bluuebunny/crossref_metadata_2025 huggingface dataset:
Real-time synchronously pulsed ir image up-conversion
Authors: Tseng D. Y.
Published: January 2004

Real-time ir image up-conversion has been achieved using a synchronously pulsed mode of operation for both the pump and ir sources. Operating at 133 pulses/sec, the up-converted images were readily viewed on an ordinary S-1 surface image intensifier tube. Optimization and adjustments of image quality were accomplished easily in real time.
PbTe rf-sputtered infrared detectors
Authors: Corsi Carlo
Published: January 2004

High-quality infrared detectors have been made by rf oxygen reactive sputtering of PbTe films. At an operating temperature of 90 °K, these devices are close to the 300 °K background-noise-limited photoconductive detection. Peak responsivities higher than 106 V/W and peak detectivities Dλ* of 8.5 × 1010 cm Hz1/2/W have been obtained with a field of view of 2π steradians.
Single-mode cw dye laser with large frequency range tunability
Authors: Liberman S. , Pinard J.
Published: January 2004

We describe in this letter a cw single-mode dye laser whose mode frequency can be tuned continuously over a relatively wide range of typically 10 GHz.
Model for the first-order phase transition in MnBi
Authors: Streifer W. , Huberman B. A.
Published: January 2004

We present a thermodynamic model which describes the first-order phase transition observed in the magneto-optic material MnBi. The variables in the model are the magnetization and the percentage of interstitial Mn atoms. Parameters include the ionic spin state, interstitial activation energy, and exchange energy. Numerical results, which show good agreement with experimental data, are presented.
Attenuation of c propagating acoustic waves in CdS: Grüneisen parameter calculations
Authors: Wasilik John H. , Hickernell Fred S.
Published: January 2004

The room-temperature attenuation for longitudinal acoustic waves propagating in the c direction in high-purity CdS has been measured from 0.1 to 0.6 GHz. At 0.5 GHz the attenuation is 46 dB/cm (tanδ=0.0015). From the observed attenuation corrected for phonon-electron contributions and a lattice loss theory of Woodruff and Ehrenreich, a Grüneisen parameter of ± 1.51 is calculated. An alternate method of calculating the Grüneisen parameter by using the pressure dependence of the elastic constants gives a Grüneisen parameter of -1.37.
rf-sputtered aluminum nitride films on sapphire
Authors: Shuskus A. J. , Reeder T. M. , Paradis E. L.
Published: January 2004

Single-crystal films of aluminum nitride were fabricated on (0001)- and (011̄2)-oriented sapphire substrates by reactive rf sputtering an aluminum target in ammonia gas. Films sputtered on either sapphire orientation were clear, smooth, and piezoelectric. Effective surface acoustic wave piezoelectric coupling constants as large as k2 = 0.2% were found for films sputtered on (0001)-oriented sapphire.
Circular stacking faults in silicon
Authors: Tice W. K. , Huang T. C.
Published: January 2004

An electron microscopic diffraction study for circular stacking faults in silicon has been carried out. For the first time it has been possible to make direct correlation between the faults and subsurface precipitates, and to confirm that circular fault growth involves climb of a Frank dislocation from a precipitate site.
dc effects in elastic surface waves
Authors: Nakagawa Yasuhiko , Yamanouchi Kazuhiko , Shibayama Kimio
Published: January 2004

We report the observation of dc effects in elastic surface waves on 131° rotated Y-cut X-propagating LiNbO3. A simple model to account for these effects is suggested.
Acoustic microscope—scanning version
Authors: Lemons R. A. , Quate C. F.
Published: January 2004

This letter reports the development of a mechanically scanned acoustic microscope showing 10-μm resolution. Using single-surface lenses an acoustic beam is focused with negligible spherical aberration in a water cell. The image is formed by mechanically scanning an object through this focused beam in a raster pattern. Transmitted power is detected with a piezoelectric transducer, and this signal modulates the synchronized raster of a CRT display. By employing piezoelectric detection, sensitivities of 10−8 W/cm2 are obtained, yielding images of excellent clarity and contrast.
Bulk wave generation by surface interdigital transducers operating near resonance
Authors: Vella P. J. , Goruk W. S. , Stegeman G. I.
Published: January 2004

The fraction of electrical power converted into spurious bulk waves at a surface interdigital transducer operating on and near surface wave resonance was measured. Bulk wave generation on y-z lithium niobate was found to be strong below, at, and above resonance and to increase with decreasing number of finger pairs.
Schottky-barrier solar-cell calculations
Authors: Pulfrey D. L. , McOuat R. F.
Published: January 2004

Calculations are presented which indicate that the maximum theoretical solar conversion efficiency of Schottky-barrier solar cells is very similar to that of conventional homojunction solar cells, e.g. values of 22–24% apply to Si, and ∼ 25% to semiconductors having a band gap between 1.4 and 1.6 eV.
Effect of refraction on spot-size dependence of laser-induced breakdown
Authors: Feit M. D. , Fleck J. A.
Published: January 2004

Detailed calculations have been performed to show the importance of refractive effects on laser-induced breakdown in gases. The refraction, which results from gradients in the density of plasma electrons, can cause a loss of energy from the beam and an apparent dependence of breakdown threshold on beam or focal spot size.
Relationship of self-focusing to spatial instability modes
Authors: Campillo A. J. , Shapiro S. L. , Suydam B. R.
Published: January 2004

