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18 Apr 2005

Volume 86, Issue 16, Articles (16xxxx)

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Nanoscale Fabry–Pérot Interferometer using channel plasmon-polaritons in triangular metallic grooves

D. F. P. Pile and D. K. Gramotnev

Appl. Phys. Lett. 86, 161101 (2005); http://dx.doi.org/10.1063/1.1905799 (3 pages) | Cited 31 times

Online Publication Date: 11 April 2005

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In this letter, we demonstrate the possibility of an effective nanoscale Fabry–Pérot interferometer in a subwavelength plasmonic waveguide in the form of a triangular groove on a metal surface, guiding channel plasmon-polaritons. The resonant cavity is formed by two semitransparent metal membranes (mirrors) placed into the groove. Effective filtering effect of the cavity is demonstrated, resulting in single-mode output from the cavity. Typical quality factor for the cavity of the resonant length is determined to be Q ∼ 100 for the silver-vacuum structure with the 30° groove angle. Possible ways of increasing this factor are discussed.
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07.60.Ly Interferometers
42.79.Gn Optical waveguides and couplers
42.79.Bh Lenses, prisms and mirrors
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Low threshold edge emitting polymer distributed feedback laser based on a square lattice

A. E. Vasdekis, G. A. Turnbull, I. D. W. Samuel, P. Andrew, and W. L. Barnes

Appl. Phys. Lett. 86, 161102 (2005); http://dx.doi.org/10.1063/1.1898430 (3 pages) | Cited 17 times

Online Publication Date: 11 April 2005

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We report the demonstration of a low-threshold, edge-emitting polymer distributed feedback laser based on a square lattice. The lattice constant was 268 nm, which corresponds to a lattice line spacing in the ΓM symmetry direction of the Brillouin zone of 189 nm. The latter was employed to provide feedback at 630 nm via a first order diffraction process. The device operated on two longitudinal modes, which were situated on the band-edge near the M symmetry point. The two modes had thresholds of 0.66 nJ and 1.2 nJ—significantly lower than comparable surface-emitting DFB lasers. Angle dependent photoluminescence experiments were performed to investigate the effect of the square lattice on the laser operation and the origin of the low threshold.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

All-optical dynamic correction of distorted communication signals using a photorefractive polymeric hologram

Guoqiang Li, Muhsin Eralp, Jayan Thomas, Savaş Tay, Axel Schülzgen, Robert A. Norwood, and N. Peyghambarian

Appl. Phys. Lett. 86, 161103 (2005); http://dx.doi.org/10.1063/1.1898432 (3 pages) | Cited 6 times

Online Publication Date: 11 April 2005

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All-optical real-time dynamic correction of wave front aberrations for image transmission is demonstrated using a photorefractive polymeric hologram. The material shows video rate response time with a low power laser. High-fidelity, high-contrast images can be reconstructed when the oil-filled phase plate generating atmospheric-like wave front aberrations is moved at 0.3 mm/s. The architecture based on four-wave mixing has potential application in free-space optical communication, remote sensing, and dynamic tracking. The system offers a cost-effective alternative to closed-loop adaptive optics systems.
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42.40.Eq Holographic optical elements; holographic gratings
42.70.Jk Polymers and organics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.30.Wb Image reconstruction; tomography
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Simple color tuning of phosphorescent dendrimer light emitting diodes

Ebinazar B. Namdas, Thomas D. Anthopoulos, Ifor D. W. Samuel, Michael J. Frampton, Shih-Chun Lo, and Paul L. Burn

Appl. Phys. Lett. 86, 161104 (2005); http://dx.doi.org/10.1063/1.1899256 (3 pages) | Cited 9 times

