bluuebunny/crossref_metadata_2025 huggingface dataset:
Peak Voltage of the Pyroelectric Response to Short Infrared Laser Pulses
Authors: Shaulov A. , Simhony M.
Published: January 2004

The peak voltage of the response in a pyroelectric sample to ir signals much shorter than the thermal and electronic time constants of the sample is shown to be proportional to the energy absorbed per signal, and independent of load resistance and signal repetition frequency, as long as temperature is far enough from the Curie point. These results were checked experimentally in triglycine sulphate and strontium-barium niobate.
Electrostatic Instabilities of a Mirror-Confined Plasma with Anisotropic Velocity Distribution
Authors: Hasegawa Akira , Nishihara Katsunobu
Published: January 2004

Electrostatic instabilities associated with the bounce frequency are studied for a mirror-confined plasma. A plasma with a monochromatic energy distribution perpendicular to the magnetic field is shown to introduce a new mode at ω∼nωb which is unstable when ωp/ωb ≳ 0(1), where ωb and ωp are the bounce and plasma frequencies, respectively.
Transient Phenomena of the Light-Induced Memory in Amorphous Semiconductor Films
Authors: Hamada A. , Kurosu T. , Saito M. , Kikuchi M.
Published: January 2004

Transient phenomena of write-in and erasing processes of the light-induced memory in Te81Ge15Sb2S2 films were observed by the transmission mode using a He–Cd laser. Crystallization was completed in 50 μsec under illumination, which supports the photon-enhanced crystallization.
Ga1−xAlxAs LED Structures Grown on GaP Substrates
Authors: Woodall J. M. , Potemski R. M. , Blum S. E. , Lynch R.
Published: January 2004

Ga1−xAlxAs light-emitting diode structures have been grown on GaP substrates by the liquid-phase-epitaxial method. In spite of the large differences in lattice constants and thermal-expansion coefficients, room-temperature efficiencies up to 5.5% in air have been observed for a peak emission of 8500 Å. Previously, in order to achieve high external efficiencies it was necessary to grow thick Ga1−xAlxAs layers on GaAs substrates and then remove the substrate. However, using undoped GaP substrates, which are transparent to the infrared and red portions of the spectrum, thin structures of Ga1−xAlxAs with large external efficiencies can now be made.
Measurement of the Gain Line Shape of a Gas Laser Using a Tunable Semiconductor Laser
Authors: Blum F. A. , Nill K. W. , Calawa A. R. , Harman T. C.
Published: January 2004

Using a cw tunable PbS0.6Se0.4 semiconductor diode laser operating near 5.3 μm we have fully resolved the gain (loss) line shape of several vibration-rotation lines of a CO gas laser amplifier.
Broadening of Fast-Beam Spectral Lines Due to Diffraction at the Entrance Slit of a Spectrometer
Authors: Leavitt John A. , Stoner John O.
Published: January 2004

We show experimentally and theoretically that adjustment of a spectrometer for observation of fast-beam spectral lines under conditions of minimum linewidth requires consideration of the effects of diffraction at the spectrometer's entrance slit. We obtain an approximate expression for the optimum entrance slit width to be used in order to avoid the pronounced broadening of the spectral lines that occurs for very narrow entrance slits.
Submillimeter Wave Generation by Difference-Frequency Mixing in GaAs
Authors: Bridges T. J. , Strnad A. R.
Published: January 2004

Non-phase-matched generation of 29.9 cm−1 is obtained by difference mixing of pulsed CO2 laser radiation in room-temperature GaAs, with a detection signal-to-noise ratio of 103. Calculations show that comparable results could be obtained from 10 to 200 cm−1.
Novel GaAs–(AlGa)As Cold-Cathode Structure and Factors Affecting Extended Operation
Authors: Schade H. , Nelson H. , Kressel H.
Published: January 2004

A novel planar cold-cathode structure has been developed based on a GaAs–(AlGa)As heterojunction and a negative electron affinity GaAs surface. As an important feature of the device, the lateral confinement of the current flow to the desired area of the emitting surface is obtained by the selective diffusion of zinc. Under pulsed conditions, emission efficiencies as high as 4% and emission current densities as high as 7 A/cm2 have been achieved. The release of impurities from the anode as a result of electron-stimulated desorption has been found to be a major factor affecting the cathode life under dc operation. The influence of this factor can be greatly minimized by different techniques such as using low anode voltages and magnetic field deflection.
Mössbauer Effect of 57Fe and 119Sn Atoms Isolated in Solid Nitrogen
Authors: Micklitz H. , Barrett P. H.
Published: January 2004

The Mössbauer resonances of nitrogen-matrix-isolated 57Fe and 119Sn atoms have isomer shifts, which are within the experimental errors, identical with the isomer shifts of the same atoms isolated in rare-gas matrices. Despite an observed quadrupole splitting of the 57Fe and 119Sn resonances, the relatively small photoelectric cross section of nitrogen makes the nitrogen matrix useful for matrix-isolation Mössbauer studies of nuclei which require relatively thick Mössbauer absorbers.
Convolution of Surface Waves in a Structure of Semiconductor on LiNbO3
Authors: Wang Wen-Chung
Published: January 2004

We report here some experimental results on surface-wave convolution in a structure of Si on LiNbO3 or of CdS on PZT. The semiconductor plate is dc biased. Convolved signals at both the sum and difference frequencies have been observed from the terminals attached to the semiconductor. A simple expression is obtained on the convolved signal amplitude vs the difference in wave vectors of the two input signals. The experiment is in general agreement with the theory. A series of pictures on the convolved signal as a function of the applied dc field is presented.
Transverse Excitation Pulsed Laser in Gas-Dynamically Cooled Mixtures
Authors: Vallach E. , Zeevi A. , Greenfield E. , Yatsiv S.
Published: January 2004