The spatial distribution of focal spots formed when laser beams self-focus in materials is shown to originate from the growth of certain instability modes. These modes are determined by a simple mathematical relationship derived from instability theory, which has been verified experimentally. Because of these instabilities, the threshold power for self-focusing is inversely proportional to the self-focusing length for high-power laser beams.
Measurement of 9.6-μ CO2 laser transition probability and optical broadening cross section
Authors: Murray Edward R. , Kruger Charles , Mitchner Morton
Published: January 2004

Measurements of the 9.6- and 10.6-μ CO2 laser transition probabilities and optical cross sections have been made by using a tuneable CO2 laser and room-temperature absorption cell. In order to increase the accuracy of the resulting constants, two measurements, one in the combined Doppler-and pressure-broadened regime and one in the pure pressure-broadened regime, provided data for the simultaneous solution of the transition rate and cross section. The 10.6-μ results are in general agreement with previous studies and knowledge of the 9.6-μ values permits performance predictions and quantitative use of gain data in this laser band.
Optical transfer 42-atm N2O laser
Authors: Chang T. Y. , Wood O. R.
Published: January 2004

A powerful excitation technique for mixtures of molecular gases using a combination of optical pumping and resonant energy transfer is described. By using an N2O–CO2 mixture as an example, laser action in N2O at 10.5 and 10.8 μm has been achieved at total pressures up to 42 atm.
Carrier lifetimes in epitaxial InAs
Authors: Dalal V. L. , Hicinbothem W. A. , Kressel H.
Published: January 2004

A comparison has been made of the minority-carrier lifetime (77–300 K) in relatively pure InAs prepared by liquid phase epitaxy, vapor phase epitaxy, and from the melt. The data suggest that the lifetime is controlled by Auger recombination in the material prepared by liquid phase epitaxy. This is not the case for the other materials.
Intrinsic fluctuations in the output intensity of double-heterostructure junction lasers operating continuously at 300°K
Authors: Paoli Thomas L.
Published: January 2004

Measurements of the intrinsic noise fluctuations in the light intensity from a stripe-geometry double-heterostructure junction laser operating continuously at room temperature are reported. The frequency spectrum of the fluctuations has been measured from 10 MHz to 4 GHz for currents both above and below threshold. The above-threshold noise spectra show the resonant peak due to excitation of the spiking resonance by the quantum shot noise intrinsic to the lasing process. Near threshold the frequency of this resonance varies between 200 and 1000 MHz as a function of laser current. In addition, as the pumping current is increased above threshold, the low-frequency (< 100 MHz) noise shows the pronounced reduction expected of an amplitude-stabilized oscillator. However, over the same range of currents, the high-frequency (> 2 GHz) noise continues to increase in apparent contradiction with theoretical predictions.
Self-phase modulation of picosecond pulses in optical fibers
Authors: Ippen E. P. , Shank C. V. , Gustafson T. K.
Published: January 2004

Low-intensity picosecond optical pulses from a mode-locked cw dye laser have been observed to be self-phase modulated upon propagation through a CS2-filled glass fiber. This self-phase modulation occurs in the absence of self-focusing and has several interesting consequences with respect to pulse shaping and ultrashort-pulse propagation.
Efficient electroluminescence from InP diodes grown by LPE from Sn solutions
Authors: Shay J. L. , Bachmann K. J. , Buehler E.
Published: January 2004

We report the observation of efficient room-temperature electroluminescence from InP p-n junctions at wavelengths near the 1.05-μ window of low-loss glass fibers. External efficiencies of 1% and peak wavelengths variable between 0.98 and 1.10 μ have been obtained.
Grating filters for thin-film optical waveguides
Authors: Flanders D. C. , Kogelnik H. , Schmidt R. V. , Shank C. V.
Published: January 2004

The fabrication and evaluation of corrugation grating filters with reflectivities better than 75% and bandwidths less that 2 Å is reported. Grating filters were fabricated on glass waveguides using standard interferometric and ion-beam machining techniques and evaluated with a tunable dye laser. Measured and calculated filter responses are found to be in excellent agreement. Tolerances for realizing ideal filter performances are given.
Simultaneous exposure and development technique for making gratings on positive photoresist
Authors: Tsang Won-Tien , Wang Shyh
Published: January 2004

A simultaneous exposure and development technique for forming diffraction gratings and recording holograms in positive photoresist is described. This technique not only reduces the exposure time significantly, but is also able to produce gratings with deep grooves and sharp ridges. With the photoresist placed in a liquid-filled prismlike container, the smallest period obtainable by this method is reduced by a factor equal to the index of refraction of the liquid.
Auger and ellipsometric study of phosphorus segregation in oxidized degenerate silicon
Authors: Chou N. J. , van der Meulen Y. J. , Hammer R. , Cahill J.
Published: January 2004

Phosphorus redistribution during thermal oxidation of degenerately doped silicon was investigated using Auger electron spectroscopy and ellipsometry. Concentration profiles were determined with a combination of chemical and sputter etching techniques. A substantial phosphorus pileup was observed in the oxide in a thin layer near the ellipsometrically determined Si–SiO2 interface. Calibrated against standards of known concentration, this layer was found to contain ∼2×1021 phosphorus atoms/cm3, independent of the oxidation temperature between 850 and 1000 °C.
cw HF chemical laser from the reaction of F atoms with C3H8 and C4H10
Authors: Hon J. F. , Novak J. R.
Published: January 2004

cw laser emission has been obtained from vibrationally excited HF produced by the reaction of F with C3H8 and C4H10. F atoms are obtained by combusting F2 and D2, diluted with He, with F2 in excess. The combustor products are mixed with C3H8 or C4H10 using parallel flow (pressure matched) produced by supersonic nozzles for both the F, F2, DF, and He combustor product mixture and C3H8 and C4H10.
Measurement of CO2-laser-generated impulse and pressure
Authors: Lowder J. E. , Pettingill L. C.
Published: January 2004

