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1 Jun 1973

Volume 22, Issue 11, pp. 557-613


Bragg diffraction of light by two orthogonal ultrasonic waves in water

W.P. Chu and L.E. Mauldin

Appl. Phys. Lett. 22, 557 (1973); http://dx.doi.org/10.1063/1.1654507 (3 pages) | Cited 2 times

Online Publication Date: 16 October 2003

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The diffraction of a light beam by two orthogonal traveling ultrasonic waves in water under Bragg angle incidence is described. It is shown that under low index modulation, only the zero order (0, 0), the two minus one orders (−1, 0 and 0, −1), and the cross minus one order (−1, −1) predominate in the diffraction process. Equalization of the four beam intensities, which is required in a two‐component cross‐beam laser Doppler velocimeter system, can be achieved with the transducers being driven at low power levels.

Electro‐optic switching in low‐loss liquid‐crystal waveguides

J.P. Sheridan, J.M. Schnur, and T.G. Giallorenzi

Appl. Phys. Lett. 22, 560 (1973); http://dx.doi.org/10.1063/1.1654508 (2 pages) | Cited 5 times

Online Publication Date: 16 October 2003

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Observation of low‐loss optical guidance in thin films of a number of well‐aligned nematic liquid crystals is reported for the first time. Evaluation of waveguiding properties of the oriented films and polarized microscopic techniques indicates a high degree of alignment can be attained and, indeed, is essential for good waveguiding. Propagation losses in the best samples are measured to be less than 1 dB∕cm. Amplitude modulation and switching in these waveguides have also been achieved using the unique electro‐optic properties of nematic materials. The response times for these phenomena are on the order of a few milliseconds.

Tunneling in a finite superlattice

R. Tsu and L. Esaki

Appl. Phys. Lett. 22, 562 (1973); http://dx.doi.org/10.1063/1.1654509 (3 pages) | Cited 980 times

Online Publication Date: 16 October 2003

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We have computed the transport properties of a finite superlattice from the tunneling point of view. The computed I‐V characteristic describes the experimental cases of a limited number of spatial periods or a relatively short electron mean free path.

Measurement of density and temperature of a hydrogen plasma using an argon laser

Kenneth W. Billman and James R. Stallcop

Appl. Phys. Lett. 22, 565 (1973); http://dx.doi.org/10.1063/1.1654510 (3 pages) | Cited 11 times

Online Publication Date: 16 October 2003

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Curves relating the absorption of the argon ion laser lines at 0.488 and 0.515 μm to the electron density and plasma temperature of a hydrogen plasma are presented. A technique for determining these plasma parameters by means of simple absorption measurements is discussed.

Estimation of impurity profiles in ion‐implanted amorphous targets using joined half‐Gaussian distributions

J.F. Gibbons and S. Mylroie

Appl. Phys. Lett. 22, 568 (1973); http://dx.doi.org/10.1063/1.1654511 (2 pages) | Cited 65 times

Online Publication Date: 16 October 2003

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A probability distribution function appropriate for nonsymmetrical impurity distributions in ion‐implanted targets is defined to consist of two half‐Gaussian distributions that join at a modal projected range RM. For projected distances Xp<Rm the distribution has standard deviation σ1, while for Xp>Rm the distribution has standard deviation σ2. For appropriate choices of RM, σ1, and σ2, the proposed distribution is found to provide an extremely good fit for experimental impurity profiles.

Enhanced diffusion during the implantation of arsenic in silicon

F.N. Schwettmann

Appl. Phys. Lett. 22, 570 (1973); http://dx.doi.org/10.1063/1.1654512 (3 pages) | Cited 19 times

Online Publication Date: 16 October 2003

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The ``tail'' that is observed on the arsenic carrier profile formed by the implantation of arsenic in silicon is shown to be due to enhanced diffusion during implantation. The position of the tail is unaffected by postimplant annealing at temperatures up to 1000 °C. The arsenic ions comprising the tail are electrically inactive after implantation, and temperatures in excess of 700 °C are required to achieve complete activation. While the nature of the migrating species is unclear at this time, the results are consistent with an interstitial mechanism.