We report laser emission from a pulsed transverse electric discharge in fast-flowing adiabatically cooled gas mixtures. The discharge is in the downstream parallel section of a supersonic nozzle. Both electrical excitation of CO2 and CO and chemical excitation of CO in the reaction of CS2 + O2 yield laser emission. The cooling in the nozzle is demonstrated by the low J values of the observed transitions. The gain for CO transitions was more than an order of magnitude greater at the low temperatures than at room temperature. Fast cooling during the supersonic expansion permits lasing in highly supersaturated gas mixtures. This extends laser operation to temperatures beyond the capability of cryogenic methods and permits higher laser energies and efficiencies.
Optical Generation of Intense Picosecond Electrical Pulses
Authors: Auston D. H. , Glass A. M.
Published: January 2004

Electrical pulses, 4 A in 10 psec, have been generated by rectification of 1.06-μm pulses in LiTaO3: Cu++. Their amplitude and duration were measured by photographing the birefringence induced by the pulses propagating along an electro-optic transmission line illuminated transversely in a Pockel's cell arrangement. The principal mechanism responsible for the generation is the macroscopic polarization resulting from the difference in dipole moment between the ground and excited states of the absorbing Cu++ impurities.
Dye Laser Forced Oscillator
Authors: Magyar G. , Schneider-Muntau H. -J.
Published: January 2004

The narrow-band output of a small flashlamp-pumped coaxial dye laser is injected internally into a large close-coupled oscillator. When frequency locked, an effective power gain of ∼ 4000 and an energy output of ∼ 600 mJ in a width of ∼ 0.01 nm is achieved.
Surface Characterization of Stainless Steel Using Proton-Induced X Rays
Authors: Musket R. G. , Bauer W.
Published: January 2004

Proton-induced characteristic X rays (1–10 keV) have been used to study, in situ, the alloy composition of 304L stainless steel surfaces as a function of the vacuum annealing temperature. Effects of 15-min isochronal vacuum anneals between 700 and 1450°K were determined by probing to depths of about 1 μm with 150- to 400-keV protons. In particular, chromium depletion was significant above 1200°K. For 200-keV protons, the Cr(Kα)/Fe(Kα) ratio decreased from about 0. 8 for 700–1200°K to 0. 19 at 1450°K; this corresponds to a decrease in the chromium content from 19 to about 6 wt%.
Electrohydrodynamic Solutions for Nematic Liquid Crystals
Authors: Penz P. Andrew , Ford G. W.
Published: January 2004

We have solved the boundary value problem associated with the Williams domain mode and the variable grating mode in nematic liquid crystals. Using linearized electrohydrodynamic equations of motion, standard constitutive relations, and experimentally observed material constants, we reproduce the significant experimental observations.
Position of the Band Edges of Silicon under Uniaxial Stress
Authors: Kramer P. , van Ruyven L. J.
Published: January 2004

Schottky barrier heights of metal-silicon contacts have been measured as a function of temperature at high uniaxial 〈111〉 stress (100 kbar). The change in band gap, as compared to the zero-pressure band gap, can be attributed to a change in position of the conduction band edge alone, i.e., a change in electron affinity.
Spatial and Temporal Dependence of the Gain of a Transversely Excited Pulsed CO2 Laser
Authors: Deutsch Thomas F. , Rudko R. I.
Published: January 2004

The gain of a transversely excited pulsed CO2 laser with distributed electrodes has been examined with and without the addition of hydrogen. Spatially, the gain shows a sharp peak a few millimeters from the cathode, followed by a region of relatively uniform gain. The gain of the latter region increases from 13 to 18 dB/m upon the addition of hydrogen. The gain-vs-time curves show peaks which propagate from cathode to anode at velocities ranging from 600 to 1200 m/sec.
Evidence for the Heating of a High-Density θ Pinch When Transversely Irradiated by a Pulsed CO2 Laser Beam
Authors: Engelhardt A. G. , Fuchs V. , Neufeld C. R. , Richard C. , Décoste R.
Published: January 2004

A high-density θ pinch has been irradiated by the 0.2-J 180-nsec pulse of a CO2 laser. Fast photography and spectroscopy monitor the plasma behavior, temperature, and density and permit a comparison with theory.
Anisotropic Ultrahigh Gain Emission Observed in Rotational Transitions in Optically Pumped HF Gas
Authors: Skribanowitz N. , Herman I. P. , Osgood R. M. , Feld M. S. , Javan A.
Published: January 2004

Gain and laser oscillations are obtained on rotational transitions of the first excited vibrational state of HF gas at room temperature, resonantly pumped by the 2.7-μ lines of a pulsed HF laser. Pumping the P-branch transitions connecting the ground and first excited vibrational states produces gain at the coupled rotational transitions at 36, 42, 51, 63, 84, and 126 μ. The gain exhibits directional properties characteristic of a unidirectional amplifier predicted by a recent theory. The incremental gains of these lines are very large, in excess of 1/cm, and the lines oscillate easily without mirrors (``superradiance'').
Orange Laser Emission and Bright Electroluminescence from In1−xGaxP Vapor-Grown p-n Junctions
Authors: Nuese C. J. , Sigai A. G. , Gannon J. J.
Published: January 2004

