bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-modulation of an intense relativistic electron beam
Authors: Friedman M. , Serlin V. , Drobot A. , Seftor Larry
Published: February 2003

High levels of coherent current and energy oscillations appeared on an intense relativistic electron beam traversing a smooth drift tube in which two or more coaxial cavities were inserted. The frequency of oscillation depended strongly on the geometry of the drift region but only weakly on beam current and voltage. The frequency spectrum of modulation was monochromatic. By changing geometry, frequencies of up to 3 GHz were observed. Relativistic electron beams with voltages varying from 0.25 to 1 MeV and currents from 1 to 8 kA were modulated with efficiencies approaching 100%. The structure of the electron bunches was tailored by changes in the geometry. Both theory and particle simulation show that the presence of the cavities along the drift tube altered the simple streaming motion of the beam in a smooth drift tube resulting in a highly nonlinear beam behavior. The complex beam dynamics was governed by formation of virtual cathodes, reflexing electrons, and autoacceleration. Shaped electron bunches have many applications in collective acceleration, high power microwave production, and plasma heating.
Scaling of collisionally pumped 3s-3p lasers in the neon isoelectronic sequence
Authors: Feldman U. , Seely J. F. , Bhatia A. K.
Published: February 2003

Population inversions between the 3p and 3s levels of neonlike ions with atomic numbers Z=14, 18, 22, 26, 32, and 36 have been calculated. The population inversions result from the preferential population of the 3p level by electron collisional excitation from the ground configuration of the ion and occur over a wide range of electron temperature and electron density (from 1017 cm−3 for Si V to 1022 cm−3 for Kr XXVII). For all ions that are studied, the maximum value of the population inversion (N3p/g3p−N3s/g3s) for the transition 3p 1S0−3s uP1 (where u represents the upper of the singlet and triplet levels) is found to be approximately equal to 4×10−3 NI, where NI is the total density of neonlike ions. With the exception of Si V, laser gains greater than 1 cm−1 are possible for all the ions that are considered, and the gain increases with atomic number Z. For Si V and lower-Z ions, electron collisional mixing of the upper and lower laser levels restricts the electron density at which the population inversion occurs and limits the laser gain to values less than 1 cm−1. The scaling of the laser gain and the plasma parameters with atomic number Z is presented. For an electron density of 1021 cm−3, the optimum atomic number Z that results in the highest gain on the 3p 1S0−3s uP1 transition is Z=26 (Fe XVII), and the gain is equal to 30 cm−1.
Analysis of thermal generation of Rayleigh waves
Authors: Royer D. , Dieulesaint E.
Published: February 2003

We have developed an analysis for thermal generation of surface acoustic waves (Rayleigh waves) valid for anisotropic materials. The analysis, based on the complex reciprocity relation, provides expressions for the mechanical displacement, the electrical potential, and the acoustic power density of the Rayleigh waves launched by harmonic heating of zones on the surface. These quantities are evaluated for an isotropic substrate. They are compared with those obtained by R. M. White in his work on thermal generation of bulk waves. Our theoretical results are in good agreement with two previous experiments carried out with a piezoelectric crystal of lithium niobate.
Magnetic field measurements in tokamak plasmas
Authors: Feldman U. , Seely J. F. , Sheeley N. R. , Suckewer S. , Title Alan M.
Published: February 2003

The measurement of the poloidal magnetic field in a tokamak plasma from the Zeeman splitting and polarization of the magnetic dipole radiation from heavy ions is discussed. When viewed from a direction perpendicular to the toroidal field, the effect of the poloidal field on the circularly polarized radiation is detectable using a photoelectric polarimeter. The Zeeman splittings for a number of magnetic dipole transitions with wavelengths in the range 2300–9300 Å are presented. An imaging polarimeter is proposed that can measure the poloidal magnetic field with space and time resolution.
Aluminum-related acoustic loss in AT-cut quartz crystals
Authors: Martin J. J.
Published: February 2003

The substitutional aluminum ions present in all quartz requires charge compensation. In as-grown synthetic quartz, interstitial alkali ions serve as the charge compensators. Irradiation at temperatures above 200 K replaces the alkali with either a proton or a hole trapped on an adjacent oxygen. Electrodiffusion (sweeping) can be used to replace the alkali with either a proton or another specific alkali. A study of the acoustic loss spectra of a series of 5-MHz fifth overtone AT-cut resonator blanks as a function of sweeping and irradiation has been completed. No acoustic loss peaks were observed at temperatures less than 100 °C which could be attributed to either the Al-Li+ or Al-OH− centers. Na-swept samples showed the expected large loss peak at 53 K while unswept samples had only very small 53 K peaks. This shows that in as-grown synthetic quartz lithium is the primary charge compensating ion. Irradiation removed the 53 K peak and introduced new peaks at 23, 100 K, and 135 K. Annealing studies show that these peaks can be attributed to the Al-hole center. The anneal study also shows that the decay of the Al-hole center is matched by the return of the alkali to the aluminum site.
On the anomalous phonon mode behavior in HgSe
Authors: Talwar D. N. , Vandevyver M.
Published: February 2003

From the recent information on the neutron scattering data of phonon dispersions, we have established an eleven parameter rigid-ion model to understand the vibrational properties of both perfect and imperfect HgSe. Model calculations for the lattice dynamics, frequency spectrum, and the temperature dependence of the specific heat are shown to be in very good agreement with the recent experimental measurements. Our Green’s function calculations suggests that the possibility of a gap mode (due to Hg in HgSe) for the observed anomalous structure in infrared reflectivity experiments near ∼110 cm−1 cannot be completely ruled out. More optical (infrared and Raman) experiments regarding the influence of uniaxial compression are very much needed to help at least in assigning the symmetry of the defect center involved in the observed behavior.
Stimulated emission of cresyl violet pumped by N2 laser or rhodamine 6G dye laser
Authors: Castelli Francesco
Published: February 2003

