bluuebunny/crossref_metadata_2025 huggingface dataset:
Localized measurements during intense relativistic electron beam interaction with a cool theta-pinch plasma
Authors: Dove W. F. , Gerber K. A. , Hammer D. A.
Published: February 2003

A 1-MeV 40–80-kA 60-nsec 40-cm2 electron beam was injected into a 3-eV 2×1015-cm−3-density plasma. Plasma density and temperature within the beam channel were measured by Thomson scattering, and local time-dependent magnetic probe measurements were made across a plasma diameter. The observed plasma heating rate was an order of magnitude larger than can be explained on the basis of classical collisional processes.
Photodichroic materials as adaptive spatial filters in real-time optical spectral analysis
Authors: Collins W. C. , Marrone M. J.
Published: February 2003

Adaptive spatial filters based on the photodichroic property of anisotropic color centers in alkali halide crystals have been constructed for use in real-time optical spectral analysis. Operating as change detectors in continuous spectrum surveillance, the photodichroic filter essentially sensitizes the monitoring system to detect only ’’new’’ signals. Long-term background signals have been attenuated by factors as high as 30 000.
Enhancement of second-harmonic generation in zinc selenide by crystal defects
Authors: Hocker Lon O. , Dewey C. Fobes
Published: February 2003

Tunable radiation in the 0.43–0.52-μm spectral region was produced by frequency doubling a tunable dye laser in ZnSe. At wavelengths shorter than the band gap of ZnSe (λ<0.46 μm), second-harmonic power was limited by crystal absorption, whereas for longer wavelengths the second-harmonic power was as much as 1500 times larger than that predicted for a single-domain crystal. This enhancement is predicted by a simple theory which accounts for the favorable nonlinear optical effects of rotational twins and crystal defects.
Population inversions with respect to the ground level of an ion or atom by the rapid cooling of a plasma
Authors: Green J. M. , Silfvast W. T.
Published: February 2003

General conditions are derived for achieving an inversion with respect to the ground level of an atom or ion by rapid cooling of a plasma. As an example, gain on the He+ 304-Å resonance transition in a laser-produced helium plasma is considered in detail.
Determination of optical fiber refractive index profiles by a near-field scanning technique
Authors: Sladen F. M. E. , Payne D. N. , Adams M. J.
Published: February 2003

A simple and rapid method is described for determining the refractive index profile of an optical fiber by observation of the near-field intensity distribution. It is shown that in many cases the presence of tunnelling leaky modes is unavoidable and that these cause a length-dependent error in the measurement. A correction factor is developed which may be applied to the measured intensity profile once the fiber length, core diameter, and numerical aperture are known. Examples are given of measurements made on both step and graded-index fibers.
Two-photon spectroscopy using picosecond light continua
Authors: Penzkofer A. , Falkenstein W. , Kaiser W.
Published: February 2003

Two-photon absorption is measured using two picosecond pulses: a monochromatic pulse and a pulse with broad frequency spectrum. Single pulses of high peak intensity were applied to crystalline samples without damage. Introducing a time delay of several picoseconds between the two pulses, possible two-step processes can be elucidated. As an example, two-photon absorption in CdS was investigated over an energy range from 2.4 to 3.5 eV.
Radiation-induced effects in GaAs thin-film optical (10.6 μm) waveguides
Authors: Share S. , Epstein A. S. , Monse T. , Chang W. S. C. , Chang M. S.
Published: February 2003

Two types of GaAs thin-film optical waveguide structures operating at 10.6 μm were examined before and after exposure to neutron and γ irradiation. The attenuation rate of the GaAs/n+-GaAs structure was particularly sensitive to neutron irradiation of 1013 cm−2 and exhibited postirradiation annealing at 150 °C. This is in contrast to the relative neutron irradiation insensitivity of a GaAs/GaAs1−xPx/n+-GaAs structure. The effect of γ radiation is less pronounced for both structures. The radiation-induced changes are discussed in terms of free-carrier absorption, index of refraction, scattering centers, and absorption by complexes.
The physical state of implanted tungsten in copper
Authors: Cullis A. G. , Poate J. M. , Borders J. A.
Published: February 2003

The physical state of W implanted in Cu has been studied by 4He+ ion channeling and transmission electron microscopy. At implant concentrations ≲1 at.%, W is in solid solution but may form elemental bcc precipitates on annealing to ≳450 °C. For implant concentrations of ∼10 at.%, a disordered layer of Cu and W is formed with the W occupying no regular lattice sites; on annealing W precipitates are formed with dimensions of a few hundred angstroms.
Distributive Tee couplers
Authors: McMahon D. H. , Gravel R. L.
Published: February 2003

A distributive coupling technique is described in which some portion of the light signal is coupled into and out of all fibers of a bundle in parallel. Tees employing distributive coupling require no mixer rods, dissipate no power via packing fraction losses, and hence exhibit a throughout coupling loss which asymptotically approaches zero as the power coupled to the side arm decreases.
Solid phase epitaxial studies using vacuum deposition on heated silicon substrates
Authors: Davey J. E. , Christou A. , Day H. M.
Published: February 2003

Thin epitaxial films of silicon have been grown at 600 °C on (111) silicon surfaces by vacuum deposition. The silicon deposition and growth was performed subsequent to a hot deposition (125 °C) of 300-Å gold film on the substrate.
The strip acoustic surface waveguide: Comparison between measurement and theory
Authors: Yen K. H. , Oliner A. A.
Published: February 2003