In1−xGaxP laser diodes which emit coherently at 80 °K at wavelengths as short as 6105 Å with threshold current densities of 4000–6000 A/cm2 have been fabricated from vapor-grown In1−xGaxP p-n junction structures. This is the shortest-wavelength laser emission and the first example of coherent orange emission yet reported from a semiconductor p-n junction. From vapor-grown In1−xGaxP spontaneous-light-emitting diodes, external quantum efficiencies in excess of 0.1% have been obtained for orange and red emission at room temperature.
Space-Charge Dependence of the Barrier Height on Insulator Thickness in Al-(Al-Oxide)-Al Sandwiches
Authors: Gundlach K. H. , Kadlec J.
Published: January 2004

It is observed that the barrier height in Al-(Al-oxide)-Al sandwiches is a strong function of the Al-oxide thickness; it is also a strong function of the illumination, particularly at low temperatures. These results offer conclusive evidence that the effect is due to space charge trapped in the Al-oxide.
Magnetic Properties of Cobalt-Samarium with a 24-MG Oe Energy Product
Authors: Foner S. , McNiff E. J. , Martin D. L. , Benz M. G.
Published: January 2004

The magnetic moment and hysteresis properties of a high-density nearly completely oriented Co5Sm magnet alloy have been measured from 300 to 4.2 K and in applied fields up to 140 kOe. A saturation moment per gram of 98 G cm3/g is measured at 300 K and shows a slight increase as temperature is decreased. After adjustment for voids and oxide, the saturation moment per gram of the Co–Sm alloy is 102 G cm3/g, or equivalent to 11 000 G for the saturation magnetization 4πJs. An energy product of approximately 24 MG Oe is attained at 300 K.
Neutralization of Na+ Ions in ``HCl-Grown'' SiO2
Authors: Kriegler R. J.
Published: January 2004

Current-voltage measurements and radiotracer experiments have been carried out to examine the nature of the passivation mechanism responsible for the reduction of sodium ion instabilities in MOS structures prepared from oxides grown in the presence of HCl. It has been found that the ions in the passivated oxides can still migrate to the vicinity of the silicon interface, but have no effect on the surface potential because they become neutralized, probably in the interaction with a chlorine-associated species. The exact identity of this species and the details of the charge transfer to the Si electrode remain unresolved.
Thermomagnetic Recording in Thin Garnet Layers
Authors: Krumme J.-P. , Verweel J. , Haberkamp J. , Tolksdorf W. , Bartels G. , Espinosa G. P.
Published: January 2004

Thermomagnetic flux reversal has been studied in single-crystal layers of Y3Ga1.1Fe3.9O12 with 5-μm thickness, prepared by liquid-phase epitaxy (LPE) on a (111) Gd3Ga5O12 wafer. By structuring the layers in a checkerboard pattern of squares with 10-μm periodicity and 2-μm width and depth of the surface grooves, arbitrary stable domain patterns have been obtained. Individual squares have been switched magnetically using heat pulses from a laser beam of 20-mW intensity at 5145-Å wavelength with fields as low as 13 Oe in case of a nearly demagnetized domain distribution. The beam energy for reversing the magnetization of a square is below 1 erg.
Proton- and Electron-Excited Auger Electron Spectra of Molybdenum Surfaces
Authors: Musket R. G. , Bauer W.
Published: January 2004

Proton- and electron-excited Auger electron spectra of molybdenum surfaces have been measured. From the conditions of the experiments, the yields (i.e., Auger electrons/incident particle) for the two cases were comparable. The value of proton-excited Auger electron spectra is discussed with regard to quantitative surface-composition determinations.
Three-Josephson-Junction Interferometer
Authors: Stuehm D. L. , Wilmsen C. W.
Published: January 2004

The three-Josephson-junction asymmetric-feed quantum interferometer has been analyzed and shown to have increased magnetic field sensitivity and amplitude deviation over the two-junction interferometer. The critical current at zero applied field is shown to be less than the critical current at zero flux in the interference loop.
Capacitive Weak Links and Finite Load Lines
Authors: Blackburn James A. , Warman J.
Published: January 2004

A transformation is described which connects the already solved problem of a capacitive superconducting weak link driven by a constant-current source to the physically more realistic situation of a source with finite load line. Hysteresis is found to persist although the loop may be quite narrow. It is shown that the minimum-current dependence on the Josephson tunneling amplitude can distinguish between capacitive and inductive devices.
TEA Laser Medium Diagnostics
Authors: O'Neil R. W. , Carbone R. J. , Granek H. , Kleiman H.
Published: January 2004

From an interferometric study of the medium in a 10.6-μ transverse electric discharge pulsed laser amplifier, a time history of the index of refraction is presented from t=0 to t=21.5 μsec. These data agree favorably with the predictions based on a linearized hydrodynamic model for pulsed heat deposition in a gas by a row of discrete discharge pins. The spatial extent of the gain profile is comparable to the refractive-index distribution for times appropriate for lasing (<10 μsec). In this time interval, medium distortion is less than 0.1 fringe at 10.6 μ.
Measurement of Vibration-Vibration Energy Transfer Time in HF Gas
Authors: Osgood R.M. , Javan A. , Sackett P. B.
Published: January 2004

An experiment which yields a value of 6.6×105 Torr−1 sec−1 for the vibration-vibration decay rate of the v=2 state in HF gas is described. The technique involves observation of the rise time of the HF v=2 vibrational fluorescence emanating from a gas sample pumped with a HF laser operating on a v=1→v=0 transition. An analytic model which predicts the temporal behavior of the HF v=1 and collisionally populated v=2 vibrational levels is also described. This model predicts an apparent decay rate of the v=2 fluorescence, which is twice that for v=1. Experimental measurements confirm this prediction.
Increased Resistance to Photodegradation of Rhodamine 6G in Cooled Solid Matrices
Authors: Fork R. L. , Kaplan Z.
Published: January 2004

