bluuebunny/crossref_metadata_2025 huggingface dataset:
SMALL-AREA HIGH-CURRENT-DENSITY GaAs ELECTROLUMINESCENT DIODES AND A METHOD OF OPERATION FOR IMPROVED DEGRADATION CHARACTERISTICS
Authors: Burrus C. A. , Dawson R. W.
Published: January 2004

Diffused-junction GaAs electroluminescent diodes of small area and high radiance have been fabricated. It has been observed (1) that the degradation of these high-current-density cw diodes can be reduced greatly by superimposing a periodic reverse-bias pulse on the normal dc forward bias, and (2) that a previously degraded diode is restored to its initial light output by the influence of the built-in junction fields, or an applied dc reverse bias, at an elevated temperature.
MICROWAVE HOLOGRAPHY BY MEANS OF OPTICAL INTERFERENCE HOLOGRAPHY
Authors: Iizuka Keigo
Published: January 2004

A microwave hologram was made by mapping the pattern of the thermal expansion of a resistive surface illuminated by a microwave field. The distribution of the displacement of the surface was mapped making use of optical interference holography techniques. The microwave hologram thus recorded was then photographically reduced in size. This hologram was next illuminated by a laser beam to yield the optical reconstruction of the microwave image.
SPECTROSCOPIC DETECTION OF SO2 AND CO2 MOLECULES IN POLLUTED ATMOSPHERE BY LASER-RAMAN RADAR TECHNIQUE
Authors: Kobayasi Takao , Inaba Humio
Published: January 2004

Raman backscatter of a Q-switched ruby laser beam from SO2 and CO2 molecules were selectively detected in the polluted atmosphere by means of a laser-Raman radar system. The spectrum of these Raman components was compared quantitatively with that for the ordinary and sulphur dioxide atmospheres, along with the estimation of relative concentrations of these molecules.
INTERACTION OF A MONOENERGETIC NITROGEN MOLECULAR BEAM WITH A SOLID NITROGEN SURFACE
Authors: Arnold Fred , Dawbarn Ronald , Busby M. R.
Published: January 2004

Capture coefficients and reflected flux distributions have been measured for nitrogen molecular beams impinging on solid nitrogen surfaces. For a beam intensity of 1.53×1016 molecules/sec cm2 and incident energies from 0.44 to 0.76 eV, the capture coefficient was found to decrease with increasing angle of incidence as measured from the surface normal. The angle of maximum reflected intensity was approximately 75° from the surface normal and independent of incident angle and energy. Transient effects were observed for surfaces without a previous cryodeposit.
ENHANCED LIGHT EMISSION FROM A POSITIVE COLUMN BY MEANS OF CURRENT MODULATION
Authors: Polman J. , van der Werf J. E.
Published: January 2004

It is shown that the light emission of the positive column of a low-pressure are discharge and its efficiency can be enhanced, up to a factor of 6, by pulsing or modulating the discharge current with a repetition time (or modulation period) between the diffusion time τD and the energy relaxation time τE of the electrons (τD ≫ τE). Calculations indicate this phenomenon to be due to an increase of the number of electrons in the high-energy tail of the energy distribution function, as compared with that of a steady-state discharge.
INFLUENCE OF SAMPLE PREPARATION AND SPATIAL DEPENDENCE OF THE MICROWAVE EMISSION FROM n-InSb
Authors: Heinrich Helmut , Kokoschinegg Peter
Published: January 2004

The microwave emission from n-InSb was measured at 1.5 GHz in order to obtain information about the strong anisotropy observed when B is rotated in the transverse plane. It was found that the preparation technique has a great influence on the emission. Cylindrical samples with etched surfaces behave isotropically; purposely introduced surface damage by sandblasting a narrow strip parallel to the sample axis reduced the emission for the case that B is normal to the blasted area. Generation of the emission occurs in the whole sample.
HYSTERESIS IN THE dc SWITCHING CHARACTERISTICS OF JOSEPHSON JUNCTIONS
Authors: Scott W. C.
Published: January 2004

The driven-pendulum model for superconducting tunnel junctions, if solved using the true quasiparticle tunneling curve as the damping term, yields solutions for the observed hysteresis in the dc-IV characteristic which are in very good agreement with experimental data.
COBALT-SAMARIUM PERMANENT MAGNETS PREPARED BY LIQUID PHASE SINTERING
Authors: Benz M. G. , Martin D. L.
Published: January 2004

The preparation and measurement of magnetic properties of cobalt-samarium permanent magnets prepared by liquid-phase sintering are discussed. Energy products in excess of 15×106 G Oe were observed. Long time exposure to air at 150°C did not degrade the samples.
POSITION OF THE ENERGY LEVELS OF TRIVALENT RARE-EARTH ACTIVATOR IONS RELATIVE TO THE ELECTRONIC ENERGY BANDS OF LANTHANUM OXYSULFIDE: A NEW PICTURE OF EXCITATION AND RELAXATION
Authors: Wickersheim K. A. , Buchanan R. A.
Published: January 2004

It is shown that most rare-earth activators in lanthanum oxysulfide show anomalous thermal quenching effects similar to those previously reported for Eu3+. An analysis of the activation energies derivable from regions of unusually rapid thermal quenching indicates, for all ions observed to date, that the quenching processes represent strong interaction between the 4f electron levels of the rare-earth ions and the conduction band of the host. It thus becomes possible to locate experimentally the positions of the rare-earth levels relative to the host-bands. This in turn allows a general explanation of the excitation and relaxation characteristics of the rare-earth oxysulfide phosphor system.
HIGH EFFICIENCY CO LASER AT ROOM TEMPERATURE
Authors: Bhaumik M. L.
Published: January 2004

