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 disclosed method of making microstructured optical fiber comprises providing a mold, with a multiplicity of elongate elements extending into the mold and being maintained in a predetermined spatial arrangement with respect to the mold. Silica-containing sol is introduced into the mold and is caused to or permitted to gel, such that a gel body results. After removing the elongate elements from the gel body and removing the gel body from the mold, the gel body is dried, sintered and purified, and the microstructured fiber is drawn from the sintered body.

Abstract: Our method of making high bandwidth silica-based multimode optical fiber comprises provision of a non-circular preform, and drawing fiber of chiral structure from the preform. The non-circular preform can be made by maintaining the inside of the tubular preform under reduced pressure during at least part of the collapse, resulting in a non-circular core and cladding. It can also be made by removal (e.g., by grinding or plasma etching) of appropriate portions of the preform, resulting in a circular core and non-circular cladding. In the latter case, fiber is drawn at a relatively high temperature such that, due to surface tension, the cladding assumes substantially circular shape and the core assumes a non-circular shape. The chiral structure is imposed on the fiber in any appropriate way, e.g., by twisting during fiber drawing the fiber alternately in clockwise and couterclockwise sense relative to the preform.

Abstract: Disclosed is an article that comprises an optical waveguide mode converter for converting light of wavelength &lgr; in a few-moded optical waveguide from a given guided mode (e.g., LP01,f) to another guided mode (e.g., LP02,b). The converter comprises a tilted refractive index grating in the core of the waveguide. Appropriate choice of the refractive index profile n(r), photosensitivity p(r) and tilt angle &thgr; makes possible substantial nulling of the coupling between some guided modes (e.g., LP01,f to LP01,b and LP01,f to LP11,b), and substantial maximization of the coupling between other guided modes (e.g., LP01,f to LP02,b). Mode converters according to the invention can be advantageously used in optical fiber communication systems in add/drop multiplexers.

Abstract: A display apparatus according to our invention comprises a multiplicity of nominally identical smart pixels, a given pixel comprising an organic light emitting diode and an organic or inorganic (e.g., amorphous or polycrystalline Si) pixel FET. The display also comprises drive/compensation circuitry adapted for mitigating or eliminating non-idealities associated with the organic components. Among the non-idealities are variations in mobility and/or threshold voltage of the pixel FET from transistor to transistor, change in mobility and/or threshold voltage with time in a given pixel FET, change over time of the LED characteristics, capacitive signal feed-through through the gate insulator of the pixel FETs by short rise/fall time pulses, poor on-off ratio of the pixel FET, and charge leakage through the gate dielectric. Exemplary drive/compensation circuitry is disclosed.

Abstract: Some mechanical, electrical, and thermal properties of high Tc superconductors such as (Ba, Y) cuprates can be substantially improved by the dispersal of an appropriate metal in the superconductive body. For instance, mixing Ag particles with superconductive powder of nominal composition Ba2YCu3O7 and processing the mixture in the conventional manner can produce superconductive bodies having Tc of about 93 K and substantially greater fracture strength and normal state electrical and thermal conductivity than otherwise identical bodies that do not contain Ag particles.

Abstract: Disclosed are a method of making GaAs-based enhancement-type MOS-FETs, and articles (e.g., GaAs-based ICs) that comprise such a MOS-FET. The MOS-FETs are planar devices, without etched recess or epitaxial re-growth, with gate oxide that is primarily Ga2O3, and with low midgap interface state density (e.g., at most 1×1011 cm−2 eV−1 at 20° C.). The method involves ion implantation, implant activation in an As-containing atmosphere, surface reconstruction, and in situ deposition of the gate oxide. In preferred embodiments, no processing step subsequent to gate oxide formation is carried out above 300° C. in air, or above about 700° C. in UHV. The method makes possible fabrication of planar enhancement-type MOS-FETs having excellent characteristics, and also makes possible fabrication of complementary MOS-FETs, as well as ICs comprising MOS-FETs and MES-FETs.

Abstract: Waveguides according to this invention have a chalcogenide glass core that comprises Se and one or both of As and Ge, and further comprises one or more dopant elements selected from the elements that cause a change in optical energy gap Eg of the glass core. The amount of dopant is selected such that Eg is equal to or less than a 2-photon energy 2h&ngr;, where h is Planck's constant and &ngr;=c/&lgr;, where c is the speed of light in vacuum and &lgr; is an operating wavelength. The dopant elements furthermore are selected such that the chalcogenide glass core has a nonlinear refractive index n2 greater than 200n2 (SiO2), where n2 (SiO2) is the nonlinear index of silica at &lgr;. Typically, &lgr; is about 1.55 &mgr;m. Exemplary, the dopant elements are selected from Sb, Bi, Sn, Pb, In, Tl, Cu, Ag and S. Currently preferred dopants are Te, Sb, Tl, Cu and Ag.

