bluuebunny/crossref_metadata_2025 huggingface dataset:
Degradation of AlxGa1−xAs heterojunction electroluminescent devices
Authors: Ettenberg M. , Kressel H. , Lockwood H. F.
Published: January 2004

Experimental results are presented correlating the operating life of (AlGa)As heterojunction diodes with recombination region doping and Al concentration. For a given doping level, the operating life is shown to increase with the addition of Al. The relationship between spontaneous emission degradation and lasing properties has also been studied.
Efficient high-energy-density molecular xenon laser
Authors: Hughes William M. , Shannon John , Hunter Robert
Published: January 2004

Electron beam excitation of pure Xe and Xe–Ar and Xe–Ne gas mixtures have been studied. Significant differences in the temporal character of ultraviolet output were observed. Under the best conditions laser output of 75-MW peak power and 0.76-J output energy were achieved. The molecular xenon laser is established as having the highest power in the wavelength region short of red.
Superconducting current capacities of composite-processed Laves phase tapes, V/HfxZr1−x
Authors: Inoue K. , Tachikawa K.
Published: January 2004

C-15 crystal-type Laves phase compounds, V2HfxZr1−x, were fabricated into a tape by a composite process in which the Laves phase layers were formed by the diffusion between the vanadium sheath and the HfxZr1−x alloy core. In the composition range 0.4 ⩾ x ⩾ 0.3, the composite tape showed the maximum values of superconducting transition temperature, upper critical field, and critical current density. The critical current of the tape did not degrade by winding into coils with diameters larger than 20 mm.
Wetting of thin layers of SiO2 by water
Authors: Williams Richard , Goodman Alvin M.
Published: January 2004

We have measured the contact angle θ of water on silicon and on very thin layers of silicon dioxide grown on silicon. The silicon is hydrophobic and θ is near 90°. Oxides thicker than 30 Å are hydrophilic and θ is near 0°. For intermediate thicknesses, θ varies smoothly between these limits. Our results show that the interaction energy between water and the solid surface depends strongly on the oxide thickness. Consideration of different possible interactions leads us to conclude that this is due to corresponding changes in the structure or composition of the oxide surface.
CdS bolometer for detecting heat pulses in a magnetic field
Authors: Ishiguro Takehiko , Morita Shigeo
Published: January 2004

The characteristics of a new low-temperature bolometer, insensitive to magnetic fields, are reported. The bolometer consists of an evaporated CdS film with interdigital electrodes, and the underlying mechanism is attributed to preferential electron-trapping influences on the dc photoconductivity.
Acoustic surface wave detection of radiative absorption
Authors: Parks J. H. , Rockwell D. A. , Colbert T. S. , Lakin K. M. , Mih D.
Published: January 2004

A new technique is presented to study surface absorptive properties by utilizing the interaction of an acoustic surface wave with a radiatively heated surface region. Phase changes are induced in a surface wave on Y-cut quartz by the absorption of 10.6-μ laser radiation. Quantitative measurements of the process agree with a theory describing the interaction in which there are no free parameters. The sensitivity and response time of this detection process are indicated by phase change signals occurring in a ∼10-μ absorbing film which correspond to a radiative heating of ∼13 μJ and have a rise time of ∼125 nsec.
Harmonic mixing characteristics of metal-barrier-metal junctions as predicted by electron tunneling
Authors: Faris S. M. , Gustafson T. K.
Published: January 2004

The bias dependence of the nonlinear mixing characteristics of metal-barrier-metal junction currents is deduced assuming an electron tunneling model. The difference-frequency beat voltage at frequency ω1−nω2, where n is an integer and ω1 and ω2 are the assumed frequencies of two induced currents, is found to have n zeros as the diode bias is varied. Recent experimental observations have demonstrated such characteristics.
Secondary electron emission from the GaN:Cs–O surface
Authors: Martinelli Ramon U. , Pankove J. I.
Published: January 2004

High secondary emission ratios have been obtained for the GaN:CsO surface. A peak ratio of 51 at 3 keV primary electron energy has been observed. At 20 keV the ratio is 24, compared with 2 when the GaN is uncesiated. Analysis of the data indicates that the diffusion length in the material is between 300 and 800 Å, and the surface escape probability for secondary electrons is 0.36. These results indicate that the GaN:CsO surface has been activated to negative electron affinity (NEA).
Large enthalpy extraction experiments in a nonequilibrium magnetohydrodynamic generator
Authors: Tate E. , Marston C. H. , Zauderer B.
Published: January 2004

A measure of the performance of a magnetohydrodynamic (MHD) generator is the enthalpy extraction (power out/heat in) which generally must exceed 20% to operate efficiently in a thermodynamic Brayton power cycle. For the first time 1.82 MW which represented 19.3% enthalpy extraction was achieved in a nonequilibrium plasma MHD generator. Cold electrodes were used. Theoretical calculations show that 30% enthalpy extraction could be achieved with thermionically emitting electrodes.
A new light modulator using perturbation of synchronism between two coupled guides
Authors: Tada Kunio , Hirose Keikichi
Published: January 2004

A new device that can be used as a light modulator as well as an optical directional coupler is proposed. It consists of p+,n,n+,n and n+-type semiconductor layers. Two n-type layers operate as coupled optical waveguides. The exchange of light power between two coupled waveguides can be controlled by a reverse voltage applied on the p+-n junction. When the voltage was changed from 0 to 10 V in a GaAs test sample of length 1 mm, the output light power from each guide changed by approximately 15% of the total output light power from the two guides at a wavelength of 1.15 μm.
Optical pulse compression
Authors: Grischkowsky D.
Published: January 2004

