Abstract: The disclosed method of making a mixed glass optical fiber exemplarily comprises providing a high-silica tube, and causing molten non-high silica glass to flow into the bore of the tube by application of a pressure differential. In order to prevent cracking, the tube desirably has an outer diameter/inner diameter ratio of at least 5, preferably about 10 or even more, and an inner diameter of at most 1 min. In a preferred embodiment, a conventional SiO.sub.2 tube is partially collapsed to an inner diameter less than 1 mm, a quantity of a non-high-silica glass is placed in a neck of the partially collapsed tube and heated such that molten glass communicates with the reduced-diameter portion of the bore and can be drawn into the reduced-diameter portion by means of a vacuum. The resulting mixed glass body is then further stretched to result in a core rod of core diameter at most 0.3 min. After overcladding the core rod with SiO.sub.2, fiber is drawn from the thus produced preform. A thus produced fiber with SiO.

Abstract: Garnet material according to the invention exhibits a substantially rectangular magnetization loop, with .vertline.H.sub.S .vertline.>.vertline.4.pi.M.sub.S .vertline.Oe, where H.sub.S is the switching magnetic field of the loop, and 4.pi.M.sub.S is the saturation magnetization. The material exhibits "latching" behavior, and can advantageously be used in magneto-optic isolators and other magneto-optic devices. For instance, the material enables manufacture of isolators that do not contain a permanent magnet. An exemplary garnet according to the invention has nominal composition Bi.sub.0.75 Eu.sub.1.5 Ho.sub.0.75 Fe.sub.4.1 Ga.sub.0.9 O.sub.12.

Abstract: The inventive optical fiber connector comprises a glass ferrule that is strengthened by etching of the outer surface of the ferrule, followed by deposition thereon of a protective layer. Exemplarily, the ferrule is a vitreous silica ferrule drawn from a preform that was made by a sol-gel process. The ferrule is etched in buffered HF, and the protective layer is electroless deposited Ni, with a thin layer of Au thereon. Significant strength increases, exceeding 200%, are obtainable, with the strength being relatively unchanged after even a severe abrasion test.

Abstract: In accordance with the invention, a new type of monolithic optical waveguide filter comprises a chain of optical couplers of different effective lengths linked by differential delays of different lengths. The transfer of the chain of couplers and delays is the sum of contributions from all possible optical paths, each contribution forming a term in a Fourier series whose sum forms the optical output. A desired frequency response is obtained by optimizing the lengths of the couplers and the delay paths so that the Fourier series best approximates the desired response. The filter is advantageously optimized so that it is insensitive to uncontrolled fabrication errors and is short in length. The wavelength dependence of practical waveguide properties is advantageously incorporated in the optimization. Consequently, the filter is highly manufacturable by mass production. Such filters have been shown to meet the requirements for separating the 1.3 and 1.551 .mu.

Abstract: We have discovered that hydrogen-related loss in silica-based single mode transmission optical fiber can be reduced or eliminated by use of a substrate tube that contains hydrogen getter sites. Exemplarily, substrate tubes according to the invention are doped with Ge or P.

Abstract: Articles according to the invention comprise an improved organic thin film transistor (TFT) that can have substantially higher source/drain current on/off ratio than conventional organic TFTs. An exemplary TFT according to the invention comprises, in addition to a p-type first organic material layer (e.g., .alpha.-6T), an n-type second organic material layer (e.g., Alq) in contact with the first material layer. TFTs according to the invention can be advantageously used in, for instance, active liquid crystal displays and electronic memories.

Abstract: In accordance with the invention, a field emission device is made by disposing emitter material on an insulating substrate, applying masking particles to the emitter material, applying an insulating film and a gate conductor film over the masking particles and emitter material and removing the particles to reveal a random distribution of apertures to the emitter material. The result is a novel and economical field emission device having numerous randomly distributed emission apertures which can be used to make low cost flat panel displays.

Abstract: Si-based photodetectors according to the invention can have high speed (e.g.,.gtoreq.1 Gb/s) and high efficiency (e.g.,>20%). The detectors include a relatively thin (e.g.,<0.5.alpha..sup.-1, where .alpha..sup.-1 is the absorption length in Si of the relevant radiation) crystalline Si layer on a dielectric (typically SiO.sub.2) layer, with appropriate contacts on the Si layer. Significantly, the surface of the Si layer is textured such that the radiation that is incident on the surface and transmitted into the Si layer has substantially random direction. The randomization of the propagation direction results in substantial trapping of the radiation in the Si layer, with attendant increased effective propagation length in the Si. Detectors according to the invention advantageously are integrated with the associated circuitry on a Si chip, typically forming an array of detectors.

Abstract: The disclosed method of making a glass body by a sol/gel process comprises electrochemically assisted release of the gel body from the mold in which the body was formed. More specifically, the method involves gelation of a sol in a mold that comprises a first conductor member, with a second conductor member also being in contact with the sol and/or gel, and causing the flow of a current between the first and second conductor members, with the first member being the cathode. In consequence of the current flow a substantially liquid lubricating layer that facilitates removal of the gel body from the melt exists at the cathode/gel interface.

Abstract: Organic thin film transistors having improved properties (e.g., on/off ratio>10.sup.5 at 20.degree. C.) are disclosed. The improved transistors comprise an organic active layer of low conductivity (<5.times.10.sup.-8 S/cm at 20.degree. C., preferably less than 10.sup.-8 or even 10.sup.-9 S/cm). A method of producing such materials is disclosed. Rapid thermal annealing was found to have beneficial results. An exemplary and preferred material is .alpha.-hexathienylene (.alpha.-6T). The improved transistors are expected to find use for, e.g., active liquid crystal displays and for memories.

