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Applied Physics Letters

Issue 10 • Date Nov 1983

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Displaying Results 1 - 25 of 37
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • Stable longitudinal mode operation in a multiple twisted double‐heterostructure laser

    Page(s): 889 - 891
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    A multiple twisted double‐heterostructure laser is fabricated by connecting a terraced substrate laser and a channeled substrate laser alternately. In addition to a stable tranverse‐mode oscillation due to the built‐in refractive index variation, a stable longitudinal‐mode oscillation is achieved by interferometric effects which are caused by internal reflection at twisted parts of the composite cavity where transition in the laser structure occurs. The laser with two twisted regions shows a threshold current of 92 mA, and wavelength locking over a temperature range of more than 25 °C within which the wavelength changes at a rate of 0.6 Å/ °C. View full abstract»

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  • Intensity‐dependent index of refraction in multilayers of polydiacetylene

    Page(s): 891 - 893
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    We have grown multilayer samples of a polydiacetylene upon a metallized grating forming a planar waveguide structure. By measuring the change with optical intensity in the coupling angle between an input laser beam and a planar waveguide mode in the structure we estimate the intensity‐dependent index of refraction, n2≂10-6 (MW/cm2)-1 (λ≫7500 Å), for the polydiacetylene. Also, a large resonant enhancement of the optical nonlinearity was observed. View full abstract»

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  • Low loss waveguides grown on GaAs using localized vapor phase epitaxy

    Page(s): 894 - 895
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    New type of optical waveguides grown on GaAs by localized epitaxy using vapor phase epitaxy is presented. The guides are grown through a strip opened in a dielectric film and have a triangular cross section. The loss measurements have been performed on waveguides of lengths varying from 1 to 10 mm. Losses as low as 1.5 dB have been found. An original light coupling technique into the guide—through the substrate—has been used. Because of an improved optical confinement due to the structure of the guides and because of their low losses, these waveguides have numerous potential advantages and applications in integrated optics. View full abstract»

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  • Optical fiber loss increase in the infrared wavelength region induced by electric current

    Page(s): 896 - 897
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    A new phenomenon of silica‐fiber loss increase, which is induced by an electric current applied in water, is reported. It is found from experimental results that the loss increase is caused by hydrogen gas, which is electrolytically produced and is diffused into the fiber interstitially. View full abstract»

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  • B→X transition in 136Xe 19F

    Page(s): 898 - 900
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    The B→X emission spectrum is analyzed for the single isotopomer 136Xe 19F. Thirteen v′‐v″ bands spanning v′=0–4 and v″=0–5 have been rotationally analyzed. The analysis yields greatly improved spectroscopic constants, permitting precise identification of most of the features in the XeF laser spectrum. No evidence is found for C→X emission in the normal sense. However, it is possible that several previously unassigned features, including one or more reported laser lines, constitute C→X emission enabled through intensity borrowing from B‐X by B‐C perturbative mixing. View full abstract»

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  • Infrared transparent and electrically conductive thin film of In2O3

    Page(s): 901 - 903
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    High quality infrared (1–12 μ) transparent and electrically conductive thin films based on thermal reactively evaporated In2O3 have been developed. Optical constants of these films have been obtained by the use of an iteration technique, which involves the formulas for multiple transmission and reflection. The details of the film deposition process and the theoretical foundation leading to its development are discussed in this letter. It has been found that the transparency and conductivity of these films are primarily due to their high electron mobility coupled with an appropriate electron concentration. A multilayer design of a bandpass induced transmission and antireflection coating has been developed and implemented on ZnS and ZnSe substrates for the wavelength range of 8–12 μ. Typical transmittance of 65%–80% with a film sheet resistance of 20–50 Ω/⧠ has been achieved. Such a design is applicable to forward‐looking infrared systems where a window having both high electromagnetic (rf and microwave) shielding effectiveness and good infrared transparency are required. The properties of these films lend themselves to many other potential applications. View full abstract»

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  • Monolithic high‐power dual‐wavelength GaAlAs laser array