Measurements of impulse transferred to large metallic targets in air produced with a variable-pulse-length high-power 10.6-μm laser beam are presented. Peak focal spot pressure measurements in Plexiglas are also presented which show that the peak pressure increases approximately as the 3/2 power of the peak power density and that at a fixed power density higher peak pressures are obtained by increasing the focal spot size.
Holographic coupler for integrated optics
Authors: Ash E. A. , Seaford E. , Soares O. , Pennington K. S.
Published: January 2004

Coupling optical energy into an integrated optical circuit is essentially a problem of mode conversion from a Gaussian laser beam to the specific mode of waveguide excitation desired. This paper describes preliminary experimental results obtained with couplers in which mode conversion is performed by holographic wave-shaping techniques.
Properties of nematic liquid crystals doped with hydroquinone and p-benzoquinone: Long-term dynamic scattering under dc excitation
Authors: Ohnishi Yoshitake , Ozutsumi Minoru
Published: January 2004

The effect of a charge-transfer complex pair on dynamic scattering (DS) properties in nematic liquid crystals is reported. With the use of a hydroquinone-quinone complex pair as dopant, more than one-year continuous dc operation of DS has been achieved. Purification of materials and use of hermetically sealed cells are necessary. Since nematics doped with conventional organic electrolytes do not show long lives under dc operation, a reversible oxidation-reduction process was found to play a fundamental role in achieving long dc operation lives of DS in the present nematics. The mechanism of the electrochemical process in DS is briefly discussed.
Resonant three-photon ionization of potassium with circularly and linearly polarized light
Authors: Agostini P. , Bensoussan P.
Published: January 2004

We report observations of the ionization of atomic potassium by simultaneous absorption of three dye laser quanta. The laser wavelength is tuned through the two-photon resonances with the 6S1/2 and 4D3/2,5/2 states, and the dependence of the ionization probability on the laser wavelength is investigated for linearly and circularly polarized light. Our results are in agreement with the selection rules and theoretical estimates of the ionization probability.
Picosecond infrared holography on bismuth film
Authors: Olsen J. N.
Published: January 2004

Thin films of bismuth provide a holographic recording medium that requires no development and is sensitive into the infrared. At a spatial frequency of 1730 lines/mm the diffraction efficiency is 5% for an exposure of 50 mJ/cm2 at 1.06 μm. Interference holograms using a diffusive beam splitter for a picosecond Nd:YAG laser show sufficiently high resolution for plasma holography applications.
Junction electroluminescence in CuInSe2
Authors: Migliorato P. , Tell B. , Shay J. L. , Kasper H. M.
Published: January 2004

We report the first observation of homojunction electroluminescence in a ternary chalcopyrite compound. Diffused junctions in CuInSe2 emit in a narrow band near 1.34 μ with an internal quantum efficiency of ∼10% at 77°K and ∼0.1% at room temperature.
Stimulated emission from the recombining afterglow of an electron-beam discharge in several atmospheres of helium
Authors: Collins C. B. , Cunningham A. J. , Curry S. M. , Johnson B. W. , Stockton M.
Published: January 2004

Stimulated emission from excited states of He2 has been observed as a consequence of the collisionally stabilized recombination of He2+ ions with electrons in the afterglow of a pulsed gigawatt electron-beam discharge into 3 atm of helium. Peak gains of the order of 0.04 cm−1 were found in components of the 3s3Σu+→ 2p3Πg transition of He2 in the 6400-Å region by directly measuring the time-resolved gain spectra using a tunable dye laser.
Cavity self-induced step for a Dayem bridge
Authors: Levinsen M. T.
Published: January 2004

The existence of radiation from a Dayem bridge is demonstrated by the observation of a self-induced cavity step. The form of the step is explained in terms of a dc-current-biased resistively shunted ideal Josephson device coupled to a resonance circuit. The behavior when a capacitor is included is also discussed.
Crystal defect mapping via impurity-activated luminescence in gadolinium gallium garnet
Authors: Stacy W. T. , Metselaar R. , Larsen P. K. , Bril A. , Pistorius J. A.
Published: January 2004

Faceting and growth striations have been revealed by the photographic mapping of the Tb3+- or Eu3+-activated luminescence in Czochralski-grown gadolinium gallium garnet. Both fluorescence and thermoluminescence topographs have been prepared. For the case of Tb3+ luminescence, facet cores exhibit a contrast in thermoluminescence topographs which is the opposite of that in fluorescence.
New noncollinear acousto-optic tunable filter using birefringence in paratellurite
Authors: Yano T. , Watanabe A.
Published: January 2004

A new type of acousto-optic tunable filter was designed using anisotropic Bragg diffraction far off the optic axis in a TeO2 crystal. The acousto-optic figure of merit Me (n 6p 2/ρν3) of this filter is 1200 × 10−18 sec3/g. The filter properties are different for different values of the incident angle. For example, with 30°, tuning from 6500 to 4500 Å is obtained by changing the acoustic frequency from 72 to 117 MHz. At 6328 Å, the filter bandwidth is 8 Å and 100% transmission is obtained at an acoustic power of 170 mW for a square transducer.
Spatial distribution of electrons in a high-pressure plasma produced by two-step photoionization
Authors: Levine J. S. , Javan A.
Published: January 2004