Cresyl violet solutions have been shown to lase when pumped with a N2 laser or a rhodamine 6G dye laser. In the latter case the efficiency is much higher, and for appropriate solution concentrations the dye lases at the wavelength peak of its spontaneous emission. Under these conditions, the gain is so high that superradiance is obtained using only a 10−kW exciting pulse with 10% lasing efficiency.
Electron density measurements in collision−dominated plasmas
Authors: George T. V. , Denes L. J.
Published: February 2003

A simple technique, based on the absorption of far−infrared radiation, is shown to provide direct electron number density data in atmospheric large−volume plasmas. Spatially and temporally resolved measurements of electron density were obtained from a 10−cm plasma over the range 1011−3×1013 cm−3 using a 337−μm laser source. The measurement configuration allowed a 0.5−cm spatial resolution and a 200−nsec temporal resolution.
Thomson scattering from a CO2−laser−heated magnetically confined plasma
Authors: Pearlman J. S. , Pietrzyk Z. A. , Vlases G. C.
Published: February 2003

Measurements of the interactions of CO2 laser radiation with a theta pinch plasma have been made using laser scattering as a diagnostic technique. The plasma was heated axially with a TEA CO2 pin laser. The scattering measurements have shown the time evolution of the laser−heated plasma during and after heating by the ’’spike’’ of the CO2 laser. The energies involved in the change of plasma conditions agree well with the theoretical absorption associated with the inverse bremsstrahlung mechanism.
Observation of three mechanisms of optical modulation caused by acoustic domains in CdS
Authors: Hata Tomonobu , Hara Tsutomu , Ishigaki Masaji , Hada Toshio
Published: February 2003

This paper presents experimental results concerning optical attenuation caused by acoustic domains in CdS. Three mechanisms are assumed: These are (i) shift in the energy gap, (ii) light scattering by acoustic flux, and (iii) rotation of the plane of polarization of the incident light. These mechanisms are experimentally distinguished. And it is found that in the case of e∥c (where e is the polarization of the incident light and c the c axis of the crystal) three kinds of optical modulation exist, but in the case of e⊥c only the effect of scattering is substantial.
Influence of fluid-dynamic phenomena on the occurrence of constriction in cw convection laser discharges
Authors: Wiegand W. J. , Nighan William L.
Published: February 2003

The influence of gas residence time, turbulence, and discharge uniformity on the electrical power density threshold for glow constriction has been investigated for conditions typical of high-power cw convection-cooled molecular lasers. Relatively independent evaluation of the effect of these properties indicated that each has an important bearing on plasma stability. Reduction of fluid residence time in the discharge region was found to result in an approximately proportionate increase in the electrical power density at which constriction occurred in CO2 laser mixtures for pressures in the 20–200-Torr range.
Threshold effects on relative intensities in LMM Auger spectra of Ge and Se
Authors: Barrie A.
Published: February 2003

Relative intensities for Auger transitions involving 2p3/2 and 2p1/2 initial vacancies are found to be dependent upon incident photon energy. At higher photon energies, and when electron impact ionization is used, the statistical ratio of 2 : 1 is observed. In the region just above threshold (1.0<U<1.04), however, a higher ratio than expected is found and this is interpreted as being due to a rapidly increasing 2p subshell cross section.
Low-divergence beams from grating-coupled composite guide heterostructure GaAlAs diode lasers
Authors: Burnham R. D. , Scifres D. R. , Streifer W.
Published: February 2003

Room-temperature operation of a new grating-coupled heterostructure diode laser is reported. The laser contains two GaAs layers separated by a GaAlAs layer. One of the GaAs layers is electrically pumped, whereas the other is corrugated. Light is distributed over both layers and the grating couples out low-divergence polarized beams approximately normal to the p-n junction. Room-temperature thresholds as low as 2 kA/cm2 have been observed.
Astigmatism and coma-free prism dye ring laser
Authors: Marowsky Gerd
Published: February 2003

The characteristics of two prism ring lasers for cw operation have been experimentally studied. With improved compensation for aberrations due to astigmatism and coma, cw ring lasers operated in the traveling-wave mode provide high output efficiency, stable narrow bandwidth in multimode and single-mode operation, and a broad tuning range.
Low-threshold cw LiNdP4O12 laser
Authors: Chinn S. R. , Hong H. Y-P.
Published: February 2003

We have studied cw room-temperature lasing behavior of LiNdP4O12. A threshold of 360-μW optical excitation power at 0.582-μm wavelength was measured, with 18% power conversion efficiency to 1.048-μm radiation at 1-mW output. The crystal structure is found to be monoclinic (C2/c) rather than orthorhombic as previously reported.
Ranges of ions with Z1⩾54 in Al and Al2O3
Authors: Andersen H. H. , Bo/ttiger J. , Jo/rgensen H. Wolder
Published: February 2003

Ranges of Xe, Cs, Eu, Au, and Tl in polycrystalline Al and anodic Al2O3 at 75–100 keV are reported. Ranges in Al2O3 are found to be about 30% higher than predicted by the LSS theory for all Z1. The shapes of the depth distributions are in excellent agreement with theoretical calculations. In Al, considerable deviations from theory for the most probable ranges and for the shapes of the distributions are found. These deviations are attributed to crystalline effects.
Third harmonic generation in phase-matched alkali metal vapors
Authors: Bloom D. M. , Bekkers G. W. , Young J. F. , Harris S. E.
Published: February 2003

