bluuebunny/crossref_metadata_2025 huggingface dataset:
High-efficiency secondary-electron emission from sputtered MgO–Au cermets
Authors: Henrich Victor E. , Fan John C. C.
Published: January 2004

We have obtained high-efficiency secondary-electron emission from a new sputtered cermet system, MgO–Au. Peak yields of 8 and quantum gain for primary-electron energies as low as 17 eV have been achieved on thick films without the presence of surface charging. The very small insulator particle sizes (< 50 Å) in the films permit removal of surface charge by tunneling to adjacent metallic regions. This type of emitter is potentially useful for secondary-emitting cathodes in high-power device applications as well as low-power electron multiplication.
Dense plasma discharges for solid-target heating
Authors: Vitkovitsky I. M. , Levine L. S. , Mosher D. , Stephanakis S. J.
Published: January 2004

Dense plasma channels formed by exploding-wire discharges have been used to form very-high-current-density electron beams. The interaction of the beam with the plasma lowers the mean electron energy relative to that to be gained in the accelerating potential of 106 V applied across the plasma. The current density of electrons incident on the anode and their energy distribution have been determined. Approximately 10% of the current at the anode contains electrons with energy greater than 25 keV. The current density associated with these electrons exceeds 107 A/cm2. The power delivered to the anode approaches 1012 W/cm2, which leads to strong anode heating. X-ray spectroscopy of the radiation emitted from the anode and of neutron production in deuterated anodes was used to deduce a target temperature of 0.1–1.0 keV.
A new piezoelectric crystal: Ba2Ge2TiO8
Authors: Kimura Masakazu , Doi Kikuo , Nanamatsu Satoshi , Kawamura Tsutomu
Published: January 2004

A Ba2Ge2TiO8 single crystal is synthesized by the Bridgman method. The space group of Ba2Ge2TiO8 is determined to be C2v21-Iba2, where the lattice constants a, b, and c are 12.30, 135.2, and 10.70 Å, respectively. The crystal includes a wedge-shaped domain structure which resembles those observed in Gd2(MoO4)3 and Rochelle salt. Both X and Y plates have a large electromechanical coupling factor in a thickness shear mode, k15 = 0.27 and k24 = 0.31.
Phase of ultrasonic reflection at Rayleigh angle incidence
Authors: Plona Thomas J. , Mayer Walter G.
Published: January 2004

The phase of an ultrasonic beam reflected from a liquid-solid interface at and near Rayleigh angle incidence is measured using a new technique. Results indicate that two waves comprise the reflected beam, i.e., a specularly reflected wave and a reradiated surface wave, which do not change phase as the angle of incidence varies, which maintain a 180° phase difference between them, and which propagate collinearly only at the Rayleigh angle.
Electron irradiation dilatation in SiO2
Authors: Sigsbee R. A. , Wilson R. H.
Published: January 2004

Negative dilatation (shrinkage) induced by 10-keV electron bombardment of SiO2 films thermally grown on Si has been studied. Measured deflection changes in continuous SiO2 bridges etched following irradiation showed a maximum shrinkage of [inverted lazy s] 0.8%, which occurred at 0.2 C/cm2, followed by a slight expansion, and subsequent saturation at higher exposures. Exposures up to 3 C/cm2 were utilized. Isochronal annealing studies show the activation energy for recovery to be approximately 1 eV with 2% recovery occurring in 1 h at 400°C.
Brillouin spectra of CaF2 microcrystals using a stable 3-pass Fabry-Perot interferometer
Authors: Brody E. , Roychoudhuri C. , Hercher M.
Published: January 2004

The elastic properties of single-crystal grains in polycrystalline material can be studied through Brillouin scattering using a laser probe beam. The Brillouin spectra of hot-pressed CaF2 (Irtran-3), having a typical grain size of 150 μm, is presented. We have observed scattering from both longitudinal and transverse phonons, despite the presence of a large elastically scattered signal, using a stable 3-pass Fabry-Perot interferometer having a contrast of 106.
Electrical properties of proton-bombarded Ga1−xAlxAs
Authors: Favennec P. N. , Diguet D.
Published: January 2004

We have shown the feasibility of forming insulating walls in Ga1−xAlxAs by proton bombardment, and have demonstrated their stability up to a temperature of 180°C. The mean projected range of protons in Ga1−xAlxAs is determined for energies ranging from 200 to 1200 keV. The insulating properties of proton-bombarded layers are applied to the realization of cross-bar integrated arrays of electroluminescent diodes.
Spark pumped dye laser with high repetition rate and low threshold
Authors: Ferrar C. M.
Published: January 2004

A short unconfined spark is imaged by a spherical reflector into a small dye cell. Lasing is achieved for electrical inputs as small as 5 mJ. Pulse repetition rates as high as 2000 pulses/sec (pps) have been attained. A tilted etalon permits wavelength tuning of the laser output.
Defects in arsenic-implanted p-n junctions
Authors: Bogardus E. H. , Poponiak M. R.
Published: January 2004

High-dose (300 keV) ion implant damage has been observed, by infrared microscopy, to extend approximately 1.4 times the junction depth or 4 times the projected range. No such damage has been seen for shallow implants that were diffused to a corresponding junction depth. Leakage currents were identical for both implant conditions. No ``tailing'' was identified in the profile that could explain the extent of damage.
Fast acoustic diffraction-type optical waveguide modulator
Authors: Shah Manhar L.
Published: January 2004