New measurements now permit a comparison to be made with various theories for the propagation characteristics of the strip acoustic surface waveguide in order to determine which theory is the most accurate. These new measurements are presented in the framework of all previously available measurements and theories for the strip waveguide. The ways in which the theories differ are indicated, and recommendations are made as to which theory should be used in which parameter range.
Optical second harmonic generation in periodic multilayer GaAs-Al0.3Ga0.7As structures
Authors: van der Ziel J. P. , Ilegems M.
Published: February 2003

Using a tunable laser operating near 2 μm we have observed second harmonic generation in a GaAs-Al0.3Ga0.7As multilayer. Phase matching of the backward-traveling harmonic wave is observed and corresponds to k2=2(k1−κ) <0 where k1<κ/2 and κ is the wave vector of the periodic structure.
Foil scattering in a reflex triode intense ion beam accelerator
Authors: Antonsen Thomas M. , Ott Edward
Published: February 2003

The electron and ion current densities flowing in a reflex triode are calculated. Our analysis self-consistently determines the electron distribution function resulting from electron collisions with a foil anode and the potential in the triode. The electron and ion currents diverge for a sufficiently thin anode.
Temperature dependence of photoluminescence from Be-implanted GaAs
Authors: Chatterjee Pallab K. , McLevige W. V. , Vaidyanathan K. V. , Streetman B. G.
Published: February 2003

Photoluminescence data from Be-implanted GaAs are presented for the temperature range 3–120 °K. A luminescence band at 1.493 eV is associated with recombination from the conduction band to neutral Be acceptors, based on the temperature dependence. The binding energy of Be acceptors in GaAs is estimated to be 28.4 meV from the temperature dependence of the peak energy of this band.
Mode-locked unstable-cavity HF laser
Authors: Simonis George J.
Published: February 2003

We report the successful passive mode locking of a single-line unstable-cavity HF laser. Saturable absorption for the passive mode-locking process was provided by low-pressure HF gas in a separate cell internal to the optical cavity. Experimental results are consistent with mode-locking theory and behavior in other systems.
Generation of 12-μm radiation by difference-frequency mixing of CO2 laser radiation in GaAs
Authors: Lee N. , Aggarwal R. L. , Lax B.
Published: February 2003

Step-tunable infrared radiation in the 12-μm region can be generated by two-step noncollinear difference-frequency mixing of CO2 laser beams in GaAs at liquid-helium temperature. With 3-MW peak input power from each of the two CO2 lasers operating at 9.6 and 10.6 μm, peak output power of ∼4 kW was obtained at 11.8 μm.
Disorder produced by high-dose implantation in Si
Authors: Csepregi L. , Kennedy E. F. , Lau S. S. , Mayer J. W. , Sigmon T. W.
Published: February 2003

Channeling measurements with MeV 4He ions were used to investigate the disorder distributions produced in 〈111〉 and 〈100〉 Si samples by implantation at substrate temperatures from −180 to 300 °C. The results indicate that for high implantation doses (1015–1016 ions/cm2) a deep stable disordered region is present in both orientations for the samples implanted at temperatures above room temperature but is absent for room-temperature and lower implants. The colors that have been observed on the surface of samples with similar implants are found to be correlated with the thickness of a thin crystalline layer at the surface.
Room-temperature cw operation of an efficient miniaturized Nd:YAG laser end-pumped by a superluminescent diode
Authors: Washio K. , Iwamoto K. , Inoue K. , Hino I. , Matsumoto S. , Saito F.
Published: February 2003

A miniaturized Nd:YAG laser is described, in which a 3-mm-diam×5.4-mm-long laser rod is end-pumped by a single AlxGa1−xAs superluminescent diode (SLD) having 20-μm×1.4-nm stripe geometry. A 4.5-mW laser power was obtained at room temperature in a 1-ms pulse operation. Emitted power from the SLD was 50 mW with 1.7% external power efficiency. When continuously pumped, a 1.5-mW laser power was obtained at room temperature.
A new method for the efficient interconnection of high-index planar waveguides to low-index transitional waveguides
Authors: Sopori B. L. , Chang W. S. C. , Phillips C. M.
Published: February 2003

An efficient method for interconnecting two planar optical waveguides on the same substrate is described. Efficiencies better than 80% have been obtained in coupling from high-index GaAs and LiNbO3 waveguides to low-index AZ 1350 and polyurethane waveguides. This method is important for the coupling of high-index waveguides to optical fibers.
Surface-produced parallel alignment of nematic liquid crystals by polynuclear dicarboxylatochromium complexes
Authors: Matsumoto Shoichi , Nakagawa Daisuke , Kaneko Nagao , Mizunoya Kiyoshi
Published: February 2003

Dicarboxylatochromium complexes have produced very stable parallel molecular alignment of nematic liquid crystals, in contrast with a recently described perpendicular orientation by monocarboxylatochromium complexes. The complexes used are μ-dicarboxylato-bis (tetranitro-μ-hydroxodichromium (III))’s which bond chemically to substrate surfaces.
Study of the equivalent electron drift field characteristics in LiNbO3 by phase holography
Authors: Kim Dae M. , Shah Rajiv R. , Rabson T. A. , Tittel F. K.
Published: February 2003

An analysis of the diffraction efficiency of photorefractive holograms in ferroelectric crystals is shown to provide a novel technique for determining the nature and magnitude of the equivalent electron drift field. For a Fe-doped lithium niobate crystal (0.05% per mole) we find that the total field consists of an intensity-independent internal field of 8.5 kV/cm and a photogenerated field given by the conversion factor 1.4 ×106 V cm/W.
Ultraviolet laser action in He-Ag and Ne-Ag mixtures
Authors: McNeil J. R. , Johnson W. L. , Collins G. J. , Persson K. B.
Published: February 2003