Experimental and theoretical investigations are made into the spatial distribution of photoelectrons produced in a high-pressure gas containing trace amounts of tri-n -propyl amine. The results show that in such a system photoelectrons may be produced over large distances, suggesting the possibility of large-volume high-pressure photoelectron-pumped lasers.
Least-squares integration method in intensity fluctuation spectroscopy of macromolecular solutions with bimodal distributions
Authors: Lee S. P. , Chu B.
Published: January 2004

This letter presents a new least-squares integration method of analysis for time-dependent correlation functions consisting of two exponentials. It also contains an investigation of the effect of sample time on the accuracy that can be achieved in a given intensity correlation measurement by means of 24- and 48-channel single-clipped photon-correlation spectrometers. Comparison is made with the least-squares normal equation method using experimental as well as simulated results.
Transmission properties of rib waveguides formed by anodization of epitaxial GaAs on Alx Ga1−x As layers
Authors: Reinhart F. K. , Logan R. A. , Lee T. P.
Published: January 2004

Two-dimensional rib waveguides were formed by anodization etching of single-heterostructure GaAs–Alx Ga1−x As slab waveguides. Low transmission losses (<2 cm−1) were observed for GaAs layer thicknesses ≳ 0.8 μm. Efficient preferential excitation of individual discrete modes and good mode stability were obtained in rib guides 0.8 μm thick, with 0.1-μm-high steps and width ≤10 μm.
Enhanced HBr chemical laser output with the addition of SF6
Authors: Oodate H. , Obara M. , Fujioka T.
Published: January 2004

A TE–HBr chemical laser output was considerably enhanced, by adding SF6 to a H2 + Br2 mixture, compared with that without SF6 addition, and the simultaneous and parasitic HF chemical laser emission was observed.
Effect of hydrostatic pressure on photoconductivity and electroluminescence of GaP:N
Authors: Wolfe M. I. , Kressel H. , Halpern T. , Raccah P. M.
Published: January 2004

The electroluminescence and photoconductivity of GaP:N diodes have been studied as a function of temperature and hydrostatic pressure. The A-line absorption and emission is relatively unaffected despite the large decrease in the electron binding energy with hydrostatic pressure. A model is discussed which accounts broadly for the experimental facts.
Photoluminescence of Zn-implanted GaN
Authors: Pankove J. I. , Hutchby J. A.
Published: January 2004

The photoluminescence spectrum of Zn-implanted GaN peaks at 2.87 eV at room temperature. The emission efficiency decreases linearly with the logarithm of the Zn concentration in the range 1–20×1018 Zn/cm3.
Ion implantation in silicon films on sapphire
Authors: Eklund K. H. , Holmén G. , Peterström S.
Published: January 2004

Silicon films on sapphire have been implanted with energetic boron and phosphorus ions. The annealing behaviour of the implanted layer, measured by sheet conductivity, has been found to be almost the same as for implantations in bulk silicon.
Precise measurement of coupling between optical waveguides
Authors: Zernike F.
Published: January 2004

A method to measure the coupling length between optical waveguides, for synchronous and asynchronous conditions, is described.
Study of noise in He–Cd+ laser
Authors: Brown David C. , Ginsburg Nathan
Published: January 2004

An experimental investigation into noise-generating processes in the He–Cd+ laser is described. We report the lowest output noise (0.14%) to date for the 4416-Å transition, as well as excellent dc stability.
High-speed low-power x-ray lithography
Authors: Lenzo P. V. , Spencer E. G.
Published: January 2004

High-speed low-power x-ray lithography has been accomplished using 8.34-Å radiation excited by a 75-W electron beam. Incident x-ray flux at the polymer film was 50 μW/cm2. Exposure was through a 3.4-μm-thick silicon mask substrate with patterns in a 4000-Å-thick gold film. Resist thickness was 4000–5000 Å. Both positive and negative resists have been used. Exposure times were 4 min for both poly(diallyl orthophthalate) and poly(butene-1 sulfone), 100 sec for poly(glycidyl methacrylate-co-ethyl acrylate), and 15 sec for epoxidized polybutadiene.
Laser-machined GaP monolithic displays
Authors: Dapkus P. D. , Weick W. W. , Dixon R. W.
Published: January 2004

The feasibility of producing electrically and optically isolated monolithic devices from planar GaP p-n junction material by the use of laser-machining techniques has been demonstrated. By machining deep narrow grooves through the p-n junction and around the areas to be contacted, it is possible to produce monolithic displays without the use of photolithography or critical etching steps. The resultant mesa devices have excellent optical definition and electrical properties. As an illustration of the technique, small (2.5-mm-high) monolithic seven-bar numerics have been fabricated from green-emitting GaP. This laser-machining technique should be applicable to other semiconductor materials and devices such as GaAs lasers.
Plasma-polymerized films as orientating layers for liquid crystals
Authors: Dubois J. C. , Gazard M. , Zann A.
Published: January 2004

Plasma-polymerized films from hexamethyldisiloxane are suitable for giving a homeotropic alignment to p-methoxybenzylidene, p, n-butylaniline. A 500-Å-thick layer of this polymer on substrates gives a very stable liquid crystal orientation.
Effect of dielectric anisotropy on twisted nematics
Authors: Baise A. I. , Labes M. M.
Published: January 2004

The electrical and optical threshold voltages for the twisted nematic field effect have been measured using Schiff base mixtures having Δε values from 2 to 16. The electrical threshold was measured by capacitance techniques, and was smaller than the optical threshold by a factor of ∼ 1.5. By using response time data to estimate changes in average elastic constants of the mixtures, the expected variation of the electrical threshold with Δε was found.
Ion-beam production using thermionic ion emission from sodium silicate in a plasma
Authors: Sato N. , Hatta Y. , Hatakeyama R. , Sugai H.
Published: January 2004