A fast acoustic diffraction-type thin-film optical waveguide modulator is described. Modulation was observed for the drive signal over the 150–550-MHz frequency range. A depth of modulation of 10% per electrical watt was estimated from the diffracted spots. The scheme presented here widens the selection of materials for acousto-optic modulations in an optical waveguide and may find some useful applications in the infrared region where suitable electro-optic materials are few.
Beam deflection and amplitude modulation of 10.6-μm guided waves by free-carrier injection in GaAs–AlGaAs heterostructures
Authors: McFee J. H. , Nahory R. E. , Pollack M. A. , Logan R. A.
Published: January 2004

Beam deflection and amplitude modulation of 10.6-μm guided waves by photoinjected free carriers are demonstrated in thin-film GaAs–AlGaAs heterostructure waveguides. At high injection levels (N ≳ 5 × 1017 cm−3), amplitude modulation (up to 100%) of the 10.6-μm guided wave dominates, but at lower injection levels beam deflection is dominant. External deflection angles of the order of 1° are obtained with nanosecond response times.
Closed-form solution for excited-state populations in temporally and spatially varying lasing media
Authors: Curry B. P. , Zwick S. A. , Aliprantis C. D.
Published: January 2004

We solve a class of equations in which excited-state populations are coupled by radiative, collisional, and pumping terms having specified time and position dependence. These equations are decoupled by expansion of the excited-state populations and the pumping terms in eigenvectors of the collisional transition matrix. The solutions are ordered in such a way that the first-order solution is equivalent to neglecting temporal variations in radiation intensity, and higher-oder solutions introduce time-dependent state mixing effects as a consequence of strong transitions. The second-order solution is stated explicitly and a prescription given for obtaining higher-order corrections.
New magneto-optic memory concept based on compensation wall domains
Authors: Krumme J. -P. , Hansen P.
Published: January 2004

A new concept of thermomagnetic localized reversible magneto-optic storage is proposed based on the application of compensation wall domains (CWD). Individual CWD's of 12 × 12-μm dimensions in an LPE film of composition Y2.34Gd0.52Yb0.14Fe3.74Ga1.26 O12 with 3-μm thickness have been switched by laser flashes of 10−2 erg/μm2 energy in 5 μs at 5145-Å wavelength using a stationary field of 41 Oe normal to the film plane.
Lithium niobate stress gauge for pulsed radiation deposition studies
Authors: Graham R. A. , Jacobson R. D.
Published: January 2004

The piezoelectric response of impact-loaded z-cut lithium niobate is investigated to determine whether the material can be used as a time-resolving nanosecond-resolution stress gauge. The material is found to have appropriate properties for stresses up to 15 kbar. A gauge from this material should prove particularly useful for measurements of stress pulses resulting from the absorption of pulsed radiation in solids.
Depth distribution of implanted helium and other low-z elements in metal films using proton backscattering
Authors: Blewer Robert S.
Published: January 2004

The depth profiles of helium implanted into copper foils have been observed experimentally by a proton backscattering technique. Carbon and oxygen on the front and rear surfaces of the foils have also been resolved. The mean depth of the helium implanted at 50, 100, and 150 keV is in agreement with projected range calculations, though the rms spread in the distributions is smaller than predicted. The shape of the profiles is the Gaussian form expected from single energy implants with no evidence of tails extending deep into the foils. Detection sensitivity is greater than 1 at.% for He in Cu under the experimental conditions investigated. The mean depth (peak) of the implanted helium distributions can be determined to within ± 100 Å.
High-sensitivity thin-film strain sensor
Authors: Jeffers Frederick J.
Published: January 2004

Evaporated cadmium sulfide thin-film resistors have been fabricated which exhibit remarkable strain sensitivity. Electrodes are arranged in sandwich fashion so that electrons flow perpendicular to the plane of the CdS layer. The layers are doped and heat treated so that nominal unstrained resistivities are of the order of 3 × 105 Ω cm. Tensile and compressive strain in the plane of the film causes the resistance to increase and decrease, respectively, by as much as a factor of 15.
Laser mirror damage in germanium at 10.6 μm
Authors: Emmony D. C. , Howson R. P. , Willis L. J.
Published: January 2004

Damage in the germanium output mirror of a TEA CO2 laser shows a periodicity of 10.6 μm, the laser wavelength. A mechanism is proposed in which scattered and cavity radiation interfere. An interference mechanism is confirmed by experiments outside of the laser cavity. Periodic damage is obtained in thin films irradiated at angles other than the normal where the fringe spacing is modified.
CO2 laser beam refraction in a linear discharge plasma
Authors: Molen G. M. , Kristiansen M. , Hagler M. O.
Published: January 2004

Beam guiding and focusing have been observed for CO2 laser propagation in a high-density low-temperature annular plasma. A TEA laser was fired along the axis of a cylindrical plasma column of densities in the 1016–1017-cm−3 range. Several radial density profiles were investigated. Beam guiding and focusing were observed when the density had a minimum on the axis. A density maximum on-axis refracted the beam toward the tube walls, and intense ``hot spots'' resulting from apparent filamentation inside the plasma were recorded.
Role of coating defects in laser-induced damage to dielectric thin films
Authors: DeShazer L. G. , Newnam B. E. , Leung K. M.
Published: January 2004

The laser-induced damage thresholds of two different dielectric thin-film coatings increased with decreasing spot size and were invariant for spot sizes greater than 150 μm. A simple model has been suggested that the distribution and nature of coating defects have played an important role in this spot-size dependence, e.g., the probability of the laser beam striking a defect site will be greater for larger spot sizes and that damage in materials can be distinguished as defect damage and intrinsic damage.
Dynamic stabilization and parametric excitation of instabilities in liquid-gas interfaces with nonharmonic oscillations
Authors: Hoffmann Friedrich M. , Wolf Gerd H.
Published: January 2004

