Abstract: A method of detecting whether a valid DS1 signal is being received by a receiver. If the receiver does not have a valid signal (loss of signal), then the receiver reads consecutive fixed sized N bit blocks of the received digital signal. Each of the blocks or windows is checked for minimum 1s density. Received consecutive 0s are counted and checked against a maximum. If two sequential blocks of bits satisfy the 1s and consecutive 0s tests, then the received signal is judged valid and an acquisition of signal flag is asserted.

Abstract: A communication card includes a housing and a shank rotatably mounted thereto. The shank defines an axis along its length around which the shank can rotate. A connector is mounted on the shank. The shank and connector are extendable beyond an edge of the housing to an extended position. In the extended position, the connector and shank are rotatable about the shank axis.

Abstract: A wet chemical etching technique is disclosed for forming a lensed optical fiber. In particular, the fiber is placed in a mixture comprising buffered hydrofluoric acid (e.g., HF and NH.sub.4 F) and a treating agent comprising acetic acid or citric acid. The relative concentrations of the constituents are adjusted so that a double conical lens is formed which requires no further operations (such as fire polishing) to provide coupling efficiencies of about 80% with a standard deviation of less than .+-.2%.

Abstract: A solution of H.sub.2 O.sub.2 and EDTA selectively etches GaAs-containing Group III-V compounds in the presence of other Group III-V compounds. Illustratively, Al.sub.y Ga.sub.1-y As (y.ltoreq.0) is selectively etched in the presence of Al.sub.x Ga.sub.1-x As(x>y), and InGaAs is selectively etched in the presence of either InAlAs or InP.

Abstract: A wavelength selective structure is coupled to an adiabatic Y-coupler via a multimode section which supports both symmetric and antisymmetric modes. One single mode branch of the coupler converts guided light to a symmetric mode, whereas the other single mode branch converts guided light to an anti-symmetric mode. The structure, which includes a pair of single mode waveguide arms coupled to the common section and a reflection device (such as a grating or ROR) located in each arm, converts reflected light from a symmetric mode to an anti-symmetric mode and conversely. Applications described include a channel dropping filter and channel balancing apparatus for WDM systems, and a dispersion compensator for fiber optic systems.

Abstract: A TE-TM polarization manipulating (i.e., splitting, combining or filtering) device is constructed from substrate-supported dielectric thin film waveguides. In a 3-port device, two waveguides have cores of different materials and different effective refractive indices. The waveguide cores overlap in a first transition section and one waveguide core has an adiabatic taper; in this section they also separate adiabatically in and are coupled to a second (e.g., output) section where the waveguides are physically separate and optically decoupled. In a 4-port device, two additional waveguides are coupled in a second adiabatic transition section to the first transition section to enable TE or TM modes to be coupled straight through the device from one input port to a directly opposite output port or to be crossed-over from one input port to a diagonally opposite output port.

Abstract: An optical circulator/isolator is implemented in a semiconductor package formed by a semiconductor substrate, which supports integral thin film waveguide polarization splitters and combiners, and a semiconductor lid, which supports four spherical lenses and a polarization rotator. The latter is a composite of at least two adjacent slabs of optically active material, one slab serving as a nonreciprocal 45.degree. rotator (e.g., a Faraday rotator) and the other as a reciprocal 45.degree. rotator (e.g., half-wave device). The lenses, serving both as beam expanders/condensers and as collimators, are positioned between the waveguide ends and major surfaces of the composite slab. When used with means for reversing the direction of the magnetic field in the nonreciprocal rotator, the device functions also as a switch. Also described are system architectures made possible by these devices; e.g.

Abstract: Group III-V compound MISFETs include a low-doped diffusion barrier layer disposed between a source/drain contact-facilitating layer and the channel layer.

Abstract: A reflection filter is disposed on a solid state laser so as to preferentially reflect TE or TM modes and to suppress oscillation within the resonator of the non-reflected modes. In one embodiment, the filter includes a layer having a plurality of grooves which may be straight and parallel or curved to approximate the mode shape. In another embodiment, the filter includes a polarization sensitive film, without grooves, which either absorbs or transmits the undesired mode. Specifically described is a buried heterostructure semiconductor DFB laser with such a reflection filter formed on at least one facet thereof.

Abstract: Described is a heterostructure semiconductor laser comprising a pair of wide bandgap layers having an active region sandwiched therebetween characterized in that the active region includes a plurality of thin narrow bandgap active layers interleaved with a plurality of thin relatively wider bandgap passive layers. The passive layers are thin enough (e.g., about 10-500 Angstroms) to permit electrons to distribute among the active layers either by tunneling through, or by hopping over, the energy barriers created by the passive layers. The active layers are thin enough (e.g., about 10-500 Angstroms) to separate the quantum levels of electrons confined therein. These lasers exhibit wavelength tunability by changing the thickness of the active layers. Also described is the possibility of threshold reductions resulting from modification of the density of electron states.

