bluuebunny/crossref_metadata_2025 huggingface dataset:
An accelerometer/velocimeter with a range from 105g to 1010g and a time resolution of a few nanoseconds
Authors: Graham R. A.
Published: February 2003

A piezoelectric accelerometer is described which simultaneously measures acceleration and velocity for materials subjected to very rapid impulsive loading. The acceleration signal is derived from a measure of the rate of change of the short-circuited current of a piezoelectric disk in contact with the accelerated surface. The maximum acceleration which the device can measure is about five orders of magnitude greater than the maximum acceleration capability of conventional accelerometers.
High quantum efficiency photoemission from GaAs1−xPx alloys
Authors: Escher J. S. , Antypas G. A.
Published: February 2003

Photoemission from GaAs1−xPx alloys activated to negative electron affinity has been studied over the band-gap range 1.4<Eg (eV) <2.1 (0<x<0.55). Quantum yields up to 50% (electrons/incident photon) have been measured in the visible.
Photovoltaic properties of n-CdS/p-CdTe heterojunctions prepared by spray pyrolysis
Authors: Ma Yale Y. , Fahrenbruch Alan L. , Bube Richard H.
Published: February 2003

Heterojunction solar cells of n-CdS/p-CdTe have been prepared by deposition of CdS films by spray pyrolysis on single-crystal CdTe to produce solar efficiencies greater than 6% without optimization or correction for reflection loss. Cells prepared by this method therefore compare favorably with cells prepared by vacuum evaporation of CdS. In addition, the highest open-circuit voltage (0.74 V) observed to date in an efficient n-CdS/p-CdTe solar cell has been produced by this fabrication process.
Broadband generation of acoustic surface waves on GaAs by conversion from acoustoelectrically amplified bulk waves
Authors: Mishra S. , Bray Ralph
Published: February 2003

This paper describes the first observation of the generation of surface waves in a broad frequency band (0.2<f<1.0 GHz) by conversion from bulk acoustic waves. The latter are obtained by acoustoelectric amplification from thermal background in GaAs samples at 300 K. The surface waves are generated in the form of narrow propagating domains. Both group and phase velocity measurements, carried out on the principal crystallographic surfaces, served to identify the surface waves.
Decay time of twist cells with liquid crystals of shortened pitch
Authors: Aftergut S. , Cole H. S.
Published: February 2003

Chiral nematogens of natural pitch p0 and layer thickness d were investigated over the regime d<p0<4d in cells with π/2 twist imposed by wall orientation. The decay times in this regime were smaller than for p0⩾4d.
Ultrafast echotomographic system using optical processing of ultrasonic signals
Authors: Bruneel C. , Torguet R. , Rouvaen K. M. , Bridoux E. , Nongaillard B.
Published: February 2003

An ultrafast ultrasonic tomograph has been developed in our laboratory for direct observation of the living tissues inside the human body. Acousto-optic interaction is the basic principle of our system. The information carried by the acoustic wave is impressed on a light beam diffracted during the acousto-optic interaction and an optical system is used for displaying a real image of an isonified object. A first and simple realization has been used to check the principle of operation. Directions for future improvements are iscussed.
Suppression of Li2O out-diffusion from Ti-diffused LiNbO3 optical waveguides
Authors: Ranganath T. R. , Wang S.
Published: February 2003

Light guides fabricated by Ti diffusion into y-cut LiNbO3 are attractive because of the possibility of using the larest electro-optic coefficient (r33). However, the accompanying Li2O out-diffusion gives rise to unwanted guided modes which are a problem in electro-optic modulators. To overcome this problem it is necessary to reintroduce Li back into the crystal by some means. Here we report on a simplebut effective process (using Li2O) to suppress Li2O out-diffusion and realize single-mode Ti-diffused LiNbO3 light guides in a y-cut orientation. A natural extension of the above process to Ti-diffused LiTaO3 light-guiding structure should be possible.
Efficient Raman conversion of XeF laser output in Ba vapor
Authors: Djeu N. , Burnham R.
Published: February 2003

Intense Raman emission at 585 nm has been observed from Ba vapor pumped by the XeF laser. Near-unit photon conversion efficiency was measured.
Seventh harmonic conversion of mode-locked laser pulses to 38.0 nm
Authors: Reintjes J. , She C. Y. , Eckardt R. C. , Karangelen N. E. , Andrews R. A. , Elton R. C.
Published: February 2003

Seventh harmonic generation in helium is used to produce coherent light at 38 mm from laser pulses at 266.1 nm. The variation of both the fifth and seventh harmonic signals with helium pressure is described.
On the punch-through of Bloch loops in magnetic bubbles
Authors: Konishi S. , Hsu T. , Brown B. R.
Published: February 2003

Bubble translational motion in gradient drive fields has been carefully studied for both as-grown and ion-implanted films of (YEuTmCa)3(GeFe)5O12 by using the rocking method. At a critical gradient amplitude which is found to depend on the drive pulse width, the motion of a bubble in an as-grown film becomes nonreproducible as evidenced by the fuzzy appearance of the bubble. Under the same critical amplitude drive condition, the skew angle of an S=1 bubble in an ion-implanted film decreases abruptly. This is attributed to punch-through of nucleated Bloch loops. The punch-through time was measured as a function of drive, and a reasonably linear relation between the inverse punch-through time and gradient drive field was found.
Multiple liquid phase epitaxy of In1−xGaxP1−zAsz double-heterojunction lasers: The problem of lattice matching
Authors: Wright P. D. , Rezek E. A. , Holonyak N. , Stillman G. E. , Rossi J. A. , Groves W. O.
Published: February 2003