Experiments on the dynamic stabilization of the Rayleigh-Taylor instability are described, where the applied oscillations are modulated in their frequency or chosen to be strongly anharmonic. While, compared to the application of harmonic oscillations, an expected rise of the excitation threshold of parametric instabilities could be observed, a corresponding shift of the boundary discriminating against the slowest Rayleigh-Taylor mode did not allow to obtain a measurable increase of the over-all stability region.
Optical isolation using a Doppler-broadened molecular absorber
Authors: Keilmann F. , Sheffield R. L. , Feld M. S. , Javan A.
Published: January 2004

A new principle for optical isolation based on the saturation of a Doppler-broadened resonance is described. It depends on an initial difference in the power levels of the incident and reflected waves. The technique is demonstrated using an SF6 absorber to isolate the P(18) line of the CO2 transition at 10.57 μm.
Photodetection by barrier modulation in Cu-diffused Au/CdS junctions
Authors: Bücher H. K. , Burkey B. C. , Lubberts G. , Wolf E. L.
Published: January 2004

Modulation of essentially thermionic forward current by light-induced lowering of an electrostatic barrier leads to steady-state electron per photon gain of order 106 in narrow Cu-compensated Au/CdS junctions. The light dependence of the barrier, whose peak lies within the semiconductor, is measured directly by internal photoemission. A model of the junction is presented and the limiting threshold and gain of this type of device is estimated.
Single heterojunction Pb1−x Snx Te diode lasers
Authors: Walpole J. N. , Calawa A. R. , Ralston R. W. , Harman T. C. , McVittie J. P.
Published: January 2004

Single heterojunction diode lasers in the Pb1−xSnx Te alloy system have been fabricated by low-temperature vacuum deposition of n-PbTe on a p-Pb0.88Sn0.12 Te substrate. The lasers have lower threshold current densities and operate cw at higher temperatures than homojunction devices in this material. At laser threshold the incremental diode resistance drops abruptly from 0.5 Ω to a series resistance limited value of 0.08 Ω, a previously unobserved effect in diode lasers which indicates very high internal quantum efficiency.
Analysis of a collisionally induced dipole laser
Authors: Christiansen Walter H. , Greenfield E.
Published: January 2004

An electric dipole moment is induced in homonuclear molecules during collisions, allowing radiative transitions which are otherwise forbidden. This effect, coupled with high-pressure electrical excitation, may be used to achieve laser action in a homonuclear gas. Properties of this type laser include a very broad gain bandwidth and a new type of partial inversion. A mixture of H2 and Xe is analyzed as a prospective system wherein efficiencies of about 20% are predicted for picosecond pulses at 2.8 μm.
Efficient low-band operation of a CO chemical laser
Authors: Jeffers W. Q. , Wiswall C. E.
Published: January 2004

A cw O/CS2 CO chemical laser has been operated at a chemical efficiency of 37.5%. This result was achieved by the use of N2O as a diluent whose V-V transfer effects on the chemically formed CO are such as to strongly enhance emission in the low vibrational bands. The free-running oscillator spectra start at v = 12 → 11 and continue to v = 2 → 1, with more than 50% of the output in the low bands 6 → 5 to 2 → 1. These results again emphasize the importance of vibrational energy transfer in chemical laser media.
Periodic breakup of optical beams due to self-focusing
Authors: Campillo A. J. , Shapiro S. L. , Suydam B. R.
Published: January 2004

Transverse spatial periodic breakup of an optical beam due to self-focusing has been experimentally observed. Each focal spot evolves from a zone with well-defined dimensions. The formation from these zones is consistent with an instability theory. Calculated and experimentally observed zone dimensions and powers are in good quantitative agreement.
Pulsed high-power HF laser holography with gelatine detectors
Authors: Braun W. , Decker G. , Röhr H.
Published: January 2004

Holographic interferograms are produced on gelatine films with pulsed HF laser light (λ ≈ 3 μm). The sensitivity is about 2 J/cm2, and the resolution at least 300 lines/mm. The spectrum of the HF laser is measured by means of holography.
Acoustic amplifier for detection of atmospheric pollutants
Authors: Dewey C. F. , Kamm R. D. , Hackett C. E.
Published: January 2004

Kreuzer has demonstrated the feasibility of detecting atmospheric pollutants using acoustic signals produced by volumetric absorption of infrared radiation. We have investigated a substantial improvement of this technique wherein the optical excitation beam is modulated at a frequency corresponding to a natural acoustic resonance of the sample chamber. Acoustic amplification factors exceeding 100 have been observed.
Electrical effect of growth striations in the silicon vidicon-type camera tubes
Authors: Yoshikawa Shigeo , Chikawa Jun-ichi
Published: January 2004

Camera tubes with a CdTe–Si heterojunction target have been fabricated to observe the electrical effects of the growth striations in dislocation-free Si crystals grown by the floating-zone technique. Their video images under a uniform illumination showed spiral patterns due to the growth striations. The origin of the patterns is attributed to the electric fields which are formed locally in the growth striations and drive the photoinduced holes toward the growth direction.
High-field magnetization and coercivity of amorphous rare-earth-Fe2 alloys
Authors: Clark Arthur E.
Published: January 2004