By using thermionic ion emission from a water glass (sodium silicate, Na2O · 2SiO2) an ion beam is easily produced in a plasma. Possible applications of the ion emission to plasma diagnostics are also described.
Formation of a virtual cathode by a relativistic electron beam flowing through a cavity
Authors: Friedman M.
Published: January 2004

A region of strong electric field (i.e., a virtual cathode) is formed when a relativistic electron beam is forced to flow through a cavity. This region is located at the entrance of the cavity and significantly affects the behavior of the beam.
Phase-matched three-wave mixing in silica fiber optical waveguides
Authors: Stolen R. H. , Bjorkholm J. E. , Ashkin A.
Published: January 2004

We have observed phase-matched nonlinear mixing in a silica fiber optical waveguide using the dispersion of the guide modes to compensate for bulk dispersion. A tunable dye laser signal is mixed with a fixed-frequency pump wave to generate output in specific waveguide modes at different frequencies. The technique is useful as a probe of waveguide properties and for the study of the nonlinearities of the medium.
``Stopping effect'' on guided light in As–S films by a laser beam
Authors: Matsuda A. , Mizuno H. , Takayama T. , Saito M. , Kikuchi M.
Published: January 2004

An optical ``stopping effect'' on guided light in As–S films has been achieved using a He–Cd laser beam. Preliminary results of this newly found phenomenon are presented in this paper.
X-ray emission from a CO2-laser-produced plasma
Authors: Dyer P. E. , James D. J. , Ramsden S. A. , Skipper M. A.
Published: January 2004

A 0.3-GW, 60-ns TEA CO2 laser has been used to create plasma from a solid carbon target. Studies of the x-ray emission from the plasma at 4×1011 W/cm2 indicate the existence of a high-energy electron component with an equivalent temperature of ∼ 2 keV.
Observation of strong bulk oxidation effects in amorphous germanium by ultraviolet reflectance spectroscopy
Authors: Helms C. R. , Spicer W. E. , Pereskokov V.
Published: January 2004

The effect of air exposure on the reflectance of evaporated amorphous and crystalline germanium for photon energies 2.5 ≤ h ν ≤ 11.7 eV has been studied in order to compare their oxidation rates. For h ν ≳ 4 eV, much larger changes in reflectance are observed in the amorphous films than are found in the crystalline films.
Thermally stimulated current measurements and their correlation with efficiency and degradation in GAP LED'S
Authors: Fabre E. , Bhargava R. N.
Published: January 2004

Thermally stimulated current (TSC) measurements have been performed on p-n junctions in GaP grown by double liquid phase epitaxy. Several deep states have been observed in both the n and p sides of the junction, and a correlation has been established between the presence and concentration of some of these traps and the quantum efficiency of the corresponding light-emitting diode (LED). It has also been observed that the degradation of the LED by heating under forward bias leads to the appearance or increase of the intensity of some peaks in the TSC spectrum.
Luminescence, laser, and carrier-lifetime behavior of constant-temperature LPE In1−x Gax P (x=0.52) grown on (100) GaAs
Authors: Campbell J. C. , Hitchens W. R. , Holonyak N. , Lee M. H. , Ludowise M. J. , Coleman J. J.
Published: January 2004

Photoluminescence and carrier lifetime data are obtained on low-dislocation-density (etch pits ≳ 5 × 103/cm2) n-type In1−x Gax P (x=0.52) epitaxial layers grown on (100) surfaces of GaAs by means of a constant-temperature liquid-phase-epitaxial (CT-LPE) process. These crystals are of exceptional quality and readily lase from 77 to 300 °K. The index dispersion relation (n-λ dn/dλ) is determined from the laser mode spacing Δλ in the temperature range 77–300 °K and indicates that at higher thresholds laser operation shifts toward donor tail states. By means of optical phase shift measurements the carrier lifetime (77°K) is examined as a function of wavelength from the spontaneous regime to well above laser threshold. The lifetime data indicate that there is a correlation between a dip in the lifetime due to stimulated emission and the region of the spectrum where the first laser modes appear. These data, and similar data on p-type crystals, indicate that CT-LPE In1−x Gax P should be very promising for the development of room-temperature visible spectrum lasers.
Amorphous semiconductor devices displaying memory in one polarity and threshold switching in the opposite polarity
Authors: Nicolaides R. Vogel
Published: January 2004

A novel switching effect has been found in amorphous semiconductor devices having an aluminum interlayer on one electrode. These devices operate as memory devices in one polarity and as threshold switching devices in the opposite polarity. The setting time is very short if the aluminum side of the device is positive. If no aluminum interlayer is present, a long pulse with special trailing edge is necessary to accomplish memory setting. Threshold switching voltage and memory breakdown voltage of the device with an interlayer have the same value.
Josephson junctions at 45 times the energy-gap frequency
Authors: McDonald D. G. , Petersen F. R. , Cupp J. D. , Danielson B. L. , Johnson E. G.
Published: January 2004

Superconductive Nb–Nb point contacts have been studied with 9.5-μm radiation from CO2 lasers. Two models are considered to explain the experiments: one is Werthamer's Josephson junction model and the other is a thermally modulated Josephson junction. The evidence favors Werthamer's model but is not conclusive.
Preferred orientations in MgO films deposited on amorphous substrates
Authors: Aboelfotoh M. O.
Published: January 2004