We report eight new laser transitions which span the wavelength region from 220 to 400 nm. Six of the ultraviolet transitions are observed in Ne-Ag mixtures and two are observed in He-Ag mixtures. The 227.8- and 224.3-nm laser transitions of Ag II, 4d3D2-5p3P01 and 4d1S0-5p1P01 respectively, are the shortest-wavelength cw laser transitions reported in the literature to date. Output characteristics of the ultraviolet laser transitions as a function of buffer gas pressure and discharge current are presented. The strongest laser transition 4d85s2 1G4→4d95p3F03, at 318.1 nm, provides single-line peak output power of 350 mW. The output power does not appear to saturate at the limit of our input current, 50 A.
Copper oxide as the metal source in a discharge-heated copper vapor laser
Authors: Anderson R. S. , Bricks B. G. , Karras T. W.
Published: February 2003

Copper oxide has been used as the lasant in a copper vapor laser producing up to 2 W average power at 12 kHz repetition rate. Operation could be sustained for several hours at over 1 W using radiative cooling to maintain the thermal balance.
Energy levels of nitrogen isoelectronic impurities in AlxGa1−xAs
Authors: Gonda Shun-ichi , Makita Yunosuke , Mukai Seiji , Tsurushima Toshio , Tanoue Hisao
Published: February 2003

Energy levels of nitrogen isoelectronic impurities in AlxGa1−xAs doped with 1018 N cm−3 by ion implantation were determined from the photoluminescence measurements at 2 °K. Three bound states associated with nitrogen impurities are situated below the X1 conduction-band minima and the binding energies of the excitons bound to the states decrease with increasing composition ratio x.
Laser plasma focus produced in a ring target
Authors: Saint-Hilaire G. , Szili Z.
Published: February 2003

A new geometry for generating a laser-produced plasma is presented. A toroidal mirror is used to focus a CO2 laser beam on the inside wall of a copper ring target. The plasma produced converges at the center of the ring where an axial plasma focus is formed. High-speed photography shows details of a plasma generated at a distance from the target surface. This new geometry could have important applications in the field of x-ray lasers.
Permanently stored echoes in powdered materials
Authors: Kupca S. , Maartense I. , Kunkel H. P. , Searle C. W.
Published: February 2003

A permanent echo following a two-pulse write sequence which has been observed from piezoelectric powders is also observed in other types of powders. It is shown that a simple model in which the echo originates from the mechanical alignment of particles is consistent with all known echo properties.
Temperature and wavelength dependence of the photoenhancement of nonlinear surface-wave convolution
Authors: Lim T. C. , Kraut E. A. , Morin F. J. , Oliver J. R.
Published: February 2003

Temperature-dependent structure in the photoenhancement of nonlinear surface-acoustic-wave convolution on ZnO is reported. Measurements of the temperature dependence of surface-wave convolution without light, thermally stimulated conductivity, and photoconductivity suggest that the photoenhancement effect in ZnO is sensitive to trapping and surface preparation. A possible model for the dependence of photoenhancement on photon wavelength is proposed.
Multishock compression
Authors: Armstrong B. , Ahlborn B.
Published: February 2003

We have obtained multiple-shock compression of a gas by the application of a tailored power pulse. Density increases well beyond the compression of a single strong shock were reached. No second shock could be launched if the second power step exceeded the first one by a factor of 10.
Synthesis and stability of Nb3Ge made by electron-beam codeposition
Authors: Hallak A. B. , Hammond R. H. , Geballe T. H.
Published: February 2003

Niobium-germanium (Nb-Ge) films which remain superconducting up to about 22.5 °K have been prepared using high-rate (33–133 Å/sec) electron-beam codeposition. The presence of oxygen in the deposition chamber is necessary for stabilizing the high-Tc A15 phase. Analysis of Nb-Ge films shows that oxygen extends, with some temperature dependence, the Ge-rich range of the A15 phase with an accompanying decrease in the lattice constant. An amorphous component in the films is first detected below a deposition temperature of 800 °C. It increases rapidly at lower temperatures and becomes dominant at about 600 °C. The A15 phase diagram was determined for the first time for temperatures below 875 °C.
In-depth heating by an intense relativistic electron beam
Authors: Perry F. C. , Widner M. M.
Published: February 2003

The dynamic response of a planar target irradiated by a tightly pinched intense relativistic electron beam is found to be very sensitive to in-depth heating by the beam due to x-ray deposition and to diode voltage fluctuations. We find that voltage fluctuations are primarily responsible for the observed wave structure preceding the large-amplitude shock wave while x-ray deposition affects the response to a lesser extent. The implications of these results for electron-beam fusion target and accelerator designs are noted.
X-ray replication of masks using the synchrotron radiation produced by the ACO storage ring
Authors: Fay Bernard , Trotel Jacques , Petroff Yves , Pinchaux Robert , Thiry Pierre
Published: February 2003

Synchrotron radiation emitted by the 540-MeV storage ring of the University of Orsay was used to replicate masks with submicron features on PMM resist. Exposure times were of the order of a few minutes. The masks used were gold (1500–3500 Å thick) on 2.5-μm Mylar. Calculations show that the wavelengths principally involved in making the exposure are at 540 MeV centered around 14 Å and at 400 MeV around 50 Å.
Thermomechanical heat generation in copper and a Nb-Ti superconducting composite
Authors: Easton D. S. , Kroeger D. M. , Moazed A.
Published: February 2003