We report improvements in conversion efficiency for third harmonic generation in sodium and rubidium vapor. 30-psec pulses of radiation at 1.064 μm have been converted to 0.3547 μm with an energy conversion efficiency of 10%. Factors limiting conversion efficiency are discussed.
Optical bends and rings fabricated by preferential etching
Authors: Tseng Cheng-Chung , Botez Dan , Wang Shyh
Published: February 2003

We have applied the preferential etching technique to the fabrication of optical bends and rings. Nearly perfect smooth waveguide walls formed by crystalline planes can still be obtained in the curved section. Applications of such preferentially etched optical bends and rings in integrated optics are discussed.
A new model for the negative voltage instability in MOS devices
Authors: Breed D. J.
Published: February 2003

In this letter it will be shown first that ’’hole trapping’’ is generally measured in such a way that the effect is only partly observed. Second, a new physical model is presented that explains this instability of the oxide charge in terms of a thermally assisted tunneling process, where electrons in neutral oxide centers are excited to states from which the electrons can tunnel to the silicon.
Current noise measurements in continuous metal thin films
Authors: Celasco M. , Fiorillo F.
Published: February 2003

Current noise phenomena were investigated in pure Al thin films. Noise measurements were performed on very small sample volumes (less than 10−11 cm3) obtained by electromigration damaging of the film, at current densities higher than 106 A/cm2 with an apparatus whose sensitivity was of the order of 10−19 V2/Hz. Under these conditions, which probably provide the best sensitivity limit at present available, no excess noise was detected before the destruction of the sample, except for occasional instabilities corresponding to macroscopic structural changes of the film. It is concluded that a stationary current noise cannot be observed in a metal conductor within the highest sensitivities presently attainable.
Storage of optical patterns in a zinc−oxide−on−silicon surface wave convolver
Authors: Davis K. L.
Published: February 2003

A monolithic zinc−oxide−on−silicon surface wave convolver has been used to image optical patterns and store them for long periods of time. A light pattern is stored by projecting it onto a semitransparent top convolver electrode which has an applied negative dc bias. Slow states associated with the zinc oxide are charged in the regions exposed to the light. This charge pattern, as observed using surface wave convolution, persists even when the light is removed. Retention of the pattern for several days has been demonstrated with this device.
A thermal imaging system based on the PrCl3 quantum counter
Authors: Herrington J. R. , Sewell K. G. , Volz W. B.
Published: February 2003

Ambient−temperature thermal background limited performance has been obtained for a thermal imaging system based on the PrCl3 quantum counter. The principal ’’noise’’ source in the PrCl3 quantum counter is shown to be a pump−induced emission characterized by a radiative lifetime of less than 50 nsec. Using the principle of temporal discrimination for the reduction of noise, a contrast of ∼40% was measured for a temperature difference of ∼5 °C above ambient temperature (23 °C).
Taper couplers for GaAs−AlxGa1−xAs waveguide layers produced by liquid phase and molecular beam epitaxy
Authors: Merz J. L. , Logan R. A. , Wiegmann W. , Gossard A. C.
Published: February 2003

Growth techniques and passive evaluation of tapered waveguide light couplers produced by LPE and MBE are reported. Coupling efficiencies approaching 100% for the transfer of light from a GaAs layer to a layer of Al0.1Ga0.9As are observed for MBE tapers, and tapers fabricated by LPE allow ∼50% coupling, suitable for use with LPE active devices.
Onset of convection due to horizontal laser beams
Authors: Boyd R. D. , Vest C. M.
Published: February 2003

When a horizontal cw laser beam is suddenly turned on in a quiescent isothermal fluid there is a delay time t* during which thermal blooming is governed by absorption of radiation and thermal conduction. For t≳t*, free convection becomes a significant factor. t* is determined by an approximate quasisteady hydrodynamic stability analysis and is compared with existing experimental data.
Diffused two−dimensional optical waveguides in GaAs
Authors: Garmire E. , Lovelace D. F. , Thompson G. H. B.
Published: February 2003

TE00 and TE01 optical waveguide modes have been observed in GaAs stripe p−n junctions produced by zinc diffusion through SiO2 masks into n−type substrates. Excellent agreement was found between guided light profiles at 1.15 μm and those predicted on the basis of refractive index profiles given by the free−carrier plasma effects.
Optical directional couplers and grating couplers using a new high−resolution photolocking material
Authors: Tomlinson W. J. , Weber H. P. , Pryde C. A. , Chandross E. A.
Published: February 2003

Low−loss single−mode optical waveguides (∼4×1.5 μm), optical directional couplers, and grating couplers were made by the photolocking process in a new high−resolution system using naphthalenethiol as the dopant. Index changes of up to 1.3% and optical losses typically 0.3 dB/cm were achieved (at λ=633 nm). The directional couplers had coupling lengths as short as 150 μm, with virtually complete transfer of the guided energy from one guide to another. Grating couplers were written in which the bulk index of the guiding film is spatially modulated with periods as short as 0.28 μm, giving coupling strengths of up to 15 dB/cm.
Application of surface waves to the study of semiconductor surface state using the separated−medium acoustoelectric effect
Authors: Shiosaki Tadashi , Kuroda Takao , Kawabata Akira
Published: February 2003