A water-cooled CO–He–N2–O2 laser has been operated at 20 °C with a cw output of 10 W corresponding to an efficiency of 5.5%. With addition of xenon, the same mixture gave an output of 25 W with an efficiency of 12%. The efficiency increased to 17% with addition of both xenon and mercury.
PULSED BEHAVIOR AND INVERSION MECHANISM IN THE CARBON MONOXIDE LASER
Authors: Graham W. J. , Kershenstein J. , Jensen J. T. , Kershenstein K.
Published: January 2004

Time delay of lasing transitions in carbon monoxide was investigated at 77 °K under pulsed electrical excitation. Inversion is attributed to anharmonic decoupling which makes v-v relaxation ineffective for levels above a value ve=1 + kT/hc2ωexe. Initial lasing occurs near ve with subsequent transitions resulting from cascading inversions. Measured delays ranged from 15 to 240 μ sec with undercoupled output up to 1.2 W.
MAGNETIC PROPERTIES OF PrCo5–PrCu5 ALLOYS
Authors: Samarin B. A.
Published: January 2004

The magnetic properties of some ternary alloys PrCoxCu(5−x) in the range 4.5 ≥ x ≥ 2 have been investigated. The remanence and coercive force of these alloys both directly after annealing at 1020 °C for 5 h and after tempering for 4 h at 390 °C are very low in comparison with similar alloys in the SmCo5–SmCu5 and CeCo5–CeCu5 systems.
OPTICAL ABSOPTION OF GaN
Authors: Pankove J. I. , Maruska H. P. , Berkeyheiser J. E.
Published: January 2004

The absorption edge of GaN rises exponentially to a value of about 4 × 105 cm−1 at 3.5 eV (at 300 °K) suggesting direct optical transitions and a high joint density of states. Another absorption, which sets in beyond 1.3μ, increases with the 7th to 8th power of the wavelength.
SURFACE EFFECTS AND LOW FREQUENCY LOSSES IN HARD SUPERCONDUCTORS
Authors: Sekula S. T. , Barrett J. H.
Published: January 2004

The power dissipation in a hard superconductor based on a model consisting of a bulk flux pinning region and a surface sheath is calculated. The results indicate that the losses are somewhat greater than previously calculated.
FIELD-INDUCED SURFACE REARRANGEMENT IN A FIELD-ION MICROSCOPE
Authors: van Oostrom A.
Published: January 2004

Adsorption of nitrogen on tungsten at 78°K was studied in a field-ion microscope equipped with a channel-plate image intensifier. Field-induced surface rearrangement was observed using argon as the image gas. The changes in the field-ion pattern are attributed to surface diffusion of tungsten-nitrogen complexes.
CRITERION FOR SELECTION OF cw LASER HOST MATERIALS TO INCREASE AVAILABLE POWER IN THE FUNDAMENTAL MODE
Authors: Massey G. A.
Published: January 2004

Present Nd:YAG lasers are subject to thermal birefringence and bifocusing which contribute to large reductions in polarized and/or fundamental mode output when the laser is pumped at high average powers. By replacing the cubic YAG host with a suitably oriented birefringent host material, this limitation can be overcome. We suggest this consideration as an important criterion for the selection of crystalline laser host materials, since an order-of-magnitude increase in the brightness of cw lasers may result. One new material which has the required properties is YAlO3.
THERMAL BLOOMING OF A 10.6-μ LASER BEAM IN CO2
Authors: Kenemuth J. R. , Hogge C. B. , Avizonis P. V.
Published: January 2004

Thermal blooming of a 10.6-μ laser beam in a CO2 absorption cell has been investigated with high time and position resolution. Good agreement has been found between experimental results and calculations made using an eikonal treatment.
PIEZOELECTRIC LEAKY SURFACE WAVE IN LiNbO3
Authors: Takayanagi A. , Yamanouchi K. , Shibayama K.
Published: January 2004

Velocities and attenuations of piezoelectric leaky surface waves in LiNbO3 are computed. As the result, we have found that the effective electromechanical coupling coefficient of the leaky surface wave propagating along the x axis of the 64° rotated y-cut plane is very large, K2=0.113; and by radiating the energy into the solid this wave attenuation is 0.36 dB/wave-length for the free surface and goes to zero for the metalized surface.
MEASUREMENTS OF PHOTOELECTRIC COUNTING DISTRIBUTIONS FOR A LASER NEAR THRESHOLD
Authors: Meltzer D. , Davis W. , Mandel L.
Published: January 2004

Photoelectric counting probabilities have been measured for a laser operating near the threshold of oscillation, for various values of the pump parameter and various counting time intervals. The results are compared with values derived from the recent calculations of Lax and Zwanziger (based on the rotating-wave van der Pol oscillator model of a laser) and show very good agreement.
SOME INITIAL OBSERVATIONS OF TiNi IN THE FIELD-ION MICROSCOPE
Authors: Melmed A. J. , Carroll J. J.
Published: January 2004

It is demonstrated that TiNi specimens can be successfully imaged with the field-ion microscope using liquid-nitrogen cooling, with hydrogen as the imaging gas. The material examined is shown to be structurally inhomogeneous, with relatively well-ordered regions in a less-ordered matrix. It is also shown that alternate atomic planes are different within some ordered regions.
CONDUCTANCE MODULATION IN A COUPLED SEMICONDUCTOR-PIEZOELECTRIC SYSTEM
Authors: Fischler C. , Zucker J. , Conwell E. M.
Published: January 2004

We have observed reductions of as much as 75% in the current in thin silicon plates measured transverse to the propagation direction of elastic waves in a contiguous plate of PZT. Evidence is given that this is due to trapping of free carriers at the surfaces of the silicon plate. This effect can reduce the gain of surface wave amplifiers at high power.
DIRECT OBSERVATION OF SINGLE-DOMAIN SrTiO3
Authors: Chang T. S. , Holzrichter J. F. , Imbusch G. F. , Schawlow A. L.
Published: January 2004

