bluuebunny/crossref_metadata_2025 huggingface dataset:
Aging characteristics of Ga1−xAlxAs double-heterostructure lasers bonded with gold eutectic alloy solder
Authors: Fujiwara K. , Fujiwara T. , Hori K. , Takusagawa M.
Published: February 2003

Aging characteristics of Ga1−xAlxAs DH lasers bonded with gold eutectic alloy solder and indium solder were studied. In the lasers bonded with indium solder, it was found that thermal resistance increased during the aging test and the activation energy for the increasing rate of thermal resistance was 0.6 eV. Sixteen lasers bonded with gold-tin eutectic alloy solder have been operating at 70 °C over 1800 h with no increase in thermal resistance and a slight increase in the driving current required to maintain the cw optical power constant during the aging test; and lasers bonded with gold-germanium eutectic alloy solder have been operating at 70 °C over 10 000 hours with a slight increase in driving current. The use of gold eutectic alloy solder makes possible the long-lived lasers.
Measurement of thin-film optical absorption at the air-film interface within the film and at the film-substrate interface
Authors: Temple P. A.
Published: February 2003

A measurement technique is described where the absorption introduced by the addition of a single-layer thin film is separated into three parts: absorption (a) within the bulk of the film; (b) at the air-film interface; (c) at the film-substrate interface. The technique employs a scanning adiabatic calorimeter to measure substrates which are partially coated on the entrance surface with films of continuously varying thickness. By measuring the absorption on the bare substrate and at various film thicknesses, and by making use of changes in relative power density within the film for λ/4 versus λ/2 optical thickness films, we have determined (a) αf, the bulk absorption coefficient of the film, (b) aaf, the specific absorptance of the air-film interface, and (c) afs, the specific absorptance of the film-substrate interface. The analysis assumes that the films are highly transparent and of known index of refraction. In addition, the film thickness must range from λ/4 to 3λ/4 optical thickness, or from λ/2 to λ optical thickness. Representative data are shown for absorptance measurements at 2.7 and 2.9 μm for a film of As2Se3 on CaF2. This example exhibits predominantly film-substrate interface absorption with very little of the absorption taking place in the bulk of the film.
Quantitative measurements of fast ions from CO2 laser-produced plasmas
Authors: Joshi C. , Richardson M. C. , Enright G. D.
Published: February 2003

The asymptotic behavior of the fast-ion energy spectra has been studied by using a Thomson parabola ion spectrometer to analyze ionic species produced by a 10.6-μm laser-produced polyethylene plasma. The use of cellulose nitrate film detectors has yielded for the first time quantitative information about the charge state and energy distribution of these high-energy ions as a function of laser energy and beam polarization.
Interface chemistry of metal-GaAs Schottky-barrier contacts
Authors: Waldrop J. R. , Grant R. W.
Published: February 2003

A survey of the metal-semiconductor interface chemistry for GaAs and seven metals, Ag, Al, Au, Cr, Fe, Sn, and Ti, by using x-ray photoemission spectroscopy (XPS) is reported. Sn and Ag each form an abrupt inert interface with GaAs. Au, Al, Fe, Cr, and Ti each form a chemically reacted nonabrupt interface with a trend for increasing dissociation of GaAs in the order listed. Also reported is the first observation of epitaxial Fe growth on GaAs.
Al/Al2O3/InP MIS structures
Authors: Favennec P. N. , Le Contellec M. , L’Haridon H. , Pelous G. P. , Richard J.
Published: February 2003

Metal-insulator-semiconductor (MIS) structures were produced by electron-beam deposition of Al2O3 on InP. The electrical properties of such structures were investigated. For optimum conditions, capacitance/voltage (C/V) measurements show that the interface state density can be reduced to 1011 states cm−2 eV−1 by heat treatments. Capacitance transient measurements lead to an estimate of 2×103 cm sec−1 for the surface recombination velocity.
Electroabsorption in GaInAsP
Authors: Kingston R. H.
Published: February 2003

Electroabsorption, or the Franz-Keldysh effect, has been measured in Ga0.24In0.76As0.52P0.48 with an energy gap of 1.03 eV. Absorption coefficients were determined by measuring the transmission versus bias through a double-heterostructure photodiode. The results are in good agreement with theory and are particularly applicable to modulators and detectors in the 1.25–1.30-μm band of interest in optical-fiber transmission.
Correlation of electrolytic-etch and surface-photovoltage techniques for the detection of electrically active defects in silicon
Authors: Deines J. L. , Philbrick J. W. , Poponiak M. R. , Dove D. B.
Published: February 2003

Electrically active defects in a 2-μm n-type epitaxial layer on a p-type silicon wafer were mapped using a scanning-surface-photovoltage technique (SSP). The crystal was then subjected to an anodic etch which preferentially attacks electrically active defects, permitting a detailed correlation to be made between defects revealed by the two techniques. Defects visible in the SSP image usually gave rise to etch pits during anodic exposure in HF solution. The results are discussed in terms of the theory of the SSP and anodic-etch techniques.
Superstructures of submonolayer indium films on silicon (111)7 surfaces
Authors: Kawaji M. , Baba S. , Kinbara A.
Published: February 2003

Superstructures of submonolayer films of indium on a clean silicon (111)7 surface have been investigated using techniques of molecular-beam deposition and reflection high-energy electron diffraction. A two-dimensional phase diagram including four superstructures, 7, (3)1/2, (31)1/2, and 4×1, are presented at substrate temperatures between 300 and 600 °C.
GaAs-AlxGa1−xAs strip-buried-heterostructure lasers with lateral-evanescent-field distributed feedback
Authors: Tsang W. T. , Logan R. A. , Johnson L. F.
Published: February 2003