Dramatic and controllable reshaping of frequency-modulated dye laser pulses has been observed. The pulses, nearly resonant with the 2P1/2 line (7948 Å) of Rb, first passed through a LiNbO3 frequency modulator, and then through a cell containing dilute Rb vapor where the reshaping took place. Large pulse compressions were obtained with only 400 MHz of frequency modulation due to the extremely large frequency dispersion of the group velocity.
Photoemission and electron energy loss spectroscopy of GeO2 and SiO2
Authors: Rowe J. E.
Published: January 2004

The electronic structure of GeO2 and SiO2 has been studied by ultraviolet photoemission spectroscopy (UPS) and electron energy loss spectroscopy (ELS) using thermally grown films prepared in ultrahigh vacuum (p ∼ 10−10 Torr). A consistent energy level model of both filled and empty states is constructed from the UPS and ELS data. The filled states correspond to localized bonding or nonbonding O(2p) molecular orbitals. The empty states observed in ELS correspond to excitons formed from either localized antibonding states or more extended ``conduction'' band states.
Production of negative ions and generation of intense neutral beams by laser irradiation
Authors: Wong A. Y. , Dawson J. M. , Gekelman W. , Lucky Z.
Published: January 2004

10 A of H− ion current is produced by a CO2 laser on NaH targets. A scheme of resonant detachment of electrons from negative ions by the laser is also discussed.
Operation of an amorphous-emitter transistor
Authors: Petersen Kurt E. , Adler David , Shaw M. P.
Published: January 2004

A unique device employing a threshold-type chalcogenide glass as the emitter of a heterojunction transistor has been fabricated. The device exhibits strikingly different behavior depending on whether the amorphous semiconductor is in the on or off state. The several modes of transistor operation can be explained in terms of recently proposed heterojunction band models. An additional implication of the data is the predominance of electrons rather than holes in the one state of the glass, in direct contrast to the low-field behavior.
New method of determination of a metal-semiconductor barrier height
Authors: Guinet C.
Published: January 2004

By using a Pb–Al2O3–Al–n–Ge structure, it is demonstrated that the Schottky barrier height eVB at the Al–n–Ge contact can be determined through a study of the tunneling currents in this device at 1.2°K. One obtains a value for eVB = 0.49 eV.
II-VI photovoltaic heterojunctions for solar energy conversion
Authors: Fahrenbruch Alan L. , Vasilchenko Valery , Buch Fredrik , Mitchell Kim , Bube Richard H.
Published: January 2004

Several different II-VI heterojunctions show possible promise for photovoltaic conversion of solar energy. Two of these are p-CdTe/n-CdS and p-CdTe/n-Zn0.35Cd0.65S, which have a maximum solar efficiency of 17 and 23%, respectively. We report here specifically on the properties of p-CdTe/n-CdS cells prepared (a) by close-spaced vapor transport of CdTe onto single-crystal CdS, and (b) by two-source vacuum evaporation of CdS onto single-crystal CdTe. Cells with efficiency of 4.0% have been produced without detailed attention to optimization of cell design; these cells have quantum efficiencies as high as 0.85.
Room-temperature heterojunction laser diodes from vapor-grown In1−xGaxP/GaAs structures
Authors: Nuese C. J. , Ettenberg M. , Olsen G. H.
Published: January 2004

Vapor-grown epitaxial structures of In0.5Ga0.5P/GaAs have yielded heterojunction laser diodes with room-temperature threshold current densities as low as 8000 A/cm2 for a 2.5-μm GaAs laser cavity width. Differential external quantum efficiencies as high as 30% have been attained. Measurements suggest the existence of internally ``trapped'' laser modes due to the large refractive-index discontinuity at the In0.5Ga0.5P–GaAs interfaces.
Monolithic GaAs injection mesa lasers with grown optical facets
Authors: Blum F. A. , Lawley K. L. , Doerbeck F. H. , Holton W. C.
Published: January 2004

Nondiscrete GaAs electrical injection lasers with vapor-grown optical facets have been fabricated for the first time.
Effects of Sn concentration on the critical current density of Nb3Sn formed at the Nb–(Cu–Sn alloy) interface
Authors: Suenaga M. , Horigami O. , Luhman T. S.
Published: January 2004

Critical current densities Jc (4 T) were measured for Nb3Sn formed by heat treating at 700°C composite wires of single-core Nb in various Cu–Sn alloy matrices. For given thicknesses of the Nb3Sn layers Jc increased with increasing Sn concentration in the matrix up to the single-phase limit of Sn in Cu. Sn concentrations in excess of 8 at.% exceed the solid solubility limit of Sn in Cu at 700°C, and the Jc of the Nb3Sn formed when the composite is heat treated is an order of magnitude less than the Jc obtained for those samples whose Sn content is within the single-phase limit. The highest Jc (4.0 T) was ∼1.8×106 A/cm2 for a 1-μm Nb3Sn layer formed in a 25-mil wire with a Cu–Sn matrix composition of 7.5 at.% (13 wt%) Sn.
Amplification of microwaves by superconducting microbridges in a four-wave parametric mode
Authors: Parrish P. T. , Chiao R. Y.
Published: January 2004

We have observed an electronic gain of 12 dB at 10 GHz in a parametric amplifier whose nonlinear element is a series of unbiased Anderson-Dayem microbridges. The bandwidth was measured to be 1 GHz and the noise temperature to be less than 20 K.
Causes of arcing in cw CO2 convection laser discharges
Authors: Nighan William L. , Wiegand W. J.
Published: January 2004