A single-domain SrTiO3 crystal is obtained by stressing along the [110] direction at 2°K and is observed optically for the first time. Domain structure under [001] stress is also examined. The importance of understanding the domain structure is discussed.
EXTENSION OF LASER HARMONIC-FREQUENCY MIXING INTO THE 5-μ REGIONS
Authors: Sokoloff D. R. , Sanchez A. , Osgood R. M. , Javan A.
Published: January 2004

Using laser harmonic-frequency mixing in a metal-metal point-contact diode, absolute frequency measurement is extended into the 5-μ region. The frequency of the P(13) transition of the 7–6 vibrational band in CO is measured to be 58 024 341 ± 55 MHz.
LONGITUDINAL MODES IN A HIGH-GAIN LASER
Authors: Casperson Lee , Yariv Amnon
Published: January 2004

In lasers employing high-gain narrow-linewidth transitions the theory predicts major departures of the mode-splitting frequencies from their low-gain values as well as a new type of mode splitting. The first of these effects consisting of a reduction by a factor of 2.5 of the mode splitting in a xenon 3.51-μ laser is observed experimentally.
ORIENTATION EFFECTS IN THE RESISTIVITY OF Ta FILMS SPUTTERED IN OXYGEN
Authors: Westwood W. D.
Published: January 2004

Tantalum films deposited by sputtering in an O–Ar mixture consist of the tetragonal β phase. As the flow rate of the mixture into the sputtering system increases, the preferred-growth orientation changes from (200) to (202) and the resistivity ρ increases from 265 to 1100μΩ-cm. The value of Δρ/ΔT decreases monotonically with increasing (202) orientation, suggesting that the electrical properties are due to the β-Ta phase rather than to intergrain tunneling.
ACOUSTIC SURFACE WAVES ON METALLIZED AND UNMETALLIZED Bi12GeO20
Authors: Kraut E. A. , Tittmann B. R. , Graham L. J. , Lim T. C.
Published: January 2004

New values for the elastic and piezoelectric constants of Bi12GeO20 and for their temperature derivatives are reported. With these new constants, the predicted value of Δv/v for acoustic surface waves is significantly increased. This prediction has been verified by measurements of the acoustic surface-wave velocity on the metallized and unmetallized (001) surface of Bi12GeO20 and by comparing the observed values with theory. On the (001) plane, the maximum Δv/v occurs in the 〈110〉 direction. The predicted Δv/v is 66×10−4 and the experimentally observed value is (77±15)×10−4.
METHOD TO SEPARATE THE DESIRED RAYLEIGH WAVES FROM SPURIOUS ACOUSTIC MODES
Authors: Cho Frederick Y. , Peterson Kenneth M. , Hunsinger Bill J.
Published: January 2004

A surface-wave path containing a fluid interface region which couples Rayleigh waves from one crystal to another is an effective filter for passing Rayleigh waves while rejecting other in-band spurious modes. Results of tests made on a wide-band (50% bandwidth) variable delay line (5–15 μsec) incorporating this fluid interface filter are shown.
OPERATING CHARACTERISTICS OF A TRANSVERSE-FLOW DF–CO2 PURELY CHEMICAL LASER
Authors: Cool Terrill A. , Shirley John A. , Stephens Ronald R.
Published: January 2004

Experimental results are presented giving the operating characteristics of a newly developed DF–CO2 purely chemical laser. The present oscillator is capable of a maximum cw output power of 162 W at 10.6 μ with no external energy source used to initiate or sustain laser excitation. An optical axis has been employed aligned transverse to the flow direction with a view toward achieving operation which can be directly scaled to high output powers. Measurements of saturation parameter, unsaturated gain coefficients, and vibration-rotation state populations for P- and R-branch CO2 (00°1) → CO2 (10°0) transitions, power output, operating temperatures and pressures, and chemical efficiency are presented.
ELECTROMIGRATION-INDUCED FAILURES IN ALUMINUM FILM CONDUCTORS
Authors: Blair J. C. , Ghate P. B. , Haywood C. T.
Published: January 2004

Electromigration-induced failures in aluminum film conductors have been studied. It is shown that large-grain films have a longer mean time to failure (MTF) than the small-grain films. A further increase in MTF is observed for films with a glass overcoating. This increase can be understood in terms of the observed grain growth which results from the glass overcoating process. Histograms showing the location of failures are interpreted to indicate that effects due to both temperature gradients and microstructural inhomogeneities are important.
EFFICIENT CONVERSION OF A RUBY LASER TO 0.347 μ IN LOW LOSS LITHIUM IODATE
Authors: Nath G. , Mehmanesch H. , Gsänger M.
Published: January 2004

The second harmonic of a ruby laser has been produced in LiIO3 crystals, showing hardly any optical absorption at 0.347 μ. Using these new crystals external to the laser cavity conversion efficiencies up to 40% have been achieved using an incident unfocussed beam of about 130 MW/cm2. After 5–10 shots, a first small internal damage spot appeared inside the LiIO3 crystal. For a beam diameter of 3 mm several hundred shots with a conversion efficiency of 40% were possible.
CHARACTERISTICS OF FORWARD-BIASED LONG SILICON P+PN+ STRUCTURES AT LOW TEMPERATURE
Authors: Brousseau M. , Barrau J. , Brabant J. C.
Published: January 2004

Conduction processes in long Si P+PN+ structures at low temperature have been investigated. Using an impulse method which separates the potential drop across the P region, we have obtained a very good agreement with the Lampert-Ashley model for high-level double injection.
REDUCTION IN SHG EFFICIENCY IN TELLURIUM BY PHOTOINDUCED CARRIERS
Authors: Gandrud W. B. , Abrams R. L.
Published: January 2004

Absorption of 10.6-μ pump radiation by photoinduced carriers has been found to seriously degrade the performance of Te as a frequency doubler for the CO2 laser. Simultaneous absorption of 5.3- and 10.6-μ photons is shown to be the most likely mechanism for carrier production. The effect limits the peak SHG efficiency to 15% and the average efficiency to 5% under the conditions of this experiment. The effect may also degrade the performance of proposed parametric oscillators using Te as the nonlinear element.
REFLECTION AND TRANSMISSION SECONDARY EMISSION FROM SILICON
Authors: Martinelli Ramon U.
Published: January 2004