A GaAs-AlxGa1−xAs strip-buried-heterostructure laser with distributed feedback provided through lateral-evanescent-field-grating interaction is demonstrated. The diode is shown to operate stably in single transverse (fundamental) and longitudinal modes up to about 3×Ith over a temperature range 0–36 °C under pulsed operation. The light-current characteristics of these lasers exhibit the characteristic linearity of conventional strip-buried heterostructure lasers.
Optoacoustic Raman gain spectroscopy of liquids
Authors: Patel C. K. N. , Tam A. C.
Published: February 2003

We report the first optoacoustic Raman gain spectroscopy (OARS) of liquids, using two synchronized pulsed dye lasers, and gated optoacoustic detection of the energy deposited in the liquid due to the stimulated Raman (Stokes) scattering. We demonstrate this sensitive technique with several neat liquids, including benzene, acetone, 1,1,1-trichloroethane, toluene, and n-hexane. This technique seems competitive or superior to other techniques like intracavity inverse Raman scattering or coherent anti-Stokes Raman spectroscopy. OARS can thus be advantageously used in many liquids, including water.
Microbolometers for infrared detection
Authors: Hwang Tien-Lai , Schwarz S. E. , Rutledge D. B.
Published: February 2003

We describe a novel room-temperature detector for the wavelength range 10–1000 μm. This detector consists of a thin bismuth bolometer film with dimensions much smaller than a wavelength. The small size of the detector results in reduced NEP and faster response. A video NEP of 1.6×10−10 W/Hz1/2 is obtained at 119 μm, remaining within a factor of 10 of this value for modulation frequencies up to 25 MHz. When used as a mixer, the device is predicted to have an NEP of 3.5×10−18 W/Hz. It is easily fabricated with conventional planar processing techniques and can be replicated in arrays. The device is expected to be most useful when the radiation to be detected is spatially coherent.
Sublimation of ionic crystals in the presence of an electrical field
Authors: Yacamán M.José , Munir Z. A. , Ocaña T. , Hirth J. P.
Published: February 2003

A direct observation of the influence of an externally applied electrostatic field on the sublimation steps on (100) surfaces of KCl is reported. Typically, round-cornered square spirals were found to be distorted into round-cornered rhombical spirals in the presence of a field. The results are interpreted in terms of charged kinks on the surface.
Characterization of light emission from amorphous chalcogenide switches
Authors: Walsh P. J. , Pooladdej D. , Thompson M. J. , Allison J.
Published: February 2003

Narrow-bandwidth infrared radiation has been detected from amorphous As50Te50 threshold switches in the ’’on’’ state of thin parallel plane devices which possess optical feedback. The radiation has a fast rise time and is dependent on a minimum threshold ’’on’’ current which is independent of device area. The radiation output is substantially independent of device temperature and is thus not thermally activated. The output is not observed in heterojunction devices which have little optical feedback.
Lattice constants and band-gap variations of the pentenary semiconductor system Cu1−yAgyInS2(1−x)Se2x
Authors: Chapman G. H. , Shewchun J. , Loferski J. J. , Garside B. K. , Beaulieu R.
Published: February 2003

Much interest has been expressed in the ternary IB-III-VI2 group semiconductors for use in electro-optical devices such as solar cells. Subsets of these, AgInS2, AgInSe2, CuInS2, and CuInSe2, have been combined to form the pentenary alloy system Cu1−yAgyInS2(1−x)Se2x. With such an alloy the band gap may be varied while keeping the lattice constant fixed. Samples were prepared by reacting stoichiometric powder mixtures at about 900 °C. X-ray diffractometry tests suggest the alloys maintained complete solid solubility throughout the system in a chalcopyrite-type crystal structure. From cathodoluminescence studies on pressed bars of these powders the band-gap energies were estimated at 300 °K. These tests suggest that the alloys are all direct-band-gap semiconductors.
Temperature sensitivity of ion-implanted MOS capacitors
Authors: Topich James A.
Published: February 2003

The temperature sensitivity of ion-implanted MOS capacitors has been studied. The results show that the damage due to the implantation process results in a frequency-dependent temperature sensitivity. The range over which the temperature sensitivity occurs can be varied by changing both the implanted dose and energy. Since the phenomena is due to damage, postimplant annealing will reduce or eliminate the temperature sensitivity depending on the annealing time and temperature. Temperature sensitivities on the order of 2.5%/°C have been measured.
The growth of tin oxide films at room temperature
Authors: Ghandhi S. K. , Siviy R. , Borrego J. M.
Published: February 2003

This report outlines the growth of highly transparent films of undoped tin oxide at near ambient temperatures (∼30 °C). Films were deposited by a technique based on the reaction of rf plasma-activated oxygen with tetramethyltin. Growth rates as high as 160 Å/min have been achieved with a 100-μm partial pressure of tetramethyltin and an overall system pressure of 500 μm. The growth kinetics have been explained by a model in which the tetramethyltin is the rate limiter, and the concentration of active oxygen is independent of the flow rate of molecular oxygen.
Resolution of photon-recoil structure of the 6573-Å calcium line in an atomic beam with optical Ramsey fringes
Authors: Barger R. L. , Bergquist J. C. , English T. C. , Glaze D. J.
Published: February 2003

The photon-recoil components of the Ca 6573-Å line have been resolved using the three-zone optical Ramsey interference technique with an atomic beam. Linewidths as narrow as 3 kHz HWHM (line Q of 8×1010) are reported for zone separations up to 7 cm. An indication of the light-shift-induced contraction of the recoil splitting predicted by C.J. Bordé is obtained. Techniques are discussed which should lead to an optical wavelength/frequency standard with an accuracy of better than 10−14.
Large-signal theory of phase-conjugate backscatterings
Authors: Hsu Hsiung
Published: February 2003