The factors causing glow-to-arc transition in volume-dominated molecular gas discharges have been analyzed in terms of the collisional processes taking place in the plasma. It has been shown that arcing can be initiated by the growth of disturbances in either vibrational or translational temperature. Calculations indicate that thermal and/or vibrational instabilities will occur for most conditions of importance to high-power cw CO2 convection lasers, and that the growth time for these instabilities is typically on the order of 1 msec.
An empirical corresponding states relationship for the ratio of the heat capacities of polymers
Authors: Warfield R. W. , Pastine D. J. , Petree M. C.
Published: January 2004

An empirical corresponding states relationship between the ratio of the heat capacities Cp/Cv of polymers and the reduced temperature T/Tg has been found. This relationship is discussed in terms of corresponding states behavior. This relationship is significant and useful in that the ratio Cp/Cv is a fundamental quantity for a solid polymer and a knowledge of the value of this ratio is useful for converting adiabatic data into the corresponding isothermal values and vice versa.
Improved performance of a double discharge initiated pulsed HF chemical laser
Authors: Voignier F. , Gastaud M.
Published: January 2004

Operation of a pulsed HF chemical laser initiated by electric discharge is reported. Uniform transverse capacitive discharge through high-pressure mixtures of SF6 and H2 is effected by the use of a double discharge. For the mixture SF6, H2, He (250, 20, and 280 Torr, respectively) laser output of more than 1 J per pulse with 4% electrical efficiency from an active volume of 0.06 1 has been achieved. Pulse shapes of the different transitions, spectrum measurements, and SF6 decomposition rate are reported.
Transverse double-discharge high-pressure glow excitation of uv lasing action in molecular nitrogen
Authors: Hasson V. , Preussler D. , Klimek J. , von Bergmann H. M.
Published: January 2004

Pulsed high-pressure photostabilized glow discharges can be used to pump ultraviolet lasers on nanosecond time scales. This capability is demonstrated by efficient glow excitation of ultraviolet lasing action in molecular nitrogen. The glow can be generated by simultaneously initiating many electron avalanches over the cathode surface. This glow mode of operation was achieved using a transverse double-discharge excitation principle.
Generation of multiband 1-ns pulses in CO2 lasers
Authors: Figueira J. F. , Sutphin H. D.
Published: January 2004

A technique of generating 1-ns pulses of CO2 laser radiation using a CdTe electro-optic gate driven by a laser-triggered Blumlein structure is described. By the use of intercavity absorbers, simultaneous output is obtained on multiple rotational lines of both the 9.4- and 10.4-μm vibrational bands.
Theoretical efficiency in an organic photovoltaic energy conversion system
Authors: Reucroft P. J. , Takahashi K. , Ullal H.
Published: January 2004

The maximum theoretical solar conversion efficiency is calculated for an organic photovoltaic energy conversion system based on PVK-TNF. Charge separation is assumed to take place at a Schottky barrier. At high fields (108 V m−1) the theoretical energy conversion efficiency approaches a maximum value of 2% with a 2-eV barrier. Lower efficiencies are found for barriers greater than or lower than 2.0 eV and at lower fields.
Gamma spectroscopy with insulated CdS crystals
Authors: Eichinger P. , Kallmann H.
Published: January 2004

The technique of using thin insulating layers as blocking contacts has been applied to CdS crystals for γ spectroscopy. Detector operation at temperatures up to 100 °C was possible with an energy resolution of 8 keV at 122 keV for a 125-μm-thick crystal. During counting no external bias has been applied: Internal fields of the order of 105 V cm−1 can be generated if the insulator-semiconductor interfaces are charged by illumination under external bias. By comparison of the amounts of charge generated by single γ quanta in a germanium crystal and in a CdS crystal, the mean energy to create a pair has been determined to 6.3 eV for CdS.
Acoustic Fresnel zone plate transducers
Authors: Farnow S. A. , Auld B. A.
Published: January 2004

Experimental focal plane intensity distributions are presented for a 10-zone acoustic zone plate operating at approximately 10 MHz. The results are related to the spatial frequency response of the transducer. Some initial imaging experiments with this transducer are described along with preliminary results for an acoustic phase plate.
Optical imaging using second harmonic generation of acoustic surface waves
Authors: Schenker P. S. , Lee C. W. , Gunshor R. L.
Published: January 2004

Conversion of an optical image into an electrical signal is obtained by means of a harmonic generation process. The device consists of a high-resistivity silicon semiconductor coupled to acoustic surface waves propagating on a YZ lithium niobate substrate.
Enhancement of transverse thermoelectric voltages in thin metallic films
Authors: von Gutfeld R. J. , Caswell H. L.
Published: January 2004

A correlation between the surface morphology of slant-angle deposited films and the magnitude of the transverse thermoelectric voltage has been observed. This finding has been mainly responsible for the fabrication of optical detectors with responsivities greatly enhanced over those previously reported, extending to 10.6 μ and into the cw range.
Surface scattering at LSD-wave initiation sites on nonmetallic materials
Authors: Walters C. T.
Published: January 2004

Elliptical and circular fringe damage patterns have been observed at laser-supported detonation (LSD) wave initiation sites on acrylic plastic and fused silica surfaces irradiated in air with 10.6-μ laser radiation. The patterns are believed to result from a surface scattering mechanism at point-scattering centers which may play a significant role in LSD-wave initiation on nonmetallics.
Formation of substitutional alloys by ion implantation in metals
Authors: Poate J.M. , DeBonte W.J. , Augustyniak W.M. , Borders J. A.
Published: January 2004