Frequency stabilization of a cw dye laser

R. L. Barger, M.S. Sorem, and J.L. Hall

Appl. Phys. Lett. 22, 573 (1973); http://dx.doi.org/10.1063/1.1654513 (3 pages) | Cited 52 times

Online Publication Date: 16 October 2003

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A cw dye laser system frequency stabilized to a high‐finesse optical reference cavity is described. Laser frequency is servo controlled to the cavity resonance with residual fluctuations less than 50 kHz for short times (20 μsec) and 100 Hz for long times (10 sec). Drift in absolute laser frequency of about 1.5 MHz∕min is observed due to drift of the unstabilized reference cavity. A saturated absorption spectrum of I2 obtained with this system is shown.

Vibrational excitation and relaxation of the CO(v=1) and CO(v=2) states

John C. Stephenson

Appl. Phys. Lett. 22, 576 (1973); http://dx.doi.org/10.1063/1.1654514 (3 pages) | Cited 47 times

Online Publication Date: 16 October 2003

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Pulses from a CO2 laser have been frequency doubled in a tellurium crystal and used to optically pump the first vibrational level in room‐temperature CO. By monitoring infrared fluorescence from the v=1 and v=2 states, the rate constant for the process CO(v=1) + CO(v=1) → CO(v=0) + CO(v=2) has been determined. Other rate constants involving the CO(v=1) level are also reported.

Ionization instability in CO2 laser discharges

William L. Nighan, W.J. Wiegand, and Roger A. Haas

Appl. Phys. Lett. 22, 579 (1973); http://dx.doi.org/10.1063/1.1654515 (4 pages) | Cited 25 times

Online Publication Date: 16 October 2003

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Criteria are established for calculation of plasma conditions leading to ionization instability in plasmas generally employed in high‐power molecular laser applications. Negative ion formation is found to play an important role in causing this instability. For conditions typical of electrically excited CO2 laser mixtures, appearance of an ionization instability requires a negative ion concentration greater than one‐tenth that of the electrons, combined with an electron temperature value below approximately 1.5 eV. Satisfactory agreement between theoretically determined stability boundaries and data obtained experimentally confirms the significance of fundamental collisional processes as regards ionization instability in CO2 laser discharges.

Plasma chemistry of CO2 ☒N2 ☒He discharges

W.J. Wiegand and William L. Nighan

Appl. Phys. Lett. 22, 583 (1973); http://dx.doi.org/10.1063/1.1654516 (4 pages) | Cited 29 times

Online Publication Date: 16 October 2003

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Analysis of plasma‐chemical phenomena occurring in electrically excited mixtures of CO2, N2, and He has shown that the principal dissociation products CO and O accumulate to significant levels in approximately 10−4 sec, a time less than typical fluid residence times in convection lasers. In addition, numerous secondary minority species are produced on the same time scale, reaching concentrations significantly in excess of the charge particle densities. The dominant ionic species are found to be directly related to these discharge‐generated minority species. These investigations have shown that negative ion concentrations can become comparable to the electron concentration for typical laser discharge conditions.

cw CO chemical laser directly fueled by carbon monosulfide

W.Q. Jeffers, C.E. Wiswall, J. Daniel Kelley, and R.J. Richardson

Appl. Phys. Lett. 22, 587 (1973); http://dx.doi.org/10.1063/1.1654517 (3 pages) | Cited 15 times

Online Publication Date: 16 October 2003

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A cw CO chemical laser has been operated with CS produced externally by a microwave discharge. Use of CS as a laser fuel produces large increases in output power, as compared with CS2, by a factor of 5.6 or more. The reasons for this power enhancement and the details of the experiment are discussed in this letter.