The large-signal characteristics of conversion efficiency and gain saturation for phase-conjugate backscattering processes are discussed in detail to explain the large deviation of the simple small-signal theory from many experimental observations. As characterized by the nature of the inherent feedback in backward-traveling-wave interactions, complete power conversion from the pump to signal can often be accomplished. The understanding of this unique feature will provide new concepts for many high-power laser applications including, for example, power transmission to space vehicles and military applications concerning missiles.
Chromium profiles in semi-insulating GaAs after annealing with a Si3N4 encapsulant
Authors: Huber A. M. , Morillot G. , Linh N. T. , Favennec P. N. , Deveaud B. , Toulouse B.
Published: February 2003

Quantitative Cr profiles have been determined on semi-insulating GaAs by secondary-ion mass spectrometry (CAMECA IMS 300). It is shown that after thermal annealing (900 °C, 20 min) under Si3N4, Cr diffuses towards the GaAs surface, leaving a Cr concentration depletion zone underneath. This zone becomes conductive with a carrier concentration of n∼2×1016 cm−3. Some consequences of these findings are considered.
Inversion of atoms and molecules to the ground state by optical pumping
Authors: Falcone R. W.
Published: February 2003

A technique is proposed for inverting atoms and molecules with respect to the ground state. The process is based on simultaneous excitation of colliding species by absorption of a photon. Visible wavelength lasers with millijoule energy outputs and several nanosecond pulse widths should be capable of demonstrating inversion of resonance lines in high-density metal-vapor mixtures.
Laser-induced recrystallization and damage in GaAs
Authors: Tsu Raphael , Baglin John E. , Lasher Gordon J. , Tsang James C.
Published: February 2003

We have investigated the recrystallization of ion-implanted amorphous GaAs using a frequency-doubled 10−8-s pulsed Nd : YAG laser. The best results were obtained by spatially overlapping laser pulses at 20 MW/cm2. At power densities above 20 MW/cm2, not only does the GaAs surface begin to show uneven solidification, but also an increasing degree of disorder is revealed in Raman scattering and by a broad hump in the spectrum of channeled He-ion backscattering. This laser-induced damage is similar for single-crystal and ion-implanted GaAs samples. We attribute the damage at high power densities to the loss of arsenic and subsequent rapid cooling of a gallium-rich liquid.
A densely packed monolithic linear array of GaAs-AlxGa1−xAs strip buried heterostructure laser
Authors: Tsang W. T. , Logan R. A. , Salathe R. P.
Published: February 2003

Strip buried heterostructure lasers were formed with a center-to-center spacing of 15 μm to give a densely packed monolithic linear array. Excellent uniformity in individual laser characteristics persisted across the entire array. The laser output power-current characteristics of such arrays were linear and symmetric from both mirrors for the entire injection current range up to catastrophic damage. Pulsed-out power of ∼1.6 W/mirror has been obtained for a five-laser array. Spectral behavior of the arrays indicated that there was some field interaction between the neighboring lasers.
Temperature dependence of transient capacitance of Al/SiO2/Si capacitors
Authors: Bharat R. , Fitzgibbons E. T. , LaPrade J. E.
Published: February 2003

The capacitance transient of an aluminum/silicon dioxide/n-silicon structure in response to a negative voltage step applied to the aluminum electrode was measured at several temperatures between +70 and −40 °C. The automated measurement method is outlined and the data obtained are interpreted in terms of an activation energy for minority-carrier generation. The activation energy is 0.64 eV, which is not identifiable as any known impurity level in silicon.
Real-time Fourier transformation via acousto-optics
Authors: Berg N. J. , Lee J. N. , Casseday M. W. , Katzen E.
Published: February 2003

An implementation of the chirp transform algorithm for performing a real-time Fourier transform is described. The implementation is based upon an acousto-optic convolver with a large time-bandwidth product An instantaneous bandwidth of about 75 MHz was achieved for the Fourier transformer with a dynamic range in excess of 60 dB for a cw time-gated waveform. By using an almost-uniform light-beam intensity across the device, the measured sidelobe amplitudes were within 0.5 dB of the theoretical values. The corresponding measured phase errors were less than 5°. The adaptability of this acousto-optic implementation is demonstrated by the ease with which one can vary both the sidelobe weighting function and the time rate of the transform.
Observation of transverse and longitudinal modes in non-neutral electron clouds confined in a magnetic mirror
Authors: Eckhouse Shimon , Fisher Amnon , Rostoker Norman
Published: February 2003

Electrostatic modes on non-neutral electron clouds confined in a magnetic mirror field have been investigated. The cloud contains 2×1011 electrons at an average kinetic energy of 0.3 MeV for a magnetic field with a peak intensity of 9 kG at the midplane. It was found that the cloud is moving azimuthally as well as longitudinally. The azimuthal motion has an m=1 spatial nature. The longitudinal modes have a more complicated nature, but their frequency equals that of the azimuthal mode.
Effects of a multipole magnetic field on characteristics of a multifilament plasma source
Authors: Oka Y. , Kuroda T.
Published: February 2003

A multipole magnetic field is applied in a multifilament plasma source. By changing the strength of the magnetic field, the instability of the discharge, the change of the density profile, and the increment of the ion density are investigated. It is shown that the stable plasma with a rather high density on the order of 1012 cm−3 and with a uniform density profile within ±5% over the 9-cm diameter is obtained in the lower discharge current compared with the discharge without the magnetic field, and the total heater current of the filament can be reduced by about 10%. The ratio (0.93) of the discharge current to the heater current without a magnetic field is improved to 1.8 with the field.
Measurement of gain on the XeF (C-A) blue-green band
Authors: Hill R. M. , Trevor P. L. , Huestis D. L. , Lorents D. C.
Published: February 2003

