bluuebunny/crossref_metadata_2025 huggingface dataset:
Stimulated Raman and Brillouin backscattering along a magnetic field
Authors: Willett Joseph E. , Bilikmen Sinan
Published: February 2003

The decay of a circularly polarized electromagnetic wave propagating along a magnetic field into a backscattered circularly polarized electromagnetic wave and a Langmuir wave or ion acoustic wave in a bounded plasma is analyzed.
Performance of a cw double electric discharge for supersonic CO lasers
Authors: Stanton A. C. , Hanson R. K. , Mitchner M.
Published: February 2003

The results of an experimental investigation of a cw double discharge in supersonic CO mixtures are reported. Stable discharges in CO/N2 and CO/Ar mixtures, with a maximum energy loading of 0.5 eV/CO molecule, were achieved in a small-scale continuous-flow supersonic channel. Detailed measurements of the discharge characteristics were performed, including electrostatic probe measurements of floating potential and electron number density and spectroscopic measurements of the CO vibrational population distributions. The results of these measurements indicate that the vibrational excitation efficiency of the discharge is approximately 60%, for moderate levels of main discharge current. These experiments, on a small scale, demonstrate that the double-discharge scheme provides adequate vibrational energy loading for efficient CO laser operation under cw supersonic flow conditions.
Technological aspects of cryogenic laser-fusion targetsa)
Authors: Musinski D. L. , Henderson T. M. , Simms R. J. , Pattinson T. R. , Jacobs R. B.
Published: February 2003

Most current laser-fusion targets consist of hollow spherical glass shells which have been filled with a mixture of gaseous deuterium-tritium fuel. Theoretical considerations suggest that optimum yields can be obtained from these targets if the fuel is condensed as a uniform liquid or solid layer on the inner surface of the glass shell at the time it is irradiated. In principle, this can be accomplished in a straightforward way by cooling the target below the condensation or freezing point of the fuel. In practice, cryogenic targets can appear in routine laser experiments only when the necessary cryogenic technology is reliably integrated into experimental target chambers. Significant progress has been made recently in this field. The authors will discuss the scientific basis and the various technological features of a system which has allowed the successful irradiation of uniform solid-fuel-layer targets.
MHD electrical potentials: Uniqueness of solutions to an extended class of elliptic boundary value problems
Authors: Sacks R. A.
Published: February 2003

The electrostatic potential describing the fields interior to a magnetohydrodynamic (MHD) power generating channel obeys a linear uniformly elliptic partial differential equation. The physically natural boundary conditions, however, do not fall within a class for which the solution has previously been shown to be unique. We discuss the boundary conditions appropriate to this situation and then generalize the discussion in Courant and Hilbert to demonstrate the uniqueness of the solution to an extended class of boundary value problems which includes the MHD channel as a special case.
A small electrostatic retarding field energy analyzer with compensating differentiation circuit
Authors: Oertl M. , Störi H. , Hatakeyama R.
Published: February 2003

A small electrostatic retarding field energy analyzer is constructed in order to measure locally the ion energy distribution functions parallel and perpendicular to a magnetic field. A compensating differentiation circuit enables it to yield the energy distributions clearly in spite of the smallness of the signal available in a low-density plasma. An application is performed to reveal local anisotropic heating due to a plasma instability.
Photoluminescence of shallow acceptors in epitaxial AlxGa1−xAs
Authors: Stringfellow G. B. , Linnebach R.
Published: February 2003

The low-temperature (2 K) photoluminescence (PL) of AlxGa1−xAs (0<x<0.25 was studied in an effort to characterize shallow acceptors in material grown by organometallic vapor phase epitaxy and liquid phase epitaxy techniques. The dominant shallow acceptor in nominally undoped AlxGa1−xAs specimens grown by both techniques was identified as Carbon, with EA=26 meV for x=0. EA was observed to increase with increasing x to ∼36 meV at x∼0.20, as expected for an effective mass like center where EA ∝[m*(x)/ε(x)2]. The PL peak due to the conduction band to acceptor transition was found to become progressively broader with increasing x, which is attributed to increasing donor plus acceptor concentration. The acceptor Ge was studied in intentionally doped LPE specimens. It also behaves as a simple effective masslike center, with EGe∼40 meV for GaAs and 55 meV for Al0.2Ga0.8As, contrary to earlier reports of anomalous behavior.
Cathodoluminescence study of SiO2
Authors: Koyama H.
Published: February 2003

Cathodoluminescence spectra from thin films of silicon dioxide on silicon dioxide were investigated. Four luminescence bands are observed in silicon dioxide in a conventional semiconductor device. Band A at 290 nm (4.27 eV) and band C at 560 nm (2.21 eV) increase substantially with increasing electron irradiation and originate from the electron beam induced defects. Band B at 415 nm (2.99 eV) is not intrinsic in pure silicon dioxide, but is observed in carbon implanted silicon dioxide. The depth-dependent concentration of the luminescence centers for band B from carbon implanted oxide was close to the distribution of the implanted carbon and the luminescence center of band B was attributed to carbon in the silicon dioxide. Band D at 650 nm (1.91 eV) may originate from residual and/or adsorbed H2O. The technique of cathodoluminescence presented in this paper will be able to provide useful information on the defects and impurities in silicon dioxide.
Stimulated emission and optical gain spectrum in highly excited CdSe
Authors: Cingolani A. , Ferrara M. , Lugarà M.
Published: February 2003

