Abstract: Measurement of the delamination resistance of polymer coated optical fiber can provide valuable information for quality control and/or coating development, and a method of making polymer coated optical fiber that includes determination of the delamination resistance is disclosed. Also disclosed is apparatus that facilitates determination of the delamination resistance.

Abstract: Optical fiber according to the invention comprises a core, with an inner cladding surrounding the core, and an outer cladding surrounding the inner one. The fiber comprises preform-derived glass. The outer cladding comprises a first outer cladding region between the inner cladding region and a second outer cladding region. The first outer cladding region is selected to have an effective refractive index less than 1.35, and such that the optical characteristics of the optical fiber are essentially independent of the second outer cladding, and/or such that the fiber is re-coat insensitive. The first outer cladding typically comprises elongate features extending in the fiber axial direction, with a web material joining the inner cladding to the second outer cladding. The elongate features are filled with a low-index material, exemplarily air, but could of course be evacuated. Fibers according to the invention have many uses, e.g., cladding-pumped optical fiber or fiber with a long period grating.

Abstract: It has been found that a Ga-oxide-containing layer is substantially not etched in HF solution if the layer is a Ga-Gd-oxide with Gd:Ga atomic ratio of more than about 1:7.5, preferably more than 1:4 or even 1:2. This facilitates removal of a protective dielectric (typically SiO.sub.2) layer after an ohmic contact anneal, with the Ga-Gd-oxide gate oxide layer serving as etch stop and not being adversely affected by contact with the HF etchant. Gd-Ge-oxide also exhibits a composition-dependent etch rate in HCl:H.sub.2 O.

Abstract: It has been found that previously known quantum cascade (QC) lasers have a shortcoming that substantially decreases their usefulness as radiation sources for pollution monitoring and other potential applications that involve absorption measurements. Except at cryogenic temperatures, these lasers have to be driven in pulse mode and are inherently multimode. We have now established that this shortcoming can be overcome by provision of appropriate distributed feedback. Resulting lasers (QC-DFB lasers) can have single mode mid-IR output at or near room temperature, can have significant optical power, and be continuously tunable over a significant spectral region.

Abstract: An organic laser according to the invention comprises an electrically pumped source of incoherent radiation with organic active region, and further comprises a waveguide structure that receives the incoherent radiation. The core of the waveguide comprises organic material that absorbs the incoherent radiation and emits coherent radiation of longer wavelength. The laser forms a unitary structure, with the source of incoherent radiation being close to the waveguide core, exemplarily less than 10.lambda. from the core, where .lambda. is the laser wavelength. Exemplarily the laser is embodied in a planar waveguide laser, in a microdisk laser, or in a laser comprising a photonic bandgap structure.

Abstract: A dispersive optical waveguide tap comprises a blazed and chirped refractive index grating in the core of the waveguide, coupling 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 chirp serves 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: Coating phosphor (typically particles) with a thin layer of Si, Ti, Al, Zr, In or Sn-containing material can result in significantly improved lifetime of the phosphor. A preferred coating technique involves exposing the phosphor to an alkoxide (e.g., TEOS) solution having ph>7, preferably >9 or 10.

Abstract: The disclosed novel doping method makes it possible to tailor the effective activation energy of a dopant species in semiconductor material. The method involves formation of very thin layers of .delta.-doped second semiconductor material in first semiconductor material, with the second material chosen to have a bandgap energy that differs from that of the first material. Exemplarily, in a Be-doped GaAs/AlGaAs structure according to the invention the effective activation energy of the dopant was measured to be about 4 meV, and in conventionally Be-doped GaAs it was measured to be about 19 meV. The invention can be advantageously used to dope III-V and II-VI semiconductors. In some cases it may make possible effective doping of a semiconductor for which prior art techniques are not satisfactory.

Abstract: A dispersive optical waveguide tap comprises a blazed and chirped refractive index grating in the core of the waveguide, coupling 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 chirp serves 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 high quality interface between a GaAs-based semiconductor and a Ga.sub.2 O.sub.3 dielectric an be formed if the semiconductor surface is caused to have less than 1% of a monolayer impurity coverage at completion of the first monolayer of the Ga.sub.2 O.sub.3 on the surface. This is achieved, for instance, by preparing the surface of a GaAs wafer under UHV conditions in a first growth chamber, transferring the wafer through a transfer module under UHV to a second growth chamber that is also under UHV, and growing the dielectric by evaporation of Ga.sub.2 O.sub.3 from a solid source, the process carried out such that the integrated impurity exposure of the surface is at most 100 Langmuirs. Articles according to the invention have low interface state density (<10.sup.11 /cm.sup.2 .multidot.eV) and interface recombination velocity (<10.sup.4 cm/s). Semiconductor/Ga.sub.2 O.sub.3 structures according to the invention can be used advantageously in a variety of electronic or optoelectronic devices, e.g.

Abstract: The conversion efficiency of a cascaded Raman laser (CRL) can be significantly improved if it comprises one or more of the below recited design features. The CRL comprises an intracavity section between an input section and an output section. The CRL is adapted for receiving pump radiation of wavelength .lambda..sub.p, and for emitting output radiation of wavelength .lambda..sub.n >.lambda..sub.p, and each of the input section and output section comprises fiber Bragg gratings of center wavelengths .lambda..sub.1, .lambda..sub.2 . . . .lambda..sub.n, where n.gtoreq.2 and .lambda..sub.1 <.lambda..sub.2 < . . . .lambda..sub.n-1. Among the efficiency-increasing features is ordering of the fiber Bragg gratings such that in the input section and the output section the gratings of center wavelengths .lambda..sub.1 . . . .lambda..sub.n and .lambda..sub.1 . . . .lambda..sub.