Multiple liquid phase epitaxy of In1−xGaxP1−z Asz-InP double heterojunctions, from a single set of In-rich melts, is demonstrated, and is shown to be a useful technique for the study of the problem of lattice matching at heterojunction interfaces and for growing large numbers of low-threshold (’’defect-free’’) DH laser wafers (λ∼1 μm).
Inverted-ridge-waveguide double-heterostructure injection laser with current and lateral optical confinement
Authors: Figueroa Luis , Wang Shyh
Published: February 2003

Epitaxial growth over chemically etched channels is used to fabricate inverted-ridge-waveguide (IRW) lasers with current and lateral optical confinement; the former is provided by a two-step LPE process which results in a p-n-p-n structure in regions away from the channel, and the latter by a thickness variation of the waveguide in the lateral direction. Threshold currents using broad-area contacts range from 1 A to 600 mA for 30 and 6 μm, respectively, under pulsed operation at room temperature. The lasers exhibit single filament and clear mode spectrum with currents up to 1.5 threshold currents and a linear power-current relation up to 2Ith.
Thin-film VO2 submillimeter-wave modulators and polarizers
Authors: Fan John C. C. , Fetterman Harold R. , Bachner Frank J. , Zavracky Paul M. , Parker Christopher D.
Published: February 2003

Submillimeter-wave modulators and switchable polarizers have been fabricated from VO2 thin films deposited on sapphire substrates. By passing electric current pulses through elements made from these films, the films can be thermally cycled through the insulator-to-metal transition that occurs in VO2 at about 65 °C. In the insulating state, the films are found to have negligible effect on the transmission at submillimeter wavelengths, while above the phase transition the transmission is strongly reduced by the free-electron effects characteristic of a metal. Other possible applications of such switchable VO2 elements include variable bandpass filters and diffraction grating beam-steering devices.
Enhancement of MIS solar-cell ’’efficiency’’ by peripheral collection
Authors: Godfrey R. B. , Green M. A.
Published: February 2003

Significant enhancement of the short-circuit current of small-area MIS and Schottky solar cells can occur by collection of carriers generated around the periphery of the cell. The amount of peripheral collection boost is predicted and studied experimentally. Very small-area cells (<0.02 cm2) can have their short-circuit currents boosted by over 80%. For cells over 1 cm2, the increase is generally less than 10%. These results highlight the importance of basing efficiency measurements on the total front surface area of the cell.
Power enhancement of continuous ultraviolet lasers
Authors: Lüthi H. R. , Seelig W. , Steinger J.
Published: February 2003

High-power cw laser radiation from nine Ar and five Kr laser transitions in the spectral range 275 <λ<365 nm has been generated in a highly ionized low-pressure dc discharge. The output increases without saturation up to the maximum available discharge current of 480 Å. The most intense emission is 61 W obtained from the combined 351.1- and 363.8-nm Ar III lines.
Use of electron-trapping region to reduce leakage currents and improve breakdown characteristics of MOS structures
Authors: DiMaria D. J. , Young D. R. , Ormond D. W.
Published: February 2003

A trapping layer of W (≈1014 atoms/cm2) has been deposited between 70 Å of thermal silicon dioxide grown from a polycrystalline silicon substrate and 520 Å of deposited pyrolytic silicon dioxide in an MOS structure to reduce high leakage currents and low-voltage breakdowns associated with asperities at the polycrystalline Si–thermal SiO2 interface. MOS structures without the W layer but with the pyrolytic SiO2 layer were also found to be effective. This improvement is ascertained to be due to localized electron trapping in the W or pyrolytic oxide layer at low average fields which reduces the locally high fields and therefore high dark currents associated with the asperities. At higher average fields uniform trapping is believed to be dominant. This uniform effect can also enhance the breakdown characteristics if the trapped charge is not detrapped by the applied field.
Laser fusion ion temperatures determined by neutron time-of-flight techniques
Authors: Lerche R. A. , Coleman L. W. , Houghton J. W. , Speck D. R. , Storm E. K.
Published: February 2003

Measurements have been made of the energy spectrum of neutrons emitted as a result of laser compression of D-T-filled glass microshells using a time-of-flight spectrometer. From the width of unfolded energy spectra, plasma ion temperatures of approximately 6 keV have been determined for 90-μm-diam targets irradiated with 2 TW of 1.06-μm light. The measured mean neutron energy of 14.00±0.10 MeV agrees with the expected value of 14.05 MeV.
Photoionization of He and N2 by uv radiation from a copper plasma produced by a CO2 laser
Authors: Drouet Michel G.
Published: February 2003

Measurements of the attenuation in a background gas, He or N2, of the uv radiation produced by a 1.7-ns 4-J CO2 laser irradiation of a copper target are reported. Photoionization cross sections of 0.4 Mb in He and 0.9 Mb in N2 are obtained. The photoionizing radiation is attributed to the 110.6-Å M1 transition in copper.
Determination of concentrations of donors and acceptors in GaAs by an optical method
Authors: Nam Sang Boo , Langer D. W. , Kingston D. L. , Luciano M. J.
Published: February 2003

The concentrations of donors (ND) and acceptors (NA) in a high-quality GaAs epitaxial layer sample are determined by the optical method. The numerical values of ND and NA are deduced from the limiting values of combinations of the excitation-dependent integrated emission intensities due to the conduction-band–to–neutral-acceptor, neutral-donor–to–valence-band, and neutral-donor–to–neutral-acceptor transitions.
Frost suppression in photoconductor-thermoplastic holographic recording devices
Authors: Reich S. , Rav-Noy Z. , Friesem A. A.
Published: February 2003