Transient gain has been observed on the C→A transition of XeF*. Measurements made at 488.0 and 475.9 nm showed a peak gain of 8% through a short cell filled with Ar/Xe/NF3 mixtures and excited by a short electron-beam pulse. A stimulated emission cross section of 5×10−18 cm2 is derived, consistent with the measured linewidth and radiative lifetime of the C-A transition. Weaker amplification was observed at 514.5 nm.
Optical damage thresholds of thin-film and in-diffused waveguides
Authors: Normandin R. , So V. C. Y. , Teh G. A. , Stegeman G. I.
Published: February 2003

The behavior of a number of glass and Ti in-diffused LiNbO3 waveguides was investigated as a function of laser power, and the damage thresholds were evaluated and compared to the bulk material values.
Semiconducting CdF2 : Mn—A new material for efficient blue-green electroluminescence
Authors: Langer T. , Krukowska-Fulde B. , Langer J. M.
Published: February 2003

Efficient blue-green (λmax=520 nm) electroluminescence in MIS structures on CdF2 : Mn Y crystals was obtained. The structures are driven by asymmetric voltage pulses with accelerating amplitude in the range 50–100 V and active current density less than 10−5 A/cm2. The average quantum and power efficiencies at 10 fL exceeding 10 and 0.5%, respectively, and a uniform emitting area up to 1 cm2 were achieved, indicating the suitability of CdF2 : Mn for display purposes.
Laser annealing for solid-phase thin-film reactions
Authors: Liau Z. L. , Tsaur B. Y. , Mayer J. W.
Published: February 2003

We propose a scheme for calculating the amount of thin-film reaction as a result of the pulsed annealing induced by laser irradiation. Under ideal conditions, simple analytical solutions are obtained for reaction temperature T (t) if the absorbed laser power P (t) is a step, linear, or polynomial function of t. The thickness of the reacted film is equivalent to that of a thermal (furnace) annealing at an effective temperature Teff for an effective annealing time Δteff. Teff is the peak value of T (t) and Δteff ≃ (kTeff/Ea)mΔt, where m=1 or 1/2 [determined by the function form of T (t) near Teff], Ea is the activation energy of the process, and Δt is the duration of the laser pulse. The present results can also be used as an approximation in some cases of the laser annealing of ion-implanted semiconductors. Effect of antireflective coatings is thus predicted. Preliminary experimental results on the laser annealing for metal-silicide formation are discussed and are compared with the present calculation.
Deep exponential distribution of traps in naphthalene
Authors: Campos M. , Giacometti J. A. , Silver M.
Published: February 2003

The long-time decay of the surface potential of corona-charged naphthalene crystals has been analyzed. The decay curves are explained using an exponential distribution of traps of the form exp[−(E−1.1 eV)/kTc], where Tc∼600 °K. The total number of traps is estimated to be approximately 1013/cm3. The long-time decay is also evidence for dispersive transport in crystalline material due to a distribution of traps.
p-n junction diodes in InP and In1−xGaxAsyP1−y fabricated by beryllium-ion implantation
Authors: Armiento C. A. , Donnelly J. P. , Groves S. H.
Published: February 2003

Mesa and planar InP p-n junction diodes have been fabricated by beryllium-ion implantation. These devices exhibit abrupt reverse-bias breakdowns and low leakage currents. Similar mesa diodes have been produced in In1−xGaxAsyP1−y (Eg≈1.0 eV). Diodes operated in the punch-through mode exhibited uniform breakdown over the area of the device, without any apparent edge effects.
A model for predicting acoustic material signatures
Authors: Weglein R. D.
Published: February 2003

Unique acoustic material signatures (AMS) may be obtained in the reflection acoustic microscope. The proposed model shows that they result from interference between two components reradiated into the immerson fluid at the materials critical Rayleigh angle ϑR. The characteristic period ΔzN of this interference signature varies as the square of the Rayleigh wave velocity and is empirically given by ΔzN=λR/sinϑR, where λR is the Rayleigh wavelength. Materials covering a greater than 3 : 1 velocity range agree well with this physical model. Substitution of the longitudinal wave velocity in the expression extends the range of measurable AMS to acoustically slower materials. A variety of applications for AMS is suggested.
The acoustic measurement of stress intensity factors
Authors: Resch M. T. , Khuri-Yakub B. T. , Kino G. S. , Shyne J. C.
Published: February 2003

The maximum stress intensity factor of a surface crack has been inferred by measuring the reflection coefficient of a Rayleigh wave incident to the crack. An acoustic surface wave wedge transducer was used to excite the incident wave and to measure the reflected-wave amplitude. The fracture stress of Pyrex glass specimens containing the acoustically measured cracks was determined in biaxial flexure. The values of the fracture stress predicted from acoustic data were found to be in excellent agreement with the measured values, with less than a 15% error.
Experimental results on the multiphoton ionization of molecular nitrogen
Authors: Baravian G. , Godart J. , Sultan G.
Published: February 2003

The experimental study of the multiphoton ionization (MPI) of nitrogen by a neodymium glass laser gives the value n=13±2 for the nonlinear interaction order and a maximum kinetic energy of 3 eV for the produced charges. An analysis of the multiphoton absorption processes is made taking the experimental results into account.
Application of selective chemical reaction concept for controlling the properties of oxides on GaAs
Authors: Chang R. P. H. , Coleman J. J. , Polak A. J. , Feldman L. C. , Chang C. C.
Published: February 2003