High-field magnetization studies were made from 4 °K to room temperature on rapidly sputtered TbFe2, DyFe2, and SmFe2. At 4.2 °K the magnetic moment resembles that of polycrystal samples, whereas at room temperature it is substantially lower. Huge coercive forces (20–30 kOe) were observed at 4.2 °K. Partial crystallization of TbFe2 from the sputtered amorphous state yields high-energy products and coercivities (> 3 kOe) at room temperature.
Source materials for ion implantation
Authors: Axmann A.
Published: January 2004

A survey is given of source materials which can be used to draw ion currents from a Nielsen source. More than 50 different ion species are listed including Pd+, Ir+, Pt+, and Au+. Actual currents obtained during implantation are also reported.
Secondary defects in phosphorus-implanted silicon
Authors: Tamura Masao
Published: January 2004

Transmission electron microscopic observations have been made on 100-keV phosphorus-implanted silicon layers with a dose of 5 × 1014/cm2 as a function of implantation temperature and the subsequent annealing treatment. The annealing behavior of secondary defects is strongly dependent upon the implantation temperature. Also, the nature of dislocation loops formed in the implanted layers shows implantation temperature dependence: dislocation loops in room-temperature implanted layers are predominantly interstitial in nature, whereas in layers implanted at higher temperatures than 500 °C they are predominantly of vacancy type, and both types of loops coexist in 200–400 °C implanted samples.
Laser damage threshold for dielectric coatings as determined by inclusions
Authors: Milam David , Bradbury R. A. , Bass Michael
Published: January 2004

By studying the morphology of threshold damage and observing for the first time the predicted ``pulse duration-inclusion size'' relationship, it is shown that the threshold for laser damage to nonabsorbing dielectric coatings is determined by the presence of metallic or highly absorbing nonmetallic inclusions.
Laser-induced inclusion damage at surfaces of transparent dielectrics
Authors: Boling N. L. , Dubé G.
Published: January 2004

Q-switched laser-induced damage to transparent surfaces is shown to occur in many cases without the formation of a bright plasma. This ``aplasmic'' damage is apparently due to absorption by submicron inclusions. The prominence of damage is a function of material, polishing compound, and geometry of the test situation. Because aplasmic damage can be difficult to detect, it is suggested that the results of experiments conducted with small beams, especially when plasma formation is used as a definition of damage, be interpreted with caution. Damage thresholds of several materials are reported incidentally.
The role of linear dispersion in plane-wave self-phase modulation
Authors: Fisher Robert A. , Bischel W.
Published: January 2004

It is shown by computer calculation that linear dispersion and self-phase modulation can strongly couple to influence pulse propagation phenomena. Pulses become distorted temporally as they propagate, and, under certain circumstances, optical shocks can form on the leading edge (in time) of a pulse. Some interesting cases are considered for pulse propagation in CS2. The pulse compression scheme of Fisher, Kelley, and Gustafson is modified to take self-dispersive effects into consideration.
Effect of alloying behavior on the electrical characteristics of n-GaAs Schottky diodes metallized with W, Au, and Pt
Authors: Sinha A. K. , Poate J. M.
Published: January 2004

Electrical studies of W/n-GaAs Schottky diodes have shown that aging at 350 or 500 °C does not significantly change the forward I-V characteristics of the diodes. Using 4He+ backscattering analysis, it is shown that the W/GaAs interface of simulated diodes does not exhibit any evidence of interdiffusion or reaction. By contrast, considerable alloying occurs in both Au/GaAs and Pt/GaAs systems. In the former, Ga outdiffuses to the surface of Au and Au diffuses into GaAs upon aging at 250 or 350 °C; this has the effect of decreasing the barrier height φB from 0.9 to [inverted lazy s] 0.6 V and increasing the ideality parameter n from 1.0 to [inverted lazy s] 1.2. Interdiffusion in the Pt/GaAs couples, aged at 500 °C, results in the formation of a layered arrangement of type PtGa/PtAs2/GaAs. The PtAs2/n-GaAs interface is associated with a slightly higher φB ([inverted lazy s] 0.89 V) than that found for the Pt/n-GaAs interface (φB [inverted lazy s] 0.84 V).
Phase-matched far-infrared generation by optical mixing of dye laser beams
Authors: Yang K. H. , Morris J. R. , Richards P. L. , Shen Y. R.
Published: January 2004

We report the use of a dual-frequency dye laser system to generate continuously tunable far-infrared radiation over the frequency range from 20 to 190 cm−1. We have investigated both collinear (forward and backward) and noncollinear phase matching in LiNbO3 over most of this frequency range and forward collinear phase matching in ZnO, ZnS, CdS, and CdSe at selected frequencies.
Short-pulse excitation of a xenon molecular dissociation laser at 172.9 nm by relativistic electrons
Authors: Wallace Stephen C. , Hodgson R. T. , Dreyfus R. W.
Published: January 2004

Laser action at 172.9 nm has been observed in xenon and krypton-xenon mixtures following short-pulse excitation (2.5 nsec) by a relativistic electron beam. Peak powers [inverted lazy s] 80 kW cm−2 in a 5-nsec pulse were obtained. The pumping sheme used in this work is noteworthy because its high efficiency has made it possible to utilize a simple compact electron accelerator (total electron beam energy 6 J) for excitation. The present short-pulse data suggest that the rapid decrease in energy efficiency of this laser at high xenon pressures may be due to excited-state quenching by ground-state xenon atoms.
Velocity dependence of collision-broadening cross section observed in an infrared transition of NH3 gas at room temperature
Authors: Mattick A. T. , Sanchez A. , Kurnit N. A. , Javan A.
Published: January 2004