Heat generation via tensile stresses in both pure copper and a superconducting Nb-Ti composite was studied at 300 and 4.2 K. Linear thermoelastic behavior was found at room temperature but not at 4.2 K. At 4.2 K, stress levels on the order of 88 MPa and 0.1% strain produced energy losses of 1 to 2×105 J/m3. When stress cycled under adiabatic conditions, the composite showed a temperature increase with each cycle as a result of nonlinear (hysteretic) stress/strain behavior.
Use of a graphical representation of the Hall effect for the quality control of epitaxially grown PbTe layers
Authors: Lopez-Otero A.
Published: February 2003

A simple procedure based on a graphical representation of the Hall effect is used to quickly identify the electrical properties of PbTe epitaxial layers. This procedure helps to avoid possible misinterpretations of isolated Hall-effect measurements.
Surface wave memory correlator with optical write-in
Authors: Takada S. , Hoh K. , Hayakawa H. , Tokumaru Y.
Published: February 2003

A surface wave memory device in which a light pulse emitted from a GaAs laser diode is used to store surface wave signals is described. The storage of 87-MHz surface wave signals in surface states in silicon is obtained by using a light pulse with a duration of 0.5 nsec. Pulse compression experiments are also demonstrated by storing linear FM chirp signals with this method.
High-frequency shear instability in nematic liquid crystals
Authors: Scudieri F.
Published: February 2003

The behavior of MBBA nematic liquid cells under an applied shear is studied at high frequency. It is shown that hydrodynamic roll instabilities can be excited. The rolls develop in a direction perpendicular to the shear motion of the cell plates. Interference between two roll patterns can be obtained with nonparallel glass plates of the cell.
Multiple-wire array load for high-power pulsed generators
Authors: Stallings C. , Nielsen K. , Schneider R.
Published: February 2003

Exploding wire loads have been used for several years to generate a hot dense plasma. For a generator with a rise time of tens of nsec and an impedance of 1 Ω or less, the inductance of the wire load and the tendency of current to flow outside the wire limits the energy that can be transferred to the wire. An array of several wires has now been used to lower the inductance and improve the energy transfer.
Long-time storage of surface-acoustic-wave signals in zinc-oxide–on–silicon structure
Authors: Hoh K. , Takada S. , Hayakawa H.
Published: February 2003

A surface-acoustic-wave memory device with very long storage time is demonstrated using a ZnO/SiO2/Si monolithic convolver. Stored signals in the form of the charge grating in the SiO2/Si interface is duplicated in the second storage centers in the ZnO by injecting electrons from the metal electrode. A storage time of more than 10 h has been obtained.
Model of magnetic compression of relativistic electron beams
Authors: Young T. S. T. , Spence P.
Published: February 2003

A theoretical model for the magnetic compression of relativistic electron beams is described. Calculations of the beam fraction transmitted through the magnetic mirror are in agreement with several experiments covering a broad parameter range.
Observation and analysis of very rapid optical degradation of GaAs/GaAlAs DH laser material
Authors: Monemar B. , Woolhouse G. R.
Published: February 2003

We have observed and analyzed a very rapid form of degradation caused by the optical excitation of GaAs/GaAlAs DH laser material. It consists of the very rapid (50 μ/sec) development of 〈110〉-oriented lines originating at a mechanically damaged area and restricted to the optically excited area. TEM analysis shows that the degraded region consists of an orthogonal array of misfit dislocations of 60° type at the interface between the p-ternary layer and the active region. It seems likely that the dislocations are generated by glide as a result of the lattice misfit stress between GaAs and GaAlAs and that their energy of motion is supplied through nonradiative recombination events.
MIS silicon solar cells
Authors: Fabre E.
Published: February 2003

A careful analysis of I-V curves under illumination makes it possible to characterize the different parameters leading to an increase of the open-circuit voltage Voc of MIS silicon solar cells with respect to classical Schottky barrier solar cells. The separate influence of the effective barrier height and of the quality factor of the diode upon Voc is emphasized. An over-all conversion efficiency over 8% under AM1 illumination is reported for a large-area (2.5 cm2) MIS cell.
Pressure study of the external quantum efficiency of N-doped GaAs1−xPx light-emitting diodes
Authors: Nelson R. J. , Holonyak N. , Coleman J. J. , Lazarus D. , Keune D. L. , Herzog A. H. , Groves W. O. , Kleiman George G.
Published: February 2003

The change in electroluminescence intensity as a function of hydrostatic pressure is measured for N-doped GaAs1−xPx diodes in the composition regions x∼0.48 and ∼0.65. A large decrease with pressure is observed for the short-range N transition (x∼0.48) reflecting the effect of the nearby Γ conduction band edge. The longer-range NX transition (x∼0.65) is observed to be much less sensitive to pressure, which agrees with the expected smaller effect of Γ on NX at this composition. Based on N and NX oscillator strengths provided by a recent theoretical model for GaAs1−xPx : N, calculations of the relative change in external quantum efficiency are found to fit the data well.
Observation of inverted population levels in the FM-1 spherator
Authors: Suckewer S. , Hawryluk R. J. , Okabayashi M. , Schmidt J. A.
Published: February 2003

Inversions in the population of excited levels in hydrogen and He II were observed in the FM-1 spherator. The inversion increases strongly as the ratio of the decay time of the electron temperature to the decay time of the electron density was decreased. Time-dependent numerical calculations of the populations were in good agreement with the experimental measurements. More general calculations for high-Z hydrogenlike ions are discussed.
Meniscus lines as nucleation sites for the active layer of a double-heterostructure laser grown by LPE
Authors: Small M. B. , Blum J. M. , Potemski R. M.
Published: February 2003