We demonstrate how GaAs can be selectively oxidized in a plasma to control the physical and chemical properties of the oxides. Electrical measurements indicate that charged traps can be removed.
Mechanical properties of i
n s
i
t
u multifilamentary Nb3Sn superconducting wires
Authors: Foner S. , Roberge R. , McNiff E. J. , Schwartz B. B. , Fihey J. L.
Published: February 2003

The mechanical properties of in situ Cu–36 wt% Nb–x wt% Sn superconducting wires are presented where 5<x<20 wt% Sn. For high x, no degradation of critical current Jc is observed for stresses σ up to 700 MPa (∼100 ksi) and a maximum Jc occurs at σ≃450 MPa. Strains of ∼0.6–0.9% are measured at 300 and 77 K for 450 MPa, and ∼1.5–2% for 700 MPa. Cyclic stress data are consistent with a prestress model for composite materials.
Single-polarization optical fibers: Slab model
Authors: Kaminow I. P. , Ramaswamy V.
Published: February 2003

Calculations for a simple three-layer slab model show that sufficient anisotropic strain birefringence can be introduced into germanosilicate, phosphosilicate, and borosilicate single-mode fibers to reduce the coupling between orthogonally polarized modes to a level of practical interest for single-mode single-polarization propagation.
Terraced-substrate GaAs- (GaAl)As injection lasers
Authors: Sugino T. , Wada M. , Shimizu H. , Itoh K. , Teramoto I.
Published: February 2003

A new structure of stripe-geometry lasers has been reported in which a double heterostructure is fabricated on a terraced substrate. Due to the lateral change of the effective refractive index along the junction plane, the optical gain distribution is restricted within a narrow stripe between two adjacent bends of the active layer regardless of the current spreading. This simple structure constantly exhibits a fundamental longitudinal mode oscillation as well as a single transverse-mode oscillation. No kinks have been observed in light-output-current characteristics. The linearity continues up to 10 times the threshold where the power output is 150 mW/facet.
cw oscillation in a Nd : phosphate glass laser
Authors: Kishida S. , Washio K. , Yoshikawa S. , Kato Y.
Published: February 2003

A stable cw operation in a Nd : phosphate glass laser has been acheived for the first time. An end-pumping scheme with an Ar laser in combination with a new kind of phosphate glass material has been successfully used to reduce thermal problems. More than 10 mW cw output power has been obtained in the TEM00 mode.
High-performance Te trilayer for optical recording
Authors: Bell A. E. , Bartolini R. A.
Published: February 2003

The optical-recording characteristics of a fully encapsulated Te trilayer structure are reported. The results demonstrate a 400% improvement in sensitivity compared to a Ti trilayer, at a recording wavelength of 488 nm, while maintaining high SNR (≳50 dB) on playback. This Te trilayer can be optimized for use with a GaAs diode laser recording system.
Estimation of plasma temperature from recombination continuum
Authors: Sinha B. K.
Published: February 2003

The reliability of the estimation of plasma temperature for a carbon plasma from bremsstrahlung emissions has been assessed using the steady-state corona model for the ionization states. It is observed that even at a temperature as high as 225 eV the temperature estimated from the bremsstrahlung continuum can give an error as high as 55%, whereas the temperature estimated from the recombination continuum can be taken as the true temperature of the plasma.
The effect of free-carrier absorption on the annealing of ion-implanted silicon by pulsed lasers
Authors: Lietoila A. , Gibbons J. F.
Published: February 2003

The temperature rise in an ion-implanted silicon sample illuminated by a pulsed laser (ruby or Nd : YAG) is determined by numerical solution of the heat-diffusion equation. The temperature dependence of the thermal conductivity and the free-carrier absorption are included in the calculations. The latter was found to have a very significant effect when the laser is operated in the Q-switched mode. The analysis shows that annealing in this mode almost certainly involves melting of the sample surface. In the free-oscillation mode, however, free-carrier absorption is negligible, and this mode may therefore provide a method of melt-free annealing.
Quasiparticle heterodyne mixing in SIS tunnel junctions
Authors: Richards P. L. , Shen T. M. , Harris R. E. , Lloyd F. L.
Published: February 2003

The rapid onset of quasiparitcle tunneling current in superconductor-insulator-superconductor (Josephson) junctions at voltages above 2Δ/e is being used for millimeter-wave heterodyne mixing. Junctions with a 2-μm diameter and RN=50 Ω have little capacitive shunting at the signal frequency of 36 GHz. Because there is no series resistance, residual capacitance can be tuned out. Double sideband conversion efficiencies of 0.32 and mixer noise temperatures as low as TM⩽7 K=4hν/k have been observed. The results are compared with shot-noise-limited mixer theory. Photon-assisted tunneling effects are seen which indicate the approach to photon-noise-limited operation.
Depth of melting produced by pulsed-laser irradiation
Authors: Narayan Jagdish
Published: February 2003

The depth of melt front penetration induced by Q-switched ruby-laser irradiation has been measured by electron microscopy for laser pulses of different duration and energy density in silicon crystals diffused with phosphorous. In as-diffused specimens (1100 °C 1-h PH3 source) dislocation loops and phosphorous precipitates were distributed to a depth of about 1.0 μm. The precipitates and loops were dissolved to certain depths by irradiation with Q-switched ruby-laser pulses. Dissolving of precipitates provides evidence for melting by the laser radiation, and the depth over which precipitates are dissolved provides a measure of the melt front penetration depth.
Tunable stimulated Raman scattering in the far infrared
Authors: Patel C. K. N. , Yafet Y.
Published: February 2003