The stimulated emission from CdSe at 80 °K under nitrogen or dye laser excitation has been studied. Its dependence on the pumping laser wavelength, on the excitation intensity, and on the excited length of the sample has been investigated. Optical gain spectrum measurements confirm the attribution of the light amplification process to two different radiative mechanisms involving, respectively, the exciton-exciton interaction and the electron-hole plasma recombination, for a photoinjected electron-hole density nc?1017 pairs/cm3.
Field effect studies in p-type InSb MIS structures
Authors: Mathur P. C. , Taneja O. P. , Krishna K. V. , Sen A. D. , Dawar A. L.
Published: February 2003

Field effect studies on MIS structures of silver-glass p-type InSb have been made in the temperature range 77–300 K. It has been observed that the effect of negative gate voltage is to decrease the Hall coefficient, Hall mobility, and grain boundary barrier potential, while the effect of positive gate voltage is opposite but less significant. The results can be explained in terms of accumulation and depletion layers, induced on the surface.
Approximate nonlinear optical susceptibility of cubic boracites
Authors: Delfino M. , Gentile P. S.
Published: February 2003

Optical second-harmonic generation at 1.06 μm was demonstrated in the cubic (4̄3m) and orthorhombic (mm2) phases of Cr-Cl, Cu-Cl, Fe-I, and Ni-Br boracite. The discontinuous change in the second-harmonic intensity is consistent with the known first-order nature of the ferroelectric phase transition. Both phases of boracites are suggested to be non-phase-matchable for second-harmonic generation and for cubic boracites; indirect methods result in nonlinear optical coefficients (d123=d213=d312) in the range (0.20 to 0.26) ×10−9 esu. in the range (0.20 to 0.26)×10−9 esu.
Etch structure on microdefects in floating-zone silicon wafers as affected by dopants and surface treatment
Authors: Roksnoer P. J. , van den Boom M. M. B.
Published: February 2003

The microdefect distribution in dislocation-free floating-zone silicon crystals has been investigated by means of preferential etching. The etch structures developed on the microdefects are found to depend upon the presence of dopants and the surface treatment of the crystal sections. Strong indications were obtained that microdefects in chemically–mechanically polished slices are saturated with atomic hydrogen, developed during the polishing treatment, and which affects the etching behavior of the microdefects in a different way than hydrogen that dissolved in the crystal during the growth process. Low concentrations of dopants appeared to suppress the effect of hydrogen introduced during polishing.
The electron effective mass in In1−xGaxAsyP1−y
Authors: Restorff J. B. , Houston Bland , Allgaier R. S. , Littlejohn M. A. , Phatak Sunil B.
Published: February 2003

The electron effective masses in four epitaxial samples of In1−xGaxAsyP1−y lattice matched to InP (x?0.45y) have been measured by fitting temperature dependent Shubnikov-de Haas data to the appropriate theory. For y=0.764, 0.705, 0.756, and 0.467 we have obtained band-edge effective masses of 0.0464, 0.0471, 0.0478, and 0.0639me, respectively. The compositions were obtained from the band gap using an empirical relation due to Nahory et al. The method has been verified by applying it to bulk and epitaxial GaAs.
Short derivation of the influence of particle size ratio on the conductivity threshold in binary aggregates
Authors: Janzen Jay
Published: February 2003

A model developed by R.P. Kusy for predicting the composition at which the sudden onset of conductivity occurs in polymer/metal powder compacts is shown to yield quantitative results practically equivalent to those given by a previously published solution to the same problem. Significant differences nevertheless exist in the two theoretical developments leading to the concurring results; both approaches are appraised with reference to these differences.
Electrical resistivity and galvanomagnetic properties of evaporated nickel films
Authors: Ghosh C. K. , Pal A. K.
Published: February 2003

Electrical resistivity, temperature coefficient of resistivity, Hall coefficient, and Hall mobility of nickel films were measured simultaneously in situ at temperatures ranging from 30 to 150 °C. Ordinary (R0) and extraordinary (R1) parts of Hall constant were determined from the plot of Hall electric field per unit current density per thickness versus magnetic field for various thicknesses. An oscillatory behavior in the R1-vs-thickness plot was observed.
The effect of a capacitance in I-V characteristics in small superconducting tunnel junctions with high-frequency radiations
Authors: Koyanagi Masao , Endo Tadashi , Nakamura Akira , Matsui Tadayuki
Published: February 2003

I-V characteristics due to quasiparticles are observed with electromagnetic radiations of 96 MHz and 12 GHz in In/Au/Pb–oxide–Pb/Au/Pb tunnel junctions. The situation is clearly understood with the equivalent circuit model where the Josephson junction is connected in parallel with a resistance and a capacitance. The behaviors of the quasiparticle current are well classified into two groups according to whether the ratio of the resistance and the capacitive impedance is larger than or smaller than unity.
Quantum noise effects in tunnel junctions in the 0–1-mV bias range
Authors: van der Ziel A.
Published: February 2003

According to Tucker’s theory of the admittance and the noise of tunnel junctions there should be interesting quantum effects around 1011 Hz, 2 °K, and a 0–1-mV bias range. These effects are evaluated in detail for a metal-oxide-metal tunnel diode. The results apply equally to p-n tunnel junctions. The effects appear to be measurable.
Determination of carrier concentration and compensation microprofiles in GaAs
Authors: Jastrzebski L. , Lagowski J. , Walukiewicz W. , Gatos H. C.
Published: February 2003