Reflection high-energy electron diffraction patterns show that the crystal orientation of MgO films deposited on amorphous substrates at 30 °C at normal vapor incidence varies with film thickness. Films in the thickness range of 50 Å to less than 1000 Å have a random orientation. As the film thickness is increased a 〈 111 〉 preferred orientation develops. The 〈 111 〉 preferred orientation remains unchanged upon annealing in vacuum at a temperature in the range from 400 to 550 °C for 1 h. The origin of these orientations is discussed.
Alignment and wetting properties of nematic liquids
Authors: Haller Ivan
Published: January 2004

Contrary to recent claims, no correlation of useful predicting power exists between the tendency of a nematic liquid to align transverse to a solid surface and the difference between the surface free energies of the nematic liquid and of the substrate. Observations that lead to this conclusion are reported for systems in which (i) the composition but not the surface tension of the nematic liquid, (ii) the adsorbed layer and hence the surface free energy of the substrate, and (iii) the temperature is varied.
A critique of a recent thin-film field-effect experiment using detached electrodes
Authors: Sinclair W. Robert , Murr L. E.
Published: January 2004

As a result of a study of the dc electric field effect on vapor-deposited metal films using electrodes detached from the substrate, Murr and Singh recently observed no significant effects for fields applied in the plane of the substrate, ranging from 10 to 103 V/cm. It is demonstrated in the present paper that a linear gradient did not exist during these experiments, and that due to a counteracting influence of the displacement current, the potential gradient at the substrate surface probably approached zero almost instantaneously at elevated substrate temperatures. An analysis of the field conditions attendant to thin-film field-effect experiments with detached electrodes indicates that the effect of dc electric fields on nucleation and growth of vapor-deposited thin films in such an experiment can only be established when the substrate temperature is relatively low.
Reaction rates for Pt on GaAs
Authors: Coleman D. J. , Wisseman W. R. , Shaw D. W.
Published: January 2004

The rate at which GaAs reacts with Pt has been determined at selected temperatures between 300 and 400 °C. The amount of GaAs reacted is determined by measuring the movement of the original Pt Schottky-barrier contact into the GaAs. Data are presented which show the amount of GaAs reacted as a function of anneal time at several different temperatures. The reaction follows a parabolic rate law with activation energy of 1.6 eV. Some change in the electrical characteristics of the Schottky barrier is observed.
Auger and secondary electrons excited by backscattered electrons
Authors: Goto K. , Ishikawa K. , Koshikawa T. , Shimizu R.
Published: January 2004

The contribution of backscattered electrons to Auger and secondary electron yields was examined by in situ measurements while evaporating Be onto Cu substrate at constant rate of 1.2 Å/min. The ratios βA and βs of Auger (KVV) and secondary yields of Be due to backscattered electrons to those due to primary electrons were experimentally obtained from the Auger and true secondary electron yields versus backscattering coefficient η curves, and were evaluated to be 1.6 and 4.4 at a primary energy of 1.0 keV, respectively. The backscattering factor r for Be (KVV Auger) was experimentally found to be 1.1 at a primary energy of 1.0 keV.
Photoemission from surface centers
Authors: Pierret R. F. , Roesner B. B.
Published: January 2004

A technique is described whereby photoemission from surface centers can be effectively isolated and carefully monitored. Electronic photoexcitation from interface states in the Si–SiO2 system has been observed using the technique and a photocapture cross-sectional area ∼ 1 × 10−19 cm2 has been measured for states positioned energetically in the upper central portion of the silicon band gap.
Reducing the effective height of a Schottky barrier using low-energy ion implantation
Authors: Shannon J. M.
Published: January 2004

A thin highly doped layer at the surface of a semiconductor has been used to increase the surface field of a Schottky barrier and reduce the barrier height by an amount insensitive to applied bias. The effective barrier height of Ni–Si barriers of this type made using ion-implantation techniques has been reduced by an amount in the range 0–0.2 eV without significant degradation of the reverse characteristic.
Efficient upconversion of long-wavelength uv light into the 200–235-nm band
Authors: Massey G. A.
Published: January 2004

Phase-matched nonlinear generation of the second harmonic of visible laser sources has been limited to wavelengths longer than about 230 nm because the dispersion of available materials with high ultraviolet transmission cannot be compensated by their birefringence. Parametric upconversion of uv in the range 250–325 nm to the 200–235-nm band by mixing with a strong infrared signal can be accomplished with 90° phase matching in 45° z-cut crystals of ADP. A particularly useful embodiment of this idea is the upconversion of dye laser second-harmonic wavelengths by mixing with the 1.064-μm output of the Nd:YAG laser. Preliminary experiments in upconverting 266-nm light to 213 nm have demonstrated stable conversion efficiencies above 50% for this process with peak and average powers above 5 kW and 0.5 mW, respectively.
Subpicosecond kilowatt pulses from a mode-locked cw dye laser
Authors: Shank C. V. , Ippen E. P.
Published: January 2004

Subpicosecond pulses (0.5–1.0 psec) have been generated by passive mode locking of a composite medium dye laser. Both the gain medium and saturable absorber are placed in a single free-flowing dye stream located near the center of the resonator. Peak pulse powers of several kilowatts have been obtained by acousto-optically dumping the mode-locked pulses from the optical cavity at repetition rates up to 105 pps.
Rotational relaxation rate constants for CO2
Authors: Jacobs Ralph R. , Pettipiece Kenneth J. , Thomas Scott J.
Published: January 2004