Our findings indicate that the frost-formation phenomenon common to many photoconductor-thermoplastic devices can be attributed to spinodal decomposition processes. This decomposition is induced by the inherent electrical field of about 106 V/cm in the plasticized and polydispersed thermoplastic melts. By using monocomponent polystyrene of sharply defined molecular weight distribution for the thermoplastic layer the frost formation is suppressed, so that holograms having high signal-to-noise ratio can be readily recorded.
Application of Monte Carlo calculation to fundamentals of scanning Auger electron microscopy
Authors: Shimizu R. , Aratama M. , Ichimura S. , Yamazaki Y. , Ikuta T.
Published: February 2003

Spatial distributions of Auger signals generated in an aluminum target in scanning Auger electron microscopy were obtained by Monte Carlo calculations including secondary electron generation. In the low-energy region, the cross sections calculated by the partial wave expansion method were used instead of the screened Rutherford cross section to describe the elastic scattering process. The result suggests that secondary electrons of high energy are a significant source of Auger signals, particularly LVV-Auger electrons, in scanning Auger electron microscopy.
Strong adhesion of vacuum-evaporated gold to oxide or glass substrates
Authors: Zydzik G. J. , Van Uitert L. G. , Singh S. , Kyle T. R.
Published: February 2003

Interposed films of CdF2, SnF2, PbF2, InF3, or BiF3 can be used to bond vacuum-evaporated gold onto oxide or glass substrates. The fluoride adheres well even when deposited at relatively low temperatures; however, except for SnF2, mp 220 °C, thin (e.g., 300 Å) gold films adhere best when the fluoride-coated substrate temperature is between 120 and 180 °C, at least initially, during gold deposition. For these cases, discontinuous growth for thin gold films is avoided by remaining well below the upper temperature. Thicker gold films (e.g., 2000 Å) adhere well and are continuous at higher temperatures.
Picosecond gain and saturation measurements of the 353-nm XeF laser line
Authors: Tomov I. V. , Fedosejevs R. , Richardson M. C. , Sarjeant W. J. , Alcock A. J. , Leopold K. E.
Published: February 2003

The spectral characteristics, temporal gain profile, and saturation energy have been measured for the 353-nm XeF laser line using a picosecond probe pulse of the third harmonic of a Nd : glass laser.
Growth of platinum silicide under protective layers
Authors: Joubert P. , Auvray P. , Guivarc’h A. , Pelous G.
Published: February 2003

Fast growth and total formation of platinum silicide can be obtained by using a chromium, silicon nitride, or sputtered silicon film to protect the platinum from the unfavorable effects of small amounts of oxygen contained in the furnace during annealing. X-ray diffraction and Rutherford backscattering analysis were used for identifying the silicides and studying their growth kinetics. The simultaneous growth of the two phases Pt2Si and PtSi was observed. The thickness of Pt2Si and PtSi increased in proportion to the square root of the annealing time with an activation energy of about 2 eV. At higher temperature (∼800 °C), solid-phase epitaxial growth (SPEG) of silicon was found in the (Si〈111〉)/PtSi/Si amorphous system.
Negative resistances in n-type CdCr2Se4 single crystals
Authors: Nakano Yukio , Mitsuzawa Kazuo , Kodama Kunihiko , Niimi Tatsuya
Published: February 2003

On a specimen of n-type CdCr2Se4 single crystals, both the current- and voltage-controlled negative resistances have been observed simultaneously at temperatures below 131 °K, while at temperatures from 131 to 198 °K, only current-controlled negative resistance had been observed; above 198 °K, neither had been observed.
Continuously operated (Al,Ga)As double-heterostructure lasers with 70 °C lifetimes as long as two years
Authors: Hartman R. L. , Schumaker N. E. , Dixon R. W.
Published: February 2003

Lifetimes longer than two years, and decreases in light output power less than 15% at constant current after one year, both at 70 °C, are reported for selected continuously operated double-heterostructure (Al,Ga)As lasers. Also, a median 70 °C lasing lifetime of 4500 h is reported for 100 lasers chosen randomly from 10 slices. This median lifetime is thought to correspond to 3.0×105 h (34 yr) of continuous operation had the devices been operated at 22 °C. The corresponding mean time to failure is 1.3×106 h (≳100 yr).
Electron and hole drift mobility in amorphous silicon
Authors: Moore A. R.
Published: February 2003

Electron and hole drift mobility have been measured in n- and p-type amorphous Si Schottky-barrier solar cells. At room temperature μdn= (2–5) ×10−2 cm2/V sec and μdp= (5–6) ×10−4 cm2/V sec. Both mobilities are trap controlled with ΔE=0.19 eV for electrons and ΔE=0.35 eV for holes above 250 °K and ΔE=0.16 and 0.26 eV, respectively, below 250 °K. Majority-carrier lifetimes are estimated to be 1 μsec for electrons and 25 μsec for holes.
Detection of excess crystalline As and Sb in III-V oxide interfaces by Raman scattering
Authors: Farrow Roger L. , Chang Richard K. , Mroczkowski Stanley , Pollak Fred H.
Published: February 2003

Raman backscattering from oxidized GaAs and InAs yielded two anomalous peaks of large scattering strength which we have concluded to be from excess As in the interface between the oxides and underlying semiconductors. Similarly, we concluded that the two anomalous peaks from GaSb and InSb are from excess interface Sb. From the frequencies, line shapes, and polarization selection rules, we deduced that the excess As and Sb are in the crystalline semimetal phase, as distinct from the amorphous phase.
Effect of O2 pressure during deposition on properties of rf-sputtered Sn-doped In2O3 films
Authors: Fan John C. C. , Bachner Frank J. , Foley George H.
Published: February 2003