Simultaneous microprofiling of semiconductor free carrier, donor, and acceptor concentrations was achieved for the first time from the absolute value of the free carrier absorption coefficient and its wavelength dependence determined by ir absorption in a scanning mode. Employing Ge- and Si-doped melt-grown GaAs, striking differences were found between the variations of electron concentration and those of ionized impurity concentrations. These results showed clearly that the electronic characteristics of this material are controlled by amphoteric doping and deviations from stoichiometry rather than by impurity segregation.
Cathodoluminescence observation of SiO2 layers in a semiconductor device
Authors: Koyama H.
Published: February 2003

Dispersive cathodoluminescence images from thin films of SiO2 in a Test-Element-Group pattern of a conventional Large Scale Integrated circuit device were observed. Band A (290 nm) and band C (560 nm) of the cathodoluminescence were characteristic of a thermally grown SiO2 covered with chemically vapor-deposited (CVD) SiO2 and may be useful for the study of irradiation induced damages in SiO2. Band B (415 nm) and band D (650 nm) were intense in the surface CVD SiO2 and may provide information on process induced impurities in SiO2 layers. The spatial resolution of a cathodoluminescence image is 2 μm, and it is possible to survey SiO2 layers on a conventional LSI device with this technique.
All-Nb low-noise dc SQUID with 1-μm tunnel junctions
Authors: Voss Richard F. , Laibowitz Robert B. , Raider Stanley I. , Clarke John
Published: February 2003

Tunnel-junction dc SQUIDs are being fabricated from Nb films using electron-beam lithography to define linewidths as small as 0.5 μm. The barriers in the Nb-NbOx-Nb junctions are grown in an oxygen plasma discharge, and the Pd2Si resistive shunts are formed by annealing Pd on the Si substrates. These devices have excellent storage and recycling properties. At a measurement frequency of 40 kHz, a SQUID with an inductance of about 1 nH, a critical current of about 4 μA, and a parallel shunt resistance of about 15 Ω had an intrinsic energy resolution of 2.5×10−32 J Hz−1 at 4.2 K and 1.1×10−32 J Hz−1 at 1.6 K, in good agreement with a model of the dc SQUID.
An investigation of the shock-induced transformation of graphite to diamond
Authors: Morris D. G.
Published: February 2003

The transformation of graphite to diamond by impact-produced shock waves has been examined using a gas gun to launch projectiles onto graphite and a graphite-metal mixture. Analysis of the mechanism of transformation is complicated by the post shock graphitization of most of the diamond produced. It is argued that the previously proposed models of shock-wave transformation are incomplete and a revised model of assisted diffusion in a highly defective lattice is proposed to explain the observations.
Electrical properties and the surface characteristics of dispersions of colloidal particulates in coal-derived liquid
Authors: Lockhart N. C.
Published: February 2003

The conductivity, permittivity, dielectric loss, and electrolytic polarization of solvent-refined coal dispersions are measured with respect to frequency (10–105 Hz), to concentration in the range from solids-free liquid to nearly dry solid, and to some extent temperature in the range 290–313 K. Some measurements are also made on the oil, asphaltene, carbene, and insoluble carboid/mineral fractions isolated from centrifuge sediment and supernatant liquid. Washed insoluble matter samples having bulk mineral ash contents from 3 to 63% are also examined, using optical and scanning electron microscopy and surface analysis via electron spectroscopy. The asphaltenes, and to a lesser extent the carbenes, are distributed between the liquid and the particle phases; the latter contains all of the carboids, covering a core of mineral matter. Electrolytic polarization at the electrodes gives the ion concentration, which is about 1.7×10−9 molar for the liquid. Conductivity probably involves both ionic and electronic mechanisms, with the former arising mainly from alphaltenes. The presence of particulate matter decreases the conductivity and electrolytic polarization compared to the solids-free liquid; this is particularly marked up to about 8% solids concentration and is likely to reflect association of acidic asphaltene and basic carbene ionizable species at the outer surfaces of the particles. Induced surface polarization of this associated ionic species, for which the maximum surface charge density is about 1.8×1010 charges/cm2, appears to be responsible for the increased permittivity in the presence of solids. The frequency dependence of the conductivity and permittivity correspond to Cole-Cole dielectric relaxation, and suggest a narrow size distribution, with a mean of about 5 μm in diameter, for the relaxing species. The temperature dependence of conductivity and permittivity indicate that the concentration and mobility components of the activation energies are nearly equal. A small electrophoretic separation and a larger low-frequency dielectrophoretic separation of particles and fluid are predicted.
Stress dependence of tellurium-bound excitons in GaAs1−xPx(Te)
Authors: Ameziane E. L. , Merle P. , Camassel J. , Mathieu H.
Published: February 2003

We present an investigation of the low-temperature piezoluminescence of the (D °X) complex in GaAs1−xPx (Te) in the composition range associated with the direct-indirect crossover (x?0.45). Both the composition dependence and the uniaxial-stress dependence of the low-temperature luminescence peaks are satisfactorily described in the effective-mass approximation if one takes into account all Γ1c and X1c band extrema. The participation of Γ and X1c Bloch functions in the wave function of the neutral donor bound excitons is then deduced versus composition.
Use of space-charge-limited current measurements to determine the properties of energetic distributions of bulk traps
Authors: Ne?purek S. , Sworakowski J.
Published: February 2003

