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Applied Physics Letters

Issue 4 • Date Feb 1980

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Displaying Results 1 - 25 of 47
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Be‐implanted (GaAl)As stripe geometry lasers

    Page(s): 233 - 235
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    (GaAl)As double‐heterostructure stripe geometry lasers have been fabricated using Be ion implantation. Pulsed threshold currents as low as 21 mA have been found. The light‐vs‐current characteristics were kink‐free up to 10 mW output power and the measured differential quantum efficiency was 45%. View full abstract»

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  • A cw x‐ray preionizer for high‐repetition‐rate gas lasers

    Page(s): 235 - 237
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    Continuous‐wave x‐ray exposure was first used as a preionizer on a pulsed‐discharge HF laser. We investigated experimentally the preionization effect of this cw x‐ray preionizer on a pulsed HF laser. Although the cw x‐ray preionizer resulted in a characteristic performance similar to that of the flash x‐ray preionizer, the cw x‐ray generator has a much larger dose than a flash x‐ray generator. Applicability of a cw x‐ray preionizer to a high‐repetition‐rate pulsed laser was discussed. View full abstract»

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  • MOS rib waveguide polarizers

    Page(s): 237 - 240
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    The transmission properties of single‐heterostructure GaAs‐AlxGa1-xAs rib waveguides (RWG) clad with thin anodized oxides (0–200 Å) covered by gold (MOS structures) are investigated both theoretically and experimentally. Efficient polarizers having extinction ratios of 35 dB and insertion losses ≪1 dB can be achieved with short (250 μm) polarizing sections. Details of attenuation characteristics depend on the dielectric constants and can be used to investigate the dielectric interface properties of MOS structure. View full abstract»

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  • Self‐sustained pulsations in GaInAsP diode lasers

    Page(s): 240 - 242
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    Self‐sustained pulsations in light output have been observed for several GaInAsP double‐heterostructure lasers. Although these pulsations are similar to those occurring in AlGaAs lasers, their rate of incidence is much lower and their occurrence does not appear to be increased by aging, in marked contrast to observations for AlGaAs lasers. Most of the GaInAsP lasers exhibiting pulsations appear to have come from a small region of one wafer, suggesting that the pulsations are related to defects originating in the growth process or subsequent fabrication procedures. View full abstract»

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  • The effect of ground state population on the XeF laser performance

    Page(s): 243 - 245
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    In this letter we describe an investigation of the effect of the bound ground state of XeF on the laser performance. This was accomplished by observing the intensity of the sidelight fluorescence of the B (v′=0) →X (v=3) as a function of laser flux at 353 nm. Our data indicate that the ground state dissociates more rapidly as the laser mixture temperature is increased from 300 to 500 °K. As a result of the faster dissociation rate at 500 °K, the XeF laser efficiency increases by ≈1.5 as the mixture temperature is increased from 300 to 500 °K. View full abstract»

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  • Frequency‐modulated shot noise limited stimulated Raman gain spectroscopy

    Page(s): 245 - 247
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    We demonstrate for the first time an electro‐optic frequency‐modulated stimulated Raman gain laser system which achieves shot noise limited detection. The frequency modulation technique reduces the otherwise large thermal background produced by absorbing substrates by a factor of 104–105, thereby permitting the full use of the ultrahigh sensitivity which is sufficeint to observe the vibrational spectroscopy of monolayers. View full abstract»

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  • Intensity self‐pulsations in (GaAl)As injection lasers operating in an external cavity

    Page(s): 248 - 250
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    We present an experimental and theoretical study of a self‐pulsing (GaAl)As injection laser operating in an external cavity. We have observed suppression of the self‐pulsations when the external cavity is in the range 6≪L≪10 cm. Suppression of self‐pulsations can also be obtained by using a multimode graded index optical fiber as the external resonator. These results can be explained by a model which includes the effects of an external cavity and electron trapping. For long cavity lengths, the self‐pulsation frequency locks to an external cavity harmonic with no significant quenching, as observed in some earlier experiments. View full abstract»

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  • Implementation of a novel procedure to optimize electron optical systems through the use of orthogonal functions

    Page(s): 251 - 253
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    It is shown how Fourier‐Bessel series solutions published recently, representing the electric potential in various electrostatic electron optical configurations with rotational symmetry, can be used in a constrained optimization procedure through which local minima of an aberration function A=A (B1, B2, ...) can be found by direct search or by descent methods. The variables Bi are Fourier coefficients. As a simple illustration, a Bessel Box with a coaxial annular aperture is obtained, which produces a tangential ray image of low field curvature and distortion. Optimization with respect to both paraxial and zonal focal properties can be carried out, because the method is not restricted by the use of the paraxial ray equation. The procedure can be applied to one‐foil, and open systems. View full abstract»

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  • Picosecond signal processing with planar, nonlinear integrated optics