Abstract: In an optical fiber communication system a pulse reshaper can transform a distorted input light pulse into a reshaped output light pulse. The disclosed pulse reshaper is an all-optical pulse reshaper that comprises an optical waveguide having an effective length, the waveguide connecting the input and the output and comprising optical non-linear material, with a periodic variation of an effective refractive index of the optical waveguide. The optically non-linear material and the periodic variation are selected such that the reshaped output light pulse is a substantially transform-limited output light pulse.

Abstract: Many potential applications of CVD diamond film require the ability to remove a predetermined quantity of material from a surface of the film. We have discovered that such removal is advantageously accomplished by contacting the surface of the polycrystalline diamond film with a metal selected from Fe, Ni, Mn and Ti (preferably Fe and Mn, most preferably Mn), and maintaining the metal-contacted diamond film at a temperature in the range 600-1100° C. (preferably 800-1000° C.) without relative lateral motion between the film and the metal, for an effective time for removal of the quantity of material, exemplarily less than 100 hours. The metal can be in any appropriate form, e.g., a deposited layer, (including a patterned layer), a foil, or powder. We have also discovered that the local thermal conductivity of CVD diamond films typically increases with distance from the lower surface of an as-grown film.

Abstract: A multi-wavelength Raman radiation source is disclosed. The source receives pump radiation at a given wavelength, e.g., 1100 nm, and has outputs at two or more longer wavelengths, e.g., 1450 nm and 1480 nm. The cascaded Raman resonator comprises, for each desired output wavelength, an optical cavity formed by a high reflectivity grating and a low reflectivity grating, with both having the same center wavelength, equal to the desired output wavelength. Multi-wavelength Raman radiation sources have a variety of applications, e.g., they can advantageously be used in a remotely pumped optical fiber communication system.

Abstract: Optical pulse compression is of importance in very high bit rate optical fiber communication systems. We are disclosing an adiabatic optical pulse compressor that can achieve substantial compression by means of a relatively short (e.g., about 100 cm) chirped periodic structure, exemplarily an apodized and chirped fiber Bragg grating. The input pulse to the periodic structure typically are not soliton pulses, but the passage through the periodic structure results in transformation of the pulses into substantially transform-limited soliton pulses that are available (typically after appropriate modification) for transmission through conventional optical fiber towards utilization means. The input pulses can be generated by any applicable method, e.g., by combining the cw outputs of two lasers that differ with regard to the frequency of their output.

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 dispersion compensating chirped optical fiber Bragg grating according to our invention is formed in polarization maintaining (PM) fiber having birefringence of at least 10.sup.-6, preferably 10.sup.-5 or more. Use of the PM fiber makes possible substantial cancellation of the polarization mode dispersion that typically is unavoidably present in chirped Bragg gratings for dispersion compensation.

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: Bubble-free core glass can be deposited at relatively high rate (e.g., >0.3 gm SiO.sub.2 /minute, preferably 0.6 gm SiO.sub.2 /minute or more) by MCVD if the deposition conditions are appropriately selected. For instance, a relatively high torch traverse speed, a relatively low sintering temperature, and/or relatively low gas flow rates can facilitate high rate deposition of bubble-free glass. By way of example, conditions are disclosed that yielded essentially bubble-free core glass (.DELTA.=0.35%) at a rate of 1 gm SiO.sub.2 /minute.

Abstract: A bidirectional waveguide tap is disclosed. The tap comprises an appropriately blazed grating in the waveguide, with coupling means in optical co-operation with the waveguide causing transfer of light from a guided mode in the waveguide to a radiation mode. Radiation mode light of a given wavelength and propagation direction is brought to a focus on a predetermined region of utilization means, e.g., an array of photosensors.

Abstract: The disclosed superconducting multipole RF filter comprises a multiplicity of coupled circular disk resonators designed for operation in the TM 010 mode. The disk resonators are arranged in a co-axial stack, with a circular metal spacer sandwiched between any two neighboring disk resonators. Each metal spacer has a central through-aperture, with a conductive member disposed in the through-aperture and electrically connecting the two neighboring disk resonators that are sandwiching a given metal spacer. A disk resonator comprises two circular members, each circular member comprising a circular dielectric substrate, exemplarily a LaAlO.sub.3 wafer. Superconducting layers (typically YBCO) are disposed on each major surface of the substrate. The two members are joined together such that conductive layers (typically gold) electrically connect the two outside superconducting layers. The disclosed RF filter has good power handling capability, is compact, has good heat removal and relatively simple tuning.