The electrical and optical properties of rf-sputtered Sn-doped In2O3 (ITO) films have been found to depend strongly on the O2 partial pressure during deposition. For the sputtering conditions used, films with both low electrical resistivity (ρ ∼ 3 × 10−4 Ω cm) and high visible transmission (∼ 90%) were obtained only over a narrow range of O2 pressures, from 3 × 10−5 to 4 × 10−5 Torr. Our results appear to explain the difficulties that have previously been encountered in obtaining high-quality ITO films, and indicate that control of the O2 pressure during deposition is essential for reproducible preparation of such films.
A correlation method for estimating wave-number spectrum moments of fluctuations
Authors: Iwama Naofumi , Tsukishima Takashige
Published: February 2003

The covariance function of a stationary and homogeneous random field, represented by an analytic signal, is related to its wave-number spectrum moments. By using a pair of fixed probes with an appropriately small separation, one can estimate the mean wave number and the wave-number spectral spread. This method may be useful for the experimental study of fluctuation phenomena in plasmas, fluids, etc.
Studies of Ca+ implanted Mo foil by means of work-function measurements and AES
Authors: Ishida Tadashi , Sato Mamoru , Fukui Kiyoshi , Ueda Kazuyuki
Published: February 2003

In order to make a new alloy an electron emitter, several samples of Mo foils implanted with Ca+ ions were prepared. The range distributions of Ca in Mo were investigated by the use of Auger electron spectroscopy (AES) combined with Ar ion sputtering. At the same time the correlation between the surface components and the photoelectric work functions of the sample was also investigated during the sputtering. In preliminary experiment the work function of Mo foil was decreased about 1 eV due to the implantation of Ca+ ions to the amount of 1×1017 ions/cm2.
Nonlinear optical susceptibilities of AlN film
Authors: Fujii Y. , Yoshida S. , Misawa S. , Maekawa S. , Sakudo T.
Published: February 2003

The nonlinear optical coefficients of AlN have been determined as ‖d33‖= (23.2±35%) dQ11 and ‖d31‖ ≲0.04‖d33‖ for the c-plate film and for a fundamental beam at 1.064 μm. The result is discussed with reference to the bond-charge model.
The determination of plasma Z-pinch effect by intrinsic stimulated emission
Authors: Lue Juh Tzeng , Liang Jen Min
Published: February 2003

The plasma Z-pinch behavior has been observed in a relatively small-bore diameter tube and low bank voltage discharge system. The instant of the occurrence of the laser line at 4880 Å coincides with the plasma pinch time calculated by using a one-fluid snow-plow model. A determination of plasma pinch parameters by measuring the intrinsic stimulated emission of the ions is described.
Characterization of an ultradense reproducible Z pinch
Authors: Dusto D. , Rockett F P. D. , Stee D. G. , Ackenhusen F J. G. , Bach D. R. , Duderstadt J. J.
Published: February 2003

The apparent complexity of the laser-plasma coupling in laser fusion target irradiation has stimulated the need for carefully controlled experimental studies of the laser-plasma interaction at the critical surface. A helium Z pinch has been constructed which produces a high density plasma, independent of the laser, enabling the separation of the laser-plasma interaction physics from the plasma formation mechanism. Its peak electron density (4×1019 cm−3), critical density scale length (70–200 μ), and temperature (∼25 eV) make it suitable for simulating and studying laser-pellet interaction mechanisms at CO2 laser wavelengths. Detailed numerical modelling of these experiments was employed as a check against our diagnostics, as well as providing physical insight in those ranges of experimental parameters where measurements were not made.
A study of Cd diffusion into PbTe and Pb1−xSnxTe crystals using Hall-effect conductivity and Cd solubility measurements
Authors: Silberg E. , Zemel A.
Published: February 2003

Hall-effect, conductivity, and solubility measurements were carried out on Cd-diffused PbTe and Pb1−xSnxTe single crystals, doped under various Cd vapor partial pressures between 10−4 and 10−1 Torr. Most of the diffused Cd atoms are found to distribute uniformly as an electrically inactive impurity in the crystal lattice and only a small fraction act as active donors, most probably through metal vacancy sites. Saturation in electron concentration is observed at the high Cd partial pressures which can be related to the excess metal point-defect concentration of the as-grown cooled crystals.
Optical properties of mixed-oxide WO3/MoO3 electrochromic films
Authors: Faughnan Brian W. , Crandall Richard S.
Published: February 2003

The electrochromic optical absorption of mixed-oxide WO3/MoO3 amorphous films occurs at higher energy than either pure oxide alone. The systematics of the energy shifts as a function of MoO3 concentration and coloration density is determined. The data is explained by the intervalency charge-transfer model if we assume that electrons trapped at Mo6+ ions lie 0.73 eV deeper than electrons on W6+ ions. Measurements of electron diffusion in mixed oxides support this hypothesis. The maximum absorption peak of mixed oxides is 2.15 eV compared with 1.4 eV for WO3. This is close to the peak in eye sensitivity, thereby leading to improved electrochromic display devices.
A monolithic series-array solar-cell system
Authors: Warner Raymond M. , Murray Eileen M. , Smith Wiley K.
Published: February 2003

By combining solar-cell technology and the dielectric-isolation technology that was developed in the early 1960’s for integrated circuits, we have fabricated monolithic series-connected multicell arrays. Prototype devices have exhibited an efficiency of 8%.
Dopant profiles determined from enhancement-mode MOSFET dc measurements
Authors: Buehler M. G.
Published: February 2003

