By Topic

Journal of Applied Physics

Issue 6 • Date Jun 1980

Filter Results

Displaying Results 1 - 25 of 90
  • Issue Table of Contents

    Page(s): toc1
    Save to Project icon | PDF file iconPDF (228 KB)  
    Freely Available from IEEE
  • Temperature‐fluctuation noise of thin films supported by a substrate

    Page(s): 2947 - 2956
    Save to Project icon | PDF file iconPDF (700 KB)  

    A computation is given of the fluctuations in average temperature of an isolated thin film on a substrate, the noise being due to two causes: (i) fluctuations in blackbody radiation absorbed and emitted by the front surface; (ii) thermal diffusion in the sample and the substrate. The surface source results in a large 1/f range, the level of which decreases with increasing heat conductivity of the substrate; the noise goes over into a 1/f2 spectrum at high frequencies. The noise due to the volume source results in a 1/f1/2 spectrum, going over into a 1/f3/2 spectrum at higher frequencies; the noise also decreases with increasing heat conductivity of the substrate. The integrated total noise is of the order kT20/C . Under most circumstances the spectrum due to the volume source dominates. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced neutral‐beam divergence due to imperfect magnetic shielding

    Page(s): 2957 - 2960
    Save to Project icon | PDF file iconPDF (293 KB)  

    A previous calculation of neutral‐beam divergence due to imperfect magnetic shielding of the gas‐cell neutralizer is generalized to include the case in which the intrinsic magnetic‐field–free divergence of the beam is finite. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • XeI* production via laser absorption processes at 193 nm: Quenching kinetics

    Page(s): 2961 - 2964
    Save to Project icon | PDF file iconPDF (288 KB)  

    Strong fluorescence is observed on the XeI (B→X) excimer band upon excitation of a mixture containing an iodine compound and Xe with 193 nm photons. This emission is observed when I2, CH2I2, CH3I, or CF3I are used as iodine donors. Radiative lifetime and two‐body collisional quenching rate of XeI(B) by Xe, I2, and CH3I have been measured. The relevance of these results with regards to use of this excimer as a source of UV stimulated emission is discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the shifts of self‐reversed maxima of the sodium resonance radiation

    Page(s): 2965 - 2968
    Save to Project icon | PDF file iconPDF (252 KB)  

    Relationships between partial pressures and shifts of blue wing and red wing maxima of the self‐reversed D lines in a high‐pressure sodium‐mercury discharge have been calculated. A van der Waals model is used in the calculation of the interaction between sodium and mercury atoms. A useful and convenient formula has been derived for estimating mercury pressure in a sodium‐mercury discharge from easily measured parameters (the shift of red wing maximum and the shift of blue wing maximum). View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Vacuum ultraviolet absorption cross sections for halogen containing molecules

    Page(s): 2969 - 2972
    Save to Project icon | PDF file iconPDF (222 KB)  

    Vacuum ultraviolet absorption cross sections for the compounds Cl2, Br2, I2, HCl, HBr, HI, CCl4, CCl3Br, CF3Br, CF3I, HgCl2, HgBr2, and HgI2 have been measured between 170 and 230 nm. Studies of the Xe*2 discharge lamp used are reported. The absorption bands of various mercuric halides are identified. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Practical application of the thermal pulsing technique to the study of electrets

    Page(s): 2973 - 2986
    Save to Project icon | PDF file iconPDF (1263 KB)  

    The thermal pulsing technique gives information about the spatial distribution of charge and polarization through the thickness of electrets. This paper discusses methods by which this technique is applied in practice to the problem of determining these distributions. Several possible sources of systematic error in the experimental data are identified, and methods are discussed for eliminating these errors. A physical approach to data analysis is discussed which is complementary to a previously published mathematical analysis. Examples are given where this approach has yielded useful information about the charge or polarization distribution in insulators. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulation of the influence of bonding materials on electromagnetic wave propagation in laminated composites

    Page(s): 2987 - 2994
    Save to Project icon | PDF file iconPDF (602 KB)  

    Two model analyses are constructed in order to determine the influence of bonding materials on the propagation of electromagnetic waves in otherwise bilaminated composites. The geometric arrangement of the composite with the bond is treated as a special type of a trilaminated composite in which each of its major constituents is sandwiched between two bonding layers. In the first model, a recently developed continuum mixture theory of electromagnetic wave propagation in bilaminated composites is extended to treat the trilaminated composite. Here, details of the propagation process in the major components and also in the bonding layers are derived. In the second model, the entire effect of the bonds is treated as a modifier to interfacial continuity conditions. In this model the details of the propagation process in the bonding material are ignored. It is found that the results of both models correlate well with each other and also with some exact solutions for a rather wide range of frequencies. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development and investigation of relativistic electron beams with finite energy spread and improved emittance