Reflection and transmission secondary emission ratios have been measured for a thin Si sample with one surface activated to a state of negative electron affinity. Reflection-mode gains of 950 were observed at 20-keV primary energy. The highest transmission secondary emission ratio was 725 at 20-keV primary energy. The high secondary emission gains result from the effective negative electron affinity at the surface of the sample together with a long escape depth for internal secondaries.
TWO-PHONON SCATTERING PROCESSES IN THE ENERGY RELAXATION TIME OF HOT ELECTRONS IN InSb
Authors: Martin J. P. , Mead J. B.
Published: January 2004

Measurements of electrical conductivity as a function of electric field were used to obtain electron-energy relaxation times τε in n-InSb with 1014 carriers/cm3 in the temperature range from 5 to 34 K. Comparison of results with theoretical predictions demonstrated that the usual mechanisms involving single-phonon interactions cannot adequately describe τε, especially in the range between 12 and 34 K. The data are highly suggestive of a two-phonon process involving the emission of a 0.0223-eV transverse optical phonon and absorption of a 0.0054-eV transverse acoustic phonon.
OUTDIFFUSION THROUGH SILICON OXIDE AND SILICON NITRIDE LAYERS ON GALLIUM ARSENIDE
Authors: Gyulai J. , Mayer J. W. , Mitchell I. V. , Rodriguez V.
Published: January 2004

Backscattering of MeV 4He ions has been used to analyze the Ga and As content in SiO2 and Si3N4 dielectric layers deposited on single-crystal GaAs substrates. Changes in impurity concentrations and distributions are seen after isothermal annealing at both 750 and 800°C. Evidence for Ga outdiffusion is clear.
ANALYSIS OF A DYE LASER TUNED BY ACOUSTO-OPTIC FILTER
Authors: Streifer William , Whinnery John R.
Published: January 2004

A model of a dye laser electronically tuned by an acousto-optic filter is analyzed. Chirping modes are superposed to yield a steady-state periodic solution which predicts a shift of the spectrum to the high end of the filter band and appreciable spectral narrowing. For the example considered, the theory predicts a narrowing factor of 100.
EFFECTS OF ELECTRON IRRADIATION ON CONDUCTIVITY IN CdS
Authors: Yoshida Toshio , Kitagawa Michiharu , Fujino Takahiro
Published: January 2004

An investigation has been made on variations in radiation-induced conductivity of two different types of CdS single crystals near liquid-nitrogen temperature during 5-MeV electron irradiation. The conductivity of a high-conductivity crystal is decreased and that of a low-conductivity crystal is increased with irradiation. Both conductivities come nearer to each other and seem to approach a limiting value as irradiation is continued. Two possible interpretations for the experimental result are also presented.
MODE-LOCKED LASER PULSE SHAPES
Authors: Smith Archibald W. , Landon Alfred J.
Published: January 2004

The pulse shape of a mode-locked continuously pumped Nd:YAG laser has been studied using an optical correlation technique. The shape is found to be Gaussian under stable conditions with the phase-modulator frequency tuned to the cavity-mode difference frequency. This result is consistent with the theory of mode locking in lasers with homogeneous broadening.
OPTICAL COUPLING OF ADJACENT STRIPE-GEOMETRY JUNCTION LASERS
Authors: Ripper José E. , Paoli Thomas L.
Published: January 2004

The observation of coupling and consequent coherent operation of two adjacent parallel stripe-geometry GaAs lasers in a monolithic structure is reported. Coupling is obtained when the distance between the lasers is small enough to allow the optical field of one laser to penetrate into the active region of the other.
MODE LOCKING OF A TRANSVERSELY EXCITED ATMOSPHERIC PRESSURE CO2 LASER
Authors: Wood O. R. , Abrams R. L. , Bridges T. J.
Published: January 2004

Mode locking of a transversely excited atmospheric-pressure CO2 laser has been achieved through the use of a germanium acousto-optic modulator. Subnanosecond pulse widths and peak powers in excess of 1 MW have been obtained.
MODE LOCKING OF THE CO2 LASER BY INTRACAVITY PHASE MODULATION
Authors: Mann M. M. , Eguchi R. G. , Lacina W. B. , Bhaumik M. L. , Steier W. H.
Published: January 2004

Stable mode locking of a CO2 laser has been obtained with the use of a resonated internal electro-optic phase modulator driven at frequencies near the axial-mode interval. Pulses of 25-nsec duration and 147-nsec period were observed. Pulse trains at twice the fundamental mode frequency were also obtained. Stable locking was achieved with an rf input power to the modulator of less than 1 mW. Locking could be induced when the modulation frequency was within ± 130 kHz of the fundamental axial-mode frequency.
cw LASER ACTION ON 24 VISIBLE WAVELENGTHS IN Se II
Authors: Silfvast W. T. , Klein M. B.
Published: January 2004

cw laser action has been observed at 24 wavelengths in the visible spectrum of Se II in a He–Se discharge. The wavelengths range from 4604 to 6535 Å. A power output of 30 mW was measured on six lines oscillating simultaneously. We obtained as many as 13 wavelengths lasing at the same time in a cavity with broad-band high-reflectivity mirrors.
GaAs: Si LED Pumped Yb-Doped YAG Laser
Authors: Reinberg A. R. , Riseberg L. A. , Brown R. M. , Wacker R. W. , Holton W. C.
Published: January 2004

A GaAs: Si light-emitting-diode (LED) pumped 1.03-μm laser employing a YAG: Yb laser rod has been constructed with the rod and LED's cooled at ∼80 K. Pulsed operation with a peak laser power of 0.7 W is observed.
Large Diameter rf Plasma for Pre-Ionization in Confinement Devices
Authors: De Dionigi R. , Fontanesi M. , Sindoni E. , Lisitano G.
Published: January 2004