A simple analytical method is put forward in this paper, enabling one to extract quantitative information about an arbitrary energetic distribution of traps for current carriers from a single experimental space-charge-limited current-voltage characteristic. The applicability of the method is illustrated with computer-simulated characteristics, calculated for various typical distributions of traps. The effect of the nonstability of the current, nonuniformity of the spatial distribution of traps, and temperature on the accuracy of the determination of the parameters of traps is briefly discussed.
Transient photoinduced phenomena in amorphous chalcogenide thin films
Authors: Iijima Makoto , Kurita Shoichi
Published: February 2003

The transient photoinduced transmission change under intense band-gap light irradiation was investigated in amorphous chalcogenide thin films. Spectral distribution, temperature dependence, and the relation with the photocurrent of the change were examined. It appears that the change is due to the excitation of electrons trapped in normally unoccupied states near the valence band edge.
Photogeneration and transport of carriers in atactic polystyrene
Authors: Crine J. P. , Yelon A.
Published: February 2003

We have studied the photoconductivity of atactic polystyrene at room temperature under both positive and negative polarity (of the unilluminated electrode). There is a maximum in the response under 5.2-eV uv illumination. If this illumination is sufficiently intense, the total current may have positive polarity even with negative voltage polarity. This is due to the fact that the photocurrent is always positive, due to the diffusion of holes. This may be understood in terms of the Onsager model of geminate generation and recombination. The microscopic phenomena underlying the behavior are discussed as is the applicability of the Onsager model to other polymers.
General formulation of the current-voltage characteristic of a p-n heterojunction solar cell
Authors: Fonash Stephen J.
Published: February 2003

A derived current-voltage (I-V) characteristic for p-n heterojunction solar cells of the form window/absorber is obtained. The development lends itself to a simple, diagrammatical interpretation of the step-by-step collection of the photocurrent flowing out of the base of the absorber. The resulting general I-V characteristic under illumination is in a form useful for the design of these devices and for the interpretation of their performance.
Weak-field magnetoresistance in noncubic (111)-oriented epitaxial films of n-type PbTe
Authors: Allgaier R. S. , Restorff J. B. , Houston Bland , Jensen J. D. , Lopez-Otero A.
Published: February 2003

Measurements of the weak-field magnetoresistance (WFMR) were carried out at 300 and 77 K on two (111)-oriented n-type PbTe epitaxial films, 4 and 10 μm thick. A recently developed single-sample four-measurement technique and a cubic-trigonal-hexagonal extension of the Seitz–Pearson–Suhl WFMR phenomenology were used to obtain and analyze the data. Significant deviations from the requirements of cubic symmetry were detected, the effect being larger in the thinner film and at the lower temperature. A WFMR coefficient ratio, which would have been unity for a cubic environment, ranged from 1.3 to 6.8. These noncubic results are tentatively ascribed to the effects of substrate-induced strain on the films. The four WFMR coefficients were fitted to a simple trigonally distorted three-parameter model of the PbTe conduction band. For reasons not yet identified, the fit was very good for the thinner film and quite poor for the other one.
Effect of Schottky barrier on alternating current response of lead phthalocyanine
Authors: Yasunaga Hitoshi , Shintaku Hiroyuki
Published: February 2003

Measurements were made of the capacitance (1 kHz) and the dc conductivity of degassed, oxygen-doped, and iodine-doped single crystals of lead phthalocyanine (PbPc) as a function of temperature between room temperature and 250 °C. As the temperature was increased, the capacitance initially remained constant as expected, followed by an exponential increase similar to that of the conductivity and then saturated with an extraordinarily large value. Frequency dependence below 1 MHz of the capacitance and the loss tangent of PbPc film with aluminium electrodes was also measured at degassed and oxygen-doped states. An apparent Debye-type dispersion was observed. All the results obtained are consistently understood in terms of the Schottky barrier capacitance associated with the PbPc-electrode contact. The oxygen doping exhibited remarkable influence on the alternating current response and this effect is considered to be due to changes in the barrier capacitance and the dc conductivity with doping.
Asymmetry in the SiO2 tunneling barriers to electrons and holes
Authors: Ng K. K. , Card H. C.
Published: February 2003

The potential barriers of ultrathin (%40 Å) SiO2 layers to electrons and holes tunneling between the semiconductor and the metal have been measured independently on the same MOS samples by a new experimental technique introduced in this paper. The method combines dark measurements of current and capacitance versus voltage with measurements of photocurrent suppression under optical illumination. The results show that the tunneling barriers for holes are consistently much larger than those for electrons.
Reverse current-voltage characteristics of indium tin oxide/silicon solar cells under illumination
Authors: Smith P. , Singh R. , DuBow J.
Published: February 2003

Recently, Rodriquez and co-workers [J. Appl. Phys. 50, 6011 (1979)] reported anomalous photocurrent in reverse-biased tin oxide/silicon solar cells. We have observed no anomalous photocurrent in our indium tin oxide/silicon semiconductor-insulator-semiconductor (SIS) solar cells. In this paper we have offered a possible explanation of why the authors of the above referred paper have observed anomalous photocurrent in tin oxide/silicon solar cells whereas no such effect has been observed in our indium tin oxide/silicon SIS solar cells.
Radiation effects in synthetic berlinite (AlPO4)
Authors: Halliburton L. E. , Kappers L. A. , Armington A. F , Larkin J.
Published: February 2003