Simplified algorithms are described which allow the determination of the dopant profile in the gate region of a four-terminal enhancement-mode metal-oxide-silicon field-effect transistor (MOSFET). The method calls for the dc measurement of the source-body voltage VSB as a function of the gate-source voltage VGS for a fixed minority-carrier channel current. The profile depth is proportional to dVSB/dVGS and the dopant density is inversely proportional to d2VSB/dV2GS. Only the oxide and silicon dielectric constants and the oxide thickness are needed in the computations. The data acquisition was computerized and includes the use of an operational amplifier circuit. The method is illustrated by the profile of a phosphorus layer implanted in an n-type silicon substrate.
Dislocation pinning effect of oxygen atoms in silicon
Authors: Hu S. M.
Published: February 2003

A definitive proof has now been obtained of the existence of a dislocation pinning effect by oxygen atoms in silicon. Ambiguities caused by uncertain material variables in different crystals or different parts of a crystal are avoided in this investigation by making oxygen out-diffusion from a wafer, creating a continuous variation of oxygen concentration in a ∼60-μm-deep surface layer. Dislocation movement at different depths of this layer was studied using indentation dislocation rosettes (IDR) on a 2° beveled surface. The method of IDR is uniquely suitable for this study because microdislocation half-loops are generated and confined to move within each ∼10-μm-deep layer in a series of precisely determined microregions down the bevel. The size of IDR increases steadily toward the sample surface, in good correlation with the steady decrease of oxygen concentration toward the same sample surface. The effect at the maximum oxygen concentration in this case increases the critical resolved shear stress in silicon by a factor of 4. This is a most beneficial effect in reducing thermal slip in the practical matter of silicon wafer processing.
Effects of 30-GeV-proton irradiation on the critical currents of NbTi multifilament wire
Authors: Snead C. L. , Nicolosi L. , Tremel W.
Published: February 2003

Multifilamentary wires of NbTi have been irradiated at 4.2 K with 30-GeV protons and the changes in critical current Ic measured in situ in fields up to 4 T. Reductions of Ic of 20% were found for a fluence of 1.5×1018 p/cm2. Annealing to room temperature recovers 60–70% of the Ic degradation. The decrease in Ic is attributed to an increase in the Ginzburg-Landau parameter κ of cell cores relative to the dislocation cell walls, thereby lowering the pinning strength of the cell walls. This increase in κ is directly related to an increasing radiation-induced normal-state resistivity. A saturation of the decreases in Ic is indicated for low-temperature proton irradiation in keeping with an observed saturation following high-fluence ambient-temperature neutron irradiation. Evidence is presented indicating that multiple annealing over the fluence life of a NbTi magnet operating in a radiation field will minimize the accumulated reduction in Ic.
ZnO/Si SAW convolver with surface-controlling junctions
Authors: Arimoto Y. , Moriizumi T. , Yasuda T.
Published: February 2003

A new type of ZnO/Si monolithic convolver has been constructed for the purpose of eliminating unstable memory effects due to the traps in ZnO or due to the SiO2/Si interface states. It has controlling p-n junctions on the Si surface. It was experimentally verified that by varying the junctions bias, the convolution output can be controlled with a rapid response time and without any hysteresis. The applications of this device to a matched filter have been also demonstrated.
N2 laser (1 bar) induced micro metal plasma capable of igniting combustible mixtures
Authors: Herden W. , Bloss W. H.
Published: February 2003

On the surface of a Cu target irradiated by a uv N2 laser (TEA, pulse duration 300 ps, peak power 1 MW) a metallic plasma is generated due to the high brightness of the laser operating at atmospheric pressure. An interferometric study also using subnanosecond pulses from a N2 laser (1 bar) demonstrates the development of shock wave and plasma with high temporal and spatial resolution. The plasma with an initial pressure of 2000 bar and a temperature of 30 000 K is capable of igniting a combustible mixture of CH4-O2. A new method for optical synchronization is well proved, delivering pictures as soon as 30 ns after plasma onset.
An antenna-coupled photovoltaic detector
Authors: Hwang Tien-Lai , Schwarz S. E.
Published: February 2003

An infrared receiving antenna has been used to couple 3.39-μ radiation into an InSb photovoltaic detector. Use of antennas as noiseless collectors of radiation can potentially increase detectivity in many infrared detectors.
Threshold power density measurements for electron-beam sustained discharge excitation of XeF and KrF
Authors: Fisher Charles H. , Center Robert E.
Published: February 2003

Threshold power densities for electron-beam-stabilized discharge excitation of XeF and KrF lasers are reported for Ar+Kr+F2 and Ar+Xe+NF3 gas mixtures at 1 atm. Stable discharges were obtained with these gas mixtures for times greater than 0.5 μsec with lasing pulse width as long as 0.5 μsec. An analysis of data for several different pump power densities is presented which indicates that the threshold pump power density varies inversely with the cavity buildup time.
Single longitudinal mode operation of diode lasers
Authors: Scifres D. R. , Burnham R. D. , Streifer W.
Published: February 2003

We report single longitudinal mode operation of conventional double-heterostructure GaAs/GaAlAs diode lasers achieved by heavy p-type doping of the active region. At 77 °K a broad-area device pumped with a rectangular current pulse exhibited single longitudinal mode operation up to 2.8 times threshold, which was the limit of the pulser. With a triangular pumping pulse at 300 °K, the same laser ran single longitudinal mode up to 1.4 times threshold. We believe these results can be explained by the absence of hole injection, which eliminates spatial hole burning caused by the slowly diffusing injected holes.
The effect of electron-beam aluminization on the Si-sapphire interface
Authors: Goodman Alvin M. , Weitzel Charles E.
Published: February 2003