It is reported that the surface state of a semiconductor, e.g., germanium can be studied by the measurements of the acoustoelectric voltage due to the coupling with the elastic surface wave on an adjacent piezoelectric material, e.g., LiNbO3. The method is superior to the field−induced conductance method with regards to sensitivity, ease of sample preparation, and applicability to a sample of higher conductivity.
An aluminum/SiO2/silicon−on−sapphire light valve matrix for projection displays
Authors: Guldberg J. , Nathanson H. C. , Balthis D. L. , Jensen A. S.
Published: February 2003

A new electron−beam−addressed light valve structure has been tested which is composed of a large array of 0.002×0.002−in. 3000−Å−thick aluminized silicon dioxide electrostatically deflectable squares, suspended by a centrally located 4−5−μm−tall silicon post over a transparent sapphire substrate. The device is fabricated using conventional semiconductor processing techniques and, in particular, slits are photolithographically defined in each picture element so as to spatially separate in the schlieren stop plane the signal light produced by deflected elements from the diffraction pattern from the matrix. Experimental results include 20 lines/mm resolution, 18:1 contrast ratio, picture storage times of several months, and full erasure times of 1/30 sec.
Spin resonance matching in tunable far−infrared generation by optical mixing via spin−flip transitions
Authors: Nguyen V. T. , Bridges T. J.
Published: February 2003

The generation of continuously tunable far−infrared radiation by difference frequency mixing, using the electron spin nonlinearity and a spin−flip laser, has been significantly improved. This has been done by tuning the sharp spin resonance of the mixer to the difference frequency by correct placement of the samples in a nonuniform magnetic field.
High−energy neutron sputtering yields from gold and niobium
Authors: Jenkins L. H. , Noggle T. S. , Reed R. E. , Saltmarsh M. J. , Smith G. J.
Published: February 2003

High−energy neutron sputtering yields ≲10−4 ejected particles/ incident neutron have been measured for Au and Nb specimens irradiated under high−vacuum conditions using a neutron source based on the 9Be(d,n) reaction. These measurements are consistent with theoretical predictions, but much lower than experimental data previously reported by one research group.
Observations of small-signal gain in high-pressure pulsed CO electric discharge laser
Authors: Boness M. J. W. , Center R. E.
Published: February 2003

Measurements are reported of the magnitude and temporal behavior of small-signal gain in a pulsed high-pressure carbon monoxide electric discharge laser. These are compared with predictions derived from kinetic modeling calculations. Maximum gain of 4.5%/cm was measured on the 9P (10) and 8P (10) transitions. The measurements and calculations support the hypothesis that resonance absorption by overlapping transitions is the mechanism responsible for gain suppression on certain lines.
A method of utilizing lithium-induced nuclear reactions in the determination of carbon, nitrogen, and oxygen in thin films
Authors: Cardinal C. , Brassard C. , Chabbal J. , Deschênes L. , Labrie J. P. , L’Ecuyer J. , Leroux Marc
Published: February 2003

A method of analysis of oxygen, nitrogen, and carbon in thin samples involves the detection of charged particles from nuclear reactions induced by a 7-MeV lithium-6 beam. The particle detection with a telescope counter near 0° takes full advantage of high exothermic reactions. The sensitivity is of the order of 10−3 μg/cm2. A preliminary study of the contaminants introduced during the sputtering of niobium is presented.
Effect of electron-electron and impurity scattering on hot electron repopulation in n-Si at 77 K
Authors: Nash James G. , Holm-Kennedy James W.
Published: February 2003

The transport roles of electron-electron (e-e) and intravalley impurity scattering (neutral and ionized) in n-Si at 77 K were studied under high-electric-field (0–3000 V/cm) nonequilibrium conditions, by comparing the theoretical and experimental ratio of 〈111〉 to 〈100〉 field-dependent conductivity over a range of free-electron concentrations that fully encompasses this ratio’s variation with concentration (2×1013–2×1016 cm−3). Theoretical calculations were performed using a numerical technique which allows an ’’exact’’ solution to the Boltzmann transport equation. Electron-electron scattering was included in the calculation using the Fokker-Plank formulation. It was found that e-e scattering was primarily responsible for the decrease in the conductivity ratio with increasing concentration through its effect on repopulation; both intravalley and intervalley e-e scattering were found to be important. Neutral impurity scattering also had a significant effect on repopulation. An apparent increase in free-electron concentration with field was observed in the more heavily doped samples.
Inverted silicon island edge observation in SOS/CMOS transistors by SEM EBIC methods
Authors: Gates J. L. , Griffith O. K.
Published: February 2003

Impurity redistribution during thermal oxidation in the n-channel transistor of SOS/CMOS can result in an inversion of silicon material type (from p to n) along the island edge and extending from drain to source. This inverted island edge produces excessive drain-to-source current leakage. We show that the electron-beam-induced-current (EBIC) mode of operation in the scanning electron microscope (SEM) is an effective method of observing inverted island edges.
Acoustic surface wave velocity perturbations in LiNbO3 by diffusion of metals
Authors: Schmidt R. V.
Published: February 2003

Thin films of Ti, Ni, and Cr have been diffused into LiNbO3 to form regions of increased acoustic surface wave velocity. Velocity changes as large as 1.4% have been observed. Diffused strips of Ti have been found suitable for fabricating efficient grating reflectors.
Electro-optic light modulator with branched ridge waveguide
Authors: Ohmachi Yoshiro , Noda Juichi
Published: February 2003