    Page(s): 2995 - 3000
    Save to Project icon | PDF file iconPDF (418 KB)  

    This paper presents experimental results in the development of low‐emittance relativistic electron beams with finite energy spread, which—among other applications—is suitable for suppressing collective instabilities in an electron‐ring accelerator. The measurements were performed with a divided cathode in an electron‐beam gun, one half of which is connected via a resistor with the high‐voltage terminal. The energy difference can be varied up to 100 keV in proportion to the resistance, with equal subcurrents. The beam parts are well separated, and their radial distance is about equal to the radial difference of the corresponding electron closed orbits, such that electron‐ring formation with minimum radial betatron oscillations should be possible. The beam emittance is as small as about 100 mrad cm and the current is 800 A. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The nonlinear theory of efficiency enhancement in the electron cyclotron maser (gyrotron)

    Page(s): 3001 - 3007
    Save to Project icon | PDF file iconPDF (517 KB)  

    We present a nonlinear analysis of the single‐particle dynamics in an electron cyclotron maser oscillator and show that the efficiency can be dramatically enhanced by appropriately contouring the system parameters. The beam electrons can be prebunched in phase to form a macroparticle in phase space such that beam kinetic energy is not extracted. After forming a phase‐bunched electron beam, either the applied magnetic field or the cavity electromagnetic field can be spatially varied in such a way as to extract virtually all the electron transverse kinetic energy. Without such contouring, the transverse efficiency is typically ?40%. An example is presented in which the transverse efficiency is increased from 36% (in uniform fields) to 75% by increasing the applied magnetic field by ∼6%. The present analysis can readily be extended to the case of a maser amplifier. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical extraction characteristics of homogeneously broadened cw lasers with nonsaturating lasers

    Page(s): 3008 - 3016
    Save to Project icon | PDF file iconPDF (568 KB)  

    The optical extraction characteristics of homogeneously broadened cw lasers with nonsaturating losses are calculated exactly and compared with previous analytic approximations. The extraction efficiency as a function of the output coupling is discussed in detail for medium parameters appropriate to high‐gain rare‐gas‐halide lasers. It is found that contrary to expectations, the output is comparatively insensitive to the medium parameters and output coupling, and that it is a poor diagnostic tool for laser medium characterization. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Traveling wave excitation of the nitrogen ion laser

    Page(s): 3017 - 3019
    Save to Project icon | PDF file iconPDF (273 KB)  

    A repetitively pulsed, traveling‐wave laser has been operated with a front‐to‐back ratio exceeding 1000 : 1 when producing peak powers in excess of 3 MW. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A model for the dissociation pulse, afterglow, and laser pulse in the Cu/CuCl double pulse laser

    Page(s): 3020 - 3032
    Save to Project icon | PDF file iconPDF (1029 KB)  

    A model which completely describes the Cu/CuCl double pulse laser is presented. The dissociation discharge pulse and afterglow are simulated and the results are used as initial conditions for an analysis of the pumping discharge pulse and laser pulse. Experimental behavior including the minimum, optimum, and maximum delays between pulses, and the dependence of laser pulse energy on dissociation energy are satisfactorily reproduced. An optimum tube temperature is calculated, and the dependence of laser pulse energy on tube temperature (i.e., CuCl vapor pressure) is explained for the first time. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mode locking of strip buried heterostructure (AlGa)As lasers using an external cavity

    Page(s): 3033 - 3037
    Save to Project icon | PDF file iconPDF (375 KB)  

    Active and passive mode locking of strip buried heterostructure lasers is observed using an external cavity consisting of a lens and a mirror. Using the second‐harmonic‐generation method to obtain the second‐order autocorrelation function we obtain Gaussian pulses as short as 35.7 psec (FWHM) at a 1.9‐GHz repetition rate. The optical spectrum of the mode locked laser consists of longitudinal modes of the composite cavity spaced by ∼0.05 Å, whose amplitudes are modulated by the 2.09‐Å‐mode spacing of the laser itself, and contained under a Gaussian envelope of 9.5‐Å FWHM. Additional very sharp structure (∼1.6‐psec FWHM) in the autocorrelation is shown to result from the presence of several laser mode groups. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laser action in photopumped GaAs ribbon whiskers

    Page(s): 3038 - 3041
    Save to Project icon | PDF file iconPDF (344 KB)  

    We have observed laser action in single‐crystal ribbon whiskers of GaAs. The whiskers were grown with various dopants by a vapor transport process and were used, as grown, in an ultrashort cavity composed of high reflectivity dielectric mirrors. The structure was longitudinally photopumped, and it operated in a single mode at room temperature. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measurement of gain and absorption spectra in AlGaAs buried heterostructure lasers

    Page(s): 3042 - 3050
    Save to Project icon | PDF file iconPDF (741 KB)  