Electron spin resonance (ESR), electron-nuclear double resonance (ENDOR), and optical absorption have been used to investigate radiation effects in synthetic crystals of berlinite (AlPO4). Crystals from seeded and unseeded growth were included in the study and impurities in both types of samples were determined by emission spectrographic techniques. The presence of significant concentrations of Fe3+ ions was verified by ESR measurements. When the berlinite samples were irradiated at 300 K with 1.7-MeV electrons, six distinct hole-like centers were created. Thermal anneal studies revealed that four of these centers decay near 425 K and the other two decay at 550 K. All six centers exhibited a hyperfine interaction with a 100% abundant I=1/2 nucleus. The irradiation induced a light orange coloration in the crystals and optical absorption spectra revealed a band at 520 nm along with additional absorption in the ultraviolet region. When the samples were irradiated at 77 K, two additional defects were produced which are not stable at room temperature. One of these latter centers is identified as atomic hydrogen.
Photoinduced polarization and voltage in Michler’s ketone binder layers
Authors: Pillai P. K. C. , Mollah M.
Published: February 2003

Photoinduced charge carrier generation and trapping in an organic material, viz., Michler’s ketone (tetramethyldiaminodiphenyl ketone), in the form of a binder layer, has been studied. The material forms fairly good photoelectrets, stored charge being of the order of 10−9 Coul. Photoelectret charge shows saturation effects for different polarizing parameters, viz., time of photopolarization, intensity of illumination, and applied voltage. An exponentially rising photoinduced voltage has been observed which persists even in the dark, i.e., the material forms an autophotoelectret state as well.
Overlapping pulse technique for imaging space-time-density contours in a gas
Authors: Schmieder Robert W.
Published: February 2003

A technique is proposed for obtaining high-resolution space-time-density images in an inhomogeneous gas sample. The method utilizes overlapping pulses of laser and/or microwave radiation such that avalanche breakdown occurs only where the density is a preselected value and when the pulses overlap. The breakdown produces local plasma regions of high luminosity that can be detected easily, even in the presence of high chemiluminescent or incandescent background.
Determination of a soft x-ray spectrum by photoelectron analysis
Authors: Gupta P. D. , Goel S. K. , Bhawalkar D. D.
Published: February 2003

A scheme is proposed and discussed for obtaining soft and ultrasoft x ray spectrums by photoelectron analysis. It is shown that by combining a grating or crystal spectrometer with a photoelectron spectrometer, the x ray spectrum can be obtained unambiguously over a wide range of wavelengths.
Excitation and decay study up to high pressures of the 33P level of helium pumped by an intense relativistic electron beam
Authors: Luches A. , Nassisi V. , Perrone A. , Perrone M. R.
Published: February 2003

We studied the pressure-dependent peak intensity and time history of the 388.9-nm radiation emitted from the 33P→23S transition of helium at pressures ranging from 10−2 to 55 Torr, following excitation with a short (15 nsec) and intense (25 kA) burst of high-energy (500 keV) electrons. From the decay of radiation we determined the short-lived and long-lived decay components and the values of the effective direct-excitation cross section of the 33P level at several gas pressures. At low pressures ( p?4 Torr) we also determined the quenching cross section of the 33P level by ground-state helium collisions.
Inverse synchrotron interaction
Authors: Pantell R. H. , Edighoffer J. A.
Published: February 2003

An analysis is given for the energy exchange between a focused laser beam and free relativistic electrons in a circular orbit in a uniform magnetic field. Curves are presented to illustrate the dependence of this coupling on the various system parameters. Applications for inverse synchrotron interaction include electron acceleration and amplification of electromagnetic radiation.
The cw electro-optical properties of (Al,Ga)As modified-strip buried-heterostructure lasers
Authors: Hartman R. L. , Logan R. A. , Koszi L. A. , Tsang W. T.
Published: February 2003

This paper presents a detailed study of the cw propeties of a modified-strip buried-heterostructure (MSBH) laser. Included are studies of the electrical, electro-optical, and optical beam properties, together with spectral characteristics, and temperature dependence of thresholds. A variation of this type of laser, a passive-mirror modified-strip buried heterostructure is also described. The MSBH laser possesses many desirable properties including excellent linearity of the lasing emission consistent with a second-harmonic content more than 40 dB below the fundamental, constant proportionality between the light emitted from the two mirror facets, ’’kink-free’’ emission to the maximum cw power levels measured (35 mW/mirror facet), nearly round near-field intensity distribution with an ellipicity of 1.3 : 1, lasing emission in the lowest-order transverse mode, full angle half-power perpendicular to the junction plane of 27.3° (significantly smaller than any other practical cw DH laser structure), and narrow cw spectra (emission is typically in only a few longitudinal modes). MSBH lasers are nonastigmatic signal sources so that diffraction-limited spherical optics can be used. Pulsations are not observed if the active stripe is free of absorbing defects. cw operation of 10 mW/mirror facet was obtained at ambient temperatures to 90 °C with a T0 of 126 °K. For 380-μm-long lasers pulsed threshold currents of 78 mA dc, slope efficiencies of 63%, forward resistances of 2 Ω, and zero-biased capacitances of 15 pF have been measured. At the operating power of 3 mW/mirror facet, the optical power density at the mirror facet is low (?104 W/cm2) which may have positive reliability implications. The passive-mirror form of the MSBH laser (PM-MSBH laser), with the potential for avoiding surface effects which have been implicated as a cause of pulsations and laser degradation, have been measured with thresholds of 104 mA dc and slope efficiencies of 31%.
A comprehensive model of the injection laser: Formulation and test of the current dependence of spontaneous and coherent emission
Authors: Sommers H. S.
Published: February 2003

