance adhesion of the metallic region. Typical gaseous reducing agents are hydrogen, forming gas, and ammonia while typical ferrites are nickel-zinc ferrites and manganese-zinc ferrites. To form patterned regions, portions of the substrate are masked or portions of the reduced layer are removed.

Abstract: Materials of composition La.sub.v X.sub.w M.sub.y Mn.sub.z O.sub.x, with x selected from Mg, Sc, Al, Zn, Cd, In and the rare earths that have an ionic radius smaller than that of La, with M selected from Ca, Sr, Ba and Pb, and with v, w, y, z and x in the ranges 0.45-0.85, 0.01-0.20, 0.20-0.45, 0.7-1.3 and 2.5-3.5, respectively, can have substantially improved magnetoresistance (MR) ratios, as compared to the corresponding X-free comparison material. In particular, the novel materials in polycrystalline (or non-epitaxial thin film) form can have relatively large MR ratios. For instance, polycrystalline La.sub.0.60 Y.sub.0.07 Ca.sub.0.33 MnO.sub.x had a peak MR ratio in excess of 10,000% (in absolute value) in a field of 6 T.

Abstract: We have discovered that the addition of a relatively small amount of Sr and/or Ba to La-Ca-Mn-O can yield material of improved magnetoresistive properties at room temperature and in a small applied field, as compared to the analogous Sr and/or Ba-free material. An exemplary composition is La.sub.0.55 Ca.sub.0.25 Sr.sub.0.08 MnO.sub.x. Material according to the invention has a substantially larger value of .vertline.d.rho./dH.vertline. than the analogous comparison material at 25.degree. C. and H.ltoreq.0.05 Tesla. Preferred compositions also can exhibit a substantially linear dependence of resistivity on applied magnetic field under these conditions, as well as have a relatively large value of zero field resistivity. The novel materials can advantageously be used in applications that involve sensing of a magnetic field, or of changes in such a field.

Abstract: A magnetoresistive medium for sensing magnetic fields is formed by a metallic alloy that contains spinodally decomposed ferromagnetic particles having at least one thickness dimension equal to or less than approximately 0.01 .mu.m.

Abstract: In accordance with the invention, an image is formed by applying a local magnetic field to selected regions of a magnetic composite medium comprising columns of magnetic particles distributed in a matrix medium. The particles are "hard" or "semi-hard" magnetic materials in order to retain the latent image as residual magnetism, and the image is developed by exposure to magnetic fluid or powders. The image can be erased by exposure to an AC demagnetizing field or a DC sweep magnet. Preferred apparatus for making such images comprises a sheet of such composite material having a pair of major surfaces with columns of magnetic particles oriented between the surfaces. A local magnetic field, such as a magnetic pen, can be used to write a latent magnetic image on one of the major surfaces. The magnetic columns present the latent image for development at either major surface.

Abstract: The disclosed method can produce high T.sub.c superconductor material e.g., YBa.sub.2 Cu.sub.3 O.sub.7) of substantially increased intra-grain critical current density (J'.sub.c), as compared to conventionally produced bulk material of analogous composition. Exemplarily, YBa.sub.2 Cu.sub.3 O.sub.7 pellets produced according to the invention had J'.sub.c of about 10.sup.5 A/cm.sup.2 at 77 K. in an applied magnetic field of 0.9 Telsa. The inventive method comprises providing a precursor material whose composition differs from that of the desired superconductor with respect to at least one of the metal constituents of the desired superconductor. It further comprises heating the precursor material above the decomposition temperature (T.sub.d) of the precursor material such that a multiphase material results. The multiphase material comprises, in addition to a majority first phase, a dispersed precipitate phase. The method further comprises cooling the multiphase material to a temperature below T.sub.

Abstract: A method of making a ribbon-like or sheet-like superconducting composite body is disclosed. The method is well suited for making long lengths (e.g.,>100m) of ribboon or large areas (e.g.,>100cm.sup.2) of sheet-like composite. The method comprises forming a Bi-Sr-Ca-Cu-oxide-containing layer on a metal (exemplarily Ag) substrate, and mechanically deforming (typically by rolling) the thus formed composite such that the oxide is densified to more than 80% of the theoretical density. Subsequently the oxide layer is at least partially melted and allowed to re-solidify such that a large portion of the oxide crystals has c-axis alignment. After appropriate heat treatment in an O.sub.2 -containing atmosphere, thus produced superconductor ribbons or sheets can have high J.sub.c).gtoreq.10.sup.4, frequently >10.sup.5 A/cm.sup.2) for temperatures less than about 20K and in magnetic fields less than about 5T.

Abstract: Articles comprising a quantity of superconductive oxide material can be fabricated by a process that comprises melting of part of an oxide precursor material, with resultant directional resolidification. Exemplary embodiments comprise zone melting and movement of the hot zone through the precursor material. The method can result in superconductive material having improved properties, e.g., higher critical current, as compared to prior art oxide superconductors.