The velocity-selective characteristic of the interaction between a monochromatic radiation field and a Doppler-broadened molecular transition is utilized to obtain a narrow saturation resonance for molecules with a given velocity component along the propagation direction of the radiation field. The width of the observed resonance gives the dependence of collision broadening on molecular velocity. The effect is observed in an infrared transition in NH3 for self-broadening and foreign gas broadening by Xe.
Far-infrared step-tunable coherent radiation source: 70 μm to 2 mm
Authors: Lax B. , Aggarwal R. L. , Favrot G.
Published: January 2004

Noncollinear mixing of radiation from CO2 TEA lasers has been used to generate phase-matched far-infrared difference-frequency radiation in GaAs. The wavelength of the far-infrared radiation was tuned from [inverted lazy s] 70 μm to 2 mm in small steps by selecting the frequencies of the two CO2 lasers by means of intracavity diffraction gratings. A theoretical analysis of the two-dimensional phase matching is presented.
Homogeneity requirements for minimizing self-focusing damage by strong electromagnetic waves
Authors: Jokipii J. R. , Marburger J.
Published: January 2004

The Rytov approximation for wave propagation in random media is generalized to include the effects of self-focusing. Solutions are obtained which show how the intensity fluctuations, which are either initially present in the wave or which are induced by the random inhomogeneities in the media, grow catastrophically. These solutions may be used to obtain conditions on the homogeneity of the medium, or of the incident beam, for reduction or elimination of catastrophic self-focusing in the medium.
Integrated dE-E detector system made by ion implantation
Authors: Kostka A. , Kalbitzer S.
Published: January 2004

Boron and phosphorus ions of 8-MeV and 6-keV energy, respectively, have been implanted into silicon single crystals to form a n+-n-p+-n-n+ structure. Tests of this duodiode nuclear detector system with 5.5-MeV α particles yielded resolutions of about 100 keV (FWHM).
Electron-beam-pumped semiconductor laser using a gas plasma gun (GPG)
Authors: Verdeyen J. T. , Johnson W. L. , Cherrington B. E. , Holonyak N. , Campbell J. C. , Lee M. H. , Craford M. G.
Published: January 2004

A simple gaseous plasma electron beam source for electron-bombardment excitation of semiconductor lasers is described. The gas plasma gun (GPG) is capable of electron beam energies (> 50 keV) and current densities (adjustable with magnetic field) sufficient to produce laser operation of homogeneous semiconductor samples, as is demonstrated on GaAs1−xPx (x = 0.37, 77°K).
Operation of a cold-cathode electron-beam-controlled CO2 laser oscillator at 1–3 atm
Authors: Cason Charles , Dezenberg George J. , Huff Robert J.
Published: January 2004

A cold-cathode electron gun was used to control an 8-liter CO2 laser oscillator, operated at pressures varied from 1 to 3 atm. The output energy density scaled linearly with pressure and increased with an increase in the applied drift fields up to 5 kV cm−1 atm−1. The output energy at 2 atm was 1 kJ.
Ion acceleration in high-current diodes
Authors: Gary S. Peter , Bloomberg H. W.
Published: January 2004

High-current diode discharges produce MeV ions which move against the applied electric field. This letter proposes that this effect can be explained by ion trapping in potential energy troughs of the two-stream plasma instability, and by subsequent ion acceleration as the wave phase velocity increases.
Reflective-mode ferroelectric-photoconductor image storage and display devices
Authors: Land C. E. , Smith W. D.
Published: January 2004

A new type of image storage and display device, called the Fericon, is described in which the image is stored by means of electrically induced surface deformation in ferroelectric ceramics. The preferred method of viewing or projecting the stored image is by reflected light using Schlieren optics. The device has nonvolatile storage and the capability of selective erasure of the stored image.
Valence band density of states and core level shifts of AgGaS2 as determined by x-ray photoemission
Authors: Luciano M. J. , Vesely C. J.
Published: January 2004

The first measurements of x-ray-induced electron emission for AgGaS2, a I-III-VI2 chalcopyrite compound, are reported. The measurements include both the valence band density of states and electronic core levels. The Ag 4d levels were found to be quite narrow and located 3.4 eV below the top of the valence band partially overlapping the heavy-hole p-like bands which have a maximum at 1.1 eV. The s-like band was observed at 11.7 eV.
Anomalous structure in appearance potential spectra
Authors: Ramachandran K. N. , Cox C. D.
Published: January 2004

A number of anomalous peaks were found in the low-energy end of the appearance potential spectrum obtained from a high-purity iron foil. The structure changed considerably when the foil was contaminated from an oxide-coated filament. These peaks do not correspond to any known absorption edge of the specimen.
Deep-etched silicon diode array target
Authors: Schroder D. K. , Wickstrom R. A. , Rai-Choudhury P.
Published: January 2004

A silicon diode array target is described in which heavily p+-doped silicon epitaxial contacts are grown on pedestals, formed by selective etching of the n-type silicon substrate. It offers the advantage that the top of the p+ contacts can be raised significantly higher above the oxide than is possible with other target structures. Experimentally, such targets have shown an excellent modulation transfer function (MTF), low lag, good dark-current behavior, and compatibility with tube and photocathode fabrication techniques.
Field and time thresholds for the electrical fixation of holograms recorded in (Sr0.75Ba0.25)Nb2O6 crystals
Authors: Micheron F. , Bismuth G.
Published: January 2004