It is demonstrated that at relatively low supersaturation the active layer of a DH laser nucleates on the meniscus lines on a surface which is not strongly terraced. It is further demonstrated that there is a finite angle of contact between the nucleating solid and the lower layer which results in the active layer growing as islands about each nucleation site. As a result, there is a minimum thickness of the active layer which is continuous. These observations are a possible explanation for the phenomenon which has been described as ’’rake lines’’ in DH laser structures and explains in general the difficulties encountered in trying to fabricate lasers with very thin active layers.
Barrier-controlled low-threshold p
n
p
n GaAs heterostructure laser
Authors: Lee C. P. , Gover A. , Margalit S. , Samid I. , Yariv A.
Published: February 2003

Incorporation of GaAlAs potential barrier layers into the active regions of a heterostructure pnpn injection laser makes it possible to design Shockley diode lasers with low (3 kA/cm2) room-temperature threshold currents.
Epitaxial growth of high T
c superconducting Nb3Ge on Nb3Ir
Authors: Dayem A. H. , Geballe T. H. , Zubeck R. B. , Hallak A. B. , Hull G. W.
Published: February 2003

Nb3Ir polycrystalline films with the A15 structure deposited on sapphire were used as substrates for the epitaxial growth of Nb3Ge because of the favorable lattice parameter match. The experimental results clearly show that epitaxial growth indeed occurs and helps to extend the range of homogeneity of the A15 phase up to 26.3 at.% Ge as compared with the thermodynamic equilibrium boundary at 19 at.% Ge. Furthermore, epitaxy results in a considerable rise in the superconducting transition temperature for Ge-rich samples together with a reduction in the transition width.
Laser action in Al II and He I in a slot cathode discharge
Authors: Schuebel Wolfgang K.
Published: February 2003

Laser excitation of metal vapors and gases in four types of hollow cathodes employing transverse electrical discharges is discussed. A water-cooled slot cathode is demonstrated to provide two distinct laser excitation modes. cw laser action at 7471, 7042, and 6920 Å from Al II, which is cathodically sputtered by Ne/H2 mixtures and excited in charge-transfer collisions, is reported. Pulsed laser action at 7065.21 and 7065.17 Å from He I, which is excited in direct electron impact collisions in the presence of H2 is reported. Laser performance data relating to gas pressures, currents, pulse widths, and gains are presented. The importance of H2 admixtures to the laser species is discussed.
Tunneling involving defects in LPE In1−xGaxP1−zAsz(x∼0.12, z∼0.26) double-heterojunction lasers
Authors: Rezek E. A. , Ludowise M. J. , Shichijo H. , Wright P. D. , Holonyak N. , Korb H. W.
Published: February 2003

Defect-assisted (’’two-step’’) tunneling is observed in the I-V and dI/dV characteristics of LPE In1−xGaxP1−zAsz double-heterojunction laser diodes (Jth∼4.7×102 A/cm2, λ∼1.05 μm, 77 °K). The change in conductance (’’turn-off’’) at zero bias due to resonant-elastic tunneling, and a related change at 40–60 mV involving acceptor states, are compared with similar data on Zn-diffused InxGa1−xAs laser diodes, and indicate that the Zn dopant in either type of laser diode is the main source of the defects involved in the two-step tunneling.
Study of chemisorbed oxygen on tungsten using secondary ion mass spectrometry
Authors: Yu Ming L.
Published: February 2003

Secondary ion mass spectrometry has been used to study the chemisorption of oxygen on W(100). Plots of O− versus O+ and WO−2 versus O+ show large hysteresis in the adsorption-desorption cycle. We propose to explain these observations by the structural and adsorption site changes during adsorption and thermal annealing of the adsorbed layer.
Composite superconducting transition edge bolometer
Authors: Clarke J. , Richards P. L. , Yeh N.-H.
Published: February 2003

A composite far-infrared bolometer has been constructed that uses an aluminum film at the superconducting transition temperature of 1.3 K as the temperature-sensitive element. The film is evaporated on one edge of a 4×4-mm sapphire substrate, which is coated on the reverse side with an absorbing film of bismuth. The best bolometer has an electrical NEP of (1.7±0.1) ×10−15 W Hz−1/2 at 2 Hz, and a specific detectivity D* of (1.1±0.1) ×1014 cm W−1 Hz1/2. This measured electrical NEP is within a factor 2 of the fundamental thermal noise limit.
Alternate-monolayer single-crystal GaAs-AlAs optical waveguides
Authors: Merz J. L. , Gossard A. C. , Wiegmann W.
Published: February 2003

Optical waveguides have been fabricated by repeated alternate molecular-beam depositions of ultrathin layers of GaAs and AlAs of from one to eight monolayers thickness per deposition. For an average core composition of 10% Al, optical losses of 2.0–2.5 cm−1 have been measured between 1.1 eV and the band gap. Transmission electron micrographs prove that the layered structures of these waveguides corresponds closely to the programmed deposition sequences.
The Si/SiO2 interface examined by cross-sectional transmission electron microscopy
Authors: Blanc J. , Buiocchi C. J. , Abrahams M. S. , Ham W. E.
Published: February 2003

Thin (200–300 Å) cross sections of Si/SiO2 have been examined by transmission electron microscopy at a resolution of better than 10 Å to search for crystalline Si protrusions into, or islands in, the thermally grown SiO2. Within the resolution obtained, no evidence was found for any phase separation within the amorphous oxide layer.
Effect of dust on glass fiber strength
Authors: Maurer Robert D.
Published: February 2003

A model is developed for the effect of atmospheric dust on fiber strength. It is assumed that dust striking the fiber as it is formed sticks to form flaws. Comparison of the model with experimental data shows that it provides a reasonable description and can be useful in interpreting fiber strength.
A simple mode-locking technique for large-aperture TEA CO2 lasers
Authors: Alcock A. J. , Corkum P. B. , James D. J.
Published: February 2003