We have used extended-range MIS C (V) measurements of Al-sapphire-Si capacitor structures to study the effect of metallization in an e-beam (electron-beam) evaporator on the Si-sapphire interface. Our results show that (1) this step causes the development of positive charge at or near the Si-sapphire interface, and (2) the charge is partially but not entirely removed by annealing at 400 °C in forming gas. We believe that the observed positive charge is due to (1) generation of electron-hole pairs in the sapphire by ionizing radiation (probably soft x rays) emanating from the e-beam evaporation unit, and (2) more effective trapping of holes than electrons within the sapphire. These results have important implications for CMOS/SOS technology.
In1−xGaxAs-GaSb1−yAsy heterojunctions by molecular beam epitaxy
Authors: Sakaki H. , Chang L. L. , Ludeke R. , Chang Chin-An , Sai-Halasz G. A. , Esaki L.
Published: February 2003

Smooth films of n-In1−xGaxAs and p-GaSb1−yAsy were grown by molecular beam epitaxy. As a function of the compositions, x and y, the lattice constants vary linearly while the energy gaps show a downward bowing. Abrupt heterojunctions made of these alloys with close lattice matching exhibit a series of current-voltage characteristics which change from rectifying to Ohmic as x and y are reduced. The relative location of the band-edge energies of the two semiconductors at the interface is shown to account for the unusual characteristics observed experimentally.
GaAs directional-coupler switch with stepped Δβ reversal
Authors: Leonberger F. J. , Bozler C. O.
Published: February 2003

A GaAs electro-optic waveguide switch in which the power isolation in both switch states can be electrically optimized has been demonstrated. The devices exhibit up to 25-dB power isolation in both states, with total power output constant to within ⩽0.3 dB. The device is formed on one chip and consists of two equal-length directional-coupler switches in series separated by a 25-μm gap. This structure permits the sign of Δβ, the electro-optically induced propagation constant difference between the guides, to be reversed midway along the device length. The loss associated with propagation across the waveguide gap is small (⩽0.2 dB), suggesting that similar gaps could be used to electrically isolate waveguide devices on a common substrate in future GaAs-based integrated optical circuits.
Bubble-collapse and stripe-chop mechanism in magnetic bubble garnet materials
Authors: Gallagher Timothy J. , Humphrey Floyd B.
Published: February 2003

The mechanism by which bubble domains collapse and stripe domains chop has been observed in magnetic bubble garnet materials. Single 10-nsec-exposure transient pictures taken during the collapse process show that the mechanism of stripe chop and bubble collapse is dominated by the formation of a head-on wall structure which is nucleated, presumably at one surface, and propagates through the film. In collapsing bubbles, the structure can form before the unstable equilibrium radius is reached. For long stripes in both implanted and as-grown films, it does not form uniformly along the stripe; thus, sections of stripe will chop to form bubbles. The head-on wall structure is statically unstable and can only persist for tenths of microseconds.
Interlayer diffusion in InSb/GaSb superlattice structure grown by multitarget rf sputtering
Authors: Eltoukhy A. H. , Zilko J. L. , Wickersham C. E. , Greene J. E.
Published: February 2003

The rate of interlayer diffusion during annealing of InSb/GaSb superlattice structures with layer thicknesses ranging from 12.5 to 50 Å has been investigated. The films were grown by multitarget rf sputtering on InSb-coated Corning 7059 glass slides. The InSb underlayers were deposited at 320 °C and were approximately 300 Å thick. The multilayer films had a total thickness of ∼1 μm and were grown at either 200 or 250 °C in an Ar sputtering pressure of 15 mTorr (2 Pa). Prior to annealing the samples were encapsulated in a 1000-Å-thick rf sputtered overlayer of In2O3. InSb/GaSb interlayer diffusion was investigated using x-ray diffraction techniques in which the intensity of satellite peaks around the Bragg reflection peaks were monitored as a function of annealing time. A diffusion coefficient of 4.5×10−21 cm2/sec was determined for an annealing temperature of 320 °C.
Fabrication of long fibers by an improved chemical vapor deposition method (HCVD method)
Authors: Akamatsu Takeshi , Okamura Koji , Ueda Yoichi
Published: February 2003

An improved (CVD) method was developed to fabricate long fibers. He gas mixed with O2 and raw material vapors were introduced into the CVD gas system to increase the deposition rate. This produced a sixfold increase compared to the conventional method. In addition to GeO2, a small amount of P2O5 was added as a dopant to the fused silica to lower the fusion temperature of the deposited soot and minimize tube deformation during the deposition process. Step index fibers 8.5 km long were prepared. These exhibited a mean loss of 4.4 dB/km at a wavelength of 0.85 μm. The outer and the core diameters were 125 and 62.5 μm, respectively.
Extrinsic photoconductivity in high-resistivity GaAs doped with oxygen
Authors: Tyler E. H. , Jaros M. , Penchina Claude M.
Published: February 2003

We report photoconductivity measurements on melt-grown high-resistivity GaAs : O, taken at 80, 190, 275, and 295 K. The data are shown consistent with a model involving an impurity-to-conduction band transition. The impurity binding energy is found at 0.69 eV from the conduction band, at 0 K. This energy decreases with increasing temperature. The data also indicate a Franck-Condon shift of 0.14 eV and a center of axial or lower symmetry. These results enable us to link our observations to earlier reports on GaAs : O and to conclude that they all refer to the ’’0.75-eV’’ center associated with the presence of oxygen.
Geodesic lenses in single-mode LiNbO3 waveguides
Authors: Chen Bor-Uei , Marom Emanuel , Lee Archie
Published: February 2003