    Page(s): 903 - 905
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    Monolithic integration of high‐power GaAlAs lasers is demonstrated. The new dual‐wavelength laser array is implemented by integrating a twin‐ridge substrate laser and a terraced substrate laser by the one‐step liquid phase epitaxy technique. Both lasers integrated on a GaAs chip continuously operated at the power output as high as (30+30) mW in single longitudinal modes with a wavelength separation of 31 nm. View full abstract»

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  • Quantum well structures of In0.53Ga0.47As/InP grown by hydride vapor phase epitaxy in a multiple chamber reactor

    Page(s): 906 - 908
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    A computer controlled multiple chamber chemical vapor deposition reactor, designed for the growth of InP based alloys, has been constructed. In this system, specular epitaxial layers of InP and In0.53Ga0.47As are grown in separate chambers. This allows for the uninterrupted growth of In0.53Ga0.47As/InP quantum well structures with layer thicknesses of approximately 150 Å. The photoluminescence spectra of these structures exhibit upward energy shifts as large as 71 meV from the band‐gap energy of In0.53Ga0.47As. Laser action at 1.5–1.6‐μm wavelengths has been obtained at temperatures up to 100 °C by optical pumping with a Q‐switched neodymium:yttrium aluminum garnet laser. View full abstract»

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  • Observation of optically induced molecular reorientation in films of smectic C liquid crystals

    Page(s): 909 - 911
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    A linearly polarized laser beam incident on a freely suspended film of a smectic C liquid crystal has been observed to reorient the molecules. In films of 4, 4 bis (heptyloxy) azoxybenzene, large reorientations have been observed with an incident optical power of less than 50 mW. Photographs are presented showing the change in molecular orientation as the incident polarization is rotated. A simple theory explaining the effect is also included. View full abstract»

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  • Cascade laser emission of optically pumped Na2 molecules

    Page(s): 912 - 914
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    First continuous laser oscillation at wavelengths around 2.5 μm and 1.9 μm/0.9 μm on C 1πu →(3) 1Σ+g →B 1πu/A 1Σ+u cascade transitions of Na2 has been obtained. The C 1πu state is optically pumped with cw krypton and argon ion lasers at wavelengths in the range of 333–351 nm. Gain contributions due to coherent two‐photon and three‐photon processes are involved. View full abstract»

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  • Low reflectivity surface acoustic wave transducers on GaAs

    Page(s): 915 - 916
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    Experimental results are presented for fabrication and metallization techniques which achieve low reflectivity surface acoustic wave (SAW) interdigital transducer operation on GaAs. The transducer structures considered are single finger pair, quarter wavelength designs with chrome/aluminum/chrome (surface), aluminum (recessed) or gold‐germanium/nickel/gold (surface) metallized electrodes which were fabricated directly onto a semi‐insulating GaAs substrate. Triple transit signal suppression greater than 53 dB for the recessed aluminum metallization and greater than 62 dB for the Au‐Ge/Ni/Au metallization has been achieved for test transducers operating at 159 MHz, compared to typically 30–35 dB for Cr/Al/Cr metallizations. These low reflectivity transducers provide the means for reducing spurious signal responses within monolithic programmable GaAs signal processors and for achieving higher Q performance of SAW resonator filters fabricated on GaAs substrates. View full abstract»

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  • Generation and detection of ultrasonic Lamb waves in a thin deposited film by using interdigital transducers

    Page(s): 917 - 919
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    Interdigital transducers (IDT’s) have been used to generate and detect ultrasonic Lamb waves in a composite Cu(3 μm)‐ZnO (0.45 μm) film that is much thinner than the acoustic wavelength in a bulk material. rf pulses of 29.0 and 1.31 MHz are applied to one of the pair of IDT’s with 140‐μm period, giving rise to a nondispersive quasi‐symmetric mode of phase velocity 4170 m/s and a dispersive quasi‐antisymmetric mode having a phase velocity of 184 m/s and a group velocity of 362 m/s, respectively. Possible applications to electronic signal processing and material studies are described. View full abstract»

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  • Measurements of plasma ion temperature and rotation velocity using the He II 4686‐Å line produced by charge transfer