Improved resistance to photodegradation for Rhodamine 6G was observed when the dye was held in a cooled solid matrix of polymethylmethacrylate. The fraction of dye bleached decreased with decreasing temperature as did the rate of bleaching. The minimum detectable quantum efficiency for photodegradation was φ ≅ 10−7.
New Laser Lines in the Visible from Er3+ Ions in BaY2F8
Authors: Johnson L. F. , Guggenheim H. J.
Published: January 2004

Coherent emission at 5540, 5617, and 7037 Å from Er3+ ions in BaY2F8 is reported. Oscillation at 5540 Å takes place at 77°K in a transition from 4S3/2 to a level of the 4I15/2 ground state at 406 cm−1. The line at 5617 Å is produced in a transition from 2H9/2 to a level of 4I13/2 at 6740 cm−1, and 7037 Å is generated in a transition from 2H9/2 to a 4I11/2 level at 10 336 cm−1. Pumping of the 4I13/2 state results in Q switching of the output at 5540 Å. The conditions required to produce oscillation in these lines and the detrimental effects of Yb3+ are discussed.
New Output Coupling Scheme for cw Dye Lasers
Authors: Shah Jagdeep
Published: January 2004

We have devised a simple new scheme of extracting tunable output from a cw dye laser. This scheme reduces the intensity of the background fluorescence of the dye to less than 10−7 of the laser intensity within 10 Å of the laser line and gives an output beam whose direction is independent of the dye laser wavelength. This scheme uses no external dispersing elements and permits a continuous recording of the data as a function of dye laser wavelength.
Structure of a Coincidence and Near-Coincidence Tilt Boundary in Gold
Authors: Chaudhari P. , Mader S.
Published: January 2004

The structure of tilt grain boundaries formed by a rotation of 60° and 30° about a 〈111〉 axis has been examined by transmission electron microscopy. In specimens containing 30° boundaries, low-angle dislocation arrays with a tilt angle of 2.2° are commonly observed. This is attributed to the presence of a coincidence site lattice relation at 27.8°.
Absorption at 10.6 μ via Ionic Dipole-Dipole Interactions
Authors: Nicolai V.O.
Published: January 2004

A theory is suggested to explain absorption at 10.6 μ in crystals via ionic dipole-dipole interactions. The theory indicates that minimal absorption is obtained with crystals which have symmetry with respect to optical modes and with preferred orientations of the crystals.
Vibrational Relaxation Measurements Using ``Transient'' Stimulated Raman Scattering
Authors: Kovacs M. A. , Mack M. E.
Published: January 2004

Vibrational relaxation measurements in several gases have been made, subsequent to vibrational pumping by picosecond pulse-generated ``transient'' stimulated Raman scattering. This technique permits relaxation measurements at room temperature or below in a number of gases for which previously no such measurement was possible.
New Magnetic Material Having Ultrahigh Magnetic Moment
Authors: Kim T. K. , Takahashi M.
Published: January 2004

The change of the saturation magnetization of Fe films with the pressure of nitrogen during deposition ranging from 2 × 10−5 to 7 × 10−3 Torr has been investigated systematically. We found a new magnetic material which has the highest saturation magnetization at room temperature, 2050 G, among those of all the magnetic materials. This was attributed to Fe16N2, which has a bct structure, and the magnetic moment associated with Fe atoms of Fe16N2 was deduced to be 3.0 μB.
Ionization Instability in Atmospheric-Pressure Gas Discharges
Authors: Johns T. W. , Nation J. A.
Published: January 2004

A photographic and oscillographic study of discharges in helium-carbon-dioxide mixtures at atmospheric pressure has shown that fine filaments develop in the discharge column. The origin of these nonuniform discharge paths is discussed, and a means for maximizing the energy input to the plasma prior to filamentation is presented. This process is of relevance to the design of TEA lasers.
Information Storage Using Inhibited Cathodoluminescence
Authors: Bishop H. E. , Henderson R. P. , Iredale P. , Pooley D.
Published: January 2004

It has been shown that reversible information storage in crystals can be achieved using the inhibition of cathodoluminescence by defects produced by electron irradiation. Since an electron beam of constant energy is used to access the store and to execute the binary operations of write, erase, and read, the addressing problems are minimized. The writing and erasing times are on the order of a few microseconds, and the reading time can be a few hundred nanoseconds.
Laser-Induced Refractive-Index Change in As–S–Ge Glasses
Authors: Ohmachi Yoshiro , Igo Takeo
Published: January 2004

Effect of light irradiation on evaporated chalcogenide glass films of an As–S–Ge system has been studied. In order to make quantitative measurements of refractive-index change resulting from light irradiation, light diffraction efficiency from the phase grating produced in the films with the technique of holographic storage has been measured. The maximum refractive-index change of 0.056 has been obtained in an As2S3 film. This value is two orders of magnitude higher than that of Fe-doped LiNbO3 single crystals. Light irradiation onto the films is considered to have two competing effects, one being thermal and the other purely optical.
p-Channel Charge-Coupled Devices with Resistive Gate Structure
Authors: Kim Choong-Ki , Snow E. H.
Published: January 2004

Charge-coupled devices with resistive material covering the oxide between adjacent gate electrodes are described. These devices were fabricated incorporating a continuous strip of deposited silicon with doped and undoped regions. Since the surface potential under the gap can be controlled using this structure, reliable p-channel devices with nonoverlapping gate electrodes can be made which have all the advantages of p-channel silicon gate technology. Transfer efficiencies greater than 99.3% per transfer have been obtained at up to 1-MHz bit rates for three-phase experimental devices.
Interference Effects in Laser-Modulated Electron Beams
Authors: Schmieder Robert W.
Published: January 2004