Abstract: Disclosed are normal metal-clad superconductive bodies (e.g., wires, ribbons) having a normal metal cladding that is porous during at least a part of the manufacture of the body. The porous cladding permits access of an ambient atmosphere to the superconductive material. Exemplarily, the superconductive material is an oxide such as a (Ba, Y) cuprate, the normal metal cladding comprises Ag particles (or Ag-coated particles), and the body is treated in an oxygen-containing atmosphere. Techniques for producing such a body are also disclosed.

Abstract: Electrical interconnections are made by means of a layer or sheet medium comprising chains of magnetically aligned, electrically conducting particles in a nonconducting matrix material. End particles of chains protrude from a surface of the medium, thereby enhancing electrical contact properties of the medium. The medium can be used for temporary as well as permanent connections; in the latter case the use of a nonconductive adhesive material is convenient for physical attachment to contacts on both sides of the medium.

Abstract: Superconductive oxide bodies such as wires, ribbons, rods, and other bulk bodies can be fabricated by a process that comprises melting precursor material, cooling at least of the melt such that a solid body of a desired shape results, and heat treating the solid body in an oxygen-containing atmosphere. The precursor material exemplarily is in the form of pressed superconductive oxide powder. The re-solidified superconductive material is relatively dense, typically textured, with relatively large grain size, and has improved properties, e.g., higher critical current density. An exemplary technique for melting of the precursor material is zone melting.

Abstract: An electrical interconnection medium is made as a composite of electrically conducting, magnetic particles in a nonconductive matrix material. Particles are magnetically aligned into a network which extends in at least two dimensions as, e.g., in a sheet or layer medium. A layer medium may further include additional, larger conductive particles which may be magnetically aligned into columns extending the thickness of the medium; typically, in this case, the medium serves as an anisotropically conductive medium in the direction of the columns, with slight in-plane conductivity imparted by the network aiding the dissipation of electrostatic charge.

Abstract: Devices such as, e.g., switches, flowmeters, and proximity sensors, as well as implant devices are made comprising an elongated ferromagnetic element. When the element is exposed to a variable magnetic field an electrical signal is obtained between contact points of the element in response to a change in the magnetic field. Preferred elongated elements have a helically deformed microduplex structure as may be produced by heat treatment and plastic twisting of a body of an alloy such as, e.g., an iron-nickel alloy.

Abstract: Electrical interconnection is established by means of an anisotropically conductive, composite layer medium comprising electrically conductive particles in a nonconductive matrix material. Enhanced uniformity of conductivity across the medium, and minimized incidence of lateral shorting are achieved as a result of essentially uniform distribution of electrically conductive particles which are also magnetic, such distribution resulting upon application of a magnetic field essentially perpendicular to a layer before or during hardening of the matrix material.

Abstract: Electrical signals are produced by a pressure-responsive device, such signals being indicative of the position of locally applied pressure. The device comprises a position sensor assembly which comprises a composite layer medium including electrically conductive magnetic particles in a nonconductive matrix material. The particles are aligned into chains extending across the thickness of the layer, and chains include a non-conductive gap which is bridged upon application of sufficient pressure. The medium is sandwiched between sheet electrodes, and the resulting assembly may be transparent as is advantageous in writing pad and touch-sensitive screen applications. The pressure-responsive device is suitable, e.g., as an input device in graphics information systems, in combination with transmission and display facilities.

Abstract: Essentially cobalt-free alloys are disclosed having a coercive force which is greater than or equal to 40 oersteds and having a magnetic squareness which is greater than or equal to 0.6. Such alloys comprise Fe, Ni, and Mo, and their approximate compositions are specified by 16-30 weight percent Ni and 3-10 weight percent Mo, remainder essentially Fe. Disclosed alloys are useful in memory and security devices.

Abstract: Magnetically actuated devices such as, e.g., switches and synchronizers typically comprise a magnetically semihard component having a square B-H hysteresis loop and high remanent induction. Among alloys having such properties are Co-Fe-V, Co-Fe-Nb, and Co-Fe-Ni-Al-Ti alloys which, however, contain undesirably large amounts of cobalt.According to the invention, devices are equipped with a magnetically semihard, high-remanence Fe-Mo-Ni alloy which comprises Mo in a preferred amount in the range of 2-26 weight percent and Ni in a preferred amount in the range of 0.5-15 weight percent.Magnets made from alloys of the invention may be shaped, e.g., by cold drawing, rolling, bending, or flattening and may be used in devices such as, e.g., electrical contact switches, hysteresis motors, and other magnetically actuated devices.Preparation of alloys of the invention may be by a treatment of annealing and aging or deformation and aging.

Abstract: To provide for an inexpensive magnet alloy, isotropic and nearly isotropic permanent magnet properties are developed in Fe-Mo-Ni alloys. Manufacture may be by a method which comprises steps of annealing, optional deforming by a limited amount, and aging.Typical magnetic properties of alloys of the invention are a coercive force in the range of 50-500 oersted, a magnetic remanence in the range of 7000-14000 gauss, and a magnetic squareness ratio of less than 0.9. Alloys of the invention are highly ductile even after plastic deformation, they are readily bonded to aluminum supports (as used, e.g., in the manufacture of twistor memories), and they are readily etched by etchants which leave aluminum unaffected.