Abstract: A novel superfluorescent fiber source (SFS) has high power and broad bandwidth, and can advantageously be used in a variety of applications, e.g., optical coherent tomography systems, sliced spectrum optical fiber communication systems, and optical position sensing systems. The novel SFS comprises a first and a second length of rare earth-doped optical fiber, with an optical isolator therebetween. Light from a first pump source is provided to the first length of optical fiber, and light from a second pump source is provided to the second length of optical fiber. An optional reflector is disposed to reflect at least some upstream-propagating light back into the first length of optical fiber, whereby generation of long-wavelength amplified spontaneous emission (ASE) is facilitated. The long-wavelength ASE is transmitted through the optical isolator to the second length of rare earth-doped optical fiber, where broadband ASE is generated and the long-wavelength ASE is amplified.

Abstract: A novel method of forming a GaAs-based MOS structure comprises ion implantation after oxide formation, and subsequent slow heating and cooling, carried out such that essentially no interfacial defects that are detectable by high resolution transmission electron microscopy are formed. If the MOS structure is a MOS-FET then metal contacts are provided in conventional fashion. A post-metallization anneal can result in FETs that are substantially free of drain current/voltage hysteresis. MOS-FETs made according to the novel method can be produced with high yield and can have significantly increased lifetime, as compared to some prior art GaAs-based MOS-FETs.

Abstract: The quantum cascade (QC) photon source according to this invention can emit simultaneously at two distinct wavelengths, typically both in the mid-infrared. This is accomplished through provision of a semiconductor layer structure in which, at the proper bias voltage, electrons are injected into an energy level E.sub.3 and then forced to cascade through an intermediate level E.sub.2 before reaching the ground state E.sub.1 of the active region. In the process, photons of energy E.sub.3 -E.sub.2 (wavelength .lambda..sub.1) and E.sub.2 -E.sub.1 (wavelength .lambda..sub.2) are emitted. Dual wavelength photon sources according to this invention can be used in a variety of ways, e.g., to determine the absorption of a gaseous sample at wavelengths .lambda..sub.1 and .lambda..sub.2, exemplarily to determine the concentration of a particular chemical compound in the sample.

Abstract: L-band EDFA (Er-doped fiber amplifier) characteristics are improved by provision of filter means in the C-band, the filter means having a figure of merit greater than 400dB.multidot.nm. The filter means can be discrete and/or distributed filter means. In preferred embodiments, two or more full C-band blazed fiber Bragg, gratings are used.

Abstract: A novel quantum cascade (QC) laser comprises a multiplicity of identical repeat units, with each repeat unit comprising an active region and an injector region. The injector region comprises quantum wells and barriers, selected to facilitate, under appropriate bias, resonant carrier transport from a lower energy level of a given active region to an upper energy level of an adjacent downstream active region. Carrier transition from the upper energy level to a lower energy level of an active region results in emission of infrared radiation. The laser is advantageously used in, e.g., a measurement system for detection of trace compounds in air.

Abstract: A dispersive optical waveguide tap comprises a blazed refractive index grating in the core of the waveguide, coupling means, focusing means and utilization means. The grating is selected such that guided mode light of predetermined wavelength will, in the absence of the coupling means, be directed into one or more cladding modes of the waveguide. The presence of the coupling means, in optical co-operation with the waveguide, changes the guiding conditions such that the cladding modes are substantially eliminated from a portion of the waveguide that includes the cladding, whereby the grating directs the guided mode light into one or more radiation modes. The blaze angle typically is .ltoreq.15.degree.. The focusing means serve to bring the radiation mode light substantially to a focus in at least one dimension, the focal point (or line) depending on the wavelength of the light.

Abstract: A tunable semiconductor laser comprises a gain section having an MQW active region, a uniform pitch grating DFB region, and first waveguide. A composite reflector, including a second MQW region and a second waveguide, forms a cavity resonator with the DFB region. A tuning voltage applied to the composite reflector induces a quantum confined stark effect, thereby allowing the center wavelength to be altered. A pre-chirp signal applied the composite reflector reduces signal distortion in fiber optic systems.

Abstract: At least some rare earth-doped optical fiber lasers are subject to self-pulsing and/or relatively high noise. We have found that these shortcomings can be eliminated if the cavity length of the fiber laser is increased, typically by inclusion of a length .LAMBDA. of rare earth-free conventional (single mode) transmission fiber in the cavity, with .LAMBDA.>0.3L, where L is the effective cavity length of the laser.

Abstract: A thin film inductive element according to this invention comprises an elongate conductor, and spaced apart magnetic strips that substantially surround the conductor, with dielectric material between the magnetic strips and the conductor. The inductive element can have relatively high inductance and low loss, can be used in linear form, meander on spiral form, or any other desired form, is suitable for use at RF frequencies, and can be integrated with conventional circuitry. Criteria for choosing the length of the magnetic strips and the thickness of the dielectric are disclosed.

Abstract: Disclosed is a method of making a Si-based semiconductor device comprising a contact region that comprises a thin (exemplarily less than 50 nm), substantially uniform silicide layer. The silicide preferably is CoSi.sub.2 or TiSi.sub.2. The method comprises implantation of the appropriate metal ions into a Si body, the dose and the body temperature selected such that substantially complete amorphization of the implant volume results. Subsequently, the Si body is subjected to an annealing treatment that results in recrystallization of the implant volume and formation of the silicide layer. The layer extends to the surface of the body and contains essentially all of the implanted metal ions. The invention can advantageously be used in conjunction with extremely shallow junctions, such as will be of interest in short (e.g., <0.5 .mu.m) channel CMOS devices.