A new class of electron interferometers is proposed that make use of a laser-modulated electron beam. The observable interference arises in second-order processes, since the first-order interference oscillates rapidly and averages to zero. It is shown that the detected signal varies sinusoidally with the separation of two sequential modulators, thus generating a fringe pattern with peak-to-peak spacing that may be smaller or larger than the laser wavelength. It is suggested that such devices could be used to detect and study the modulation process and, because they operate with massive charged particles, to perform a wide variety of new experiments and high-precision measurements.
Field Regions for the Modes of Acousto-electric Excitations in InSb
Authors: Seifert F. , Bauder H. , Schatzl C.
Published: January 2004

It is shown that in n-InSb at 77 K, mode I of acousto-electric excitation exists in transverse magnetic fields above 2 kG, for which qR≪ 1 (q is the acoustical wave number, and R is the Larmor radius) if the drift motion restores a mean free path l to give ql > 1. Threshold curves for mode I are calculated. Allowing for the magnetic field dependence of mobility, the applicability of quantum-mechanical and hydrodynamical theory in different field regions is discussed.
Electron-Beam-Controlled Electrical Discharge as a Method of Pumping Large Volumes of CO2 Laser Media at High Pressure
Authors: Fenstermacher C. A. , Nutter M. J. , Leland W. T. , Boyer K.
Published: January 2004

An electron-beam-controlled discharge has been used to pump a variety of CO2 laser gas mixtures at atmospheric pressure in substantial volumes. Electrical and laser properties of the pumped medium have been measured. Small-signal-gain coefficients up to 0.045 cm−1 were achieved at field strengths of 3 kV/cm.
Switching Behavior of Over-Critically Doped Gunn Diodes
Authors: Guéret P. , Reiser M.
Published: January 2004

A study is made of Gunn-diode behavior for various lengths and doping densities. Emphasis is placed mainly on very short over-critically doped diodes. Such diodes, when biased above threshold, are stable with a high-field anode layer. The transition to this stable state occurs with or without the intermediary formation of Gunn domains. The relations between the various types of diode behavior and the nature of the small-signal instability, convective or absolute, in the material is examined.
Raman Oscillation in Glass Optical Waveguide
Authors: Stolen R. H. , Ippen E. P. , Tynes A. R.
Published: January 2004

Stimulated Raman emission in the visible has been observed in glass-fiber optical waveguides. Even though the Raman cross section is quite small, relatively low threshold for Raman emission can be achieved because high optical power densities are maintained over long lengths of waveguide. The broad stimulated gain bandwidths available in glass should permit the construction of wide-band fiber amplifiers and Raman oscillators tunable over a range of 100 Å.
Far-Infrared Cyclotron Resonance in GaAs
Authors: Poehler T. O.
Published: January 2004

Cyclotron-resonance lines in n-type GaAs at 4.2°K are observed to be anomalously narrow when measured at λ = 220 μm. Analysis of the resonance line yields an effective mass ratio of 0.068m0 and an electron-impurity scattering time of 3.9×10−12 sec compared to a dc scattering time of 4×10−15 sec.
Electrical and Optical Properties of rf-Sputtered GaN and InN
Authors: Hovel H. J. , Cuomo J. J.
Published: January 2004

GaN and InN thin films were grown on sapphire, silicon, and metallic substrates using rf sputtering at temperatures of 25–750°C and presputtering vacuum of 10−8 Torr. The GaN films were high in resistivity (> 108 Ω cm), but the InN layers were highly conducting with an electron concentration of 7×1018 cm−3. The refractive index for GaN ranged from 2.1 to 2.4 at long wavelengths and was dispersive below 8000 Å; the index for InN is higher, 2.9. The absorption coefficient was measured from wavelengths of 2 μ to 2000 Å.
Transverse-Discharge Hydrogen Halide Lasers
Authors: Wood O.R. , Chang T.Y.
Published: January 2004

Laser action has been achieved in six hydrogen and deuterium halides formed in chemical reactions initiated by a pulsed transverse discharge. A total of 246 wavelengths from 2.6 to 19.7 μm was observed. Nearly 30% of these transitions have not been previously observed in laser action. All of the lasers operate at relatively high pressure and promise to give very-high-power outputs.
Neutron Damage in SiC Light-Emitting Diodes
Authors: Barnes C. E.
Published: January 2004

The effects of neutron irradiation on silicon carbide light-emitting diodes (LED's) have been studied over the temperature range 76–300°K. The results indicate that over the entire temperature range the radiative current in the low-voltage region is due to tunneling and subsequent radiative recombination in the depletion layer. Since this type of current is fairly radiation resistant, it is suggested that the SiC LED is an attractive device for operation in a neutron environment.
Elastic and Anelastic Behavior of Ion-Implanted Silicon
Authors: Tan S. I. , Berry B. S. , Crowder B. L.
Published: January 2004

Ion-implantation damage has been studied in thin reeds of silicon by resonant-frequency and internal-friction measurements. For a dose of 1016/cm2 of 28Si+, the principal effects are the appearance of an internal-friction peak and a decrease in the flexural vibration frequencies. The amorphous surface layer produced by implantation is deduced to have a Young's modulus of 1.24×1012 dyn/cm2 and a density of 0.95 of the crystal density. The internal stress in the amorphous layer has been measured and found to be far smaller than that corresponding to a purely elastic accommodation of the density change.
X-Ray—Induced Variation of Time Constant of Yb+3 Sensitizer
Authors: Hersh H. N. , Ban G.
Published: January 2004