    A new method for measuring absorption and gain spectra of lasers is presented. These spectra are deduced from measurements of spontaneous emission spectra at different laser currents supplemented by measurements of the laser line energy and the differential quantum efficiency. The spontaneous emission emerged from the side of the laser after traveling through a transparent cladding layer. At each current, the bias energy eV is determined. A simple theoretical model is used to convert eV to minority carrier density. The method is based on the application of general relations between the rates of spontaneous emission, stimulated emission, and optical absorption. A new general proof of these relations is presented. The gain versus carrier density relation at the laser line energy is measured for four samples having different active layer doping or Al composition. Gain increased superlinearly with carrier density in undoped and n‐type samples and increased slightly sublinearly in a p‐type sample. The losses at low carrier densities ranged from 100–200 cm-1. For one undoped sample, the changes in the absorption edge caused by the electron and hole densities increasing from 5×1016 to 1.1×1018 cm-3 were deduced by comparing the measured changes with a model calculation. It was found that the exponential broadening increased 20%, that the energy gap decreased 12–16 meV, and that the strength of optical absorption at low energies decreased by about a factor of 1.4. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Theory of defect‐induced pulsations in semiconductor injection lasers

    Page(s): 3051 - 3061
    Save to Project icon | PDF file iconPDF (916 KB)  

    The size of defects necessary to cause pulsations, in otherwise ideal semiconductor injection lasers, is calculated for two defect models: a nonradiative region and a number of nonradiative surfaces. The point of instability for pulsations is found by solving the linearized rate equations describing small oscillations about the steady state and determining the length of the nonradiative region or the number of surfaces for which damped oscillations change to growing oscillations. The validity of this method is verified by computer calculations of large amplitude pulsations in a particular case. An oscillating light intensity induces an oscillating component of gain. Part of the oscillating gain is in phase with the light intensity in the absorbing region, causing growth, and is directly out of phase in the amplifying region, causing damping. The laser pulsates if the in‐phase gain in the absorbing region is dominant. This component of gain is enhanced by a short nonradiative lifetime. This mechanism applies over a broad range of parameters with optimum values of about 0.06–0.10 nsec for the nonradiative lifetime and 1–2 mW for the laser power. The requirement for pulsations found in earlier studies of divided contact lasers, that the gain versus carrier density relation g(n) be nonlinear with dg/dn greater in the absorbing region than in the amplifying region, is not required for pulsations if the relaxation time is short. However, increased dg/dn in the absorbing region greatly enhances the ability of a small defect to produce pulsations. For g(n) increasing linearity with n, a defect at least 11 μ long is needed to cause pulsations, whereas for dg/dn twice as great in the absorbing region as in the amplifying region, a defect only 4 μ long can cause pulsations. The possibility of increased dg/dn and absorption in the nonradiative region due to local heating is discussed. For optimum lifetime and surface recombination velocity,- each nonradiative surface is approximately equivalent to a nonradiative region about 1/2 μ in length. Accordingly, two nonradiative cleaved surfaces are insufficient to be the sole cause of pulsations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Studies of (GaAl)As injection lasers operating with an optical fiber resonator

    Page(s): 3062 - 3071
    Save to Project icon | PDF file iconPDF (1078 KB)  

    The characteristics of an optical fiber external resonator in conjunction with (GaAl)As stripe geometry lasers are described. We have observed a 6–10% reduction in the threshold current and have obtained 150 ps pulses at gigahertz repetition rates. The fiber resonator has also been used to quench self‐pulsations in a (GaAl)As injection laser. In order to explain many of our results we have used a model that uses the conventional semiconductor rate equations modified by the addition of saturable electron traps and the effects of the external cavity. Our results predict many of the self‐locking effects observed in injection lasers operating in an external cavity. Furthermore, the degree of self‐locking will be a strong function of the external cavity length and the density of saturable absorbers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coherent cancellation of background in four‐wave mixing spectroscopy

    Page(s): 3072 - 3077
    Save to Project icon | PDF file iconPDF (490 KB)  

    A technique for the cancellation of background contribution to four‐wave mixing is proposed and demonstrated. The technique consists of the destructive interference of the background parametric waves produced by two samples that differ only in one or more properties of interest. This cancellation technique is applicable even when the background itself contains resonances in the frequency range of interest. Cancellation factors of 500 and higher were achieved using a double cell for liquid specimens. This technique is demonstrated using phenol water solution. It is shown that with full background the 1004‐cm-1 phenol line can hardly be observed at 1% phenol concentration whereas the same line is easily observed when the background is cancelled even at 0.1% phenol concentration. This technique can also be used to extract the real and imaginary parts of the nonlinear susceptibility without the use of the Kramers‐Kronig relations. We have performed this calculation in the case of 5% phenol solution in water. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal blooming in liquid N2 during high repetition rate stimulated Raman scattering