We propose a tunable electronic Raman-scattering process which yields tuning of the scattered frequency over ≳10 cm−1 in the far infrared. For a specific example of donor levels in GaAs and an incident photon frequency of ∼66.2 cm−1 (151 μm), a magnetic field of 10–30 kG yields Raman-scattering cross sections of 10−24–10−23 cm2 sr−1. We show that a tunable Raman laser covering a frequency region from ∼30.7 to ∼16.0 cm−1 (i.e., from ∼325 to ∼625 μm) is feasible.
Pressure saturation of laser-generated acoustic waves in liquids
Authors: Sigrist M. W. , Kneubühl F. K.
Published: February 2003

The generation of acoustic waves in liquids by the impact of pulses from a hybrid CO2 laser has been studied in detail. With the aid of self-developed piezoelectric transducers, a pressure saturation with increasing laser peak power has been demonstrated in carbon tetrachloride. This phenomenon is explained by a reduced absorptivity at higher laser power.
Intensity dependence of transmission of electromagnetic radiation through an overdense Z-pinch plasma
Authors: Ackenhusen John G. , Bach David R.
Published: February 2003

The interaction of a 10.6-μm-wavelength electromagnetic wave with an independently created overdense plasma has been investigated at incident intensities on either side of the field-strength condition Vosc/Vth=1. An intensity threshold for transmission of the radiation through the overdense target plasma was observed near Vosc/Vth=1. Temporal behavior of the transmitted radiation pulse was compared to that of the incident pulse over an intensity range (0.1–4) ×1011 W/cm2.
Multidielectrics for GaAs MIS devices using composition-graded AlxGa1−xAs and oxidized AlAs
Authors: Tsang W. T. , Olmstead M. , Chang R. P. H.
Published: February 2003

Metal-insulator-semiconductor (MIS) structures were prepared by dry thermal oxidation of an AlAs layer that had been grown on a composition-graded AlxGa1−xAs layer on GaAs. The epitaxial layers were grown by molecular beam epitaxy. Capacitance-voltage (C-V) measurements of these MIS structures demonstrated the achievement of inversion behavior with essentially no hysteresis and flatband voltages ranging from 0 to 0.1 V, which correspond to a fixed interface charge density of less than 2×1010 cm−2. It was also found that the stress developed between the oxide film and the epilayer was reduced in these MIS structures.
Response times and low-voltage behavior of SNS microbridges
Authors: Warlaumont John , Brown J. C. , Buhrman R. A.
Published: February 2003

We have produced very small (200×200×60 nm) superconducting microbridges in which the bridges are made from a normal metal. The critical-current–vs–temperature curves can be fit very well by theoretical curves calculated using the microscopic equations of Usadel; this fitting procedure gives reduced lengths for the bridges. The intrinsic response time of these structures has been determined, and the dependence of this time on both the reduced lengths and on the temperature is found to be in agreement with predictions based on time-dependent Ginzburg-Landau theory.
cw laser action in Nd(Al,Cr)3(BO3)4
Authors: Hattendorff H.-D. , Huber G. , Lutz F.
Published: February 2003

Room-temperature cw lasing at 1.063 μm was obtained in Nd(Al,Cr)3(BO3)4 crystals. Cross pumping via Cr3+ is as efficient as direct pumping via Nd3+. Thresholds around 20 mW and slope efficiencies up to 13% have been measured. The internal losses were high, around 15%, which we ascribed to imperfect crystal quality. Improvement of crystal quality should lead to thresholds in the mW range.
Broadband electronically tunable resonant microwave modulators for CO2 lasers
Authors: Magerl Gottfried , Bonek Ernst
Published: February 2003

An electro-optic microwave modulator generating frequency-swept sidebands 26–31 GHz offset from a CO2 laser carrier is described. Resonant enhancement of the modulating field allows as low as 8-mW microwave drive power. Electronic tuning of the resonances by a ferrite phase shifter inside the cavity increases the FWHM modulation bandwidth from 140 MHz (untuned) to 4 GHz.
Measurements of picosecond pulse shapes for the highly synchronous cw double mode-locked dye laser
Authors: Bourkoff E. , Dienes A. , Whinnery J. R.
Published: February 2003

Cross-correlation measurements of the cw double mode-locked dye laser are described for two different cases, showing that the two pulse trains are highly synchronized. A direct display of the pulse shape at the longer wavelength resulted for the first case, in which a short primary pulse was generated along with a much longer incompletely mode-locked secondary pulse. For the second case, both pulse trains were completely mode-locked and short. In each case, the jitter between the two pulse trains was less than 1.6 ps and there was zero delay between the two pulses.
Phase conjugation using gain saturation of a ND : YAG laser
Authors: Tomita A.
Published: February 2003

Phase conjugation by nonlinear mixing using local gain saturation of a Nd : YAG laser has been demonstrated. Since the laser itself is used as a nonlinear conjugator, no additional nonlinear medium is needed. In principle, any laser can be used for this purpose since laser gain saturation is inherent to all lasers. The maximum conversion efficiency measured was 0.1%.
Coherent Brillouin Spectroscopy
Authors: Jacobson A. G. , Shen Y. R.
Published: February 2003

We have established the viability of coherent Raman techniques in the study of acoustic phonon excitations. Using the Raman-induced Kerr effect scheme, we have obtained the Brillouin spectrum of CS2. The nonlinear polarization in this case is so large that the effects of Stokes gain and anti-Stokes loss must be included in the theoretical interpretation of the spectrum.
Response of a Bi12SiO20 Pockels readout optical modulator to x rays
Authors: Berzins G. J. , Graser M.
Published: February 2003