We describe a unique method for continuously and independently varying the rate-controlling time constant of excited Yb+3 ions in rare-earth up-converting phosphors. We show, in the system BaYb2F8: Er, that at all values of the time constant, the power radiated is directly proportional to the square of the observed radiative lifetime, in accordance with the 2-transfer model of Auzel. The decrease in this time constant arises from the introduction of radiation-produced defects which selectively affect the Yb+3 rather than the activator ions. The phenomenon can be used to study energy transfer from Yb+3 to any activator.
Laser Diagnostics of a Potassium Plasma Using Selective Excitation Spectroscopy
Authors: Measures R. M. , Rodrigo A. B.
Published: January 2004

A thermally tuned Q-switched ruby laser has been used to selectively excite the 6939-A transition in a potassium plasma. A burst of intensified spontaneous emission at both 6911 and 6939 A has been observed. This enhanced emission contains information on the local properties of the plasma as demonstrated by the observed dependence of the signal duration upon the free-electron density.
Neutron Damage in GaP Light-Emitting Diodes
Authors: Barnes C. E.
Published: January 2004

The effects of neutron damage on the red and green light output at 300 °K of GaP lightemitting diodes have been examined. The results indicate that the diodes are not sensitive to neutron irradiation in those voltage regions where the radiative current is due to spacecharge recombination in the depletion layer. As a consequence of this, it is shown that the response of the diodes to neutron irradiation can be used to elucidate the radiative currentflow mechanisms in these devices.
Effect of the Nonuniform dc Field on Carrier Waves in Negative-Differential-Mobility Semiconductors
Authors: Bini M. , Bisio G. R.
Published: January 2004

The growth of a carrier wave propagating through a negative-differential-mobility semiconducting sample is discussed under nonuniform dc bias conditions. A simple analytical expression for the over-all numerical gain is given in terms of current density and of the input and output carrier-wave velocities only. Applications to n-type GaAs are discussed.
Scanning X-Ray Emission Microscopy
Authors: Leamy H. J. , Ferris S. D.
Published: January 2004

This letter describes the production of continuous tone micrographs from the x radiation emitted by a specimen subjected to electron bombardment in a scanning electron microscope. The x rays are collected and energy analyzed with an energy-dispersive spectrometer so that topographically rough specimens may be examined. The images reveal variations in specimen topography and composition.
Improved Infrared-Response Technique for Determining Impurity and Defect Levels in Semiconductors
Authors: Sher A. H. , Keery W. J.
Published: January 2004

The response of reverse-biased germanium diodes to monochromatic infrared radiation has been studied. Specimens included those fabricated from crystals doped with either copper or gold, or subjected to heat treatment. Preliminary results are reported that show the technique to be useful for identifying such impurities or defects in both lithium-compensated and high-purity germanium specimens.
Selected-Zone Dark-Field Electron Microscopy
Authors: Heinemann Klaus , Poppa Helmut
Published: January 2004

Selection of image-forming electrons that have passed through a small annular zone of the objective lens drastically reduces the resolution-limiting influence of chromatic aberration. Special objective-lens aperture diaphragms are needed for this new method of obtaining high-quality images. The manufacture of the diaphragms is described. High-resolution and high-contrast images of crystallographic specimens in the light of selected Bragg-diffracted beams without preference to azimuthal orientations were obtained. In particular, {111}-lattice planes of gold were observed as well as interference fringes (``pseudo'' lattice images) between two nonsymmetrical Au {111} diffracted beams, displaying spacings and azimuthal directions characteristic of regular {200}- and {220}-lattice fringes, although the {200} and {220} diffracted beams were omitted by the specific annular aperture used. Such ``pseudo'' lattice images allow deposit orientation determinations in the same way as ``ordinary'' lattice images.
Passive Mode Locking of Flashlamp-Pumped Dye Lasers Tunable between 580 and 700 nm
Authors: Arthurs E. G. , Bradley D. J. , Roddie A. G.
Published: January 2004

Employing polymethine dyes as saturable absorbers and intracavity Fabry-Perot interferometers, a flashlamp-pumped cresyl-violet dye laser has been mode locked to produce picosecond pulses (3–5 psec) frequency tunable from 644 to 704 nm. The frequency tuning ranges of mode-locked rhodamine 6G and rhodamine B dye lasers have also been extended to cover 584 to 645 nm.
Nonlinear Materials for Acoustic-Surface-Wave Convolver
Authors: Lim T. C. , Kraut E. A. , Thompson R. B.
Published: January 2004

Acoustic-surface-wave convolution by nonlinear mixing has been observed in cubic, hexagonal, and trigonal crystals. The magnitudes of the phenomenological nonlinear surface-wave coupling constants are tabulated and compared with the linear electromechanical coupling factor 2(ΔV/V). It has been found that the basal plane of PZT-8 has a larger nonlinear coupling constant than that of the commonly used Y-cut Z-propagating LiNbO3.
Extension of Absolute Frequency Measurements to the cw He–Ne Laser at 88 THz (3.39 μ)
Authors: Evenson K. M. , Day G. W. , Wells J. S. , Mullen L. O.
Published: January 2004

The highest absolute frequency measurement yet reported is described. The frequency of the 3.39-μ line from a He–Ne laser oscillating at the methane absorption frequency was found to be 88.376245 (55) THz. The frequency was measured by beating the 88-THz radiation with the R(30) line from a cw CO2 laser and a 48-GHz klystron in a tungsten-on-nickel point-contact diode. The speed of light calculated from this frequency and previous wave-length measurements is in agreement with the accepted value and of comparable accuracy.
Electric-Discharge Gas-Dynamic Laser
Authors: Kan Tehmau , Stregack Joseph A. , Watt William S.
Published: January 2004