Ion channeling and backscattering have been used to measure the lattice location of Au implanted at room temperature into single-crystal Ni, Cu, Pd, and Ag. In all cases the Au atoms are found to be 100% substitutional with no thermal annealing. Au implanted at 15°K in Cu is found to be 100% substitutional. High-dose implantations of W, a reportedly insoluble impurity in Cu, are also observed to be highly substitutional after implantation.
High-power generation from a parallel-plates-driven pulsed nitrogen laser
Authors: Levatter Jeffrey I. , Lin Shao-Chi
Published: January 2004

Preliminary results from a recent study of high-power generation from a pulsed nitrogen laser are presented. The laser is a modified Blumlein similar to that reported by Basting et al., but uses a self-triggered spark gap for rapid repetitive switching, a third electrode in the laser cavity for preionization, and a razor blade cathode structure to provide a uniform volume discharge. So far, output power in excess of 3 MW and pulse energy greater than 20 mJ have been obtained, but there is no evidence that the discharge is operating in a traveling-wave mode.
Disorder-induced carrier localization in silicon surface inversion layers
Authors: Arnold Emil
Published: January 2004

Potential fluctuations in silicon surface inversion layers give rise to carrier localization in this quasi-two-dimensional system. A semiclassical model is used to evaluate the density of states in the tails below the bands of extended states. To investigate the carrier transport in the tails, we have measured the Hall mobility at lower temperatures and carrier concentrations than has previously been reported. The observed results cannot be accounted for by thermal excitation to extended states above a mobility gap or by thermally activated hopping in localized states. An explanation based on percolation theory is suggested.
Nb-diffused LiTaO3 optical waveguides: Planar and embedded strip guides
Authors: Standley R. D. , Ramaswamy V.
Published: January 2004

Previous results on dielectric optical waveguides made by diffusing niobium into LiTaO3 have been extended. It is shown that the propagation constants of the thin-film waveguide modes can be accurately calculated assuming that the refractive index decreases as the square of the distance into the film. Low-loss single-mode embedded strip guides made by electron resist masking techniques are also described.
Application of optical frequency shifting by means of amplitude modulation in laser-Doppler velocimetry
Authors: Lee Peter H. Y.
Published: January 2004

A simple method of optical frequency shifting a laser-Doppler signal is described. The method employs a local-oscillator heterodyne system where the signal beam is modulated in amplitude by either a light chopper or a rotating linear polarizer disk. Photomixing the signal and reference beams at the photodetector will yield an output that will contain, among other terms, a term at the sum frequency of the Doppler and amplitude modulation frequencies. Due to the low frequency of amplitude modulation, this method is uniquely suited for frequency biasing of Doppler signals from scatterers moving at very low speeds.
Single longitudinal mode operation of cw junction lasers by frequency-selective optical feedback
Authors: Paoli Thomas L. , Ripper José E.
Published: January 2004

cw oscillation in a single longitudinal mode is reported for stripe-geometry junction lasers operated at room temperature with frequency-selective optical feedback. The frequency-selective feedback, obtained by optically coupling a diffraction grating to the diode, is used to select a single mode of the normally multimode spectrum generated by the diode laser itself. Single-frequency oscillation is observed for currents up to 30% above threshold. The oscillation frequency has a linewidth determined primarily by the internal dynamics of the diode and is tunable over the entire multimode spectrum. Additional experimental results demonstrate the homogeneous broadening of the radiative line in these lasers.
Dynamic diffuse wall in magnetic bubble garnet material
Authors: Zimmer G. J. , Morris T. M. , Vural K. , Humphrey F. B.
Published: January 2004

A new dynamic domain wall has been discovered in magnetic bubble garnet materials. Single 10-nsec exposure photographs show that it is diffuse in nature with a width that is velocity dependent. The maximum width observed is 28 μm for a wall moving at 290 m/sec in expanding and collapsing bubbles. With a constant in-plane field applied (50 or 100 Oe) walls moving parallel to the field become wide and diffuse in about 100 nsec, whereas walls moving perpendicular to the in-plane field move faster but do not exhibit the diffuse boundary.
Josephson tunneling through locally thinned silicon wafers
Authors: Huang C. L. , Van Duzer T.
Published: January 2004

We have made and tested Josephson junctions in which tunneling takes place through a locally thinned region in a single-crystal silicon wafer. An etching technique is used to produce a square uniform thinned layer, 87.5 μm on a side and ≈400 Å thick. After removal of the oxide layer, superconducting metals are deposited on both sides. Temperature and magnetic field dependences of the critical current, as well as the magnitude of the current, conform very closely to the theory for a Josephson tunnel junction. This is the first type of Josephson junction employing a barrier which is accessible for modification prior to deposition of the superconducting electrodes.
Temperature dependence of ac losses and self-field critical currents in Nb3Sn
Authors: Bussiere J. F. , Garber M. , Shen S.
Published: January 2004

ac losses and self-field critical currents were measured in a Nb3Sn tape between 4.2 and 17 K. The observed dependence of losses on current at 4.2 K is adequately reproduced by assuming a surface barrier ΔH = 710 Oe and a bulk critical current density Jc = 5.7×106 A/cm2. The temperature dependence of losses above 4.2 K can also be reproduced by taking into account the observed parabolic dependence of Jc on temperature and by postulating a [1 − (T/Tc)4] dependence for ΔH. A new technique is described for measuring the critical current.
Oxygen uptake of obliquely deposited Ge films
Authors: Ma William , Anderson R. M.
Published: January 2004