A large diameter rf quiescent plasma has been created using a helical ``L'' coil fed radially with 12-cm wavelength cw microwave power. The radial profiles of electron temperature and ion saturation current show that the plasma is uniform in a 15-cm-diam region. The plasma is produced in electron-cyclotron-resonance (ECR) conditions, but it can be maintained by increasing the magnetic field up to a value four times larger than the resonant one. The plasma existence regions vs neutral gas pressure and magnetic field are studied. The performances of this plasma seem to be important in facing pre-ionization problems in confinement devices.
cw CO Laser from the CS2–O2 Flame
Authors: Pilloff H. S. , Searles S. K. , Djeu N.
Published: January 2004

Stimulated emission has been obtained from CO in a free-burning low-pressure CS2–O2 flame. cw laser oscillation was observed at 5.216-μ v(8–7)P(11), 5.297-μ v(9–8)P(12), and 5.421-μ v(11–10)P(10) with total power output on the order of 1 mW.
Relative Pressure Dependence of Chromel/Alumel and Platinum/Platinum− 10% Rhodium Thermocouples
Authors: Lazarus D. , Jeffery R.N. , Weiss J.D.
Published: January 2004

Measurement made under hydrostatic conditions to 7 kbar of the relative thermal emf's of chromel/alumel and platinum/platinum−10% rhodium thermocouples indicates a pressure correction for platinum couples of 0.57 ± 0.03°C/kbar from about 600 to 1000°C. Chromel/alumel couples are found to be pressure dependent above about 720°C and to degrade rapidly at temperatures above 800°C. Systematic differences of unknown origin are found between pressure corrections measured with increasing and decreasing pressure.
Modulation of Intervalence Band Transitions Due to Acoustoelectric Domains
Authors: Müller K.-H. , Nimtz G.
Published: January 2004

It is shown that intervalence band transitions are modulated by acoustoelectric domains. The investigations were carried out in tellurium which has an intervalence band transition at a wavelength of 11 μm. At the same wavelength a modulation of the free-carrier absorption by acoustoelectric domains was observed as well.
Layering in Sputtered Tantalum Films
Authors: Waterhouse Neil
Published: January 2004

It has been reported in the literature that the electrical properties of some sputtered tantalum films vary with depth in the film and that this might be due to the formation of ``layers'' during deposition. The characteristics of a simple two-layer model have, therefore, been examined using existing electrical data to determine the functional dependence of the layer resistivity on temperature. The predictions of this model agree quite well with experimental data for a sample exhibiting ``peaked'' resistivity-vs-temperature characteristics. Layer thicknesses used in the prediction are compatible with a previously proposed layering mechanism. Attempts to predict the experimental data using a simplified dual conduction mechanism were unsuccessful when equation constants close to physically measured values were used. Possible reasons for this disagreement are discussed.
The Use of Relativistic Energies to Overcome Energy-Resolution Difficulties in the Schwarz-Hora Experiment
Authors: Favro L. D. , Fradkin D. M. , Kuo P. K. , Rolnick William B.
Published: January 2004

The relativistic expression for the spatial damping of the Schwarz-Hora radiation is given and is compared with the latest data of Schwarz. The agreement is good and indicates that the energy resolution of the electron beam of his apparatus can be as small as 0.0055 eV. It is suggested that experiments be performed using higher kinetic energy for the electron beam where the need for small energy resolution is obviated.
High-Resolution-Laser Atmospheric-Transmission-Measurement Method
Authors: White Kenneth O. , Schleusener Stuart A. , Holt E. Howard , Calfee Robert F.
Published: January 2004

A new method of measuring the wavelength dependence of the absorption losses in atmospheric gases of solid-state laser radiation is described. The method depends upon the use of a wavelength selecting gate to identify laser spikes within a narrow wavelength range and the use of such spikes for the compilation of transmission data. Experimental results of erbiumlaser propagation losses in CO2 with a spectral resolution of 0.015 nm are compared with a theoretical calculation.
Heterojunction Photocathode Concepts
Authors: Milnes A. G. , Feucht D. L.
Published: January 2004

A three-layer voltage-biased heterojunction structure pGe/vZnSe/p+GaAs(Cs) should allow emission from the GaAs of electrons originally photoinduced in the Ge conduction band. Conceptually this is a possible approach to the development of a high-yield photocathode with low (0.7 eV) threshold energy.
Proposed Third-Harmonic Generation in Phase-Matched Metal Vapors
Authors: Harris S. E. , Miles R. B.
Published: January 2004

This letter considers the use of alkali metal vapors, phase matched with inert buffer gases for generation of third-harmonic radiation. For example, calculations show that 1.8 MW will be required for 50% conversion of 1.06-μ radiation to 0.35-μ radiation using a 1:412 part mixture of rubidium and xenon. Generation to frequencies above the ionization potential of the metal vapors is considered.
Susceptibility Echos in Linear Molecular Gases
Authors: Lin C. H. , Heritage J. P. , Gustafson T. K.
Published: January 2004

The response of a gas composed of linear molecules to a short optical pulse is considered. The evolution of susceptibility echos occurring at intervals of 1/4B, where B is the rotational constant of the molecule, is predicted.
Gas-Breakdown Dependence on Beam Size and Pulse Duration with 10.6-μ Wavelength Radiation
Authors: Smith David C.
Published: January 2004

Gas-breakdown threshold measurements with 10.6-μ wavelength radiation have been made in air, argon, and helium. The threshold was determined with 50- and 200-nsec-duration pulses and was found to depend on the peak intensity of the pulse, showing that the breakdown process is a balance between the rate of energy absorption and some rate of energy loss. The threshold also decreased as the focal spot size was increased from 10−2 to 10−1 cm, showing that the loss process is reduced for larger beam sizes. The threshold varied inversely with gas pressure from 0.1 to 4 atm, which is evidence that the loss mechanism is not electron diffusion but must be some other process which exhibits a beam-size dependence and is apparently weakly dependent on gas pressure.
Time-Resolved Spectroscopy of a Flash-Initiated H2–F2 Laser
Authors: Suchard S. N. , Gross R. W. F. , Whittier J. S.
Published: January 2004