Laser action on the CO vibrational-rotational bands between 4.8 and 5.3 μ is produced by electrical excitation of CO : N2 : O2 : He mixtures followed by expansion in a supersonic nozzle. Conversion of electrical energy into laser output occurs with ∼ 2% efficiency and small-signal gains in excess of 0.8% cm−1 have been observed.
Photodimer Distributed Feedback Laser
Authors: Fork R. L. , German K. R. , Chandross E. A.
Published: January 2004

A tunable (0.567–0.605 μ) solid-state dye laser with a small active volume (10 μ×80 μ×1 cm), which uses a nondestructively read-reversible optical-memory material to control the intensity and wavelength of the laser emission, is described. The optical-memory material, photodimers of acridizinium ethylhexanesulfonate, provides distributed feedback in the form of an adjustable-period phase grating which can be optically written (0.364 μ) or erased (0.313 μ). Reproducibility of laser switching, time and spectral structure, and operation at low temperatures where photodegradation of the dye is significantly reduced are discussed.
Efficient Variable Threshold Acousto-optic Q Switching of Flash-Pumped Nd:YAG
Authors: Scott W. C. , de Wit M.
Published: January 2004

A flash-pumped Nd:YAG laser has been effectively Q switched with an acousto-optic beam deflector in a resonator arranged such that the deflected laser beam goes into feedback while the undeflected beam is the output. This allows the laser threshold, and consequently the output pulse energy, to be electronically controlled via the rf power applied to the deflector permitting the extraction within a single pump flash of a sequence of Q-switched pulses with individually predetermined energies and spacings. Further, because the low Q state of the resonator involves almost 100% round-trip loss and no power to the deflector, high standoff capability and low-rf-power requirements are realized.
Comment on ``Required Monochromaticity of an Electron Beam Modulated at Optical Frequencies''
Authors: Pfeiffer Loren , Rousseau D. L. , Hutson A. R.
Published: January 2004

Recently revealed values for the energy monochromaticity and exit aperture in the Schwarz-Hora experiment are found to be inconsistent with the claimed beam current by orders of magnitude using the Langmuir brightness relation. Accordingly, attempts to duplicate the reported experimental conditions appear futile, and claims for the effect based upon the quoted experimental conditions may be regarded with skepticism.
Energy-Spread Structure of Electron Beams to be ``Optically'' Modulated
Authors: Schwarz Helmut
Published: January 2004

Electron beams of relatively high currents (0.5 μA) and 50-keV energy with observable modulability at optical frequencies can be produced without violating the Langmuir brightness relationship by shaping the beam in a ``filamentary'' structure, whereby each single-beam ``filament'' fulfills the recently reported monochromaticity requirement (energy spread better than 10 meV). The monochromator and the electron-optical-beam ``shaper'' have to be made adjustable for accurate spatial coherence between the electron-beam ``filaments''.
Liquid-Crystal Holography of High-Frequency Acoustic Waves
Authors: Intlekofer Michael J. , Auth David C.
Published: January 2004

A cholesteric liquid-crystal area detector has been used to make acoustical holograms at 5 MHz in water. The holograms were photographed by integrated time exposure and the original images reconstructed using laser light.
Superconducting Maser: A Critical Re-examination
Authors: Fife A. A. , Gygax Suso
Published: January 2004

The condition that the threshold current has to be less than the critical current in a superconducting injection maser is shown to be insufficient. Irrespective of the material, the number of states above the gap edge is too small to accommodate the overpopulation required to exceed all the losses in a superconductor.
Resistivity Ratio of Niobium Superconducting Cavities
Authors: Garwin E. L. , Rabinowitz Mario
Published: January 2004

Resistivity measurements have been made on Nb cavities, as well as on Pb and Cu, at 296, 77, and 4.2 °K by means of a contactless induced-current method. For superconductors, a constant magnetic field drives the material normal below the transition temperature. These measurements provide a simple means for initial material evaluation as well as a direct means of monitoring the effects of material parameters (purity, heat treatment, gas incorporation, etc.) on the electron mean free path. Approximate determinations of Hc, Hc1, and Hc2 can also be derived from these measurements. Normal-state thermal conductivity and the Ginzburg-Landau parameter κ are calculated from the resistivity measurements.
Dye Amplifiers Pumped by One- and Two-Photon Processes
Authors: Kepros John G. , Eyring Edward M.
Published: January 2004

One- and two-photon absorption (at 5300 Å) thresholds for laser action in aqueous bromocresol green and aqueous bromocresol purple were measured, and a novel method of measuring gain, requiring only one photomultiplier, is reported.
Continuous-Chemical-Laser Cavity Studies
Authors: Spencer D. J. , Durran D. A. , Bixler H. A.
Published: January 2004

The extent of the lasing medium along the jet axis in a continuous chemical laser is variable under changes in the jet temperature, pressure, velocity, reactant concentration, etc. The laser cavity must be readily tunable to accommodate the changes in lasing length in order to maintain maximum multimode laser power operation in a high-Fresnel-number cavity under variation in the jet parameters. In addition, as an aid in understanding laser performance, it is desirable to have the means to determine the multimode laser intensity distribution in the lasing region for various conditions in the jet. Techniques are presented to determine the optimum optic axis position for maximum multimode power operation, and to measure the intensity distribution along the jet and extent of the lasing medium. A flat and spherical mirror tuned during laser operation determine peak laser power position and the lasing length of the jet (typically 1. 6 in. in N2 flows). Axial local power surveys are made with this same cavity array coupled with a movable aperture which limits lasing to a small fraction of the total lasing region. A visual display of lasing length and the power distribution pattern along the jet, both axial and off-axis, is obtained by coupling power out of one of a pair of optical flats into a lucite block.
Addition-Elimination HF Chemical Laser
Authors: Padrick Thomas D. , Pimentel George C.
Published: January 2004