Abstract: The disclosed unipolar quantum cascade (QC) laser comprises a multiplicity of essentially identical active regions, with adjacent active regions separated by a superlattice carrier injection/relaxation region. A given active region contains a single quantum well with at least two electron states. Lasing is obtained without global intersubband population inversion. Instead, there is believed to exist local population inversion in a small region of k-space near k=0, corresponding to electron energies approximately within an optical phonon energy (.about.35 meV) from the bottom of the lower subband. A novel design feature that can be used to improve the thermal characteristics of substantially any QC laser is also disclosed.

Abstract: A magnetoresistance ratio of 200% (absolute value) or more at room temperature in a field of 6T can be achieved in a layer of material of nominal composition XMnO.sub.y (X is La and at least one of Ca, Sr and Ba, y in the range 2-3.5), if, after formation of the layer, the layer is heat treated in an oxygen-rich (O.sub.2 partial pressure greater than that of air) atmosphere, typically in flowing O.sub.2. The temperature and duration of the heat treatment are in the range 300.degree.-850.degree.C. and 10 minutes-12 hours, and are selected to result in the desired ratio of 200% or more.

Abstract: A method is described for selectively modifying the refractive index of an optically transmissive body having an optical propagation axis. According to this method, polarized, actinic radiation is impinged on at least a portion of the body. In contrast to methods of the prior art, the actinic radiation is at least 60% polarized with a polarization direction parallel to a plane containing the propagation axis.

Abstract: The disclosed integrated modulator/laser (I-MOD/DFB) combination comprises an active region that extends the full length of the combination without variation of layer thickness and/or composition. Because of this constancy of the active region parameters the relevant bandgap energy is the same in the laser portion of the combination as in the modulator portion thereof. The combination typically comprises a distributed feedback structure (e.g., a "grating"). In preferred embodiments the feedback structure is selected such that .lambda..sub.e >.lambda..sub.o (typically .lambda..sub.e -.lambda..sub.o in the range 20-70 nm), where .lambda..sub.e is the laser output wavelength, and .lambda..sub.o is the wavelength of the gain peak of the laser medium. The active region can be a bulk active region but preferably is a quantum well active region. Optionally an I-MOD/DFB combination according to the invention can comprise an absorbing region, e.g.

Abstract: A novel InP-based semiconductor laser comprises an unpatterned active region that is essentially co-extensive with the substrate of the laser, an electron stopper layer, and a separate confinement heterostructure (SCH) layer that has a portion of thickness greater than the thickness of the remainder of the SCH layer. The difference in thickness serves to provide lateral guiding of the laser mode. A patterned current blocking layer is disposed on the SCH layer, with a window in the blocking layer defining the region of increased thickness of the SCH layer. The inventive laser is readily manufacturable and can have improved properties.

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 advantageous substrates for III-V nitride semiconductors such as GaN. The substrate material is of the YbFe.sub.2 O.sub.4 or InFeO.sub.3 (ZnO).sub.n structure type and has general composition RAO.sub.3 (MO).sub.n, where R is one or more of Sc, In, Y and the lanthanides (atomic number 67-71); A is one or more of Fe(III), Ga, and Al; M is one or more of Mg, Mn, Fe(II), Co, Cu, Zn and Cd; and n is an integer.gtoreq.1, typically<9. Furthermore, the substrate material is selected to have a lattice constant that provides less than .+-.5% lattice mismatch with the III-V nitride semiconductor material that is to be deposited thereon. At least some of the substrate materials (e.g., ScMgAlO.sub.4) typically can be readily and relatively cheaply produced in single crystal form, are readily clearable on the basal plane, and do essentially not interact chemically with the III-V nitride under typical deposition conditions.

Abstract: In-containing III/V semiconductor materials (e.g., InGaP) can be dry etched in BCl.sub.3 in ECR apparatus. We have discovered that addition of N.sub.2 to the BCl.sub.3 can result in substantially higher etch rate (e.g., more than 50% higher). Etching is substantially without incubation period, and the resulting surface can be very smooth (e.g., RMS roughness less than 5 nm, even less than 2.5 nm). Exemplarily, the novel etching step is used in the manufacture of a InGaP/GaAs transistor.

Abstract: A synchronous rectifier for use with a clamped-mode power converter uses in one embodiment a hybrid rectifier with a MOSFET rectifying device active in one first cyclic interval of the conduction/nonconduction sequence of the power switch and a second rectifying device embodied in one illustrative embodiment as a low voltage bipolar diode rectifying device active during an alternative interval to the first conduction/nonconduction interval. The gate drive to the MOSFET device is continuous at a constant level for substantially all of the second interval which enhances efficiency of the rectifier. The bipolar rectifier device may also be embodied as a MOSFET device. The subject rectifier may be used in both forward and flyback power converters.

Abstract: A balanced driver circuit which essentially eliminates inductive noise without a power dissipation penalty is disclosed. The balanced driver circuit is similar to a conventional balanced driver circuit however the circuit is impedance matched at both ends and has resistors connected in series with the outputs of the emitter followers in the chip. The resistors are equal in value to a termination resistor less the output impedance of the emitter followers. The impedance between the pair of signal leads, referred to as the primary and secondary leads is equal to the sum of the termination resistors. The current traversing the secondary lead has the same amplitude, but the opposite sign as the current traversing the primary lead. Thus, there is negligible current return through the common ground leads.