A light modulator based on an electro-optic phase modulation and an optical interference of Mach-Zehnder type has been demonstrated. The modulator is constructed monolithically with a branching ridged optical waveguide on TiO2-diffused LiNbO3. The half-wave voltage is 19 V and the extinction ratio is 34%.
Integrated electro-optic intracavity frequency modulation of double-heterostructure injection laser
Authors: Reinhart F. K. , Logan R. A.
Published: February 2003

Integration of a taper-coupled GaAs-AlxGa1−xAs laser with a linear electro-optic modulator permits efficient optical frequency modulation of the laser emission. The pulsed room-temperature threshold current density of the device was 8 kA/cm2. Frequency modulation depth in excess of 15 GHz (corresponding to a wavelength shift of 0.4 Å) was obtained with a reverse bias change of 20 V across the modulator. Conversion of frequency modulation into intensity modulation was demonstrated with a characteristic power P0 of 10 μW/MHz for 90% intensity modulation. It is shown that reduction of P0 by an order of magnitude is easily feasible.
Observation of resonance radiation pressure on an atomic vapor
Authors: Bjorkholm J. E. , Ashkin A. , Pearson D. B.
Published: February 2003

We have used the resonance radiation pressure from 40 mW of cw dye laser light propagating axially down a tube filled with sodium vapor to increase the sodium pressure (density) up to 50% over a length of 20 cm. The magnitude of the effect agrees well with measurements of the absorbed power. These observations were made with the laser tuned to the low-frequency side of the sodium D2 resonance line; for tuning to the high-frequency side, an additional unexplained effect leading to density decreases was observed.
Powder approach for multifilamentary niobium-tin superconducting wire
Authors: Hemachalam K. , Pickus M. R.
Published: February 2003

Based on powder-metallurgy techniques, a process to fabricate Nb3Sn multifilamentary superconducting wire is described. The current-carrying capacity of the wire was above 2×105 A/cm2 at a steady transverse magnetic field of 50 kG and about 1×105 A/cm2 at 100 kG.
Retardation of Impatt diode aging by use of tungsten in the electrodes
Authors: Mahoney G. E.
Published: February 2003

Stable rf performance of Pt-GaAs Schottky barrier Impatt diodes may be affected by the platinum reacting with the GaAs, thereby producing junction movement during aging. This paper presents data which monitor the junction movement and then demonstrates the effect of using a tungsten layer to limit the Pt-GaAs reaction. The tungsten layer does not alter the rf performance. The platinum ’’chew in ’’ is controlled and the tendency of the reverse I-V characteristics to soften with age is slowed.
Acoustic storage and processing device using p-n diodes
Authors: Maerfeld C. , Defranoud Ph. , Tournois P.
Published: February 2003

Storage experiments and signal-processing techniques with surface acoustic Rayleigh waves in a p-n diode array close to a YZ LiNbO3 substrate are described. A storage time of 15 sec for a writing time constant of 1 μsec has been measured.
Identification of copper energy levels in GaAs0.6P0.4
Authors: Hawkins B. M. , Forbes L.
Published: February 2003

Four levels at 0.43, 0.24, 0.13, and 0.33 eV from the valence band in GaAs0.6P0.4 associated with copper impurities have been measured using the technique of capacitance transients to observe thermal emission of holes. Confirmation has been made of the 0.43-eV level by optical emission of electrons, and optical emission of electrons has been observed from the 0.24- and 0.13-eV levels.
Microfabrication of two-dimensional periodic arrays by laser beam interferometric technique
Authors: Tsang Won-Tien , Wang Shyh
Published: February 2003

We have fabricated two-dimensional periodic arrays of circular openings with submicrometer diameter and spacing in thin photoresist films coated on top of glass substrates using a laser beam interferometric technique coupled with the simultaneous exposure and development (SED) method. The two-dimensional grating masks generated in this way are comparable in quality to those generated by computer-controlled scanning electron beam (CCSEB). Important advantages of the method described are that it is simple in both skill and instrumentation involved and that it is economic, fast, free of electron scattering and electrical charging problems, flexible, and able to generate large areas of uniform arrays. However, with this technique only periodic lattice structures can be generated. Possible new applications utilizing these structures are discussed.
Thin-film dc SQUID with low noise and drift
Authors: Clarke John , Goubau Wolfgang M. , Ketchen Mark B.
Published: February 2003

We describe the fabrication and operation of thin-film dc SQUID’s of cylindrical geometry that make use of shunted Nb-NbOx-Pb tunnel junctions. A typical noise power spectrum is shown. At frequencies between 2×10−2 Hz and the electronic roll-off frequency, the flux resolution is 3.5×10−5 φ0/(Hz)1/2, corresponding to a magnetic field resolution of 10−10 G/(Hz)1/2. This resolution appears to be set by intrinsic sensor noise. Below 2×10−2 Hz, the spectrum is approximately 1/f. A 20-h plot of SQUID output as a function of time demonstrates an average drift of less than 2×10−5 φ0/h.
Cadmium telluride x-ray spectrometer
Authors: Zanio K. , Montano H. , Krajenbrink F.
Published: February 2003

The 3.9-keV iodine Lα x-ray line was resolved using a CdTe detector at 0 °C. A device resolution of 1.6 keV (FWHM) was obtained for the 28.6-keV iodine Kα x-ray line. Adverse polarization effects were not observed.
Acoustically read pulsed image converter
Authors: Carleton Herbert R.
Published: February 2003