    Page(s): 253 - 255
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    The convolution of picosecond optical signals is demonstrated via the nonlinear mixing of guided waves in a Ti in‐diffused LiNbO3 waveguide. Various applications are discussed. View full abstract»

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  • A new surface‐wave acousto‐optic time integrating correlator

    Page(s): 256 - 258
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    A new realization of the acousto‐optic time‐integrating correlator has been constructed. The new device uses a surface‐acoustic‐wave delay line and is configured so that no separate reference beam is required for coherent detection. Instantaneous bandwidths of 30 MHz and integration times of 30 ms have been achieved. Broadband signals, such as pseudonoise biphase modulated waveforms, with signal‐to‐noise ratios of -40 dB have been detected. In addition, center frequency, bandwidth, and relative time‐difference‐of‐arrival of these signals can be determined. View full abstract»

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  • Observation of a second bulk compressional wave in a porous medium at ultrasonic frequencies

    Page(s): 259 - 261
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    A second bulk compressional wave has been observed in a water‐saturated porous solid composed of sintered glass spheres using an ultrasonic mode conversion technique. The speed of this second compressional wave was measured to be 1040 m/sec in a sample with 18.5% porosity. The theory of Biot, which predicts two bulk compressional waves in porous media, provides a qualitative explanation of the observations. To the author’s knowledge, this type of bulk wave has not been observed at ultrasonic frequencies. View full abstract»

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  • Destruction of ground state XeCl molecules by HCl and rare gas collisions

    Page(s): 262 - 264
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    Rate constants for quenching of several XeCl (X) vibrational levels by the rare gases and HCl have been measured. The temporally resolved decay of the population densities of the XeCl (X, v=0–2) levels was monitored using a frequency‐doubled tunable dye laser. Within experimental error, the measured rate constants did not vary with vibrational number, and the temperature dependence of the rates over the range 300⩽T⩽375 °K was found to be consistent with the previously measured XeCl (X) dissociation energy (∼250 cm-1). The rate constants for the destruction of XeCl (X, v=0) state molecules by HCl, Xe, Ar and Ne at 300 °K were determined to be (2.20.5) ×10-11, (5.60.8) ×10-12, (0.60.06) ×10-13, and (1.00.15) ×10-13 cm3 sec-1, respectively. View full abstract»

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  • Injection and containment of an unneutralized electron cloud in a bumpy toroidal magnetic field

    Page(s): 264 - 266
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    We report on the successful injection, compression, and confinement of an unneutralized electron cloud in a multiple‐mirrored toroidal magnetic field geometry. About 2×1012 electrons were compressed to maximum energy of 500 keV. The lifetime of the cloud was limited by the decaying magnetic field. During its lifetime, the cloud was found to perform m=1 diocotron oscillations. Two injectors were operated in two separate mirror cells, and their mutual interaction was studied. View full abstract»

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  • Carbon segregation and arc damage of tungsten electrodes

    Page(s): 266 - 268
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    Eruptions that occur on tungsten electrodes after repeated 35‐A arcs of 1.44‐msec duration have been studied with a scanning Auger microprobe and found to contain high concentrations (20–30 at.%) of carbon. This is much greater than the average carbon concentration in the tungsten and is in the vicinity of the W‐W2C eutectic at 25 at.%. Further evidence that the eruptions are rich in W2C comes from their solubility in hot HNO3. Therefore it appears that carbon progressively segregates in the arc spots due to its low solid solubility in tungsten and the resultant lowering of the melting point is responsible for the eruptions. View full abstract»

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  • Experimental evidence of hydrodynamic instabilities in laser driven implosions

    Page(s): 269 - 270
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    Aluminium coated microballoons have been imploded by a two‐beam short‐pulse Nd laser. The plasma has been examined by space‐resolved x‐ray spectroscopy which shows that x‐ray lines from the aluminium appear in emission from the implosion core. This suggests that the targets are hydrodynamically unstable, which is contrary to expectation for this exploding pusher mode. Possible experimental errors are eliminated. View full abstract»

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  • Experimental temperature and time dependence of implantations: Al in Zn

    Page(s): 271 - 272
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    The range profiles of 60‐keV Al→Zn implantations at 25 and -196 °C were measured as a function of time with the intention to test the time and temperature dependence of the implantation. The probing was carried out using the ( p,γ) resonance broadening method. The 25 °C profile was observed to have an increasing surface peaking as a function of time, while by decreasing the target temperature during the implantation to -196 °C, the peaking was avoided. View full abstract»

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  • Stability study of laser irradiation of silicon diffused with arsenic

    Page(s): 273 - 275
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    The stability of a metastable state produced by laser irradiation on arsenic‐diffused Si is studied by measurement of the sheet resistance as a function of postlaser heat treatment between 300 and 900 °C. The good conductivity produced by laser irradiation decays at as low as 400 °C within 1 h. This preempts the advantage of good conductivity produced by transient annealing and sets a severe restriction on the application of transient processing. View full abstract»