Extrapolation of the conventional diode equation into the oscillating region gives formal expressions for the internal and external efficiencies in terms of waveguide parameters, threshold current, and the voltage derivative of laser power. The latter, which depends on band and laser theory, is examined for two models. Linear perturbation theory gives qualitative conclusions which are of little utility for actual devices. Combination of diode analysis with the band theory of Stern and the P* theory of North gives a comprehensive theory of the current dependence of the static properties of the laser. The assumptions of the extrapolation are discussed, and experimental examples are presented to illustrate the utility of the new diode analysis. The comprehensive theory is used to interpret various known properties of devices such as linearity of power with current, change of internal efficiency with waveguide thickness, change of junction resistance at threshold, and several scaling laws. The types of experiments to test the theory are discussed and, in particular, the properties peculiar to the P* interaction. Many studies of the latter have shown its rather general applicability, but its utility for ’’pure mode’’ lasers with narrow spectra has not yet been thoroughly studied.
Sequence band effect on multiline oscillation of a TEA CO2 laser
Authors: Endoh A. , Sato T. , Watanabe S. , Kashiwagi H.
Published: February 2003

The small signal gain spectra of a 10.4-μm band of a TEA CO2 laser have been measured and a distinguishable gain anomaly of a R(14) line of the 10.4-μm band has been revealed. This gain anomaly due to sequence band overlapping has been found to be responsible for the appearance of a R(14) line in the multiline oscillation of a TEA CO2 laser. The characteristics of multiline oscillation using a temperature controlled ZnSe etalon have been analyzed in detail by use of the measured small signal gain spectra and temperature- and wavelength-dependent etalon reflectivities.
The optics of twisted nematic liquid-crystal displays
Authors: Birecki H. , Kahn F.J.
Published: February 2003

A simple two-layer model explaining all the main features of angular and voltage dependences of light transmission through twisted nematic liquid-crystal devices is proposed. The model is based on the physical symmetries of the twisted nematic structure and, for the first time, provides a qualitative description of transmission patterns without need for detailed calculations.
Hysteresis-corrected calibration of manganin under shock loading
Authors: Vantine H. C. , Erickson L. M. , Janzen J. A.
Published: February 2003

The coefficient of electrical resistance of manganin was measured under shock loading and ramp unloading. We made 64 measurements of loading stress in the 1.3–40.5-GPa range and 22 measurements of unloading stress in the 1.9–23.2-GPa range. The average loading coefficient was 14% larger than the average unloading coefficient—a clear measure of resistance hysteresis. The source of the hysteresis is attributed to an irreversible resistance change in manganin caused by shock damage. We present techniques to correct for the effects of this irreversible resistance change. With this correction, both loading and unloading levels showed the same average coefficient of resistance 0.0221±0.004 per GPa. Our unified calibration procedure can be very useful for analyzing complex stress signals that are produced, for example, by reactive shock waves.
Line broadening and radiative transport in high-pressure mercury discharges with NaI and TlI as additives
Authors: Stormberg H.-P.
Published: February 2003

In a cylindrical high-pressures lamp, filled with Ar, Hg, NaI, and TlI, the plasma composition is determined by the fully vaporized Hg and the vapor pressures of NaI and TlI. The vapor pressures are controlled by the temperature and composition of the liquid iodide mixture at the coldest spot of the lamp. The calculations of the concentration profiles of all species have been performed using measured temperature profiles. The calculations take into account concentration diffusion and ambipolar diffusion. Using these concentration profiles the local absorption coefficients for the Na-D and the Tl-535 nm lines are evaluated regarding the broadening by Hg atoms. After solving the radiation transport equation the line shapes are calculated. A comparison of the calculated line shapes with the measured ones shows good agreement.
Simplified microwave measurement of uv photoplasmas
Authors: Shammas S. , Seguin H. J. J.
Published: February 2003

A simplified technique for electron density measurements in laser-type uv photoplasmas is described. This modified microwave transmission approach requires a minimum of test equipment and provides all data necessary for a full time analysis of the photoplasma from only a single photographically recorded pulsed measurement. Accuracy is comparable with that of conventional interferometers but speed and simplicity are much improved.
Acceleration of projectiles to hypervelocities using a series of imploded annular plasma discharges
Authors: Tidman D. A. , Goldstein S. A.
Published: February 2003

A mass accelerator system using a series of imploded annular plasma pinches to propel projectiles of mass ranging from grams to kilograms up to high velocities is analyzed theoretically. Such a device would have applications ranging from basic materials and impact studies to space-probe launching and impact fusion.
ISX-B neutral beam injector experiment on a prototype beam line
Authors: Kim J. , Stirling W. L. , Menon M. M. , Dagenhart W. K. , Barber G. C. , Davis R. C. , Haselton H. H. , Schechter D. E. , Tsai C. C.
Published: February 2003