The time-dependent output spectrum of a helium-diluted H2–F2 chain-reaction chemical laser has been observed. Reaction of a 50-Torr mixture with mole ratio H2 : F2 : He = 1 : 1 : 60 was initiated by flash photolysis of the F2. Strong lasing was found from P-branch vibration-rotation transitions of the v = 1 → 0, 2 → 1, 3 → 2, and 4 → 3 bands of HF. Within some bands, the time sequence of transitions suggests non-Boltzmann distributions of rotational states. No lasing from vibrational levels higher than 4 could be detected.
Temporal and Spectral Development of Mode Locking in a Ring-Cavity Nd:Glass Laser
Authors: Eckardt R. C. , Lee C. H. , Bradford J. N.
Published: January 2004

Temporal and spectral development of mode locking was investigated in a ring-cavity Nd : glass laser. It was found that whenever a mode-locked pulse formed in the ring cavity a satellite pulse would develop traveling in the opposite direction. The varying delay of the satellite pulse permitted time-resolved spectroscopy of the early stages of mode-locked oscillation. It was found that the spectral distribution broadens from 3 to 80 Å because of selfphase modulation inside the laser cavity.
The Current Dependence of the Intensity of Spontaneous Emission of GaAs Injection Lasers to Full Operating Power
Authors: Sommers H. S.
Published: January 2004

The current dependence of the intensity of the spontaneous emission from GaAs injection lasers operated at 300 °K to five times threshold is reported. The long-wavelength emission saturates before threshold, while the spontaneous intensity for wavelengths shorter than the lasing emission grows smoothly with no indication of the transit of threshold. At five times threshold the intensity is 2.4 times the threshold value and still growing. Similar behavior was observed with double-heterojunction lasers exhibiting five stripes parallel to the junction in the near field, and with single-heterojunction lasers with a single stripe. It is argued that the behavior of the spontaneous emission is in fundamental disagreement with the linear theory of lasing and that its explanation will require introduction into the rate equations of a strong nonlinearity which controls the lasing region.
Nonlinear Oscillations in n-InSb
Authors: Musha Toshimitsu , Teramachi Yasuaki , Agu Masahiro
Published: January 2004

Comb-shaped oscillations in a frequency domain were observed as a result of nonlinear interactions between helical instabilities and low-frequency oscillations. The comb-shaped oscillations were mode locked when the external signal was applied at one of the comb-teeth frequencies but quenched when the external signal was off the teeth.
Long-Wavelength Photoemission from InAs1−xPx
Authors: Sonnenberg H.
Published: January 2004

Efficient photoemission from InAs1−xPx (Cs–O) with a band-gap-limited threshold at 1.4 μ was observed. Indirect measurements of the composition and thickness of the Cs–O low-work-function surface suggest that the surface consists of about one monolayer of Cs, followed by approximately one monolayer of cesium oxide. These data make an interpretation of the low-work-function properties of Cs–O in terms of the heterojunction model (based on the bulk properties of Cs2O) questionable.
Concentration and Guidance of Intense Relativistic Electron Beams
Authors: Morrow David L. , Phillips J. Daniel , Stringfield Ray M. , Doggett Wesley O. , Bennett Willard H.
Published: January 2004

None of the field-emitting cathodes using sharp points or edges presently being used in producing pulsed intense relativistic beams has any particular advantage over a smooth well-rounded form having the same over-all dimensions when the interelectrode distance is small enough for the current to be space-charge limited. A new method is reported herein for increasing the current substantially and concentrating the increased current into a beam with a diameter less than 2 mm. A small-diameter dielectric rod or tubing inserted into the cathode and extending towards the anode forms a pinched discharge in a thin layer near the dielectric surface concentrating the current with the pinch and guiding the beam in any desired direction.
Dye-Sensitized High-Efficiency Thick Dielectric Diffraction Gratings
Authors: Files V.
Published: January 2004

Commercially available optical cements have been sensitized and exposed throughout the visible spectrum to produce volume holograms with diffraction efficiencies greater than 98% at the Bragg angle. The basic imaging mechanism is a dye-sensitized photo-induced refractive-index change on the order of 5×10−3. Upon exposure to actinic radiation, and in the presence of an organic peroxide, the sensitizer absorption and energy transfer result in image formation and bleaching of the dye to nonabsorbing (leuco) state.
Holographic Storage in VO2
Authors: Roach W. R.
Published: January 2004

Permanent erasable holographic storage has been demonstrated in a VO2 film by utilizing a change in an optical property which has a broad hysteresis at the insulator-to-metal phase transition. The implied coexistence of insulating and metallic phases at a single temperature indicates that a barrier exists which inhibits movement of the phase boundary.
Wavefront Distortion of Acoustic Surface Waves from Apodized Interdigital Transducers
Authors: Tancrell R. H. , Williamson R. C.
Published: January 2004

The acoustic surface wave launched by an interdigital transducer is experimentally shown to have a distorted wavefront when the transducer has a varying finger overlap (apodization) and is on a high-coupling piezoelectric substrate, LiNbO3. Results are shown for different transducer geometries, when an acoustic wave passes under the comb and when the apodized comb itself is driven. One geometry having extra metal fingers significantly reduces the wavefront distortion. The origin of the distortion is a retardation of the wave passing under metal fingers.
Josephson-Junction Amplifier
Authors: Clarke John , Paterson James L.
Published: January 2004