Rotational relaxation rate constants, krot, have been measured for the CO2 00°1 level in three kinds of amplifiers: one using CO2 alone and two others using mixtures of CO2–He and CO2–N2. The experiment consists of perturbing the CO2 00°1 level with a ∼2-nsec saturating pulse at P(20) in the 10.4-μ band and monitoring the subsequent repopulation of the J = 19 rotational state with a probe beam set at P(20) in the 9.4-μ band. The determined rate constants are kCO2–CO2 = 1.3±0.2, kCO2–He = 0.6±0.1, and kCO2–N2 = 1.2±0.2, all in units of 107 sec−1 Torr−1.
Photon drag and other emfs induced in tellurium by a TEA CO2 laser
Authors: Ribakovs G. , Gundjian A. A.
Published: January 2004

The longitudinal photon drag signal has been isolated from other interfering emfs generated in high-purity good-quality tellurium single crystals illuminated by 10.6-μ radiation from a pulsed TEA CO2 laser. The observed value of 10 mV/MW cm−2 at room temperature for the photon drag signal with E∥c and its temperature dependence down to 125 °K agree with the generally accepted theoretical expression. At room temperature the heavy hole momentum relaxation time has been calcualted to be 1.7 × 10−13 sec. Signals corresponding to a third-rank tensorial effect have been occasionally measured at low temperatures, particularly when defects or dislocations have been introduced into the samples.
Repetitively pulsed electron-beam-initiated chemical lasers from SF6–H2 and SF6–D2 mixtures
Authors: Aprahamian R. , Betts J. A. , Wang J. H. S. , Herrett R. H. , Barth R. W.
Published: January 2004

Up to 5 pulses/sec repetitive operation has been achieved with an electron-beam-initiated SF6–H2 chemical laser. Maximum laser energies of 250 mJ/pulse have been obtained from an active volume of 244 m1 and a total pressure of 600 Torr. Lasing was also observed from SF6–D2 mixtures with peak energies one-half of those from SF6–H2.
Kinetics and mechanism of platinum silicide formation on silicon
Authors: Poate J. M. , Tisone T. C.
Published: January 2004

The growth of platinum silicide layers has been observed using Rutherford backscattering. By simultaneous observation of the relative movement of the Pt2Si and PtSi interfaces, it is possible to deduce that Si is the diffusing species with the reaction occurring at either the Pt2Si–Pt, PtSi–Pt2Si, or PtSi–Pt interfaces. Activation energies for the growth of the Pt2Si and PtSi layers are 1.6 eV. It is possible to interact Pt with Si by means of Ar ion bombardment; however, the reacted layer acts as a barrier to Si diffusion.
Effect of high-temperature heat treatment on penetration depth of superconducting niobium
Authors: Varmazis C. , Joshi A. , Luhman T. , Strongin Myron
Published: January 2004

A discussion is given of the change in penetration depth λ at the surface of niobium with various heat treatments and of the causes of the large changes in λ. In particular, the distribution of oxygen in from the sample surface is discussed, along with the thermal faceting caused by heating niobium to high temperatures at pressures near 10−6 Torr.
Stroboscopic observation of magnetic bubble circuits using a gated image-intensifier tube
Authors: Vella-Coleiro G. P. , Nelson T. J.
Published: January 2004

A technique using a gated image-intensifier tube for stroboscopic viewing of magnetic bubble motion in field access devices is described. Adequate illumination of bubbles propagating in a 100-kHz rotating field was obtained with a conventional microscope illuminator and a 50× objective using gate pulses as short as 0.5 μsec at repetition rates as low as 10 kHz. Observation of bubbles propagating through a chevron expander showed that lateral growth is asymmetric, indicating that an asymmetrically located bubble input port would give improved performance. Shorter pulses and higher repetition rates should permit observation of bubbles propagating in excess of 1 MHz.
Additive and electrolytic coloration of NaF
Authors: Collins W. C. , Schneider I. , Klein P. H. , Johnson L. R.
Published: January 2004

It is shown that well-characterized F and M centers can be introduced into NaF crystals by both additive and electrolytic coloring techniques. This success is attributed primarily to a substantial elimination of hydroxyl-ion contamination.
Microscopic interferometry of laser-produced plasmas
Authors: Attwood D. T. , Coleman L. W.
Published: January 2004

Holographic microinterferometry is applied to the study of laser-produced plasmas. A 150-psec 1.06-μm light pulse from a neodymium laser is used for both production and diagnostics of the plasma. An interferogram, obtained 0.5 nsec after irradiation by a 1/2-J pulse, is presented. It is pointed out that spatial resolution is limited by plasma motion during passage of the 100-psec frequency-doubled diagnostic pulse.
Radiation protection of fiber optic materials: Effects of oxidation and reduction
Authors: Friebele E. J. , Ginther R. J. , Sigel G. H.
Published: January 2004

The response to ionizing radiation of a suite of high-purity silicas, a titanium-doped silica, high-purity germania, and silica fibers with germanium-doped and titanium-doped cores has been measured. The radiation sensitivity of these materials was found to depend upon the atmosphere used during a heat treatment prior to irradiation.
Variation of refractive index with wavelength in fused silica optical fibers and preforms
Authors: Presby H. M.
Published: January 2004

The variation of the refractive index of an unclad fused silica fiber and the preform from which it was pulled was determined over the wavelength range 0.5–1.1 μm, in 0.025-μm steps. The index is determined from an analysis of the backscattered radiation produced when light from an appropriately filtered xenon-arc source impinges transversely upon the fiber or preform. The variation of the index of refraction of the fiber follows those of the preform and published values for bulk fused silica material to within 2 parts in 10−4, with the exception of two points at 0.65 and 0.95 μm.
Electro-optic modulation of optical guided wave in LiNbO3 thin film fabricated by EGM method
Authors: Fukunishi Syuzo , Uchida Naoya , Miyazawa Shintaro , Noda Juichi
Published: January 2004