Germanium films, which were obliquely deposited in relatively high pressures of oxygen, were studied with TEM and ESCA. TEM photomicrographs of the films show that large elongated clusters appear as the pressure of oxygen during film deposition increases. The number of these clusters increases as the deposition angle (the angle between the source flux and the substrate plane) decreases. ESCA results indicate that the films consist primarily of Ge and HCl-soluble GeO2. The amount of oxygen uptake in the films increases as the pressure of oxygen during deposition increases and/or as the deposition angle decreases. These results are important to the understanding of the anomalous photovoltaic effect.
Analytical considerations of Bragg coupling coefficients and distributed-feedback x-ray lasers in single crystals
Authors: Yariv Amnon
Published: January 2004

Expressions for the coupling coefficients characterizing Bragg x-ray scattering in single crystals are derived. These are used to obtain the threshold gain of a new type of x-ray distributed-feedback laser.
Bremsstrahlung emission from laser - produced plasmas
Authors: Kephart J. F. , Godwin R. P. , McCall G. H.
Published: January 2004

The x-ray bremsstrahlung from 4 to 50 keV emitted by laser-produced plasmas has been measured using a Bragg crystal spectrometer. Direct spectral information was obtained in contrast to earlier filter spectroscopy. Measurements were made with focal spot powers of 1016 W/cm2 of 1.06-μm radiation and 1014 W/cm2 of 10.6-μm radiation. A definite suprathermal electron component was observed.
The 10.6-μm absorption of KCl
Authors: Deutsch Thomas F.
Published: January 2004

The 10.6-μm absorption in most KCl is shown to be dominated by a broad absorption band near 9.7 μm. The integrated absorption of this band decreases with increasing temperature. The temperature dependence is consistent with that to be expected from the dissociation of an absorbing pair. A KCl crystal has been measured whose 10.6-μm absorption, 6.6±2×10−5 cm−1, is at the intrinsic multiphonon level.
Saturation spectroscopy with a tunable spin-flip Raman laser
Authors: Patel C. K. N.
Published: January 2004

We have carried out saturation spectroscopy of the H2O line at 1889.58 cm−1 using a tunable spin-flip Raman (SFR) laser. We have observed Lamb dip widths of the order of 200 kHz, demonstrating the usefulness of the tunable SFR laser for ultrahigh-resolution spectroscopy (resolution ∼ 3 × 108).
Photobleaching of Rhodamine 6G in polyacrylonitrile matrix
Authors: Reich S. , Neumann G.
Published: January 2004

The photobleaching of Rhodamine 6G (Rh:6G) in the polyacrylonitrile (PAN) matrix was studied at 5145 Å as a function of temperature. Photobleaching yield numbers were measured at room temperature and 106 °K. The quantum efficiency for fluorescence and the absorbtion cross sections were measured both for the solid polymer dye system and the liquid monomer dye solution. The observations were compared to Rh:6G in polymethylmethacrylate (PMMA). The PAN+Rh:6G system compares well to the PMMA+Rh:6G system and offers some advantages. Laser action was induced in a PAN+Rh:6G system in a longitudinally pumped polymer plate.
Planar domains in ion-implanted magnetic bubble garnets revealed by Ferrofluid
Authors: Wolfe R. , North J. C.
Published: January 2004

Magnetic closure domains in ion-implanted surface layers associated with magnetic bubbles in the underlying garnet films have been revealed by the Bitter pattern method using Ferrofluid. This is the first direct observation of the planar magnetization produced by ion implantation in garnets with negative magnetostriction. The closure domains are very sensitive to an in-plane magnetic field and become too small to observe in rotating fields as large as those used in field-access bubble devices. Closure domains around an ion-implanted pattern in a garnet film and in a thin film of Permalloy evaporated onto a bubble garnet are also shown.
Acoustic readout of charge storage on GaAs
Authors: Grudkowski T. W. , Quate C. F.
Published: January 2004

We show that surface acoustic waves on GaAs can be used to read the amount of charge stored on an isolated Schottky barrier. This charge can be controlled by the light intensity which illuminates a given electrode and our technique allows one to monitor this light intensity. We propose that the effect can be used in a panel array suitable for imaging.
Surface state memory in surface acoustoelectric correlator
Authors: Bers A. , Cafarella J. H.
Published: January 2004

We show that surface acoustic signals can be stored in and read from electron traps at the surface of a semiconductor that is adjacent to the piezoelectric on which the surface wave propagates. The observed memory action is explained by the large-signal dynamics of the charging and discharging of the traps near a slightly depleted surface. The storage of the signal is accomplished by creating a zero-frequency k pattern which fills the traps. The reading of the signal can be done by either correlation or convolution with another surface acoustic signal. This correlation device with internal memory does not require precise signal timing, operates with all signals at the same frequency, and does not require external time inversion of the reference signal.
Reflectivity studies of laser-produced plasmas of variable density
Authors: Gruhl T. , Puell H. , Kaiser W.
Published: January 2004

Light reflecting from a laser-produced plasma was measured as a function of plasma density. Light pulses of a Nd-glass laser (100-psec duration and 1014−W/cm2 intensity) were focused on a high-pressure gas jet as a target. A distinct reflectivity maximum of 0.3 was observed for helium at a density value 30% below the critical density. The results are interpreted in terms of stimulated Brillouin scattering.
Scanning electron micrographs of self-quenched breakdown regions in Al–SiO2–(100)Si structures
Authors: Yang D. Y. , Johnson W. C. , Lampert M. A.
Published: January 2004