Response of a Pockels readout optical modulator to x rays has been measured. Sensitivity data and results of cursory imaging experiments suggest novel applications such as on-line radiography.
Fluorescence decay measurement via modulated gain spectroscopy
Authors: Barnes W. T. , Lytle F. E.
Published: February 2003

The ability to obtain a stable tunable picosecond pulse train from a synchronously pumped dye laser is shown to permit the use of modulated gain spectroscopy to study the lifetime, spectral, and concentration-dependent behavior of fluorescent species. The fluorescence of rhodamine-B in ethylene glycol at concentrations from 3μM to 5mM was observed over the range from 570 to 640 nm; a fluorescence lifetime of 2.2 ns was obtained.
Tunable optical detection and generation of terahertz phonons in CaF2 and SrF2
Authors: Eisfeld W. , Renk K. F.
Published: February 2003

A new method for tunable detection and generation of terahertz phonons is reported. It is based on our observation that the lowest energy level of excited Eu2+ ions in CaF2 and SrF2 crystals can be split by uniaxial stress into two levels with a variable separation up to 2.4 THz. Phonons are generated by one-phonon relaxation between these levels and detected by phonon-induced fluorescence radiation from the upper level. The detector is applied to study the spectral distribution of phonons generated by the heat-pulse technique.
Ge : Ga photoconductors in low infrared backgrounds
Authors: Haller E. E. , Hueschen M. R. , Richards P. L.
Published: February 2003

We report the development of infrared photoconductive detectors which are background fluctuation noise limited at photon fluxes ≲108 s−1. The detectors were fabricated from germanium doped with 2×1014 cm−3 gallium. Detectors operated in the conventional manner at T=3 K showed significant photoconductive response for wavelengths out to 120 μm with a minimum NEP of 2.4×10−17 W Hz−1/2 at 94 μm. Detectors operated at T=2 K with a uniaxial stress of 60 kgf mm−2 applied along a [100] direction showed significant response to 205 μm and gave a minimum NEP of 5.7×1017 W Hz−1/2 at ≈150 μm. The stressed detectors are four orders of magnitude more sensitive than any previous photoconductor beyond 120 μm.
Dual-wavelength laser annealing
Authors: Auston D. H. , Golovchenko J. A. , Venkatesan T. N. C.
Published: February 2003

A simple and efficient method of annealing ion-implantation damage in semiconductors is demonstrated which utilizes a relatively weak optical pulse in the visible to initiate surface melting in combination with a more energetic infrared pulse to drive in the melt front to the crystalline substrate. The efficacy of this approach is illustrated by an example in which an arsenic-implanted silicon crystal is simultaneously exposed to 530- and 1060-nm pulses. The results are discussed in relation to theoretical estimates of the melting thresholds at the two wavelengths.
Al0.5Ga0.5As-GaAs heterojunction phototransistors grown by metalorganic chemical vapor deposition
Authors: Milano R. A. , Windhorn T. H. , Anderson E. R. , Stillman G. E. , Dupuis R. D. , Dapkus P. D.
Published: February 2003

Al0.5Ga0.5As/GaAs heterojunction phototransistors have been fabricated from structures grown by the MO-CVD process. The relatively high optical gains (∼100) and short response times (≲2 nsec) obtained with these devices indicate that an optimized AlxGa1−xAs/GaAs heterostructure phototransistor could be a suitable detector for optical-fiber-communication systems using GaAs DH lasers.
An oblique shadow deposition technique for altering the profile of grating relief patterns on surfaces
Authors: Johnson L. F. , Ingersoll K. A. , Kammlott G. W.
Published: February 2003

An oblique shadow deposition technique for altering the profile of grating relief patterns on surfaces is described. The technique essentially represents a method whereby a series of grating masks may be superimposed in precise registration with each other. By appropriate choice of deposition angle, deep grooves may be generated from shallow profiles, rounded or sinusoidal profiles may be transformed to structures with planar vertical walls, and symmetric profiles may be made asymmetric. In conjunction with ion-beam milling, the technique has been used to increase the depth of fine period gratings on GaAs and to produce grooves ∼4000 Å deep on the surface of YAG, 10 times deeper than could be obtained by ion-beam milling of photoresist.
Vapor-phase epitaxial growth of quaternary In1−xGaxAsyP1−y in the 0.75–1.35-eV band-gap range
Authors: Hyder S. B. , Saxena R. R. , Hooper C. C.
Published: February 2003

Growth of In1−xGaxAsyP1−y quaternaries on InP (100) substrates was obtained over the whole band-gap range 0.75–1.35 eV. Growth conditions and gas flow ratios are described for an open tube VPE of these quaternaries.
Anomalous noise behavior in wide-bandwidth photodiodes in heterodyne and background-limited operation
Authors: Spears D. L. , Kingston R. H.
Published: February 2003

When the frequency response of a semiconductor photodiode is limited by carrier diffusion to the junction, anomalous noise behavior can result. Although the signal current decreases, the noise current remains constant since the junction shot noise is only a function of the dc current flow. Under these conditions, there is a marked decrease in high-frequency sensitivity and the noise spectrum is not a true measure of the frequency response.
Be-implanted 1.3-μm InGaAsP avalanche photodetectors
Authors: Feng M. , Oberstar J. D. , Windhorn T. H. , Cook L. W. , Stillman G. E. , Streetman B. G.
Published: February 2003

The effect of different annealing temperatures in the 450–800 °C range on the photoluminescence of Be-implanted InGaAsP has been studied. The results of these measurements indicate that the annealing temperature should be above 700 °C for optimum lattice recovery. Avalanche photodetectors with leakage currents as low as 1 μA at 100 V and with gains ≳100 at 116 V have been fabricated. The quantum efficiency for these devices is about 65% throughout the 1.00–1.30-μm wavelength range.
Reduction of surface recombination current in GaAs p-n junctions
Authors: Casey H. C. , Cho A. Y. , Foy P. W.
Published: February 2003