Reduction of threshold current density in GaAs☒Alx Ga1−x As heterostructure lasers by separate optical and carrier confinement

M.B. Panish, H.C. Casey, S. Sumski, and P.W. Foy

Appl. Phys. Lett. 22, 590 (1973); http://dx.doi.org/10.1063/1.1654518 (2 pages) | Cited 19 times

Online Publication Date: 16 October 2003

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Heterostructure lasers in which the GaAs active layer is bounded on each side by successive layers of AlxGa1−xAs to confine the carriers and AlyGa1−yAs (y>x) to confine the light have been fabricated and studied. Room‐temperature threshold current densities as low as 690 ± 40 A∕cm2 with differential quantum efficiencies of 32% have been obtained for 1‐mm cavity lengths.

Remote detection of SO2 and CO2 with a heterodyne radiometer

Robert T. Menzies

Appl. Phys. Lett. 22, 592 (1973); http://dx.doi.org/10.1063/1.1654519 (2 pages) | Cited 10 times

Online Publication Date: 16 October 2003

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A heterodyne radiometer, operating in the 9‐ to 11‐μm wavelength region, has been used to detect SO2 and CO2 in the laboratory with sensitivity adequate for remote stack monitoring and other sensing applications. CO2 lasers were used as local oscillators. The mixer was copper‐doped germanium, compensated with antimony donors, and the i.f. bandwidth was 500 MHz. Wavelengths of operation were chosen to minimize interference from water vapor.

Laser‐induced shock effects in Plexiglas and 6061‐T6 aluminum

Jay A. Fox and Dallas N. Barr

Appl. Phys. Lett. 22, 594 (1973); http://dx.doi.org/10.1063/1.1654520 (3 pages) | Cited 15 times

Online Publication Date: 16 October 2003

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See Also: Erratum

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The mass removal per unit area from Plexiglas and 6061‐T6 aluminum targets irradiated in air with a giant pulsed laser is presented as a function of incident fluence. This quantity appears to be a strong function of the focal length of the focusing lens. Air breakdown in the presence of a target occurs at fluences greater than 380 J∕cm2 for Plexiglas targets and 159 J∕cm2 for aluminum targets. Photographic evidence of the back‐face spallation of a 0.1‐cm‐thick aluminum sample irradiated in vacuum is presented. The mirror‐finished target was inclined at 45° to the incident beam and irradiated with a fluence of approximately 5000 J∕cm2.

Negative differential resistivity in superconductors at high current densities

R.P. Huebener and D.E. Gallus

Appl. Phys. Lett. 22, 597 (1973); http://dx.doi.org/10.1063/1.1654521 (2 pages) | Cited 5 times

Online Publication Date: 16 October 2003

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In the current‐induced resistive state of superconducting strips the voltage shows detailed structure as a function of the transport current. This structure is associated with the rearrangement within the sample of currents and magnetic fields. We report the observation of current regimes with negative differential resistivity in microstrips of the superconducting alloy Pb‐5 at.% Bi.

Permanent multipole magnetic fields stored in superconductors

Edward L. Garwin, Mario Rabinowitz, and David J. Frankel

Appl. Phys. Lett. 22, 599 (1973); http://dx.doi.org/10.1063/1.1654522 (2 pages) | Cited 6 times

Online Publication Date: 16 October 2003

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Hollow superconducting cylinders of Pb, Nb, and Nb3Sn were used to permanently store dipole, quadrupole, and sextupole magnetic fields with high fidelity to the original fields. Fields were trapped transversely to the axes of solid, hollow, and split hollow cylinders. This experimental demonstration indicates that it should be possible to store any multipole magnetic field configuration by this method. Important benefits should accrue to technologies dealing with the focusing of charged particle beams, such as accelerators, electron microscopes, etc. Use of field trapping permits determination of the fluxoid pinning force.