An optical image scanner which employs a piezoelectric delay line and transversal interrogation scheme is proposed. Linear scanning with a resolution of 16 lines/in. and a sensitivity of 35 μW/cm2 have been achieved in a preliminary model. Estimates of limiting performance indicate the possibility of monolithic fabrication and resolutions in the region of 300 lines/in. using existing technology.
Interaction of a 15-kJ relativistic electron beam with a mirror-confined plasma
Authors: Miller P. A.
Published: February 2003

The interaction of an intense relativistic electron beam with a mirror-confined plasma was studied. Beam parameters were nominally 600 kV, 300 kA, and 15 kJ. A 12-cm-diam cold hydrogen target plasma with ne∼2×1013/cm3 was preformed in a 2:1 mirror system with a mirror spacing of 50 cm and peak mirror field of 0.8 T. Background fill pressures from 1 to 50 mTorr were used. Beam transport through the plasma was good and net current levels were low. Energy deposition levels were near 2×1017 eV/cm3, consistent with expectations based on previous work. The use of tantalum anodes in order to increase the beam’s transverse velocity was found to quench the strong beam-plasma interaction.
Accurate and rapid reduction of experimental x-ray data
Authors: Huang T. C. , Parrish William
Published: February 2003

An automatic computer method for deriving the intensities, widths, and positions from experimental x-ray diffraction and energy spectroscopy data is outlined. Complex overlapping clusters of peaks can be resolved and the data are corrected for aberrations.
Integrated GaAs-AlGaAs double-heterostructure lasers
Authors: Hurwitz C. E. , Rossi J. A. , Hsieh J. J. , Wolfe C. M.
Published: February 2003

Integrated structures consisting of a double-heterostructure GaAs-AlGaAs etched-mesa Fabry-Perot laser coupled to a high-purity GaAs waveguide have been fabricated and tested. Room-temperature threshold current densities as low as 7.5 kA/cm2 for 1-μm-thick active layers were measured.
Energy deposition into dense collisionless plasmas by rotating beams
Authors: Chu K. R. , Kapetanakos C. A. , Clark R. W.
Published: February 2003

A nonturbulent mechanism is proposed whereby a rotating electron or ion beam pulse rapidly deposits energy on the ions of a dense, magnetized, weakly collisional plasma through excitation of the compressional Alfvén mode.
Current-pressure transitions in a magnetically supported dc sputtering system
Authors: Green F. A. , Chapman B. N.
Published: February 2003

Sputtering in a cylindrical magnetron configuration, current-pressure characteristics show an unexpected discontinuity and current–magnetic field curves exhibit a maximum. These characteristics seem to be closely related to the ratio of the height from the target of the secondary electron initial trajectory compared to the cathode dark space distance.
One-tenth-second storage of surface acoustic signal in CdS
Authors: Bastide G. , Cambon G. , Sagnes G.
Published: February 2003

We report an experiment on acoustic surface wave storage in photoconducting CdS which leads to a decay time as long as 100 ms. Both charging and storing times are deduced from the experimental amplitude of the echo restored by a readout pulse. In addition we find that charging and discharging of the memory seem to obey a two-step process.
Filaments in semiconductor lasers
Authors: Ripper J. E. , Nunes F. D. , Patel N. B.
Published: February 2003

Filament profiles in cw stripe-geometry homostructure GaAs lasers are measured from below to well above threshold through their optical spectra. It is shown that the filament appears well below threshold and its dimensions are not a strong function of injection level and consequently of the optical field intensity. These results are at variance with previously published theories.
Impact ionization coefficients for electrons and holes in In0.14Ga0.86As
Authors: Pearsall T. P. , Nahory R. E. , Pollack M. A.
Published: February 2003

We report the measurement of impact ionization rates for electrons and holes in the direct band-gap semiconductor alloy In0.14Ga0.86As. Our results show clearly that the ionization rate for holes is greater than that for electrons. The measurments were made for electric fields between 2.6×105 and 3.4×105 V cm−1. In this range, the ionization coefficients can be expressed as α=α∞ exp(-A/E) for electrons and β=β∞ exp(-B/E) for holes with α∞=1.0×109 cm−1, A=3.6×106 V cm−1, and β∞=1.3×108 cm−1, B=2.7×106 V cm−1.
Peltier-induced LPE and composition stabilization of GaAlAs
Authors: Daniele J. J.
Published: February 2003

Peltier-induced liquid-phase epitaxial growth of Ga1−xAlxAs (0.1⩽x⩽0.3) was carried out at constant temperature with the dc as the sole driving force and controlling element of the growth. Electric currents of 10–30 A/cm2 were passed through the solid-liquid (S-L) interface (which acts as a Peltier junction) thereby cooling this interface and causing growth. The growth rate is linearly proportional to the current level. GaAlAs layers of 15–58 μm thickness were grown from relatively small melts (∼5 g) at several temperatures in the range 600–850 °C. Photoluminescence microanalysis of the layers showed that the aluminum composition was remarkably uniform throughout the total layer thickness. In all cases, the variation of the aluminum concentration (x) was observed to be ±0.005 or less.
Empirical corrections to the energy loss of 4He ions in oxides
Authors: Ziegler J. F. , Chu W. K. , Feng J. S.-Y.
Published: February 2003

A survey of the experimental energy loss of 4He ions shows systematic differences between elemental solids and gases. The solid-gas differences are proposed as an empirical first-order correction to obtain solid-target values from gas-target stopping cross sections. These corrections are of the order of 20% for 4He ions of 1 MeV. A series of experiments on the energy loss of 4He ions in oxygen and nitrogen in solid oxides and nitrides are in agreement with the empirical correction factor proposed.
cw double mode locking of the dye laser experiment
Authors: Yasa Z. A. , Teschke O.
Published: February 2003