A large-aperture unstable-resonator TEA CO2 oscillator has been mode locked by injection of nanosecond pulses chopped from the 1-W output of a cw CO2 oscillator. Power gains of ∼1012 and a locking window of ∼200 ns have been observed.
Low-capacitance PbTe photodiodes
Authors: Holloway H. , Yeung K. F.
Published: February 2003

Thin-film PbTe photodiodes have been operated at 80 K with significantly reduced capacitance. The technique is based upon limitation of the voltage-induced change of the depletion-layer volume by the presence of an insulating substrate. Capacitances as low as 64 pF for a 9-mil-square diode and 35 pF for a 28-mil-square diode have been achieved with retention of background-limited detectivities, which were typically about 1.7×1011 cm Hz1/2 W−1 for peak wavelength near 5 μm.
Possible isotope enrichment in a dc discharge using effects of resonance trapping and cataphoresis
Authors: Silfvast W. T.
Published: February 2003

The combined effects of trapping of resonance radiation of a more abundant isotope of a gas or vapor (leading to a preferential ionization of the more abundant isotope) and cataphoresis (forcing the preferentially ionized isotope towards the cathode) will be shown to result in an enriched deposition of the less abundant isotope in the anode region of a dc discharge tube. Large isotope enrichment factors and high efficiencies appear to be possible for initially low-abundance isotopes.
Visible GaAs0.7P0.3 cw heterojunction lasers
Authors: Kressel H. , Olsen G. H. , Nuese C. J.
Published: February 2003

Vapor-grown heteroepitaxial structures of GaAs0.7P0.3/In0.34Ga0.66P have been fabricated into double-heterojunction laser diodes with room-temperature threshold current densities as low as 3400 A/cm2 at λL≃7000 Å. This value is about three times less than the best reported for (Al,Ga)As lasers at this wavelength. From the (Ga,As)P/(In,Ga)P lattice-matched structures, cw operation at 10 °C has been achieved.
SAW reflection and bulk-wave loss characteristics of a groove reflector grating
Authors: Tuan H. S. , Parekh J. P.
Published: February 2003

The reflection and bulk-wave loss characteristics of a SAW reflector grating comprised of shallow grooves are treated using the coupled-mode approach well known in the area of optical gratings. This approach offers the following distinct advantages over the previously reported equivalent network approach: (i) it derives the grating characteristics directly in terms of the material constants of the substrate; (ii) it provides quantitative information on the power loss resulting from bulk-wave radiation; and (iii) it can accommodate changes in groove profile or height among the individual grating elements, making this approach amenable for use in the design of tapered arrays. Computed reflection and bulk-wave loss characteristics of a grating comprised of a varying number of identical trapezoidal grooves are presented.
Channeling of boron ions into silicon
Authors: Lecrosnier D. , Paugam J. , Gallou J.
Published: February 2003

Channeled and random distributions of boron ions implanted over the energy range 50 keV–1.8 MeV into silicon have been measured using the differential capacitance technique. When implantations are performed along the 〈110〉 or 〈111〉 axis, profiles exhibit a strong orientation dependance. The best channeled profiles shows that more than 70% of the implanted dose is in the channeled peak.
Optical coupling modulation in traveling-wave cavities
Authors: Henderson D. M. , Vilnrotter V. A.
Published: February 2003

Efficient very wideband coupling modulation of the CO2 laser has been achieved in a traveling-wave cavity configuration termed ’’ring modulator’’ that avoids the usual transit-time-limited bandwidth of conventional coupling modulation. A 10.6-μm modulation experiment demonstrates flat frequency response from 10 MHz to 1 GHz.
Gettering of stacking-fault nuclei in silicon by trichloroethylene oxidation
Authors: Hattori Takeshi
Published: February 2003

Stacking-fault nuclei in silicon wafers are gettered by the incorporation of appropriate amounts of trichloroethylene (TCE) during thermal oxidation at high temperatures. Deliberate introduction of the TCE oxidation prevents the formation of oxidation-induced stacking faults during the subsequent standard thermal oxidation. Possible mechanisms for the nuclei gettering and the fault suppression are discussed.
Generation of 16-μm radiation by four-wave mixing in para-hydrogen
Authors: Loy M. M. T. , Sorokin P. P. , Lankard J. R.
Published: February 2003

A 16-μm source based upon the combined effects of stimulated rotational Raman scattering and four-wave mixing in gaseous para-hydrogen has been experimentally demonstrated. The input beams were synchronized pulses from a ruby laser and a CO2 TEA laser. Pulses with ∼2 μJ of energy were generated at 627.8 cm−1.
Nonresonant chirp compensation with counterpropagating optical pulses
Authors: Marburger J. H. , Shockley R.
Published: February 2003

We show that the chirp rate of an optical pulse emerging from a nonlinear medium may be reversed near its peak if a backward pulse is present simultaneously in the medium. This provides a nonresonant chirp compensation technique.
Tunneling observations of delayed flux entry and surface barriers in Nb3Sn
Authors: Moore D. F. , Beasley M. R.
Published: February 2003

The results of a study of flux entry into Nb3Sn using tunneling are described. It is found that barriers to flux entry as large as 170 mT, well in excess of the lower critical field Hcl, are possible in bulk Nb3Sn. Important details of the magnetic field dependence of the surface barrier are also reported.
Efficient Raman shifting of ArF and KrF laser wavelengths
Authors: Loree T. R . , Sze R. C. , Barker D. L.
Published: February 2003