Planar Zn-diffused GaAs p-n junctions have been prepared with a 2000-Å surface layer of high-resistivity O-doped Al0.5Ga0.5As. This surface layer significantly reduces the surface recombination current and permits the bulk diffusion current, I∝exp(qV/kT), to dominate at current densities as low as ∼5×10−3 A/cm2.
Controlled hydrogenation of amorphous silicon at low temperatures
Authors: Stein H. J. , Peercy P. S.
Published: February 2003

Silicon-ion bombardment of crystalline Si and hydrogen-ion implantation are used to produce high-purity amorphous Si with controlled hydrogenation at low temperatures. Hydrogen implanted into amorphous Si chemically bonds predominantly in monohydride (SiH) centers over a wide range of hydrogen concentration. Predominance of monohydride over polyhydride (SiH2) formation in bombardment-produced amorphous Si is independent of the order of hydrogenation and amorphization, and the results suggest that a high disorder level favors monohydride formation. This suggestion is supported by ion-bombardment-induced conversion of SiH2 to SiH1 centers in sputter-deposited films.
Electrical properties of indium-doped lead tin telluride
Authors: Weiser K. , Klein A. , Ainhorn M.
Published: February 2003

Starting at room temperature the Hall constant of In-doped lead tin telluride increases exponentially with inverse temperature, then decreases, and finally flattens out. This behavior is explained on the basis of autocompensation and the positive temperature dependence of the band gap.
Resistivity measurement of thin semiconductor films on metallic substrates
Authors: Hogan Steve , Wagner Sigurd , Barnes Frank S.
Published: February 2003

The resistivity of thin polycrystalline films of cadmium deposited on brass substrates has been measured by a microwave technique. The samples, of the type employed in solar-cell research, form the plane reflector of a semiconfocal Fabry-Perot millimeter-wave interferometer. The resistivity is derived by field-pertubation analysis as a simple function of the quality factors for the cavity with and without the semiconductor layer, respectively. Results are in excellent agreement with those of current-voltage measurements on samples with metallic contacts.
Stress in thermal SiO2 during growth
Authors: EerNisse E. P.
Published: February 2003

Stress present in thermal SiO2 at temperatures during growth in wet O2 has been measured as a function of growth temperature. During growth at 950 °C and below, compressive stress on the order of 7×109 dyn/cm2 is generated in the SiO2. During growth at 975 and 1000 °C, the SiO2 grows in a stress-free state. The results, which are consistent with a viscous flow point somewhere between 950 and 975 °C, are of value in avoiding mechanical failure effects in integrated-circuit processing.
Superconducting properties of i
n s
i
t
u formed Cu-V3Ga composites
Authors: Bevk J. , Habbal F. , Lobb C. J. , Harbison James P.
Published: February 2003

Cu-V3Ga composites were prepared from in situ formed multifilamentary Cu-V wires containing 20 vol.% of vanadium filaments. The highest value of the upper critical field at 4.2 K of the reacted composites was found to be 22.4 T, with a corresponding midpoint superconducting transition of 15.5 K. The overall critical-current density compares favorably with commercial V3Ga composites over the entire field range (2×105 A/cm2 at 4 T, 104 A/cm2 at 18 T).
Subharmonic energy gap structure in the Josephson radiation at 35 GHz from a superconducting thin-film microbridge
Authors: Hansen J. Bindslev , Levinsen M. T. , Lindelof P. E. , Dueholm B. , Mygind J. , Pedersen N. F. , Soerensen O. H.
Published: February 2003

Nonresonant detection of the Josephson radiation 35 GHz from a superconducting thin-film microbridge is reported. The high frequency and the accuracy of these measurements lead to a new important observation: subharmonic energy gap structure in the detected integral power. The maximum integral power measured was as large as 8×10−11 W.
Observation of fluorescence line narrowing, hole burning, and ion-ion energy transfer in neodymium laser glass
Authors: Brawer S. A. , Weber M. J.
Published: February 2003

The existence of hole burning and the degree of homogeneity in the 4F3/2→4I11/2 laser transition of Nd3+ in a silicate glass at 295 K are established by exciting the small thermal population in the 4I11/2 state with a pulsed Nd : YAG laser and observing resonant fluorescence line narrowing. Measurements of time-resolved line-narrowed 4F3/2→4I9/2 spectra show that hole filling is slow; cross relaxation rates between ions in spectrally different sites are <104 s−1 for concentrations of ⩽3 wt.% Nd2O3.
Resistivity changes in laser-annealed polycrystalline silicon during thermal annealing
Authors: Shibata Tadashi , Iizuka Hisakazu , Kohyama Susumu , Gibbons J. F.
Published: February 2003

Polycrystalline silicon layers heavily doped with phosphorus or arsenic were irradiated with a Nd : YAG pulsed laser beam. A 40–50% reduction in sheet resistivity was obtained by laser annealing. However, during subsequent heat treatments the resistivity increased to a value which was higher than the initial value before the laser anneal. The instability of the resistivity is tentatively explained by reprecipitation of dopants both within the grains and at the grain boundaries.
High-intensity subnanosecond transients from synchronously pumped submillimeter-wave lasers
Authors: Lemley W. , Nurmikko A. V.
Published: February 2003

Synchronous pumping from a mode-locked TEA CO2 laser has been used to generate high-intensity far-infrared pulses in CH3F and D2O at peak powers exceeding 100 kW. By employing an optical correlation measurement technique, pulse widths as short as 355 psec have been observed.