A mixture of rhodamine 6G and cresyl violet is pumped by a cw argon laser. Inversion of cresyl violet by the absorption of the lasing rhodamine 6G wavelength results in doubly mode-locked operation, with an ultrashort pulse at 5740 Å followed by an ultrashort pulse at 6440 Å.
Study of SAW propagation characteristics by frequency-translated holography
Authors: Shiokawa S. , Moriizumi T. , Yasuda T.
Published: February 2003

Under the condition of continuous acoustic generation the patterns of forward, backward, and standing SAW’s propagating on a y-cut z-propagating LiNbO3 crystal were observed clearly by the frequency-translated holographic technique. The parameters of surface-wave propagation velocity, reflectivity, and transmissivity for an interdigital transducer could be obtained by this technique.
Static conversion of Bloch-line number and the self-collapse of hard bubbles
Authors: Haisma J. , van Mierloo K. L. L. , Druyvesteyn W. F. , Enz U.
Published: February 2003

In bubbles carrying at least 100 Bloch lines, called superhard bubbles, the phenomenon of static conversion of the Bloch wall has been observed. Two experiments will be described in detail: (i) the dependence of the number of Bloch lines as a function of the temperature at which the material has been treated and (ii) the phenomenon of the self-collapse of bubbles having Bloch lines in a supercompressed state.
ISS depth profile analysis of anodized niobium
Authors: Gray K. E.
Published: February 2003

The first several hundred atomic layers of anodized niobium were studied using ion scattering spectrometer analysis alternated with ion milling. The results show excess oxygen at the surface followed by a layer of stoichiometric Nb2O5. Below this was an unexpected ∼ 80-Å layer of NbO and, finally, the bulk metal, with oxygen in solid solution. These results have important consequences for some ac superconducting applications since NbO is a normal metal above 1.38 K.
Optically pumped infrared V-V transfer lasers
Authors: Kildal H. , Deutsch T. F.
Published: February 2003

Laser action in OCS, CO2, N2O, C2H2, and CS2 has been obtained by resonant vibrational-to-vibrational (V-V) energy transfer from CO gas excited by a frequency-doubled CO2 TEA laser. Output energies up to 0.5 mJ, energy conversion efficiencies as high as 7%, and thresholds as low as 0.1 mJ have been observed.
Relief-type diffraction grating by amorphous chalcogenide films
Authors: Utsugi Yasushi , Zembutsu Sakae
Published: February 2003

In As-Se- (S) -Ge amorphous films, a remarkable difference of chemical etching rate between the heat-treated state and the light-irradiated state has been observed. Utilizing this characteristic, a relief-type diffraction grating of the amorphous film was obtained (the pitch between grating lines, 0.86 μm). This grating has achieved a high diffraction efficiency of 15.8%, which was about 10 times greater than before chemical etching.
Low-Z ablator targets for electron beam fusion
Authors: Sweeney M. A. , Clauser M. J.
Published: February 2003

We have calculated the behavior of composite-shell DT-filled targets irradiated by constant-power (’’unshaped’’) 1-MeV electron beam pulses. The outer part of the shell (the ’’ablator’’) is composed of a lower-Z metal than the high-density inner part (the ’’pusher’’). The lower-Z ablator decreases the bremsstrahlung heating of the pusher. The resulting colder and denser pusher is more effective. Breakeven requires about 360 TW deposited for 8 ns in a target about 3 mm in diameter. This is less than half the power required for targets composed of a single high-density metal shell filled with DT.
Effect of GaAs electronic structure on the performance of the GaAs- (Cs,O) photoemitter
Authors: Burt M. G. , Inkson J. C.
Published: February 2003

We have made a theoretical investigation of the emission process for the (111) A and B faces of GaAs activated to negative electron affinity taking into account the full Bloch nature of the wave function of the photoexcited electron. We find that, within the abrupt-step model for the potential in the surface region, the emission probability is sensitive to the amount of band bending in the space-charge region. We also find that, all other things being equal (magnitude of the negative electron affinity, amount of band bending, etc.), the emission probability for the B face is considerably higher than that for the A face.
Observation of dark line defects in GaP green LED’s under an external uniaxial stress
Authors: Iwamoto M. , Kasami A.
Published: February 2003

Dark line defects (DLD’s) have been observed in GaP green LED’s under an external mechanical stress. Excitation of minority carriers is essential to DLD formation. DLD is revealed to grow along the 〈110〉 direction and to correspond to an array of dislocation etch pits. A ’’traveling dark spot’’ was observed for the first time. It moves as fast as 1 mm/sec and becomes trapped at the edge of DLD, which results in DLD growing. DLD generation depends on both the forward current magnitude and external stress.
Torque curves and rotational hysteresis in a smectic C liquid crystal
Authors: Flanders P. J.
Published: February 2003

Static torque curves in 4,4′-terephthal-bis (butylaniline) (TBBA) as a function of temperature are reported. In the smectic A phase (between 173 and 199 °C) a simple sinusoidal torque curve is observed as expected. In the smectic C phase (between 144 and 173 °C) the torque curves are no longer sinusoidal. The torque maximum shifts from π/4 measured from the easy axis to larger angles as the temperature is decreased. Also, rotational hysteresis appears and minor loops are observed. As in the smectic A phase the shape of the torque curves is essentially independent of field, with the torque scaling as the square of the magnetic field. The observed magnetic properties can be understood in terms of the multidomain model for the smectic C phase. Comparison of the calculation with the experimental data allows a determination of the temperature-dependent cone angle from the torque curves. Assuming a rotational model, the calculated hysteresis is found to be larger than the experimental value.
Up-conversion and optical energy storage in CdS
Authors: Schmidt Martin , Perry Percival B.
Published: February 2003