A series of uv lines has been generated in the region 190–360 nm by multiple Raman scatterings of the ArF and KrF laser wavelengths. ArF has been shifted in H2 and KrF shifted in H2, D2, and CH4. For the optimized case of KrF pumping H2, better than 50% energy conversion was observed to the first Stokes at 2769 Å.
Photoionization cross sections for excited states of argon and krypton
Authors: Hyman H. A.
Published: February 2003

Calculations have been carried out for the photoionization cross sections of excited states of atomic argon and krypton, relevant to the KrF laser. At λ=2486 Å, it is found that photoabsorption due to the 3P0,2 metastable states is relatively unimportant, while the cross sections for the first excited p states are large (∼4.5 ×10−18 cm2).
A SAW pulse compression filter using the reflective dot array (RDA)
Authors: van de Vaart H. , Solie L. P.
Published: February 2003

In this letter, results are reported on the first surface-acoustic-wave pulse compression filter using the reflective dot array (RDA). The results show that the RDA approach is capable of producing very-high-performance pulse compression filters, comparable to RAC devices, but at much lower cost. The primary advantage of the RDA is that it is part of the same mask as the transducers, thus permitting single-step fabrication.
Constricted hysteresis loop and microstructure of Cu-Mn-Al alloys
Authors: Narita K. , Koga S.
Published: February 2003

The microstructure of 44.7 Cu–20.6 Mn–34.7 Al (at.%) alloy, which exhibits a remarkable constricted hysteresis loop in the as-cast state, has been investigated by transmission electron microscopy. It has been found that the constricted hysteresis loop is caused by the nonuniform precipitation of nonmagnetic Cu9Al4 particles in the ferromagnetic Cu2MnAl matrix.
Continuous operation over 1500 h of a PbTe/PbSnTe double-heterostructure laser at 77 K
Authors: Yoshikawa Mitsuo , Shinohara Kouji , Ueda Ryuichi
Published: February 2003

Continuous operation over 1500 h at 77 K has been achieved by use of a PbTe/Pb0.93Sn0.07Te double-heterostructure laser which was grown using the liquid-phase-epitaxy method. The cw threshold current changed only about 3% during the first 200 h. It is concluded that the lifetime of PbTe/PbSnTe double-heterostructure lasers at 77 K is fundamentally very long.
Negative resistances observed in InSb diodes reverse biased
Authors: Itoh Sadao , Ohta Yoshio , Fujiyasu Hiroshi
Published: February 2003

Dynamic negative resistances observed in p-n InSb diodes reverse biased at 77 °K are described. The diodes were made by zinc diffusion on the antimony side of n-type InSb wafers at 450 °C for 6 h. Coherent current pulse trains of a small duty cycle, with current pulses of amplitude 0.17 A and rise time 0.5 nsec and with great voltage drops, are generated in such a negative-resistance region which is associated with deep-level states produced by the above zinc diffusion treatment.
Suppression of output nonlinearities in double-heterostructure lasers by use of misaligned mirrors
Authors: Frescura B. L. , Hwang C. J. , Luechinger H. , Ripper J. E.
Published: February 2003

Nonlinearity (kinks) in the dependence of light output power on current has been effectively eliminated by the use of mirrors aligned at a small angle from the direction perpendicular to the stripe or filament. Such a structure increases confinement of the lasing filament and causes an increase in threshold current density that is smaller than that produced by stripe narrowing.
GaAlAs Schottky directional-coupler switch
Authors: Reisinger A. R. , Bellavance D. W. , Lawley K. L.
Published: February 2003

Electro-optic metal-gap directional-coupler switches have been fabricated in GaAlAs waveguide structures. A very thin GaAs cap facilitates the electroplating of Schottky barriers without significantly increasing the optical attenuation at wavelengths near 8600 Å, making this type of device suitable for integration with a GaAs laser source on a common chip. The performance of the switch was investigated at 1.06 m. A 17-dB extinction ratio in the coupled channel was measured at a reverse-bias voltage of 25 V.
Interstitial doping of amorphous silicon
Authors: Beyer W. , Fischer R.
Published: February 2003

Interstitial doping of glow-discharge a-Si has been achieved by in-diffusion and implantation of lithium. After doping with about 1% Li, we observe an increase of room-temperature conductivity by a factor of 106 and a decrease in the activation energy of conductivity down to 0.17 eV. Corresponding changes are observed for the thermoelectric power which, as expected for n-type material, has a negative sign.
Criteria for x-ray superradiance
Authors: MacGillivray J. C. , Feld M. S.
Published: February 2003

This paper develops a set of criteria for superradiant emission in x-ray systems. These new criteria, which must be satisfied in order to obtain efficient x-ray emission, are given in the form of simple inequalities in terms of experimental parameters.
Thermally converted surface layers in semi-insulating GaAs
Authors: Lum W. Y. , Wieder H. H.
Published: February 2003

Charge carrier transport in thermally converted surface layers in semi-insulating GaAs depends on the generation, diffusion, and occupancy of Ga and As vacancies. The amphoteric nature of C in GaAs can significantly alter the density and the distribution of donors and acceptors in the vicinity of the specimen surface and the surface layer may become either p type or n type depending on the thermal treatment conditions.
Stress effect on I
c of multifilamentary V3Ga wire
Authors: Gubser D. U. , Francavilla T. L. , Howe D. G. , Jones L. D.
Published: February 2003

Measurement of stress effects on the critical current Ic of multifilament V3Ga wire are reported, and the cryostat for performing these studies is described. Measurements were taken at 4.2 K in a magnetic field of 9.0 T and for stress values up to 5×108 Pa. Noticeable degradation of Ic did not begin in the wires reported here until stress values of 3.0×108 Pa. The first effect of stress was to produce a measurable resistance in the wire below Ic. A discussion of this low-current onset of resistance is given which suggests that improved stress characteristics in A15 wires may correlate with the reduction or elimination of this resistance.
Critical currents in sputtered copper molybdenum sulphide
Authors: Alterovitz Samuel A. , Woollam John A. , Kammerdiner Lee , Luo Huey-Lin
Published: February 2003