    Page(s): 920 - 922
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    Spatially and temporally resolved values of the ion temperature and toroidal rotation velocity near the plasma axis have been obtained in neutral beam‐heated plasmas in the Doublet III tokamak from measurements of the Doppler broadening and Doppler shift of the He II 4686‐Å line, excited by charge transfer reactions between fast hydrogen atoms in the beam and thermal helium ions in the plasma. The measurement technique, which uses visible optics and a multichannel detector, promises to be a straightforward method to obtain ion temperature profiles in beam‐heated tokamaks. View full abstract»

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  • Breakdown of the atmosphere by emission from a millimeter‐wave free‐electron maser

    Page(s): 922 - 924
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    Production of an atmospheric pressure air breakdown plasma using the emission from a short‐pulse millimeter‐wave free‐electron maser is used to demonstrate frequency tunability over the range 50–100 GHz, via breakdown standing wave patterns, and very high peak power. View full abstract»

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  • Effects of implantation energy and carbon concentration on the friction and wear of titanium‐implanted steel

    Page(s): 925 - 927
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    Dry sliding friction and wear measurements were used to evaluate two implantation processes which increase the C concentration in Ti‐implanted steels. In the first process, Ti ions were implanted at a low energy (50 keV) in order to enhance the efficiency of vacuum carburization over what is achievable at higher energies (e.g., 190 keV). In the second, a dual implantation process, C ions were implanted into steels already implanted with Ti ions at high energy (190 keV). The first process produced a low friction (μ=0.3), scuff resistant surface at a fluence of 2×1017/cm2, 40% lower than the fluence required for similar behavior by 190‐keV implants. At fluences of 2×1017/cm2 each, the dual implantation produced a modest decrease in friction (μ=0.5), accompanied by stick slip, and some wear resistance compared to nonimplanted steel (μ=0.6). Auger spectroscopy and energy‐dispersive x‐ray analysis were used to analyze the surface composition produced by the two processes at fluences of 2×1017/cm2. The dual implanted surface had more Ti, more C, and a greater C/Ti ratio than the low‐energy implanted surface. The latter, however, had more C derived from vacuum carburization than the dual implanted surface. Both processes resulted in identical surface C concentrations. We concluded, therefore, that the improved tribological surface of Ti‐implanted steel results from vacuum carburization and not just the presence of excess C. View full abstract»

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  • Conditions for metastable thermal and magnetic domain structures and for observable oscillations in dρ/dT near an electrothermal instability

    Page(s): 927 - 929
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    Experimental conditions for observing a new type of oscillations in the temperature derivative of the electrical resistivity near magnetic transition temperatures are discussed. An electrothermal instability arises due to a nonlinear electrical current‐voltage drop characteristics as in a ballast resistor. Inhomogeneous temperature distributions are found for various experimental conditions. View full abstract»

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  • Ion channeling studies of InGaAs/GaAs strained‐layer superlattices

    Page(s): 930 - 932
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    The first ion channeling studies of the InxGa1-xAs/GaAs strained‐layer superlattice (SLS) system are reported. The strong orientation dependence of the dechanneling for both axial and planar directions relative to the [100] growth axis indicates that the ≊1% lattice mismatch is accommodated by lattice strain. Tetragonal distortions along the growth direction give rise to alternating tilts for inclined crystal directions which result in significant [110] and (1¯10) dechanneling. Measurements for 40‐layer structures with different In concentrations demonstrate that the channeling technique is a depth‐sensitive probe of the degree of strain in SLS systems. View full abstract»

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  • Pyroelectric properties of the alanine and arsenic‐doped triglycine sulfate single crystals

    Page(s): 932 - 934
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    Arsenic‐doped triglycine sulfate single crystals show an enhancement in pyroelectric coefficients and the pyroelectric figures of merit p/K and p/√K by a factor of 2.2 over those of pure triglycine sulfate single crystals at the most desirable operating temperature of the pyroelectric sensors, ≂25 °C. The crystals are inexpensive to produce and show useful pyroelectric properties. View full abstract»

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  • Synthesis of novel inorganic films by ion beam irradiation of polymer films