Two PLT-injector-type duoPIGatron sources, modified further by shaping the beam-forming apertures, have been tested and experimented on a protype beam line similar to the ISX-B neutral beam injection system. The accelerator column modification has resulted in an increase of the beam power transmission efficiency from that of the straight-bore aperture by 50%. Maximum neutral beam powers achieved on a 28-cm-diam target simulating the ISX-B plasma, located 4.1 m downstream from the source, are ?910 kW of H0 at an accelerator power of 42 kV and 61 A and ?1020 kW of D0 at 43 kV and 55 A. Measurements have been made to investigate the following: the effects on beam optics of aperture shape, aspect ratio, and different ions (H+ or D+); the distribution of beam power deposition along the beam line; ion species compositions; and background pressure behavior due to scrape-off beam particles. The injectors have been shown to be characterized by an optimum perveance of 6×10−6 AV−3/2 for an effective extraction area of 142 cm2 (1799 apertures), which is approximately invariant over the beam energies tried (viz., 25-45 keV).
Near-band-edge photoluminescence in ZnSe grown from indium solution
Authors: Shirakawa Yasuhiro , Kukimoto Hiroshi
Published: February 2003

The near-band-edge photoluminescence of ZnSe crystals grown from an In solution has been studied in order to elucidate a transition mechanism of the room-temperature blue emission band which is typically observed in the photoluminescence of the low-resistivity ZnSe crystals and the electroluminescence of the ZnSe diodes of metal-insulator-semiconductor (MIS) structure. On the basis of the temperature-dependent behavior of the various near-band-edge emission bands, i.e., changes in the peak energies and the intensities over the wide temperature range, the room-temperature blue emission is attributed to the recombination between free holes and donor electrons. Special attention is paid to a relation between this emission and the low-temperature exciton emission due to the recombination of excitons bound to the ionized donor.
Electro-optic and elasto-optic effects in polyvinylidene fluoride
Authors: Broussoux D. , Micheron F.
Published: February 2003

Linear electro-optic (EO) coefficients are measured in PVF2 at room temperature and constant stress: ‖rX51‖=0.10×10−12 mV−1; ‖rX42‖ =0.21×10−12 mV−1; ‖X13 −(n32 /n31) rX23‖=0.38×10−12 mV−1. We develop a model which allows us to compute the clamped EO coefficients, from the measured free EO coefficients, the piezoelectric and elasto-optic components: ‖πE11−(n32/ n31) πE12‖=3 .6 ×10−12 m2N−1; ‖πE21 −(n32/ n31) πE22‖=1.8×10−12 m2N−1. Secondary effect (differences between free and clamped coefficients) can be neglected for rX42 and ‖rX13−(n32/ n31)rX23‖. The linear electro-optic coefficients are found to be proportional to the remanent polarization, as predicted by the model. This allows us to compute the quadratic electro-optic coefficients at constant strain and stress: ‖gx44‖=0.02 m4C−2; ‖gx13 −(n32/n31)gx23‖=0.01 m4C−2; ‖hX44‖ =14.3×10−23 m2V−2; ‖hX55‖ =6.8×10−23 m2V−2; ‖hX13 −(n32/n31)hX23‖=26×10−23 m2V−2.
Thermal wave microscopy with photoacoustics
Authors: Rosencwaig Allan
Published: February 2003

The physical processes in photoacoustic microscopy are described with an emphasis on the unique capability for microscopic thermal wave visualization of the sample.
Observation of an active photoinductive component in high intensity solar cells
Authors: Jain F. C.
Published: February 2003

The novel results reported in this paper pertain to the behavior of the moderate-to-low frequency reactance of Si and GaAs p-n junction diodes as a function of the incident photon flux density F. We have observed that the diode reactance, which is invariably capacitive under dark or low photon flux conditions, may turn inductive at a threshold photon flux density Fth depending on the diode structure and the spectral characteristics of the incident radiation. Photoinductance values of greater than 100 μH/cm2 were measured reproducibly at room temperature using a 1-MHz signal in several p+p-n, n+-p, and n+n-pp+ type Si diodes (dc open-circuited) illuminated with argon ion (4880 Å), He-Ne (6328 Å) lasers, and white light radiation sources operating at moderate-to-high photon flux densities. Specifically, the photon flux density was varied from virtually dark to about 20 times more intense as compared to the solar flux at air mass m=2. Theoretically, an explicit inductive component is shown to originate in the conductivity modulated section lcmn of the base region when the photogenerated minority carrier concentration becomes comparable to that of majority carriers. The magnitude of photoinductive reactance is computed as a function of incident photon flux density F and results are compared with experiment for a n+-pSi cell.
Formation of p-n junctions and Ohmic contacts at laser processed Pt-Si surface layers
Authors: Doherty C. J. , Seidel T. E. , Leamy H. J. , Celler G. K.
Published: February 2003

Pt-Si alloy layers are formed during 130-nsec pulsed irradiation of Pt coated Si with light from a Nd : YAG laser. The alloys form via surface melting and resolidifaction. Laser processing of arsenic of ion implanted, p-type silicon results in formation of a p-n+/Pt-Si structure that exhibits rectifying electrical behavior. This structure arises because the As and Pt impurities are zone refined to different extents during resolidification of the molten surface layer.
A prediction of the stress state in Nb3Sn superconducting composites
Authors: Easton D. S. , Kroeger D. M. , Specking W. , Koch C. C.
Published: February 2003