SEM photographs of regions of breakdown produced in vacuum (10−3 Torr) are exhibited for four basic Al–SiO2–(100)Si configurations: p substrate, field plate + and field plate -, and n substrate, field plate + and field plate -. With p-Si and field plate +, the geometry of the breakdown region reflects the anisotropic conductivity of hot electrons in Si along the (100) plane of the substrate wafer. Some properties of the breakdown correlate with the nature of the substrate surface channel (inversion versus accumulation); other properties correlate with the field-plate polarity.
CdSe down-converter tuned from 9.5 to 24 μm
Authors: Hanna D. C. , Luther-Davies B. , Smith R. C. , Wyatt R.
Published: January 2004

The signal and idler outputs from a proustite parametric oscillator have been difference mixed in a CdSe crystal to produce infrared radiation tuned continuously from 9.4 to 24.3 μm. Difference-frequency powers, monitored by a pyroelectric detector, range from 10 W at 10 μm to 100 mW at 22 μm.
Optically excited organic dye vapor laser
Authors: Smith P. W. , Liao P. F. , Shank C. V. , Gustafson T. K. , Lin C. , Maloney P. J.
Published: January 2004

We report the observation of laser action in an organic scintillator dye vapor (POPOP). The dye was heated in a suitable oven and the vapor excited with the 3371-Å radiation from a pulsed N2 laser. 30 kW of laser output at 3930 Å was obtained at a dye temperature of 330°C.
Efficient LPE-grown Inx Ga1 −x As LEDs at 1–1.1-μm wavelengths
Authors: Nahory R. E. , Pollack M. A. , DeWinter J. C.
Published: January 2004

We report the growth and fabrication of LPE multilayer Inx Ga1 −x As homojunction LEDs. Junction edge emission in the 1.0–1.1-μm wavelength range was obtained with external efficiencies of ∼1%. An important feature of the device structure is the incorporation of simple stepwise compositional grading for lattice matching of the substrate and p-n junction layers.
Quenching of laser action in cresyl violet by 6943-Å radiation
Authors: Evans D. E. , Puric J. , Yeoman M. L.
Published: January 2004

Experiments demonstrate complete quenching of laser action in cresyl violet dye pumped by the second harmonic of a ruby laser, in the presence of 6943-Å light. The mechanism responsible may be depletion by stimulated emission of the population in the upper laser level.
Photocapacitance investigation of defects in GaAs0.6P0.4
Authors: Forbes L. , Fogle R. M.
Published: January 2004

This work describes the application of the technique of photocapacitance transients to determine the photoionization cross section, thermal emission rates, and carrier capture coefficients or cross sections of defects in GaAs0.6P0.4. A coupled multiple-level defect with a large hole capture cross section has been identified in n-type GaAsP which will result in, and can account for, nanosecond nonradiative minority-carrier or hole lifetimes in this material. The photoionization crosss section has a sharp threshold at 0.9 eV, placing the main level at 0.9 eV below the conduction band; a level of 0.9 eV has often been observed in GaAs and GaP.
Tantalum oxide light guide on lithium tantalate
Authors: Lee Yong-Kyung , Wang Shyh
Published: January 2004

A technique is reported which allows formation of a light-guiding Ta2O5 film onto an electro-optic LiTaO3 crystal. We find it necessary to have an isolation layer (a 144-Å SiO2 layer in our case) between the Ta film and the substrate in order to prevent interactions between them during thermal oxidation of the Ta film. Possible applications of the structure to thin-film electro-optic and acousto-optic devices are examined.
Excitation of surface-wave acoustoelectric domains triggered by external signal
Authors: Furukawa Seijiro , Matsumoto Shigetaka
Published: January 2004

Surface-wave acoustoelectric domains were excited in a photoconductive CdS crystal. It was verified experimentally that the generation of these domains was triggered by an external signal. An adhesive tape stuck on the propagation plane prevented the excitation of the domains.
Attenuation of elastic surface waves by anharmonic interactions at low temperatures
Authors: Sakuma Tetsuro , Nakayama Tsuneyoshi
Published: January 2004

Based on the theory of surfons, we present a formalism to calculate the attenuation rate of elastic surface waves at low temperatures in the high-frequency region. A general formula for the attenuation rate due to the cubic anharmonic terms in the elastic energy of an isotropic elastic continuum is given by means of a temperature-dependent Green's function. In a frequency region between 20 and 40 GHz at T=1°K, our result shows quite different frequency and temperature dependence ω1+n T4−n (1.9 ≲ n ≲ 2.2) from that obtained in the low-frequency region.
Storage of acoustic signals in surface states in silicon
Authors: Hayakawa H. , Kino G. S.
Published: January 2004

An acoustic wave storage device capable of storing an acoustic surface wave signal for times of up to several milliseconds is described. The principle of the device is based on that of the acoustic surface wave convolver, with the information stored in surface states in silicon. It is expected that the storage time will ultimately be as much as 10–30 msec for signals with modulation frequencies of tens of megahertz. At the present time, we have seen storage of pulses approximately 0.4 μsec long for times of approximately 2 msec, but some of these early devices seem to be capable of yielding storage times as long as 7 msec.
Frequency-addressed liquid crystal field effect
Authors: Bücher H. K. , Klingbiel R. T. , VanMeter J. P.
Published: January 2004

A new nematic material in which ε∥ exhibits a dielectric loss in the audio-frequency range is reported. At 25 °C Δ ε=(ε∥−ε⊥) reverses sign at 2.5 kHz and can be as positive as 6.2 at low frequencies and as negative as −2.2 at high frequencies; the activation energy for the loss is 0.91 eV. The availability of a dielectric anisotropy of either sign depending on the frequency of the applied field allows the electrical orientation of the material with its optic axis either parallel or perpendicular to the electrodes. The possibilities for improving the voltage threshold and dynamic response of electro-optical effects by means of a two-frequency addressing scheme are demonstrated.
Photoexpansion and ``thermal contraction'' of amorphous chalcogenide glasses
Authors: Igo Takeo , Noguchi Yoshio , Nagai Haruo
Published: January 2004