Impurity-assisted red-green conversion has been observed in CdS with excitation intensities less than 1 μW. After red illumination, energy is stored in the crystals for times in the order of hours. The stored energy is detectable as green emitted light by infrared excitation.
Concentration dependence curves of cathodoluminescence of Y2O2S:Tb
Authors: Ozawa Lyuji , Hersh Herbert N.
Published: February 2003

It has been demonstrated that the concentration dependence of cathodoluminescence can be explained by a Brownian motion of the energy carriers out of the penetration volume in which they were initially created by the incident electrons. The model predicts several concentration regions and a crystal size effect. Experimental results for Y2O2S:Tb are in good agreement with the theoretical calculations.
Phonon-induced planar voltages in thin metallic films
Authors: von Gutfeld R. J. , Tynan E. E. , Budd H. F.
Published: February 2003

We have irradiated slant-angle-deposited metallic films on sapphire substrates with pulses of incoherent phonons and observed voltages in the plane of the sample. These voltages are very similar in character to those previously observed using laser irradiation as the excitation source. The new data prove unequivocally that these as well as our previously observed voltages in metal films are purely thermal in origin, consistent with a thermoelectric model.
cw CO-CS2, CO-C2H2, and CO-N2O energy-transfer lasers
Authors: Stregack J. A. , Wexler B. L. , Hart G. A.
Published: February 2003

cw laser emission has been observed from CS2 (11.5 μ), C2H2 (8 μ), and N2O (10.6 μ) transitions pumped by energy transfer from vibrationally excited CO in an electric discharge gas-dynamic laser device. Proposed energy-transfer pathways for these three lasers are described. Supersonic expansion cooling plays a critical role in depopulating the lower laser levels in the CO-CS2 and CO-C2H2 systems. Maximum output powers measured for each of these systems are presented. The dependence of output power on the flow rate of the injected laser species is discussed.
Convolution using guided acousto-optical interaction in As2S3 waveguides
Authors: Loh K. W. , Chang W. S. C. , Becker R. A.
Published: February 2003

Convolution of two acoustic surface waves (ASW) has been obtained by the acousto-optical diffraction of an optical wave in an As2S3 waveguide. A simple theory is presented to show the convolution process. Experimentally, very high acousto-optical diffraction efficiency (93% at 3 mW of acoustic power) has been observed in the As2S3 waveguide. A triangular pulse was observed on the oscilloscope through an optical heterodyne detector when two rectangular ASW pulses were convolved with each other.
Cd-diffused Pb1−xSnxTe lasers with high output power
Authors: Lo Wayne
Published: February 2003

Cd-diffused Pb1−xSnxTe (x∼0.13) diode lasers have been fabricated with cw output powers of 1.25 mW (single mode) and 2.4 mW (total) at 10.6 μm. These power levels are attributed to the low-temperature Cd diffusion, a new method of growing low-dislocation-density crystals, and to a contact resistance as low as 3×10−5 Ω cm2. Multimode emission spectra are common for cw operation, but reducing the cavity width encourages single-mode emission, indicating the filamentary nature of modes in these devices.
Epitaxial solar cells on silicon EFG ’’ribbon’’ substrates
Authors: Kressel H. , D’Aiello R. V. , Robinson P. H.
Published: February 2003

Epitaxial solar cell structures grown on polycrystalline silicon ’’ribbon’’ substrates (prepared by the edge-defined-growth process) are compared to devices made by direct diffusion into similar material. Efficiency values of 10% (AM-1) have been achieved by the epitaxial structures, which are substantially higher than achieved by diffusion. The improvement is shown to result mainly from the lower saturation current density of the epitaxial junctions.
The super-Schottky diode microwave mixer
Authors: McColl M. , Pedersen R. J. , Bottjer M. F. , Millea M. F. , Silver A. H. , Vernon F. L.
Published: February 2003

Superconductor-semiconductor (super-Schottky) diodes fabricated from Pb on p-GaAs have been extensively studied as microwave mixers. The measured performance at X-band is 9-dB conversion loss and 1.6 K diode noise temperature, resulting in a mixer noise temperature of 13 K. This result is in good agreement with theory and represents a major advance in low-noise frequency conversion.
Electrically variable channel-length changes in MNOS transistors
Authors: Lonky M. L. , Turley A. P.
Published: February 2003

Silicon gate MNOS field-effect transistors (FET’s) were fabricated with a gate dielectric consisting of 300 Å HCl oxide, and 450 Å of silicon nitride. The FET’s exhibited selective charge injection near the drain accompanied by silicon surface inversion, causing a shortening of the effective channel length. Measurements of dc drain characteristics exhibit substantial increases in transconductance. Overlap capacitance measurements also confirm the existence of a decreased channel length.
Bubble-lattice propagation by conforming periodic Permalloy patterns
Authors: Chang Hsu , Ho Charles P.
Published: February 2003

Periodic Permalloy chevron patterns are designed to allow a close-packed hexagonal bubble lattice to be aligned with and propagated by them under a rotating field. A group of bubbles is associated with each chevron, one being directly driven by a Permalloy pole while the others are indirectly driven by bubble-bubble repulsion. For different values of rotating field and bias field, propagation and failure modes are delineated.