Abstract: Described is a technique for obtaining phase matched second harmonic generation in a laminar structure with the optical radiation propagating parallel to the layers.

Abstract: Described is a double heterostructure junction laser in which the active region tapers to zero thickness within the structure, causing light to couple into an adjacent, underlying passive waveguide layer. Also described is a laser device in which the passive waveguide layer terminates in a region of increased thickness adjacent a laser output face. In addition, LPE and MBE techniques for fabricating the tapers are described.

Abstract: In the fabrication of double heterostructure GaAsAlGaAs junction lasers by molecular beam epitaxy, it has been found that suitably annealing the entire heterostructure increases the external quantum efficiency of the laser and reduces the room temperature threshold for lasing. Also described is a technique using relatively uncollimated beams to deposit continuously on the interior walls of the vacuum chamber fresh layers which getter deleterious contaminants. In addition, pyrolytic boron nitride, rather than graphite, effusion cells are utilized in order to reduce the amount of CO formation in the system.

Abstract: Surface contamination of Group III(a)-V(a) substrates prior to epitaxial growth can influence structural, optical, and electrical properties of the resulting layers. Of the common contaminants, sulfur, nitrogen, carbon, and oxygen, which are found on substrate surfaces, only carbon cannot be removed by simple heating. By passivating the substrate surface with a native oxide coating after chemical etching and before atmospheric exposure, the carbon-containing contamination can be virtually eliminated since these compounds have low sticking coefficients on the native oxide. The oxide can then be readily stripped off by heating in a vacuum to leave essentially an atomically clean substrate surface.

Abstract: A junction transistor is provided which is especially adapted for use in an amplifier circuit in which third-order intermodulation distortion is especially low. To this end, an epitaxial junction transistor is made to have a substantially linearly graded concentration of the dominant impurity over at least half of the high resistivity portion of its collector zone.

Abstract: Described is a procedure for virtually eliminating disclocations in multilayer structures of materials having a crystallographic zinc-blend structure, in particular quaternary layers of Al.sub.y Ga.sub.1.sub.-y As.sub.1.sub.-z P.sub.z grown on Al.sub.x Ga.sub.1.sub.-x As substrates (y > x .gtoreq. 0). By carefully controlling the quaternary layer thickness and the lattice parameter mismatch at the growth temperature, it is possible to change the direction of substrate dislocations as they enter the substrate/layer interface. The length of the dislocation in the interfacial plane can be extended so that it is "infinitely" long, i.e., it reaches the edge of the wafer. As a result, the epitaxial quaternary layer and all layers subsequently grown thereon will be virtually dislocation free, provided that the thickness, stress and uniformity of the layers are such that no surface dislocation souces are activated.

Abstract: An organ array comprises a plurality of optical fibers each cut to a different length with the differences between functionally adjacent (i.e., lengthwise consecutive) fibers being uniform. The fibers are arranged in a bundle so that one set of ends of the fibers is terminated in an input plane and the opposite set of ends is terminated in an output plane. Described are several embodiments utilizing the organ array including a passive spatial scanner, optical memory systems, an image converter, an optical sampling oscilloscope, and an x-y coordinate locater.

Abstract: The average stress between contiguous layers of Al.sub.x Ga.sub.1.sub.-x As and Al.sub.y Ga.sub.1.sub.-y As (y > x) is reduced by the addition of phosphorus during the growth of the latter layer to produce the quaternary Al.sub.y Ga.sub.1.sub.-y As.sub.1.sub.-z P.sub.z instead of the ternary Al.sub.y Ga.sub.1.sub.-y As. In order to reduce the average stress to less than about 2 .times. 10.sup.8 dynes/cm.sup.2 the amount of phosphorus added should satisfy the condition: ##EQU1## Also described is a double heterostructure junction laser comprising a GaAs or AlGaAs active layer sandwiched between layers of AlGaAsP.

Abstract: Described is a liquid phase epitaxy technique using conventional slider apparatus in which, after heating the source solution to saturation, the solution temperature is rapidly reduced so that supersaturation takes place but heterogeneous nucleation does not. The solution is allowed to reach convective equilibrium and only then is brought into contact with the substrate. Once in contact, the temperature is maintained constant so that convection currents in the solution are substantially reduced. This technique has several advantages: reduced edge growth, increased usable wafer area, and reduced wipe-off problems.

Abstract: A charge transfer analog signal filter is described in which a plurality of charge storage cells are connected in series to form a delay line having a time delay T between its input and output cells. In a feed-forward rejection filter the analog signal is applied to the input cell through a cell of area A.sub.1 and to the output cell through another cell of area A.sub.2. The transfer function of the rejection filter is ##EQU1## In a feedback bandpass filter the analog signal is applied to the input cell through a cell of area A.sub.1, and the output cell is coupled to the input cell through the series combination of an analog inverter and another cell of area A.sub.2.