Expansion due to illumination (photoexpansion) and contraction due to heat treatment (``thermal contraction'') of As–Se–(S)–Ge glass films have been observed utilizing the bimetal structures. This property is related to the reversible photodarkening effect of these chalcogenide glass films.
Double-heterostructure GaAs distributed-feedback laser
Authors: Shank C. V. , Schmidt R. V. , Miller B. I.
Published: January 2004

The fabrication and operation of a GaAs–GaAlAs heterostructure distributed-feedback laser are described in which fine optical corrugations (≈ 1150 Å) are etched and regrown into the interface between two layers of the heterostructure. Laser operation has been observed before and after the growth of the final layer with optical pumping.
Distributed-feedback single heterojunction GaAs diode laser
Authors: Scifres D. R. , Burnham R. D. , Streifer W.
Published: January 2004

Laser operation utilizing distributed feedback (DFB) in single heterojunction (SH) GaAs/GaAlAs diodes is reported. Laser wavelengths ranging from 8430 to 8560 Å were observed in various samples depending on grating period. The threshold current densities required were comparable to those of normal SH diodes.
On-state characteristics of amorphous/crystalline heterojunctions
Authors: Petersen Kurt E. , Adler David
Published: January 2004

Band models previously applied to off-state chalcogenide-glass/crystalline Si heterojunctions are shown to be applicable to these devices after the threshold-type glass is switched into the on state. In addition, it appears that the on state can be maintained by the injection of electrons from the amorphous semiconductor into n-type Si, contrary to some double-injection models for threshold switching.
Successful liquid phase epitaxial growth and optically pumped laser operation of In0.5Ga0.5P–Ga0.4Al0.6As double-heterostructure material
Authors: Miller B. I. , Johnston W. D.
Published: January 2004

The preparation by liquid phase epitaxy of laser-quality Aly Ga1−y As/In0.49Ga0.51P/Aly Ga1−y As double-heterostructure material is reported. The structure provided optical waveguiding and carrier confinement for y ≳ 0.6. Cleaved bars have shown laser action at ∼6200 Å, when optically pumped in the temperature range 77–130 K. The lasing threshold is 50% higher than for geometrically similar high-quality Al0.5Ga0.5As/GaAs/Al0.5Ga0.5As laser material.
EPR and optical study of Fe in Nd:YAlO3 laser crystals
Authors: Belt R. F. , Latore J. R. , Uhrin R. , Paxton J.
Published: January 2004

EPR data confirm the presence of Fe impurities in single-crystal laser hosts of YAlO3. Optical absorption in Fe:YAlO3 was measured to distinguish contributions of Fe3+ and Fe2+ to passive loss in Nd:YAlO3. YAlO3 crystals grown or annealed in H2 contain both Fe2+ and OH− which increase the absorption loss at 1.06 μm and cause fluorescence quenching.
Evaluation of CaLaSOAP: Nd for high-power flash-pumped Q-switched lasers
Authors: Steinbruegge K. B. , Baldwin G. D.
Published: January 2004

Pump-induced thermal lensing and bifocusing have been measured for flash-pumped CaLaSOAP:Nd, together with long-pulse and Q-switched laser efficiencies. The results show that CaLaSOAP:Nd maintains its high efficiency in the Q-switched mode, that it is capable of average power operation exceeding 1 J at 30 pps, and that bifocusing is less severe in CaLaSOAP:Nd than in YAG:Nd.
High-voltage bulk photovoltaic effect and the photorefractive process in LiNbO3
Authors: Glass A. M. , von der Linde D. , Negran T. J.
Published: January 2004

Photocurrents in doped LiNbO3 crystals are shown to be due to a bulk photovoltaic effect with saturation voltages in excess of 1000 V (∼105 V/cm). This effect accounts for the light-induced index changes in LiNbO3. An explanation of the photovoltaic effect, based on the asymmetry of the lattice, is proposed.
Electrically variable diffraction in spherulitic liquid crystals
Authors: Haas Werner E. L. , Adams James E.
Published: January 2004

An electrically controllable diffraction mode in liquid crystals is described. The variable grating is a stable single layer of small uniform birefringent spherulitic domains imbedded in a homeotropic matrix. The size of the domains is changed by small dc or ac voltages.
Electron irradiation experiments in gold with 2.5-MeV electrons
Authors: Ruault M. O. , Jouffrey B.
Published: January 2004

Electron irradiations were performed on six nines purity gold in the 3-MV electron microscope at Toulouse. Partially ordered vacancy tetrahedra were observed in all of the sample while interstitial loops were formed in its thick parts. Investigation of the nature and cause of the ordering are reported.
Equivalence of the electronically focused acoustic imaging device to a diode convolver
Authors: Otto O. W.
Published: January 2004

It is demonstrated that the electronically focused acoustic imaging device is equivalent to a diode convolver where the sound image is formed by using the convolver to perform a Fresnel transform of the sound field at the receiving array.
Picosecond x-ray streak camera
Authors: McConaghy C. F. , Coleman L. W.
Published: January 2004

An ultrafast x-ray-sensitive streak camera is described. Time resolution is ≈50 psec. A streak record of the x rays from a laser-produced iron plasma is included.
Comparison of radiation from laser-produced and dc-heated plasmas in xenon
Authors: Silfvast W. T. , Wood O. R.
Published: January 2004