Abstract: The inventive III/V semiconductor lasers comprise mode-shaping layers disposed in the upper and lower cladding regions, respectively, and having larger refractive index than the adjoining cladding material. Incorporation of the mode-shaping layers can significantly spread the mode structure of the laser, with attendant reduction of beam spreading. Preferred embodiments are Al-free III/V semiconductor lasers. Especially preferred are such lasers that do not have quaternary III/V semiconductor material between active region and substrate, for improved heat removal.

Abstract: The method of making a metallized magnetic substrate for devices including a magnetic component involves providing an unfired ceramic body. In one exemplary embodiment, the method further involves making one or more vias through the ceramic body, coating the via side walls with conductive material, forming an aperture through the ceramic body, such that an aperture edge intersects the via, and metallizing the unfired ceramic body such that a conductive pathway is formed that includes the conductive material in the via. Finally, the metallized unfired ceramic body is fired in conventional fashion, optionally followed by deposition of additional conductor material.

Abstract: Garnet material according to a particular embodiment of the invention exhibits a substantially rectangular magnetization loop, with .vertline.H.sub.S .vertline.>.vertline.4.pi.M.sub.S .vertline.Oe and .vertline.4.pi.M.sub.s .vertline.<100 G over a predetermined operating range (e.g., -40.degree. to +80.degree. C.), 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 improved latching behavior. In a further embodiment of the invention the composition of the garnet material is selected such that the material exhibits hard latching behavior (.vertline.H.sub.s .vertline.>500 Oe) at least at room temperature. Garnet materials according to the invention 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 bias magnet.

Abstract: Disclosed are non-periodic microstructured optical fibers that guide radiation by index guiding. By appropriate choice of core region and cladding region, the effective refractive index difference .DELTA. between core region and cladding can be made large, typically greater than 5% or even 10 or 20%. Such high .DELTA. results in small mode field diameter of the fundamental guided mode (typically<2.5 .mu.m), and consequently in high radiation intensity in the core region. Exemplarily, a fiber according to the invention has a solid silica core region that is surrounded by an inner cladding region and an outer cladding region. The cladding regions have capillary voids extending in the axial fiber direction, with the voids in the outer cladding region having a larger diameter than those in the inner cladding region, such that the effective refractive index of the outer cladding region is greater than that of the inner cladding region. Non-periodic microstructured fiber potentially has many uses, e.g.

Abstract: Known dispersion-compensating (DC) optical fibers typically are sensitive to small changes in fiber parameter (e.g., fiber diameter and/or core refractive index), and thus are difficult to manufacture. The disclosed DC fibers are relatively insensitive to small departures from the nominal fiber parameters, and are therefore more manufacturable. Exemplarily, the nominal refractive index profile of a DC fiber is selected such that the fiber supports LP.sub.01 and LP.sub.02 (and typically one or more further higher order modes), and the dispersion is substantially all in LP.sub.02. The total dispersion is more negative than -200 ps/nm.km over a relatively wide wavelength range. The nominal refractive index profile typically comprises a refractive index "ring" that is spaced from the fiber core.

Abstract: Disclosed is an improved WDM optical fiber communication system that comprises, in addition to dispersion compensating fiber, dispersion slope compensating fiber (DSCF) selected to provide substantially all channels of the WDM system with nominally zero total chromatic dispersion. Exemplary refractive index profiles for DSCF are disclosed. Such fibers exemplarily can be produced by MCVD.

Abstract: Magnetoresistive elements according to this invention comprise magnetically soft material in close proximity to the magnetoresistive material, exemplarily a perovskite manganite. The combination results in magnetic field "amplification", with large resistance changes attainable at relatively low applied fields. The invention exemplarily is embodied in magnetic sensors, e.g., magnetoresistive read/write heads.

Abstract: Dielectric material of nominal composition (Al.sub.2 O.sub.3).sub.x (Ta.sub.2 O.sub.5).sub.1-x, with 0.03<x<0.15, unexpectedly can exhibit a relatively small temperature variation of the dielectric constant (e.g., <50 ppm/.degree.C. at 1 MHz and 20.degree. C.) and a relatively large value of the dielectric constant. The dielectric according to the invention advantageously is used in capacitive elements, e.g., in MOS capacitors in integrated circuits for personal communication devices.

Abstract: A novel and advantageous cathode structure for a field emission display apparatus is disclosed. A given pixel comprises a multiplicity of spaced apart emitter bodies on a support. A given emitter body comprises diamond and/or rare earth boride, and has a relatively sharp geometrical feature that facilitates electron emission from the emitter body. By way of example, the emitter body comprises diamond bodies grown on a support, or it comprises a pre-existing diamond particle that was placed on the support. Such emitter bodies generally can be provided easily and at low cost, and typically have naturally occurring sharp geometrical features such as points and edges. We have also discovered that appropriately grown rare earth boride films of thickness 30 nm or less may substantially improve electron emission from emitter bodies, and some preferred embodiments of the invention comprise a cathode structure that comprises a thin layer of, e.g., LaB.sub.6 on the emitter bodies.