Experiments on light propagation and electro-optic modulation have been made for poled LiNbO3 single-crystal thin films fabricated by the method of epitaxial growth by melting (EGM). The values of the refractive indices are found to be no = 2.200 and ne = 2.184. A phase modulation experiment has been carried out using a Mach-Zehnder interferometer in the region of 100 Hz-3 MHz. The electro-optic coefficients of the film have been determined by the phase-compensation method, and the values obtained are r33=12 and r13=2.3×10−12 m/V.
Wide-angle electro-optic switch
Authors: Kenan R. P. , Verber C. M. , Wood Van E.
Published: January 2004

A new electric-field-actuated optical switch capable of wide-angle deflection is described. The switch element makes use of the high angular selectivity of thick Bragg gratings and can be fabricated both in bulk and in thin-film configurations. Experimental verification of the switch action in a bulk configuration is presentd. Modulation of 35% was observed in this first observation of the effect.
Optically pumped grown GaAs mesa surface laser
Authors: Blum F. A. , Lawley K. L. , Scott W. C. , Holton W. C.
Published: January 2004

Optically pumped laser oscillation has been obtained in vapor-grown epitaxial GaAs mesa structures which have vertical as-grown crystalline facets furnishing the optical feedback.
Stability of highly doped negative-differential-conductivity diodes
Authors: Torrens A. B.
Published: January 2004

If a GaAs diode is biased above threshold and if the doping N exceeds a critical value Np of about 1021 m−3, the instability due to negative differential conductivity (NDC) can settle into a stationary anode layer. This layer remains when the voltage is subsequently reduced below threshold, provided that N is sufficiently uniform near the anode. A diode in which the doping or the cross section increases toward the anode exhibits static negative differential resistance. When a diode with a small anode overdoping is biased above threshold, a depletion layer forms at the anode and, if N > Np, propagates towards the cathode. The simulation of negative conductance at 50 GHz in the LSA mode raises the possibility of high-efficiency amplification at very high frequencies by parastable diodes.
Direct comparison of low-energy ion backscattering with Auger electron spectroscopy in the analysis of S adsorbed on Ni
Authors: Taglauer E. , Heiland W.
Published: January 2004

A comparison was made between low-energy ion backscattering and Auger electron spectroscopy (AES) in the analysis of various coverages of sulfur on a nickel (111) crystal plane. For the intensity ratios S/Ni a linear relationship between both techniques was found for submonolayer coverage. Using the calibration of Perdereau for AES, ion scattering intensities are calibrated and relative values are obtained for the neutralization probabilities of Ne+ and He+ scattered from Ni and S. For 1-keV Ne+ ions neutralization is about a factor of 7 lower for scattering from S than from Ni. Ion scattering is more sensitive to the position of adsorbed atoms than AES; a shadowing effect shows that the S atoms sit on top of the Ni surface layer. Both effects result in a high sensitivity of Ne+ scattering for adsorbates such as S or O, the detection limit being some 10−4 of a monolayer.
Characterization of epitaxially grown films of (TTF) (TCNQ)
Authors: Chaudhari P. , Scott B. A. , Laibowitz R. B. , Tomkiewicz Y. , Torrance J. B.
Published: January 2004

Epitaxial films of the highly conducting organic charge-transfer salt tetrathiafulvalinium tetracyanoquinodimethanide, (TTF) (TCNQ), grown on NaCl substrates were analyzed using electron diffraction and electron and polarized optical microscopy techniques. The films were found to orient with the high-conductivity (TTF) (TCNQ) b axis along [110] directions of the NaCl. Preliminary optical, infrared, and electrical data obtained on these films are also presented.
Interaction of microwaves with ring domains in magnetic garnet films
Authors: Dötsch H. , Schmitt H. J.
Published: January 2004

Magnetic bubble and ring domains are generated in LPE garnet films by locally exciting spin precession near the ferrimagentic resonance frequency at high microwave power densities. Due to the spin precession, radial and azimuthal forces act on the bubbles. The radii of the ring domains vary with the microwave power and the bias field. The stability range of these domains extends over a bias field range of about 0.18 times 4πMs. The dynamic behavior of the ring domains could be studied by amplitude modulation of the microwaves.
Molecular hyperpolarizabilities determined from conjugated and nonconjugated organic liquids
Authors: Levine B. F. , Bethea C. G.
Published: January 2004

The magnitude and sign (positive) of the molecular hyperpolarizability γ has been determined for several mixtures of nitrobenzene and benzene. This has allowed the testing of the adequacy of Onsager's local field factors, which are found to be valid. By comparing γ of nitrobenzene with that of nitromethane, we find that the delocalized conjugated electrons are an order of magnitude more effective in contributing to γ than are the localized nonconjugated electrons.
Crossover frequencies and turn-off time reduction scheme for twisted nematic liquid crystal displays
Authors: Chang T. S. , Loebner E. E.
Published: January 2004

The sign change of dielectric anisotropy at the characteristic crossover frequency of a nematic mixture is utilized in twisted nematic liquid crystal displays for turn-off (decay) time reduction. This can be obtained by either (a) a two-frequency addressing or (b) a high-frequency erasing scheme where the high frequency is above the crossover frequency. Data are presented on Eastman Kodak 11900 nematic mixture.