The spectral radiance from a cylindrically shaped laser-produced plasma in the ultraviolet region (200–300 nm) is shown to be 2–3 times greater than that produced by a xenon flashlamp of comparable size and input energy. The experimental results suggest several advantages of laser-produced plasmas as sources for the optical pumping of lasers.
TEM observation of dislocation loops correlated with individual swirl defects in as-grown silicon
Authors: Bernewitz L. I. , Kolbesen B. O. , Mayer K. R. , Schuh G. E.
Published: January 2004

Swirl defects in as-grown silicon single crystals could be observed directly in a transmission electron microscope after application of a special sample preparation method. Complicated dislocation loops were found at positions of individual swirl defects which had been revealed as hillocks rather than as etch pits by a modified Sirtl etch.
Determination of impurity and mobility distributions in epitaxial semiconducting films on insulating substrate by C-V and Q-V analysis
Authors: Lehovec Kurt
Published: January 2004

The mobility distribution in a semiconducting epitaxial film on insulating substrate is derived from transmission line analysis of Q-V data combined with the C-V method for obtaining impurity distribution. The mobility thus obtained is found to agree with that obtained by Hall effect measurements for an n-type epitaxial GaAs layer on semi-insulating Cr-doped GaAs substrate.
Transport properties in HgI2
Authors: Martin G. M. , Bach P. , Guétin P.
Published: January 2004

Time-of-flight measurements have been performed on HgI2. The electron drift mobility varies between 55 and 75 cm2/V s for fields E ≤20 kV/cm. The plot of the electron drift velocity versus E exhibits a maximum for E ∼80 kV/cm; beyond this value the differential mobility becomes negative (∼−5 cm2/V s). an electron trapping time τe+ is found larger than 100 ns. Our measurements also yield estimations of the hole mobility and of the hole trapping time.
Influence of intensity of em field on multiphoton ionization of neon by a neodymium laser
Authors: Baravian G. , Benattar R. , Sultan G.
Published: January 2004

A neodymium laser beam is focused in neon at low pressure. We measure the number of charges created for different laser powers. For powers corresponding to values of the electric field in the focused region greater than 3×107 V/cm, there is a progressive decrease in the number of charges created.
Use of electron backscattering for smoothing the discharge in electron-beam-controlled lasers: Computations
Authors: Smith Richard Cecil
Published: January 2004

The anode material in an electron-beam-controlled gas laser strongly influences the uniformity of the sustainer discharge, because the backscattering of the beam electrons from the anode is different for different atomic numbers. As a result of switching from aluminum to, for instance, uranium, there is a 60% increase in the ionization near the anode, according to Monte Carlo computations for a typical planar laser configuration. This effect can cause a 30–60% drop in the local electric field, depending upon the field dependence of the electron-ion recombination coefficient. As an example for studying this effect, we have considered a 150-keV beam passing through an 0.8-mil Ti window into a 26-cm-wide planar cavity containing a 3:2:1 mixture of He, CO2, and N2 at 1 atm and 293 K, with Eave=4.5 kV/cm. Window power loading, electron attenuation, electron energy distributions, and sustainer field distributions were calculated for the two different anode materials.
An unstable-resonator flashlamp-pumped dye laser
Authors: Ewanizky T. F.
Published: January 2004

A negative-branch confocal unstable resonator has been found to significantly improve the beam quality of a coaxial flashlamp-pumped rhodamine 6G dye laser. In a performance comparison with a conventional parallel-plane mirror resonator, over an order-of-magnitude increase in laser beam radiance has been measured. The negative-branch unstable resonator demonstrated relatively uncritical alignment sensitivity.
Fabrication of optical waveguiding layer in LiTaO3 by Cu diffusion
Authors: Noda Juichi , Saku Tadashi , Uchida Naoya
Published: January 2004

Thermal diffusion and electrodiffusion of Cu into LiTaO3 have been investigated. By an appropriate choice of diffusion conditions, a single-mode waveguiding layer has been fabricated using the electrodiffusion method. The refractive-index change at the surface is 5×10−3 for both ne and no and the diffusion depth is about 4 μm. The layer supports only the fundamental modes TE0 and TM0, and exhibits good waveguiding properties.
Monolithic piezoelectric mirror for wavefront correction
Authors: Feinleib J. , Lipson S. G. , Cone P. F.
Published: January 2004

Experimental and theoretical analysis show that a spatially varying potential applied to one surface of a thick block of piezoelectric material will induce a piezoelectric deformation of that surface proportional to the potential at each point of the surface. There is essentially no dispersion in the piezoelectric response as a function of the spatial frequency of the applied potential even at high resolutions. This principle has been used to construct an electrically addressed monolithic piezoelectric mirror (MPM) which has high accuracy, stability, and speed of response. The MPM has been used successfully in a demonstration of real-time correction of image phase distortions caused by a turbulent atmosphere.
Observation of interband Faraday rotation at 10.59-μ wavelength in room-temperature Ge, CdTe, and GaAs
Authors: Phipps C. R. , Thomas S. J. , Lax B.
Published: January 2004

Room-temperature interband Faraday rotation has been measured in samples of intrinsic germanium, doped cadmium telluride, and gallium arsenide at 10.59-μ wavelength, in magnetic fields up to 80 kG. Measurements with a 7-mm-diam incident beam indicate that at least 33 dB isolation and a figure of merit exceeding 100 deg/dB should be attainable in a practical device based on either of the first two materials.