Magnetic anisotropy of Eu0.65Y2.35Fe3.8Ga1.2O12 films grown on garnet substrates with different lattice parameters

E.A. Giess and D.C. Cronemeyer

Appl. Phys. Lett. 22, 601 (1973); http://dx.doi.org/10.1063/1.1654523 (2 pages) | Cited 7 times

Online Publication Date: 16 October 2003

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The effect of lattice mismatch (stress) on magnetic anisotropy is studied in epitaxial films of a Eu0.65Y2.35Fe3.8Ga1.2O12 garnet grown on a series of garnet substrates with different lattice parameters. These garnet films have a negative magnetostrictive coefficient (λ ≃ 0.5 × 10−6) as predicted by simple magnetic dilution theory. A ``growth''‐induced magnetic anisotropy (Ku ≃ 8300 erg∕cm3) will exist for all of these films even when they are grown on a substrate with a perfect lattice match. Anisotropy can be increased by using an increased substrate rotation rate during film deposition.

Suppression of hard bubbles by a thin Permalloy layer

Y.S. Lin and G.E. Keefe

Appl. Phys. Lett. 22, 603 (1973); http://dx.doi.org/10.1063/1.1654524 (2 pages) | Cited 7 times

Online Publication Date: 16 October 2003

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We show experimentally that, by placing a thin Permalloy layer in intimate contact with a garnet film, hard bubbles can be suppressed. The suppression is due to exchange coupling between the Permalloy layer and the bubble walls. When the Permalloy layer is separated from the garnet film by a thin insulation layer, intermediate bubbles are observed.

Demonstration of the superconducting electron accelerator as a high‐intensity high‐resolution device

M.S. McAshan, K. Mittag, H.A. Schwettman, L.R. Suelzle, and J.P. Turneaure

Appl. Phys. Lett. 22, 605 (1973); http://dx.doi.org/10.1063/1.1654525 (3 pages) | Cited 2 times

Online Publication Date: 16 October 2003

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In recent experiments with the superconducting injector system, beam intensity and beam quality objectives for the superconducting electron accelerator have been achieved and exceeded. At 8.5 MeV and 25 μA, spreads in phase and energy of 1.2° and 9.2 keV fullwidth at half‐maximum, respectively, have been measured, and at 250 μA the spreads in the phase and energy increased by only 10%.

Elasticity effect in rotational decay experiments

George Comsa and J.K. Fremerey

Appl. Phys. Lett. 22, 608 (1973); http://dx.doi.org/10.1063/1.1654526 (2 pages)

Online Publication Date: 16 October 2003

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A general first‐order approximation correction is presented which has to be applied to the theoretical frequency decay ratio ‐ω∕ω of a rigid rotor in order to find the corresponding ratio for a real elastic rotor. The procedure is exemplified for the particular drags associated with gas friction and with the Coriolis effect acting on steel spheres. In these cases the decay ratio is at most about 1% smaller than that of the corresponding rigid sphere.

High‐resolution thermionic cathode scanning transmission electron microscope

A.N. Broers

Appl. Phys. Lett. 22, 610 (1973); http://dx.doi.org/10.1063/1.1654527 (3 pages) | Cited 13 times

Online Publication Date: 16 October 2003

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A new scanning transmission electron microscope has been built which uses a lanthanum hexaboride thermal cathode electron gun. Initial results indicate a beam diameter of 5 Å and point‐to‐point resolution of 7 Å. The vacuum level in the instrument is similar to that of standard commercially available electron microscopes. A comparison of the performance of tungsten hairpin, lanthanum hexaboride, and field emission cathodes for scanning transmission electron microscopy is given.
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Erratum: Parametric amplification and oscillation in nonlinear backward scattering

Hsiung Hsu and Chung Yu

Appl. Phys. Lett. 22, 613 (1973); http://dx.doi.org/10.1063/1.1654528 (1 page) | Cited 3 times

Online Publication Date: 16 October 2003

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