The critical current Ic as a function of applied tensile strain depends upon the residual stress state that exists in Nb3Sn bronze-process composite conductors after cooling from the reaction temperature to 4.2 K. This paper presents a simple analytical method to predict the residual stress state and the stress-strain curves of Nb3Sn composites at 4.2 K. The method requires only a prior knowledge of the volume fraction of the composite components and the percentage of Nb converted to Nb3Sn. Experimental results and analytically derived values are compared and good agreement is generally found.
Development of A-15 (V3Ga) superconducting material through controlled precipitation
Authors: Hong M. , Dietderich D. , Morris J. W.
Published: February 2003

A monolithic process has been used to produce superconducting materials by controlled precipitation of the A-15 (V3Ga) phase inside the bcc matrix of a V-rich solid solution. Ingots of V-(17∼19 at.%)Ga were prepared by arc melting, homogenization, and quenching, were deformed at intermediate temperature into tape, and were aged at temperatures in the range 600–1000 °C to precipitate the A-15 phase. The maximum critical transition temperature (∼14.8 °K) was found in materials aged at temperatures of 750 °C or below. At these aging temperatures the Tc initially increases with aging time, and passes through a distinct maximum. The source of the exceptionally high Tc is not clear, but may be attributable to a combination of high solute content and internal strain in the small A-15 precipitate particles.
Fast wall motion in garnet films with orthorhombic anisotropy
Authors: Breed D. J. , de Geus W. , Enz U.
Published: February 2003

High wall and bubble velocities have been observed in garnet films having a strong orthorhombic anisotropy. This anisotropy is induced by compressive misfit stress in garnets containing Mn3+ ions. The magnetostatics of bubbles in these orthorhombic materials differs from that in uniaxial materials, e.g., no hard bubbles have been observed for large in-plane anisotropies. Under certain conditions automotion of bubbles has been observed indicating that vertical Bloch lines may be present. Wall mobilities of 55 m s−1Oe−1 and velocities up to 1400 m s−1 have been observed. The possibilities for small bubble diameter applications will be shown.
A theory of the photomagnetoelectric effect with injection-level-dependent lifetime
Authors: Augelli V. , Vasanelli L. , Leo M. , Leo R. A. , Soliani G.
Published: February 2003

The theory of the photomagnetoelectric effect has been worked out for the case in which the lifetime is dependent on the injection level and the recombination mechanism is described by the Shockley-Read statistics. Under the small signal hypothesis, the nonlinear continuity equation has been solved by perturbative method. An example is presented which evidences the deviation of the theoretical behavior of the spectral distribution of the short-circuit current from the standard case in which the linear continuity equation is considered and the lifetime is constant.
Relationship between magnetocrystalline anisotropy, including second-order contribution, and initial magnetic permeability for monocrystalline MnZn ferrous ferrite
Authors: Stoppels D.
Published: February 2003

For monocrystalline MnZn ferrous ferrite the magnetocrystalline anisotropy constants K1 and K2, the initial permeability μi, and the saturation magnetization Ms have been measured in considerable detail as functions of temperature T. The effect of K2 has been incorporated in the commonly used expressions describing the dependence on K1 and Ms of μi due to rotation of magnetization and displacement of domain walls. It is shown that a nonzero K2 can limit considerably the secondary maximum of μi(T) at the temperature of anisotropy compensation. The results of measurements on monocrystalline Mn0.42Zn0.44Fe2.145O4 are interpreted with the aid of the theoretical expressions obtained for μi as a function of K1, K2, and Ms. Special attention has been paid to the temperature range around the secondary maximum of μi(T) at −82 °C and the temperature range around the primary maximum of μi(T) close to the Curie temperature.
Dipolar field contribution to memory echo in piezoelectric powder
Authors: Kimura Takashi , Yoshikawa Shyokichiro
Published: February 2003

On polarization echoes, dipolar field contribution was considered and the role of the effectively stimulated oscillation mode was investigated. The investigated theory was based on the torque rotation model derived by Melcher and Shiren. The model was developed here by considering the particle behavior under the effectively stimulated oscillation field and the rotation caused by the local field of oscillating dipoles of nearest neighborhood, after taking off the second electric field. As theoretical results, the echo signal was derived as anharmonicity in collection of effectively stimulated oscillations of the dipoles with deviated orientations. The deviated angles of particles due to the local dipolar field were selectively redistributed in accordance with the oscillation modes effectively stimulated by the two-pulse sequence. Experimental results for read out multipulse echoes were explained by the theoretical calculation, not only for time detection including the image echoes, but also for relaxation characteristics along the time axis.
Gas phase photoacoustic Raman spectroscopy using pulsed laser excitation
Authors: West Gary A. , Siebert Donald R. , Barrett Joseph J.
Published: February 2003

The sensitivity of a new spectroscopic technique, photoacoustic Raman spectroscopy (PARS), has been improved substantially by the use of high-peak-power pulsed lasers. The theory for generation of photoacoustic signals from stimulated Raman scattering is outlined, and vibration-rotation Raman spectra for CO2 and CH4 are presented. Applications of PARS are discussed, and a comparison is made with other Raman techniques.