A waveguide geodesic lens formed in a single-mode Ti-diffused LiNbO3 waveguide is reported. The paraxial focal length of the geodesic lens fabricated was 1.1 cm. In addition, a novel technique for ultrasonic impact grinding of profiles of arbitrary shape was developed. The paper describes the first single-mode geodesic lens fabricated in a LiNbO3 substrate.
A method for focusing scattered energy in laser fusion
Authors: Kriegsmann Gregory A.
Published: February 2003

When a laser beam impinges upon a plasma pellet, a sizeable portion of the incident energy is scattered away. This refraction is primarily caused by the electron density gradient. However, by enclosing the pellet in a metal cavity some of the scattered energy can be focused back into the plasma. When the electron density is spherically symmetric, overdense, and sufficiently steep, an optimal cavity can be constructed. This cavity transforms the scattered wave into a converging spherical wave. This wave penetrates up to the critical surface and according to the classical theory should give the most absorption.
Controlled barrier height InP Schottky diodes prepared by sulfur diffusion
Authors: Coleman J. J.
Published: February 2003

Schottky barrier diodes with adjusted effective barrier heights have been obtained by diffusing sulfur into n-type InP to form a shallow highly doped layer at the surface. The necessary geometry and doping conditions for achieving lowered barrier heights are described and the experimental procedure for the diffusion of sulfur in InP is outlined. Data are presented on several devices having different surface layer impurity concentrations and effective barrier heights.
LPE In1−xGaxP1−zAsz (x∼0.12, z∼0.26) DH laser with multiple thin-layer (<500 Å) active region
Authors: Rezek E. A. , Holonyak N. , Vojak B. A. , Stillman G. E. , Rossi J. A. , Keune D. L. , Fairing J. D.
Published: February 2003

A liquid-phase-epitaxial (LPE) double-heterojunction (DH) laser structure with an ∼1-μm ’’active region’’ consisting of ≳20 In1−xGaxP1−zAsz and InP lattice-matched thin layers is described. The thin-layer dimensions are small enough (<500 Å) to make quantum size effects relevant.
Magnetoelastic surface wave propagation in a low-anisotropy rare-earth–iron compound at 80 MHz
Authors: Webb D. C. , Davis K. L. , Koon N. C. , Ganguly A. K.
Published: February 2003

Propagation of 80-MHz surface acoustic waves on a single-crystal substrate of Ho0.58Tb0.20Dy0.22Fe2 in the presence of a magnetic field is reported. Phase velocity changes of 2%, accompanied by attenuation changes in excess of 30 dB, have been observed by varying the applied magnetic field. Measurements of velocity and attenuation variation with field magnitude and direction are presented along with qualitative explanations of the observed experimental behavior.
Anomalous dielectric behavior and reversible pyroelectricity in roller-quenched LiNbO3 and LiTaO3 glass
Authors: Glass A. M. , Lines M. E. , Nassau K. , Shiever J. W.
Published: February 2003

Vitreous LiNbO3 and LiTaO3 have been prepared by roller quenching these compositions from the melt. The transparent glasses exhibit pronounced dielectric anomalies with peaks of ε≳105 close to the crystallization temperature which are not characteristic of the crystalline phase. Pyroelectricity is induced after cooling the glass in an electric field. The data are discussed in terms of a simple theoretical model for amorphous ferroelectricity and interfacial polarization due to localized ionic motion.
Selective area growth of GaAs/AlxGa1−xAs multilayer structures with molecular beam epitaxy using Si shadow masks
Authors: Tsang W. T. , Ilegems M.
Published: February 2003

Selective growth of patterned GaAs and AlxGa1−xAs thin-film structures with well-defined optically smooth mirrorlike edges has been achieved with a Si-mask shadowing technique for molecular beam epitaxy. Single and multilayer stripe-mesa waveguides with widths as narrow as 1 μm, two-dimensional waveguide tapers, and various other epilayer patterns have been fabricated using single-level or multilevel masking. This technique has potential for use in the realization of integrated optoelectronic circuits in the GaAs/AlxGa1−xAs system.
Intensity variations in Auger spectra caused by diffraction
Authors: Chang C. C.
Published: February 2003

Auger spectra from a Si (111) surface with about 10 Å oxide were utilized to demonstrate that diffraction can cause Auger intensity changes of a factor of 2 even in data acquired using the cylindrical mirror analyzer. The diffraction mechanism was revealed by a comparison of spectra taken before and after small changes in crystal orientation and noting that Auger peaks from the amorphous surface oxide did not change amplitude significantly while peaks from the crystalline Si changed by large amounts. Diffraction of the ejected Auger electron was an important process because relative intensity changes among peaks within a single ionization series were large. The collected electron image resembling a Kikuchi pattern visible in the scanning mode of the Auger apparatus was used for accurately orienting the crystal.
Temperature effects on quartz-crystal surface-wave oscillators
Authors: Hauden D. , Michel M. , Bardeche G. , Gagnepain J.-J.
Published: February 2003

A theoretical study of the temperature frequency dependence of a quartz-crystal oscillator using surface-wave delay lines is performed and enables one to obtain the first- and second-order frequency temperature coefficients. These theoretical results are in agreement with the corresponding available experimental values, corresponding to ST and Y cuts. A new zero first-order temperature coefficient cut is presented.
Auger coefficients for highly doped and highly excited silicon
Authors: Dziewior J. , Schmid W.
Published: February 2003