Hydrogen fluoride laser emission has been observed following flash photolysis of ethylene and tetrafluorohydrazine at elevated temperatures in a Vycor laser tube. The observed emission includes only v=1→0 transitions; we believe this emission is caused by HF elimination from a chemically activated molecule formed by addition to the ethylene double bond.
Precipitation of Si from the Al Metallization of Integrated Circuits
Authors: McCaldin J. O. , Sankur H.
Published: January 2004

The Al metallization of integrated circuits is known to dissolve ½% or more Si, but the ultimate location of this Si has been uncertain. An electron microprobe operated at low beam energy so as to penetrate only the upper portion of the metallization was used to follow the movement of dissolved Si on cooling after the ``forming'' heat treatment. Dissolved Si substantially less than a diffusion length from the substrate was found to regrow there; elsewhere the Si forms precipitates in the Al matrix, preferentially near the free surface of the Al.
Carrier Recombination and Trapping in Heteroepitaxial Si/Spinel
Authors: Norris C. B.
Published: January 2004

Measurements of transient conductance in response to 80-nsec pulses of 4–20-keV electron irradiation have been used to investigate electrical properties of defects in 2–4-μ Si films on 〈111〉 MgO·Al2O3 spinel. Carrier lifetimes ∼ (2–3) × 10−10 sec are estimated from the conductance change during irradiation. Significant trapping of injected carriers is indicated by the postirradiation conductance decay, which persists beyond 10−5 sec at 300°K and 10−3 sec at 90°K. The time and temperature characteristics of the decay suggest that ionized defects equilibrate by carrier capture over a potential barrier as in neutron-irradiated silicon. Variable-energy electron irradiation was used to investigate the depth dependence of defect density, and the results indicate that trapping in Si/spinel is greater near the substrate inferface.
Thermally Stimulated Capacitance (TSCAP) in p-n Junctions
Authors: Sah C. T. , Chan W. W. , Fu H. S. , Walker J. W.
Published: January 2004

High-frequency small-signal capacitances of semiconductor junction vs temperature, from the initial conditions of filled and emptied traps in the junction depletion region, are used to determine the trap concentration and the thermal activation energies of trapped electrons and holes. Illustrations are given for silicon N + P diodes doped with gold impurity or irradiated with 1-MeV electrons, showing the room-temperature annealing for the latter.
Electron-Beam Excitation of the Nitrogen Laser
Authors: Dreyfus R. W. , Hodgson R. T.
Published: January 2004

Stimulated emission near 3371 Å is reported for the first time using a commercial electron-beam generator as an energy source. A 2 × 103-A/cm2 3-nsec pulse of 400-keV electrons from a field-emission diode traveled 160 cm down a ¾-in. tube containing N2 at pressures of 10–50 Torr. A longitudinal magnetic field of 2–10 kG helped confine the electrons in the tube. The 400-keV electrons produce secondary and subsequent cascade electrons with energies from 0–200 keV. Those electrons with 13–17 eV excite nitrogen molecules to the upper lasing (C3Πu) state. Sufficient concentration of excited nitrogen molecules is produced for the gas to show superradiance with 60 kW of light output power.
Electric-Field-Induced Orientational Deformation of Nematic Liquid Crystals: Tunable Birefringence
Authors: Kahn Frederic J.
Published: January 2004

Spatially uniform birefringences tunable over the range 0. 0–0. 15 for applied voltages less than 20 V rms and with a sharp threshold below 4 V rms are obtained for thin layers of nematic liquid crystals with negative dielectric anisotropy. The achievement of spatially uniform tunable birefringence with negative-dielectric-anisotropy materials requires a source of in-plane anisotropy which is provided by a unique previously unreported molecular configuration at zero field. At V=0, the molecules align with their long axes at a small angle to the sample normal. The experimental results are analyzed in terms of a continuum model and experimental values obtained for the relevant elastic constants.
New Noncrystalline Germanium which Crystallizes ``Explosively'' at Room Temperature
Authors: Takamori Takeshi , Messier Russell , Roy Rustum
Published: January 2004

We report herein the preparation of a form of noncrystalline Ge film by rf sputtering on to various substrates, which crystallizes with ``explosive'' velocities when triggered by a localized transient energy pulse. The films show this phenomenon only when they are thicker than about 10 μ. The crystallization wave appears to be acoustically transmitted.
Laser-Induced Turbulence
Authors: Prasad C. R.
Published: January 2004

In a recent experiment on laser beam transmission through an absorbing gas, the critical Reynold's number for the flow, induced by the heating of the gas, to become turbulent was found to be less than 30, which is many orders of magnitude smaller than that for pure shear flow in pipes. It is shown here that a Rayleigh number is the more appropriate criterion to characterize the stability of flow in this situation, and its value estimated in two limiting cases is found to bracket the expected critical Rayleigh number for vertical concentric cylinders.
New Type of Surface Sound Wave in Conducting Crystals
Authors: Gulyaev Yuri V.
Published: January 2004

The existence of a new type of surface sound wave—pure shear surface sound wave—is predicted for conducting solid materials. This wave arises due to the fact that in these materials the mechanical stress depends not only on the deformation but also on the electron concentration because of electron-lattice interaction via the deformation potential. The penetration depth of this surface wave is of the order of λε/χ≫λ, where λ is the wavelength, ε is the dielectric constant, and χ is the electromechanical coupling constant for the deformation-potential interaction