Abstract: The inventive method of making a poly-Si emitter transistor (PET) comprises opening an emitter window in a dielectric (typically SiO.sub.2) layer, and depositing onto the thus exposed surface and/or into the single crystal Si material that underlies the exposed surface at least one atomic species. This deposition step is following by the conventional poly-Si deposition, dopant implantation and "drive-in". In a currently preferred embodiment the novel deposition step comprises a low dose, low energy As implantation (5.times.10.sup.13 -2.times.10.sup.15 atoms/cm.sup.2, 0.1-5 keV). The novel method can result in significantly improved device characteristics, e.g., in a doubling of h.sub.FE, as compared to analogous prior art PETs.

Abstract: Disclosed are strained layer heteroepitaxial structures (e.g., GeSi/Si) that can have low threading dislocation density as well as a substantially planar surface. Furthermore, a large fraction (e.g., >90%) of the total surface are of the structure can be available for device processing. These advantageous features are achieved through utilization of novel "dislocation sinks" on or in the substrate whose height parameter h is less than or about equal to the thickness of the strained heteroepitaxial layer on the substrate. Exemplarily, h.gtoreq.h.sub.c, where h.sub.c is the critical thickness associated with misfit dislocation generation in the substrate/overlayer combination.

Abstract: Disclosed is a method that comprises selective deposition of titanium nitride TiN.sub.x on III-V compound semiconductor material. The TiN.sub.x can advantageously be used as contact metal. Exemplarily, deposition is by rapid thermal low pressure (RT-LP) MOCVD using dimethylamidotitanium with H.sub.2 carrier gas.

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: Disclosed is an optical communication system comprising at least two optical fibers of dissimilar core sizes, joined by a fusion splice. In one embodiment, the larger-core fiber is a communication fiber, and the smaller-core fiber is an erbium-doped amplifier fiber. A taper region is included adjacent the splice. The diameter of the smaller-core fiber increases within the taper region as the splice is approached along the smaller-core fiber. The taper region is substantially free of constrictions. As a consequence of the taper region, the optical losses associated with the splice are relatively low, even when there is relatively high mismatch between the mode field diameters (at a signal wavelength) in the respective fibers.

Abstract: An advantageous method of fabricating lasers adapted for use in a multichannel analog optical fiber communication system, e.g., a CATV system, is disclosed. A laser generally can be used in such a communication system only if it meets, inter alia, very stringent intermodulation specifications. To identify such lasers typically requires extensive testing. It has now been discovered that certain readily determinable parameters can be used to predict the intermodulation behavior of a given device. This discovery makes possible a simpler, and therefore less costly, process of identifying suitable lasers, resulting in a more economical method of making lasers for the stated application. The method comprises measuring the light versus current (L versus I) characteristic of a given laser, determining therefrom the first, second, and possibly higher, order derivatives of L with respect to I, and determining thereform a parameter that is a predictor of the distortion behavior of the laser.

Abstract: A method for fabricating a device, e.g., a semiconductor device, is disclosed which includes the step of reacting at least two reactive entities to form a metal-containing material on a region or regions of a processed or unprocessed substrate. Inherent in the method is the recognition that one of the reactive entities will often react with substrate material to produce previously unrecognized, and highly undesirable, results, e.g., the almost complete erosion of previously fabricated device components. Thus, and in accordance with the inventive method, any one of a variety of techniques is employed to reduce the reaction rate between the substrate material and the entity reacting with this material, while avoiding a substantial reduction in the reaction rate between the two entities.

Abstract: In methods of producing an article that comprises a multichip assembly, in which the (typically electronic but not excluding opto-electronic) chips are bonded to a substrate by means of spaced-apart localized solder regions (frequently referred to as "solder bumps"), it is frequently desirable to be able to remove a given chip from the substrate and to replace it with another chip. According to the invention, such chip removal is accomplished by a technique that comprises heating the solder bumps between the given chip and the substrate to a temperature below the solidus temperature of the solder in a manner such that a temperature gradient exists across the solder bumps, and applying to the given chip simultaneously a torque and a lifting force sufficient to cause separation of the given chip from the substrate. The technique can be carried out such that the solder bumps remaining on the substrate after chip removal are of substantially uniform height, facilitating attachment of the replacement chip.

Abstract: An assembly for coupling an optical fiber to a light emitter or detector comprises a silicon block having features that make possible easy alignment of the emitter or detector with the end of the optical fiber. The features comprise a through-aperture with sloping walls that receives and positions the end of the fiber in a predetermined location, and precisely defined conductive features that serve as alignment markers in the placement of the emitter or detector.

Abstract: The novel technique for stabilizing an electronic device, e.g., a semiconductor laser, is disclosed. The technique can advantageously be used to stabilize the bias current of such a laser at or near the lasing threshold of the device. A preferred application of thus stabilized lasers is in optical communication systems. The inventive technique comprises determination of a derivative of a variable characteristic of the device operation, e.g., the voltage across a laser, with respect to a parameter, e.g., the laser bias current. The derivative is determined by a novel method. For the particular case of laser bias stabilization, the method comprises injecting one or more nonsinusoidal ac current components into the laser, and phase-sensitivity detecting the voltage changes at the ac frequencies. The method can, in principle, be used to determine derivatives of arbitrarily high order.