The recombination kinetics in highly doped p- and n-type silicon has been investigated at 77, 300, and 400 K through the radiative band-to-band recombination. The minority-carrier lifetime depends quadratically on the doping concentration as expected for Auger recombination. The Auger coefficients at 300 K for p- and n-type silicon are found to be Cp=9.9×10−32 cm6 s−1 and Cn=2.8×10−31 cm6 s−1. They are nearly independent of temperature in the range investigated. The Auger coefficient in highly excited pure silicon at 4.2 K (electron-hole drops) is essentially the same as in highly doped silicon.
Long-lifetime photoconductivity effect in n-type GaAlAs
Authors: Nelson R. J.
Published: February 2003

A long-lifetime (τ∼hours, T≲60 °K) photoconductivity effect is observed in Te-doped Ga1−xAlxAs (0.25≲x≲0.7). Analysis of Hall-effect data showing a pronounced decrease in the electron mobility upon photoexcitation shows that a donor level is involved. Similar effects are observed in Se- and Sn-doped Ga1−xAlxAs (x=0.3). The magnitude of the effect which is typically of the order of the room-temperature electron concentration seems to correlate linearly with the concentration of Te, showing that a constant concentration background impurity is not responsible for this effect. A large lattice relaxation is indicated by the large difference between the thermal (0.12 eV) and optical (1.1 eV) ionization energy of the donor level. The potential barrier to electron capture by the donor level is estimated to be 180 meV (x=0.36) from time decay measurements of the photoexcited electron population at low temperatures. Extrapolation to room temperature gives a characteristic decay time of ∼0.5 nsec for the electron concentrations expected in injection lasers.
Analytic approximations for the Fermi energy of an ideal Fermi gas
Authors: Joyce W. B. , Dixon R. W.
Published: February 2003

An important function in semiconductor-device analysis and transport theory is the widely tabulated Fermi-Dirac integral, ℱ (η) =2π−1/2ℱ∞0[exp(x−η)+1]−1f dx, f=x1/2, which relates, for example, the Fermi energy ηkT to the carrier density N=ℱN0 in a parabolic semiconductor band (N0=effective density of states). We show that the classical or Boltzmann approximation to this integral (η=lnℱ, η≲−2) is extended to cover the Fermi-energy range of semiconductor lasers (η≲+2) by the expression η=lnℱ+2−3/2ℱ and by other simple differentiable approximations applicable to higher degeneracy (η≲7) or to nonparabolic bands (f≠x1/2).
Tunable damage-resistant polarization rotator for ultraviolet and visible laser radiation
Authors: Garetz B. A. , Hall G. E. , Kenney-Wallace G. A.
Published: February 2003

A 90° polarization rotator for use at 347 nm was constructed and successfully tested at peak intensities in excess of 15 MW cm−2. This liquid optical rotatory device (LORD) employs aqueous solutions of sucrose to rotate the plane of polarization of the incident beam, may be tuned to other incident wavelengths, and should be widely useful for applications involving both tunable dye lasers and high-power lasers.
Electron kinetics in the KrF laser
Authors: Long W. H.
Published: February 2003

At fractional electron densities typical of e-beam-stabilized KrF laser discharges, electron-electron collisions are shown to play a significant role in determining the metastable production rates and electron transport properties. The major effect is to reduce the E/N for optimum laser pumping, which is consistent with experimental observation. The laser quantum efficiency under discharge pumping is shown to be about 36% compared to direct e-beam pumping at 26%.
Isolated optical Ramsey fringes in the 32S–42D two-photon transitions of sodium
Authors: Salour M. M.
Published: February 2003

By inducing a 90° phase shift between pairs of coherent time-delayed laser pulses, and taking the difference between the fluorescence resulting from pairs of coherent pulses with and without the phase shift, we have eliminated the diffraction background and isolated the Ramsey’s interference fringes in the profile of Doppler-free two-photon resonances. This technique also offers enormous improvement for other situations in which interference fringe contrast is poor.
A scheme for evaluating T
e/T
i and Z̄ by light scattering
Authors: Bretz Norton L.
Published: February 2003

When highly ionized impurities are present in a plasma, the scattered spectrum of the major ion species can be distorted in a complicated way. A method is given by which Te/Ti and Z̄ (≡𝒥njzj2/ne) can be measured which does not require any knowledge of the mass, charge state, or concentration of the impurity species. A generalization of the Salpeter approximation for the integrated cross section is proven. The result is that the total cross section is a function of α (≡ 1/KλD), Te/Ti, and Z̄ as long as the temperature of all ion species is the same and Te/Ti is not too large. Thus a measurement of the integrated ion cross section at two different scattering angles can yield Te/Ti and Z̄. This method is insensitive to magnetic fields and to moderate electron drifts. For 1≲Te/Ti, Z̄≲3 the cross section must be measured to an accuracy of about 3% to give Te/Ti to within 10% and Z̄ within 20%.
Phase tuning in optical directional coupler by photostructural effect of chalcogenide glass film
Authors: Mikami Osamu , Noda Juichi , Zembutsu Sakae , Fukunishi Shuzo
Published: February 2003

A new phase-tuning method for an optical directional coupler is proposed. The method involves using the refractive-index change induced by a light exposure (<0.5 μm) of (Se-S) -based chalcogenide glass film loaded on the waveguides. The light coupling in a directional coupler, fabricated in a c-plate LiNbO3, was changed from 95 to 15% by irradiation of a halogen lamp.
Optical fiber taper couplers: Diameter and slope measurements
Authors: Marom E. , Rourke M. D.
Published: February 2003

The transmitted light from side-illuminated transparent optical fiber taper couplers is analyzed. A direct measure of the slope and the diameter variations of the taper is obtained with ease from the deflected (refracted) beam and the displayed far-field diffraction pattern.