    Page(s): 3078 - 3080
    Save to Project icon | PDF file iconPDF (228 KB)  

    Stimulated Raman scattering in liquid nitrogen was studied with a high repetition rate Nd : YAG laser. Severe distortions of the laser and Raman light beams were observed. These thermal‐blooming effects are the result of heating of the laser path by vibrational energy relaxation which changes the refractive index of the medium. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electrically pumped relativistic free‐electron wave generators

    Page(s): 3081 - 3089
    Save to Project icon | PDF file iconPDF (731 KB)  

    Stimulated scattering induced by the longitudinal electric field of a pump wave is studied theoretically for the case of dense relativistic electron beams traveling in cylindrical metal waveguides. Two processes are examined. In one, the pump wave decays parametrically into a slow and a fast space‐charge wave. In the other, it decays into a slow space‐charge wave and a TM wave of the guide. The frequency characteristics and stimulated growth rates are given for each process, as a function of beam diameter, velocity, and density. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thin‐film waveguide evanescent dye laser and its gain measurement

    Page(s): 3090 - 3092
    Save to Project icon | PDF file iconPDF (159 KB)  

    Superradiant waveguide evanescent‐type dye lasers are realized by polyurethane top layers containing Rhodamine 6G and Rhodamine B respectively on single‐mode glass waveguides with N2 uv laser pumping. A new determination method of gain factor (negative absorption coefficient) by active guide length dependence of a triangle shape top layer is proposed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A backscattering formula for acoustic transducers

    Page(s): 3093 - 3098
    Save to Project icon | PDF file iconPDF (421 KB)  

    A backscattering formula for a single transducer geometry is derived. It expresses the output voltage of the transducer in terms of the angular spectra of scalar and vector acoustic potentials on a plane. The formulation is suitable for acoustic problems involving wide angular spectrum beams. The derived formula gives a simple expression for the problem of a circular transducer facing a plane reflector. The output voltage of a transducer receiving the backscattered waves from an arbitrary size spherical flaw is also presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An analysis of transverse modes in acoustic surface wave resonators

    Page(s): 3099 - 3112
    Save to Project icon | PDF file iconPDF (966 KB)  

    A system of approximate surface wave equations employed in an earlier treatment of the reflection of straight‐crested surface waves by arrays of reflecting strips is extended to the case of variable‐crested surface waves. Although the basic straight‐crested surface wave velocities are determined as in the previous treatment, in the present case a reduction in straight‐crested surface wave velocity in the unplated region due to the adjacent plated regions, which is essential for the existence of the guided transverse modes, is determined by means of a perturbation procedure. The attendant depth dependence for each region is employed in the variational principle as in the earlier treatment, but now the variable cresting relation for the isotropic substrate is incorporated in the description. The resulting equations are applied in the determination of both the transverse modes in each region and the transmission line representation of each mode. The transverse wave numbers in a given mode are taken to be the same in the plated and unplated regions in order that the interior edge conditions be satisfied pointwise. The system of parallel transmission lines is applied in the analysis of the reflection of variable‐crested surface waves by uniformly spaced arrays. The response to a rectangular input of a particular reflecting array consisting of aluminum reflecting strips on ST‐cut quartz is calculated and compared with measurements. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization of ZnO piezoelectric films prepared by rf planar‐magnetron sputtering

    Page(s): 3113 - 3120
    Save to Project icon | PDF file iconPDF (692 KB)  

    ZnO films with an excellent crystal orientation and surface flatness have been prepared by high‐deposition‐rate rf planar‐magnetron sputtering. A detailed study of these films has been carried out using x‐ray diffraction, scanning electron microscopy, reflection electron diffraction, optical measurement, and electromechanical measurement. These films have the c‐axis perpendicular to the substrate. The value of the standard deviation angle σ of the c‐axis orientation distribution is smaller than 0.5°, and the minimum value of σ is 0.35°, where the sputtering conditions are that the gas pressure is 5×10-3–3×10-2 Torr of premixed Ar (50%)+O2(50%) and the substrate temperature is 300–350 °C. ZnO films with a thickness up to 48 μm have been reproducibly prepared without the decreases of film quality and surface flatness. The surface flatness of these films is similar to that of a glass substrate. An optical waveguide loss for the TE0 mode of the He‐Ne 6328‐Å line is as low as 2.0 dB/cm in a 4.2‐μm‐thick film, without postsputtering treatment. The effective surface wave coupling factors are greater than 95% of the theoretical values of the ZnO/glass structure, both in the case of the interdigital transducer (IDT)/ZnO/glass and ZnO/IDT/glass structure. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics

Full Aims & Scope

Meet Our Editors

Editor
P. James Viccaro
Argonne National Laboratory