Critical currents in a sputtered Chevrel-phase copper molybdenum sulphide have been measured at 4.2 K as a function of applied magnetic field. Self-field critical-current values up to 109 A/m2 were found, decreasing to 108 A/m2 at 3 T. Graphs of pinning forces versus field were found to be independent of field direction, and the pinning mechanism is sample independent. Critical-current densities for sputtered lead molybdenum sulphide are estimated to be ≳108 A/m2 at 26 T based on a scaling law for pinning.
Empirical estimation of Faraday rotation in some rare-earth iron garnets
Authors: Krishnan R.
Published: February 2003

From experimental data available for pure rare-earth iron garnets (RIG) an empirical method of estimating Faraday rotation (FR) in some mixed rare-earth iron garnets is proposed. First, the Fe3+ contribution to FR is extracted from YIG. From this value and from FR data available for several RIG, one is able to separate the contribution from different RE ions. Finally, FR in mixed rare-earth iron garnets is calculated using simple scaling and results compared with data available in the literature. The agreement obtained is quite encouraging.
Gain and fluorescence measurements in photoionization-stabilized XeF discharge lasers operating at high-energy loadings
Authors: Hasson V. , Lee C. M. , Exberger R. , Billman K. W. , Rowley P. D.
Published: February 2003

A recently developed simple photopreionization-stabilized discharge scheme was adapted successfully to the excitation of XeF and KrF lasers at pressures of 0–1500 Torr. The authors report on the stabilization and excitation characteristics of F2 and NF3 : Xe : He discharges over a wide range of energy loadings. These results summarize and compare the detailed fluorescence and gain measurements. The (nonoptimized) XeF output energies of ∼1 J/liter compare favorably with those of other devices.
A model for surface layer composition changes in sputtered alloys and compounds
Authors: Haff P. K.
Published: February 2003

Under the assumption that extracted beam energy is quickly shared among secondary cascade members of all masses, we present a model which accounts quantitatively for recently observed equilibrium surface enrichments in heavy atoms following ion bombardment of alloys and compounds. Assuming strong radiation-driven diffusion, effects of which are directly observed, and given the time required to reach equilibrium, we can calculate the thickness Δx of the enriched layer. Alternatively, knowing Δx, a calculation of the equilibration time constant is possible.
Characteristics of high-field preionized discharges for transversely excited waveguide lasers
Authors: Jain R. K. , Wood II O. R. , Maloney P. J. , Smith P. W.
Published: February 2003

We have investigated the role of the preionization cathode material and the preionization energy in high-field preionized discharges of a CO2 laser mixture at atmospheric pressure. Independent control of both the E/p and the input energy is demonstrated over a large range of values. These results are applicable to the design of waveguide lasers and other types of gas-discharge devices.
Laser-induced resonances in high n states of hydrogen-like 19F8+
Authors: Silver J. D. , Jelley N. A. , McIntyre L. C.
Published: February 2003

A laser resonance technique using Doppler tuning has been applied to measure transitions between highly excited states of highly ionized fluorine. Resonance transitions between n=9 and n=10 levels of 19F8+ with a mean wavelength of 4796.06±0.24 Å were observed. This wavelength is close to the calculated value of 4796.16 Å for the wavelength of the 92L17/2–102M19/2 transition.
On the determination of charge centroids in insulators by photoinjection or photodepopulation
Authors: Powell R. J.
Published: February 2003

Under certain conditions the centroid of a trapped charge distribution in an MOS insulator can be determined from charge and flatband shift measurements during photoinjection or photodepopulation. This technique was applied earlier by Harari and Royce, who made an erroneous assumption in deriving their equation. The correct equations are derived in the present letter, and the trap structure of pyrolytic Al2O3 films is reinterpreted.
Diffusion of fast electrons in the presence of a magnetic field
Authors: Jacob J. H.
Published: February 2003

The Bethe Age diffusion solution for high-energy electrons in the presence of a magnetic field is derived. The electron transport in the presence of a magnetic field can generally be separated into diffusion along and perpendicular to the field direction. This result is similar to diffusion of a plasma in a magnetic field. However, unlike plasma diffusion, the energy of the fast electrons is retained as the independent variable.
Investigation of atomic clustering in aged metallic glasses using positron annihilation methods
Authors: Chen H. S. , Chuang S. Y.
Published: February 2003

The positron lifetime τ1 of Pd77.5Cu6Si16.5, Fe75P16B6Al3, and Ni75P16B6Al3 glass increases from ∼170 ps to a plateau value ∼175 ps immediately following an anneal at 350 K for 30 min. With further annealing above 500 K, τ1 decreases and approaches ∼165 ps. Possible atomic clustering in metallic glasses during structural relaxation will be described.
Compensation from implantation damage in InP
Authors: Davies D. Eirug , Lorenzo J. P. , Deane M. L.
Published: February 2003

Compensation arising from ion damage has been investigated in InP. It is found that ≳10 times the irradiation that produces resistive layers in GaAs is required to similarly compensate InP. The damage anneals in two stages indicating that two distinct defects contribute to the carrier removal process. Partial annealing at ∼400 °C rather than at 500 °C as in GaAs is suggested as a means of producing low-absorption highly resistive layers. From compensation considerations annealing to at least 550 °C will be required for dopant implantations if effective electrical utilization is to be achieved.