    Page(s): 934 - 936
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    We propose a novel technique to convert polymer films into useful inorganic films by ion beam irradiation. Along the track of an ion the polymer is dissociated into smaller fragments. Volatile fragments diffuse through the film and escape. Any element which is not removed in the form of volatile species is subsequently enriched with respect to the other elements. We demonstrate this effect in a polymer poly(dimethylsilylene‐co‐methylphenylsilylene), which initially has a C:Si ratio of 4.5:1. Upon irradiation with 2‐MeV Ar+ ions at a dose of 1015 ions/cm2 the C:Si ratio changes to 3.4:1 as verified by Rutherford backscattering spectrometry. We believe that the effect of the ion beam irradiation is to produce more Si–C bonds at the expense of the C–H and Si–Si bonds, with ≲10% of the original hydrogen being present in the film at high doses. The IR spectra of the film as a function of the irradiation dose show a progressive loss of fine molecular features with significant increase of the refractive index. The IR spectrum at the high doses appears to be due to a mixture of various Si and C bonds. However, the irradiated films are very hard and scratch resistant (knoop value ≳1300), suggesting an increase in the number of silicon carbide bonds. View full abstract»

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  • Silicon self‐interstitial supersaturation during phosphorus diffusion

    Page(s): 937 - 939
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    The effect of phosphorus introduction and diffusion on the diffusivities of boron, arsenic, and antimony in silicon was studied using arsenic and antimony buried layers in a boron‐doped silicon substrate. It was found that the diffusivity of boron and arsenic was enhanced, while that of antimony was retarded directly under the silicon surface exposed to phosphorus. Since antimony diffuses primarily via a vacancy mechanism while the other two elements via a combination of vacancy and interstitialcy mechanisms, these results suggest that phosphorus predeposition enhances the silicon self‐interstitial concentration and reduces the concentration of vacancies. View full abstract»

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  • Impact ionization near GaAs grain boundaries

    Page(s): 939 - 941
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    Electroluminescence from a GaAs bicrystal has been measured at high current densities, and gives direct evidence of impact ionization near the grain boundary. Negative differential capacitance is seen at lower current densities and is associated with barrier height modulation by minority carriers. View full abstract»

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  • Hg vacancy related lifetime in Hg0.68Cd0.32Te by optical modulation spectroscopy

    Page(s): 941 - 943
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    The lifetime of excess photogenerated carriers has been measured as a function of temperature and carrier concentration in p‐type Hg0.68Cd0.32Te by contactless optical modulation spectroscopy. An excess carrier lifetime related to impurity substitution on ionized Hg sites is suggested as the dominant Shockley–Read recombination mechanism observed in this material. View full abstract»

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  • 1.54‐μm luminescence of erbium‐implanted III‐V semiconductors and silicon

    Page(s): 943 - 945
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    Well‐resolved sharply structured luminescence spectra at 1.54 μm were observed in erbium‐implanted GaP, GaAs, InP, and Si. The optical transitions occur between the weakly crystal field split spin‐orbit levels, 4I13/24I15/2, of Er3+(4f11). Typical spectral linewidths in GaAs are 2 cm-1(0.25 meV) at 6 K and 11 cm-1(1.36 meV) at room temperature. View full abstract»

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  • Wafer‐scale laser pantography: Fabrication of n‐metal‐oxide‐semiconductor transistors and small‐scale integrated circuits by direct‐write laser‐induced pyrolytic reactions

    Page(s): 946 - 948
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    A complete set of processes sufficient for manufacture of n‐metal‐oxide‐semiconductor (n‐MOS) transistors by a laser‐induced direct‐write process has been demonstrated separately, and integrated to yield functional transistors. Gates and interconnects were fabricated of various combinations of n‐doped and intrinsic polysilicon, tungsten, and tungsten silicide compounds. Both 0.1‐μm and 1‐μm‐thick gate oxides were micromachined with and without etchant gas, and the exposed p‐Si [100] substrate was cleaned and, at times, etched. Diffusion regions were doped by laser‐induced pyrolytic decomposition of phosphine followed by laser annealing. Along with the successful manufacture of working n‐MOS transistors and a set of elementary digital logic gates, this letter reports the successful use of several laser‐induced surface reactions that have not been reported previously. 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