We demonstrate that the electrical fixation of holograms recorded in (Sr0.75Ba0.25)Nb2O6 involves local polarization switching; the fixing threshold is found to be nearly the average coercive field Ec = 970 V/cm, and the minimum fixing time is the polarization switching time. The diffraction efficiency enhancement of fixed holograms is attributed to the photoinduced space charge field's overcancellation by ionic displacements associated with the polarization switching.
Thin-film calorimeter for low-energy laser pulse measurements
Authors: Koren G. , Yacoby Y. , Lotem H. , Kosower M. , Greenwald G.
Published: January 2004

A laser pulse calorimeter which enables measurements of energies within the region of 20–0.02 mJ is described. The calorimeter is a temperature-sensitive resistor, composed of a thin film of black V2O5 evaporated on an 8-μ sapphire substrate of 1-cm diameter. The characteristic peak reading pulse responsivity is 1 mV/mJ, and the accuracy of the measurements at 0.1 mJ is approximately 7%. The calorimeter is sensitive primarily to the beams' energy, and its response is independent of the shape and size of the incident beam of a given energy.
Fast acousto-optical waveguide modulators
Authors: Shah Manhar L.
Published: January 2004

Acousto-optic thin-film optical waveguide modulators having the potential of operating in the GHz frequency range with a large bandwidth are described. An experimental modulator using a shear wave propagating normal to the film was operated up to 225 MHz and produced intensity-modulated light at twice that frequency. Unlike magneto-optic, electro-optic, and induced absorption-type modulators, the scheme presented here may not require special material or hybrid structure for the waveguide; therefore, it would be easy to incorporate into integrated optics.
Focusing properties of thin-film lenslike light guide for integrated optics
Authors: Suematsu Y. , Furuya K. , Kambayashi T.
Published: January 2004

A thin-film lenslike light guide was made by rf sputtering of one glass film on another glass substrate. The one-dimensional focusing properties which depend upon the propagating mode are to be demonstrated. A basic theoretical treatment is given which shows that the focusing power increases with the mode number. The focusing parameters were determined experimentally. The over-all experimental results were in good agreement with the theoretical predictions.
Aerodynamically mixed electric discharge CO2 laser
Authors: Shirahata Hiromichi , Fujisawa Akira
Published: January 2004

An aerodynamically mixed electric discharge coaxial-type CO2 laser was investigated experimentally. Homogeneous and stable discharge was attained in the transonic gas flow region, and a small-signal gain of 11.5 dB/m and a saturation parameter of 2000 ± 150 W/cm2 were obtained.
N2O pure chemical cw flame laser
Authors: Benard D. J. , Benson R. C. , Walker R. E.
Published: January 2004

We report the first observation of laser amplification and oscillation in a continuously operating flame with N2O as the optically active species. Outputs have been observed at five wavelengths in the 001–100 vibrational-rotational band of N2O when excited by the Na-catalyzed combustion of N2O with CO in a coaxial flow laser cavity. At the equivalent wavelengths in CO2 neither significant gain nor absorption was observed although CO2 is formed as a reaction product. The performance of the N2O chemically driven laser is compared to that of an electrical discharge flow laser, where N2O is mixed with vibrationally excited N2 in the same laser cavity and flow system. It was found that a large fraction of the chemical heat release is available for N2O laser pumping.
Fresnel diffraction effects in the design of high-power laser systems
Authors: Campillo A. J. , Pearson J. E. , Shapiro S. L. , Terrell N. J.
Published: January 2004

Fresnel diffraction by circular apertures for beams commonly encountered in high-power laser systems is investigated. Striking agreement is demonstrated between experimental results and theoretical calculations for beams with uniform and Gaussian intensity profiles. It is pointed out that Fresnel diffraction patterns produced by circular apertures depend only on the incident wave front and the Fresnel number corrected for curvature of the incident beam, F = a2/λL + a2/λR. This also gives an excellent experimental method for measuring divergence. Methods are discussed for minimizing the occurrence of severe intensity variations and resulting self-focusing problems in high-power laser amplifiers.
Buildup of picosecond pulse generation in passively mode-locked rhodamine dye lasers
Authors: Arthurs E. G. , Bradley D. J. , Roddie A. G.
Published: January 2004

The buildup of picosecond pulses in a passively mode-locked rhodamine 6G dye laser has been directly studied with a picosecond streak camera. It is shown how a single isolated picosecond pulse evolves from the initial intensity fluctuations.
Face-pumped high-average-power low-distortion dye laser
Authors: Peters R. L. St. , Taylor D. J.
Published: January 2004

We have applied face-pumping techniques to reduce thermal distortion and thereby improve the high-average-power capability of flashlamp-pumped dye lasers. With our zigzag configuration, no distortion could be observed at an average input power of 1 kW. At 1.8 kW input (600 J at 3 pps) we obtained over 1 W output (nearly 0.06% efficiency) from Rhodamine 6G with no beam distortion. Proportionally higher output power is expected at higher repetition rates, and higher efficiency is expected from future versions of this laser with smaller apertures than the present 9 cm2.
Effect of saturable absorption on the behavior of spontaneous emission in semiconductor lasers
Authors: Brosson P. , Patel N. , Ripper J. E.
Published: January 2004

A substantial reduction of the spontaneous emission intensity is observed at the onset of stimulated emission in some injection lasers. It is shown that this effect is caused by the saturation of optically absorbing traps present in the active region. It is suggested that saturable optical absorption is also responsible for previously unexplained similar reduction observed by Nicoll in bulk semiconductor lasers.
Ferroelasticity in isopropyl ammonium chloroplatinate and chlorostannate
Authors: Cross L. E. , Bhalla A.
Published: January 2004