Positive feedback has been used within a double-Josephson-junction quantum interferometer to achieve a current amplification which can be adjusted from outside the cryostat over the range 1–100. The interferometer may be regarded as a three-terminal amplifying device.
Detonation of Insensitive High Explosives by a Q-Switched Ruby Laser
Authors: Yang L. C. , Menichelli Vincent J.
Published: January 2004

Immediate longitudinal detonations have been observed in confined small-diameter columns of PETN, RDX, and tetryl by using a focused Q-switched ruby laser. The energy ranged from 0.8 to 4.0 J in a pulse width of 25 nsec. A 1000-Å-thick aluminum film deposited on a glass window was used to generate a shock wave at the window-explosive interface when irradiated by the laser. In some cases steady-state detonations were reached in less than ½ μsec with less than 10% variation in the detonation velocity.
Frequency-Tunable Transform-Limited Picosecond Dye-Laser Pulses
Authors: Arthurs E. G. , Bradley D. J. , Roddie A. G.
Published: January 2004

Picosecond pulses of transform-limited durations (Δt∼3 psec; ΔtΔν∼0.5) have been obtained from a passively mode-locked Rhodamine 6G dye laser, frequency tuned over a range of 230 Å with an intracavity Fabry-Perot filter. Self-phase-modulation frequency broadening at higher powers has also been measured giving a value n2 = 10−18 cm2V−2 for the nonlinear refractive index of the ethanol dye solvent.
Stark-Effect Modulation of a CO2 Laser by NH2 D
Authors: Johnston A. R. , Melville R. D. S.
Published: January 2004

The molecular Stark effect in NH2D was used to modulate the 10. 6-μ P(20) line of a CO2 laser yielding a modulation depth of 40% from a 200-V cm−1 rms signal applied to a 19. 7-cm gas cell external to the laser. NH2D was prepared by mixing ND3 and NH3. The absorption coefficient of the M=4 Stark-split line was measured as a function of mixing ratio and pressure. The observed pressure-broadening coefficient was 32. 5 MHz/Torr.
Atmospheric-Pressure Pulsed CO2 Laser Utilizing Preionization by High-Energy Electrons
Authors: Garnsworthy R. K. , Mathias L. E. S. , Carmichael C. H. H.
Published: January 2004

An atmospheric-pressure pulsed CO2 laser is described in which the gas is preionized by the injection of high-energy electrons into the laser volume. These electrons are derived from a high-voltage (120-kV) glow discharge surrounding the laser. The preionization achieved has allowed 300 J to be delivered to 1. 7 liter of gas in a single discharge without the development of arcs, irrespective of whether the gas contained helium. The highest output energy (20 J) was obtained with a mixture of CO2, N2, and He in the proportions 3 : 3 : 4 by volume.
Excitation Mechanism of the Water-Vapor Laser
Authors: Pichamuthu J. P. , Hassler J. C. , Coleman P. D.
Published: January 2004

Experiments are described which indicate that the water-vapor laser is pumped by selective excitation of the upper lasing level through direct electron impact. A simple model based upon this idea is shown to explain the general behavior of the laser, and to give an estimate for the collision number for the relaxation of the 020 mode of H2O of the order of 20.
Self-Pumped Josephson Parametric Amplification
Authors: Kanter H. , Silver A. H.
Published: January 2004

Parametric gain has been demonstrated at 30 MHz using the nonlinear inductance of Josephson point-contact devices. SQUID-type configurations were used to achieve degenerate-mode negative-resistance amplification with self-pumping achieved via the internal Josephson oscillations. Gain as large as 11 dB was measured. The small-signal analysis predicts parametric amplification and delineates the importance of the critical current, circuit loss, and circuit coupling efficiency.
Rayleigh-Wave Propagation on Bi12 GeO20
Authors: Bridoux E. , Rouvaen J. M. , Coussot C. , Dieulesaint E.
Published: January 2004

Theoretical values of mechanical displacement, potential, and velocity of surface waves propagating in the [001] direction on [110]-cut Bi12GeO20 are reported. The results of an experimental investigation performed at 50 MHz using interdigital transducers and optical probing are presented. The velocity measured is in excellent agreement with the theoretical value and the attenuation is very low, 0. 1 dB/μsec being an estimated upper limit. Second-harmonic generation which was measured by optical probing had an intensity proportional to the square of both the interaction length and the fundamental acoustic power, indicating nonlinear effects in the propagating medium at an acoustic input power of 28 dBm.
Efficient Parametric Mixing in CdSe
Authors: Herbst R. L. , Byer R. L.
Published: January 2004

We have obtained the first phase-matched nonlinear interaction in CdSe and have observed a 35% conversion efficiency for mixing 10.6 μ with a pump at 1.833 μ to generate a signal at 2.2 μ. The mixing process phase matches at 77° to the optic axis and confirms the predicted phase-matching angle. The measured nonlinear coefficient value of 2.5 × 10−22 mks agrees with previous results. The mixing experiment shows than an angle-tuned or pump-tuned infrared parametric oscillator is possible using CdSe as the nonlinear element.
Cinnabar (α HgS), a Promising Acousto-optical Material
Authors: Sapriel J.
Published: January 2004

Several acousto-optical characteristics of cinnabar have been measured at 6328 and at 10 600 Å. All observed figures of merit are far higher than those of the most efficient photoelastic materials and the acoustic losses are quite low. For instance, at 6328 Å, the figures of merit M1, M2, and M3 are, respectively, 211, 632, and 513 times greater than the corresponding values in fused silica. The associated acoustic attenuation is only 7.1 dB/cm at 500 MHz. To demonstrate the potential of cinnabar, an XY deflector has been calculated from measured acoustic and photoelastic constants. 100% of an incident laser beam (6328 Å) could be deflected in 62 500 different positions with an access time of 1 μsec, the acoustic power needed being only 210 mW for each stage!
Xenon-Helium Laser at High Pressure and High Repetition Rate
Authors: Targ Russell , Sasnett Michael W.
Published: January 2004