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  • Heavy‐doping effects and impurity segregation during high‐pressure oxidation of silicon

    Page(s): 275 - 277
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    Silicon samples which were ion‐ implanted with boron or arsenic were oxidized in high‐pressure (10 atm) pyrogenic steam to determine the effects of heavy doping on the oxide growth rate. Heavy n‐type doping (arsenic) was found to enhance the silicon oxidation rate, but the enhancement was not as great as for oxidation at atmospheric pressure. For p‐type (boron) doping there was only slight enhancement for both high‐pressure and 1‐atm oxidations. Samples were then depth profiled using secondary‐ion mass spectroscopy (SIMS) to observe the segregation of boron and arsenic at the Si:SiO2 interface. The effective coefficients of the impurities for high‐pressure oxidation were found to deviate significantly from those for atmospheric pressure oxidation. View full abstract»

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  • Scintillation study of ZnWO4 single crystals

    Page(s): 278 - 279
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    Scintillation characteristics of the Czochralski‐grown ZnWO4 single crystal were studied. This crystal, with light red‐brown color, exhibits a maximum luminescence wavelength of 480 nm under excitation at 254 nm. The total luminescence output under x‐ray excitation at 254 nm. The total luminescence output under x‐ray excitation was found to be 2.3 times larger than that of the best Bi4Ge3O12 at room temperature with small afterglow. View full abstract»

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  • Laser irradiation of furnace preannealed (111) ion implanted silicon

    Page(s): 279 - 281
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    The regrowth of self‐ion implanted amorphous layer on (111) silicon substrate induced by laser pulse is shown to require less energy density in furnace preannealed sample. After 450 °C 30‐min thermal treatment, the energy threshold is reduced about 30%. The extended defects near the threshold exhibit different geometrical arrangement. View full abstract»

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  • Substrate temperature related degradation mechanisms in molecular beam epitaxial InP

    Page(s): 282 - 283
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    The deleterious effects of structural changes on the quality of (001) oriented InP grown by MBE at low substrate temperatures has been investigated. For deposition below Ts=300 °C, concomitant with the loss of reconstruction in the reflection high energy electron diffraction (RHEED) pattern, the electrical properties of the epilayers begin to degrade, culminating in their total collapse at Ts =145 °C, associated with the onset of twinned growth. View full abstract»

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  • Improved stacked‐structure oxide by laser annealing

    Page(s): 284 - 286
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    Laser annealing techniques were successfully incorporated into standard MOS processing to improve the quality of oxides grown over polycrystalline silicon (polysilicon). Polysilicon films (5000 Å thick) deposited over 1000 Å SiO2, grown over (100) bulk Si were exposed to a short pulse (20 nsec) of ruby laser radiation at an energy density of 1 J/cm2 and subsequently oxidized at 925 °C. The resulting oxides over the polysilicon were found to have leakage currents which are lower by over three orders of magnitude than oxides grown over polysilicon films which were not laser annealed. C‐V measurements taken on the underlying polysilicon‐SiO2‐Si structure indicate that no deleterious effects were produced in the underlying structure by the laser radiation. View full abstract»

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  • Crystalline phase transition in the copolymer of vinylidenefluoride and trifluoroethylene

    Page(s): 286 - 288
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    The measurement of the temperature dependence of elastic, dielectric, and piezoelectric constants for the film of 55/45% VDF‐TrFE copolymer suggests that the Curie temperature exists at about 70 °C. The lattice spacing sharply changes at a temperature range from 55 to 75 °C. The remanent polarization is also determined from the D versus E hysteresis loop below 75 °C. It is found that the spontaneous strain in crystal lattice is linearly related to the square of remanent polarization. The transition is ascribed to electrostriction due to dipolar orientation. View full abstract»

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  • Homogeneous nucleation of oxide precipitates in Czochralski‐grown silicon

    Page(s): 288 - 290
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    The nucleation rate of oxide precipitates in silicon at 750 °C was determined by two‐step annealing and through transmission electron microscopy. The density of oxide precipitates was found to increase by annealing in proportion to annealing time. The precipitates were of two kinds: (a) grown from microprecipitates which existed in as‐grown crystals, and (b) grown nuclei which nucleated during the annealing. The nucleation rate was obtained by discriminating (b) from (a) to be about 107 cm-3 sec-1 for an oxygen content of 11×1017 atoms cm-3. Using this result and classical nucleation theory, homogeneous nucleation mechanism of oxygen precipitation is discussed. View full abstract»

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Applied Physics Letters, published by the American Institute of Physics, features concise, up-to-date reports on significant new findings in applied physics.

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Nghi Q. Lam
Argonne National Laboratory