Isopropyl ammonium chloroplatinate (C3H7NH3)2PtCl6 and the corresponding chlorostannate (C3H7NH3)2SnCl6 are demonstrated to be ferroelastic by observation of the stress-induced motion of (100) and (001) shear domain walls. The ferroelastic transition temperatures are at 37 and 40 °C, respectively, at room pressure and increase approximately linearly with increasing hydrostatic pressure. X-ray structure analysis and the absence of measurable second-harmonic generation (SHG) in either higher- or lower-temperature phases suggest that these crystals belong to the Aizu ferroelastic species mmmF2/m.
Linear mode conversion in an inhomogeneous iterative network
Authors: Moore B. N. , Oakes M. E.
Published: January 2004

An LC lattice with nearest- and second-neighbor inductive coupling between the capacitors is described and shown to exhibit linear wave transformation properties when the capacitor values vary iteratively down the lattice structure. Possible applications as a device for selectively delaying, transmitting, or storing pulses of slightly differing frequencies are suggested.
Similarity principles for laser-induced breakdown in gases
Authors: Yablonovitch Eli
Published: January 2004

The well-known similarity principles for dc breakdown in gases are extended to the case of laser-induced breakdown. The wealth of experimental data on kinetic processes in gases may therefore be directly applied to ac breakdown. Without solving the Boltzmann equation, the ionization rate is determined as a function of pressure, frequency, electric field, etc. This has important implications for the maximum possible light intensity in high-pressure TEA amplifiers.
Electric field enhancement of escape probability on negative-electron-affinity surfaces
Authors: Howorth J. R. , Harmer A. L. , Trawny E. W. L. , Holtom R. , Sheppard C. J. R.
Published: January 2004

Electric field enhancement of photoemission from negative-electron-affinity surfaces on silicon and GaAs has been studied. It is shown that the electric field increases the escape probability and does not change the spectral response of negative-electron-affinity surfaces. The results are explained by assuming a simple surface potential barrier together with work function lowering by the Schottky effect.
Multiple potential-well structure created by electron injection in spherical geometry
Authors: Swanson D. A. , Cherrington B. E. , Verdeyen J. T.
Published: January 2004

Electron injection into a highly permeable spherical anode under high-vacuum conditions has been observed to produce a negative well within the anode. When deuterium gas is introduced into the system, experimental observations strongly suggest that a positive potential region is formed within the negative potential well, which gives rise to a multiple potential well structure within the anode.
New class of intermediate-gain laser materials: Mixed garnets
Authors: Riseberg L. A. , Brown R. M. , Holton W. C.
Published: January 2004

A new class of intermediate-gain laser materials for rare-earth ions, based upon the principle of inhomogeneous broadening of spectral lines in mixed-compound crystals, is reported. Spectroscopic evidence for Nd in YAl0.6Ga0.4G mixed garnets is presented which shows a cross-section reduction of 3.3 compared to Nd in YAlG. Other physical properties of the mixed garnets, in particular the thermal conductivity, are not degraded; consequently, the Nd-doped mixed garnet materials may prove important for increased-energy/pulse high-average-power Q-switched laser applications.
V-I characteristics of pulsed CO2 laser discharges
Authors: Denes L. J. , Lowke J. J.
Published: January 2004

The voltage-current dependence is investigated for pulsed self-sustained uniform-glow discharges by using commerical-grade mixtures of CO2, N2, and He at near-atmospheric pressures. For a given mixture, the discharge is found to stablize at a value of E/N which is independent of discharge current density, total pressure, and electrode spacing; E is the electric field and N is the number density of the gas. We interpret these observations as evidence that the glow condition is effectively controlled by attachment to CO2 and also to H2O, a gaseous impurity. Calculations of the E/N characteristic, based on a model which includes recombination and attachment losses, are in agreement with experimental results for all mixtures studied.
Temperature dependence of intrinsic multiphonon absorption in crystals
Authors: Bendow Bernard
Published: January 2004

It is shown that in predicting the temperature dependence of multiphonon absorption one must take the temperature dependence of the phonon frequencies into account. Inclusion of the latter leads to results in improved agreement with experiment, as compared to those of Hardy and Agrawal.
Influence of a transverse electric field on laser-induced gas breakdown
Authors: Tulip J. , Seguin H.
Published: January 2004

The threshold for laser-induced breakdown has been found to be influenced by an electric field transverse to the laser focus. In air at a pressure of 20 Torr a field strength of 600 V/cm was found to completely suppress breakdown. At higher field strengths the electric field was found to induce breakdown rather than suppress it. These effects are explained as being due to charge removal and electron cascade.
Second-harmonic generation due to a guided wave structure consisting of quartz coated with a glass film
Authors: Suematsu Y. , Sasaki Y. , Shibata K.
Published: January 2004

Phase-matched second-harmonic generation (SHG) was obtained in the visible spectrum by using the nonlinear waveguide. The guide consisted of quartz as the cladding and glass film as the waveguiding section. y-cut quartz was used for the nonlinear medium. A Q-switched YAG laser was used as the pumping source. The guided modes of the pump were TE00 and TM00, and that of the second harmonic (SH) was TM02. The phase-matched thickness 2b of the glass film was 2.55 μm with an allowable tolerance of about 30 Å for an interaction length of 10 mm. The peak output power was 70 mW. The results were in agreement with theory.
Kinetic model of ultraviolet inversions in high-pressure rare-gas plasmas
Authors: George E. V. , Rhodes C. K.
Published: January 2004