We report pulsed laser action in neutral xenon in the infrared at a repetition rate of 1.4 kHz, using a transversely excited helium-xenon discharge. This high prf was made possible by the use of transverse gas flow to remove the residual ions from the discharge region. We have been able to obtain 5.2 W of average power from the 80-cm-long closed-cycle device in which the flow velocity was 30 m/sec. The electrical efficiency observed in this work was 0.12% which is very close to the estimated maximum obtainable. The output spectrum included components at 2.027, 3.508, and 3.652 μ.
Ultrashort Pulse Formation in a Short-Pulse-Stimulated Raman Oscillator
Authors: Colles M. J.
Published: January 2004

A train of picosecond pulses was used to pump a stimulated Raman oscillator designed such that the generated Stokes pulse was amplified by successive pump pulses. In this way partial group velocity matching could be achieved and significant time narrowing of the Stokes pulse realized. With benzene as the Raman active material, a minimum Stokes-pulse duration of ≃ 0.3 psec was recorded.
Extending the Tuning Range of Tunable Oscillators by Upconversion
Authors: Campillo A. J. , Tang C. L.
Published: January 2004

The operation of a doubly resonant LiIO3 parametric oscillator is described. Simultaneous pumping of this oscillator and a LiIO3 upconverter by a single ruby-laser beam was employed to extend the tuning range of the parametric oscillator down to the 4200–5100-Å range. Up to 10 kW of upconverted power with a 1-MW ruby-laser pump was observed; with an intracavity upconverter, a substantial increase in the over-all efficiency should be achievable.
Emission Spectra in CdS under High Excitation by Electron Beam
Authors: Iwai Sohachi , Namba Susumu
Published: January 2004

An additional peak in CdS was observed on the long-wavelength side of the Ex-LO band in the spontaneous emission spectra under high excitation by an electron beam from 82 to 300 °K. The shift of the additional peak from the free-exciton line increased linearly with temperature. The laser emission occurred near the additional peak. The laser-transition mechanism associated with the additional luminescence is discussed.
Nonlinear Optical Properties of Hexagonal Silicon Carbide
Authors: Singh S. , Potopowicz J. R. , Van Uitert L. G. , Wemple S. H.
Published: January 2004

Optical second harmonic coefficients, refractive indices, and optical transmission of hexagonal SiC have been measured at room temperature. The nonlinear coefficients measured relative to quartz for a 1.064-μm fundamental are d15SiC=(25± 3)d11α −SiO2, d31SiC=(27± 3)d11α −SiO2, and d33SiC=(45± 5)d11α −SiO2. The observed Miller δ coefficients are in poor agreement with the values calculated from Levine's bond-charge model. Type-II phase matching should be achievable with SiC for fundamental wavelengths greater than 2.0 μm.
Pulsed CO2 Gas-Dynamic Laser
Authors: Yatsiv S. , Greenfield E. , Dothan-Deutsch F. , Chuchem D. , Bin-Nun E.
Published: January 2004

We report a pulsed combustion-operated CO2 gas-dynamic laser. A gas mixture is ignited in a combustion chamber to form heated CO2 and N2. The mixture expands through a supersonic nozzle, thereby causing population inversion in the CO2. Laser energy was about 20 J and pulse duration 0.3 sec. Variations of gain and pulse energy with gas composition and stagnation pressure are described.
Detection of Room-Temperature Blackbody Radiation by Parametric Upconversion
Authors: Falk J. , Yarborough J. M.
Published: January 2004

Room-temperature thermal (blackbody) radiation has been detected via parametric-frequency upconversion. Thermal radiation was mixed with the output of a Nd:YAG laser in proustite. The wavelength of the radiation upconverted was varied from 6.5 to 12.5 μ by rotating the proustite 20 deg. The spectral width of the blackbody radiation accepted by the upconverter was approximately 0.7 μ.
Pure Shear Elastic Surface Wave Guided by the Interface of Two Semi-Infinite Media
Authors: Maerfeld C. , Tournois P.
Published: January 2004

An acoustic shear surface wave can be guided by the interface of two semi-infinite media in contact if one, at least, of these two media is piezoelectric. After a study of the surface-wave characteristics, the existence conditions are stated. For example, such a wave can propagate along the interface of two identical crystals, in class 6 mm, when the C axes of these crystals, both parallel to the interface and perpendicular to the propagation direction, are in opposite directions.
Charge-Exchange Excitation in the He–Cd Laser
Authors: Collins G. J. , Jensen R. C. , Bennett W. R.
Published: January 2004

Experiments are described which show a dual involvement of charge exchange and Penning ionization-excitation processes in the helium-cadmium laser similar to that reported earlier by the authors in the helium-zinc ion laser. Charge exchange leads primarily to high-lying states of Cd II in which only the outer electron is excited, whereas Penning ionization mainly leads to the production of excited ionic states involving a ``hole'' in the inner d-shell configuration.
Control of the Susceptibility of Lithium Niobate to Laser-Induced Refractive Index Changes
Authors: Peterson G. E. , Glass A. M. , Negran T. J.
Published: January 2004

The origin of laser-induced refractive changes (laser damage) in LiNbO3 has been identified as iron impurities. Quantitative measurements of the damage were made using holographic techniques as the iron impurity content of crystals was varied. Holographic diffraction efficiencies from as high as 0.44 to lower than 10−6 have been achieved with crystals 0.2 cm thick, using 10 W/cm2 of 5145-Å radiation, both by varying the iron impurity concentration and by varying the valence state of these impurities. The previously observed effects of field annealing, crystal coloration, oxidation and reduction, and the role of OH- ions are all accounted for.
A Waveguide Gas Laser
Authors: Smith P. W.
Published: January 2004

This letter describes a new type of gas laser. The laser light is guided in a hollow dielectric waveguide which also serves to confine the discharge. Operation of such a laser with He–Ne mixtures at 6328 Å is reported and some characteristics of the laser operation are described.