It is shown theoretically that stimulated vacuum ultraviolet emission at [inverted lazy s] 1700 Å is possible in the afterglow of a suitably prepared ionized xenon plasma. Our model involves the dissociative recombination of Xe2+ as a key step in the kinetic scheme leading to the production of excited Xe2* dimers. It is found that the maximum value of the dimer population occurs for a plasma that is initially [inverted lazy s] 1% ionized with cold gas atoms. Both plasma heating and higher levels of ionization inhibit dimer formation. Excited state-excited state loss channels are also seen to play an important role in limiting the peak dimer density. Comparison of this theory with recent experimental results involving relativistic electron-beam-excited plasmas is good.
Determination of deep-level energy and density profiles in inhomogeneous semiconductors
Authors: Goto G. , Yanagisawa S. , Wada O. , Takanashi H.
Published: January 2004

A method is proposed for the determination of deep impurity levels and density profiles from C–V measurements and is demonstrated on GaAs Schottky barrier diodes. The technique involves measurements of the time dependence of the bias voltage instead of the barrier capacitance. The spatial distribution of a deep level is observed to exhibit a peak at the boundary between an epitaxial layer and the semi-insulating substrate. This deep center is located 0.8 eV below the conduction band.
Direct display of electron back tunneling in MNOS memory capacitors
Authors: Yun B. H.
Published: January 2004

Direct observation of back tunneling in MNOS requires the direct and continuous display of the charge previously injected into the insulator. A new experimental technique having such a feature is presented. It is characterized by its simultaneous and direct measurements of both the change in charge in the insulator and the corresponding change in the device's flat-band voltage. Charge loss via back tunneling in devices of different tunnel-oxide thicknesses is presented.
Optical technique for producing 0.1-μ periodic surface structures
Authors: Shank C. V. , Schmidt R. V.
Published: January 2004

Surface corrugations with a period of 1108 Å and a depth of [inverted lazy s] 500 Å have been fabricated in glass. These corrugations were first produced in a photoresist film on glass by the optical interference of two 3250-Å laser beams. The corrugation was transferred to the glass by ion beam etching.
Cryogenically cooled CO–He TEA laser
Authors: Champagne L.
Published: January 2004

The performance of a transversely excited atmospheric-pressure TEA CO laser under cryogenic conditions is discussed. With the addition of large amounts of helium as a buffer gas, an output energy of 35 mJ was attained. This energy output represents a considerable increase over that previously reported for a similar system.
Zone plates and field ion microscopy
Authors: Southworth H. N. , Leifer I. , Walls J. M.
Published: January 2004

Comparisons previously drawn between the image of a field ion plane and a Fresnel zone plate are reexamined. It is shown that such images are more generally described as aberrated binary zone plates, and that the relationship between their focal lengths and the imaging parameters is more complex than previously believed.
A search for laser-amplified cosmic ray tracks
Authors: Morrison R. W. , Swail C. , Dubal L.
Published: January 2004

An attempt was made to detect cosmic ray tracks using a pulsed TEA CO2 laser. Within 4 μsec of the passage of a cosmic ray through a pressurized cell, a laser beam of 4 J/cm2 energy density at 10.6 μ was fired. Pure argon and argon-krypton mixtures were studied at pressures up to 12 atm. Spots of light were seen but no tracks. Laser damage to the cell windows was the limiting factor. An alternative detector using an initial high-voltage pulse followed by a laser pulse is proposed.
Transmission of stationary nonlinear optical pulses in dispersive dielectric fibers. II. Normal dispersion
Authors: Hasegawa Akira , Tappert Frederick
Published: January 2004

Theoretical calculations supported by numerical simulations show that utilization of the nonlinear dependence of the index of refraction on intensity makes possible the transmission of picosecond optical pulses without distortion in dielectric fiber waveguides with group velocity dispersion. In the case of normal dispersion (∂2ω/∂k2 < 0) discussed here [the case of anomalous dispersion (∂2ω/∂k2 > 0) was discussed in an earlier letter], the stationary pulse is a ``dark'' pulse or envelope shock. Numerical simulations show that such pulses are stable under the influence of small perturbations, white noise, or absorption. Important considerations relating to the practical applications of both ``bright'' and ``dark'' pulses are also discussed.
Efficient infrared-to-visible conversion in BaY2F8 : Yb,Er crystal by confinement of excitation energy
Authors: Mita Yoh , Nagasawa Eiji , Shiroki Ken-ichi , Ohno Yasuo , Matsubara Tetsujin
Published: January 2004

Efficient up-conversion of near-infrared energy was realized by confinement of infrared energy in an optical cavity containing a BaY2F8 : Yb,Er single crystal. The lifetime of the ytterbium excited state showed a marked increase and, in a typical instance, became as long as 3.6 msec. Combined with 8% efficiency GaAs : Si diode, an over-all conversion efficiency of nearly 0.04% was obtained for a 50-mA diode-exciting current.
Fast electro-optic waveguide deflector modulator
Authors: Hammer J. M. , Channin D. J. , Duffy M. T.
Published: January 2004

We describe a high-speed deflector-modulator based on an electro-optically induced thick phase grating in optical waveguides of single-crystal epitaxial ZnO film on Al2O3 substrates. 40% of the beam is diffracted into first order with response times of 3 nsec. The extinction ratio in the deflected beam is greater than 95%. We predict 80% diffraction, response times of < 1 nsec, and power requirements of approximately 1 mW/MHz for an optimized geometry.