Online Publication Date: 11 April 2005

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A simple way of tuning the emission color in solution processed phosphorescent organic light emitting diodes is demonstrated. For each color a single emissive spin-coated layer consisting of a blend of three materials, a fac-tris(2-phenylpyridyl)iridium (III) cored dendrimer (Ir–G1) as the green emitter, a heteroleptic [bis(2‐phenylpyridyl)‐2‐(2′‐benzo[4,5‐α]thienyl)pyridyl]iridium (III) cored dendrimer [Ir(ppy)2btp] as the red emitter, and 4,4′-bis(N-carbazolyl) biphenyl (CBP) as the host was employed. By adjusting the relative amount of green and red dendrimers in the blends, the color of the light emission was tuned from green to red. High efficiency two layer devices were achieved by evaporating a layer of electron transporting 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene (TPBI) on top of the spin-coated emissive layer. A brightness of 100 cd/m2 was achieved at drive voltages in the range 5.3–7.3 V. The peak external efficiencies at this brightness ranged from 31 cd/A (18 lm/W) to 7 cd/A (4 lm/W).
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85.60.Jb Light-emitting devices
78.60.Fi Electroluminescence
78.55.Kz Solid organic materials

Fiber-coupled random laser

M. A. Noginov, I. N. Fowlkes, and G. Zhu

Appl. Phys. Lett. 86, 161105 (2005); http://dx.doi.org/10.1063/1.1904712 (3 pages)

Online Publication Date: 11 April 2005

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We demonstrate that in fiber-coupled random laser, the threshold energy is twofold reduced and the slope efficiency is fivefold increased when the tip of the fiber is relocated from the surface to the depth of the powder volume. High absorption efficiency, 85%, and high conversion efficiency of population inversion to stimulated emission, 90%, make fiber-coupled random laser a promising laser source. The demonstrated 5% quantum slope efficiency of the “ready to use” random laser emission delivered by the fiber can probably be significantly increased after the optimization of the coupling of emission to the fiber.
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42.55.Zz Random lasers
42.55.Wd Fiber lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Broadband difference frequency generation around phase-match singularity

Tsutomu Yanagawa, Hirohisa Kanbara, Osamu Tadanaga, Masaki Asobe, Hiroyuki Suzuki, and Junji Yumoto

Appl. Phys. Lett. 86, 161106 (2005); http://dx.doi.org/10.1063/1.1905780 (3 pages) | Cited 12 times

Online Publication Date: 12 April 2005

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It is shown that a wide tunability range of greater than 500 nm can be obtained in the 2 μm band in an 18 mm long periodically poled lithium niobate chip with a single quasiphase-matching grating period at a constant temperature. This letter demonstrates the difference frequency generation bandwidth. A tunable bandwidth of over 130 nm is experimentally confirmed in the 2 μm region. This broad bandwidth can be realized by means of the phase-match curve distortion caused by the phase-match singularity. The wavelength conversion temperature dependence is also shown for several quasiphase-matching grating periods.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Dj Gratings

Single-shot autocorrelation at relativistic intensity

Ben Liesfeld, Jens Bernhardt, Kay-Uwe Amthor, Heinrich Schwoerer, and Roland Sauerbrey

Appl. Phys. Lett. 86, 161107 (2005); http://dx.doi.org/10.1063/1.1905779 (3 pages) | Cited 3 times

Online Publication Date: 13 April 2005

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We demonstrate the single-shot autocorrelation of an ultrashort laser pulse at relativistic intensity (above 1018 W/cm2). The pulse is divided into two equally strong laser pulses which are focused into a He-gas jet under an angle of 180°. Nonlinear Thomson scattering from plasma electrons is used as second-order autocorrelation signal.
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42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Optical microfiber loop resonator

M. Sumetsky, Y. Dulashko, J. M. Fini, and A. Hale

Appl. Phys. Lett. 86, 161108 (2005); http://dx.doi.org/10.1063/1.1906317 (3 pages) | Cited 52 times

Online Publication Date: 13 April 2005

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We experimentally demonstrate an optical microfiber loop resonator. The resonator was formed in free space by creating a loop from the subwavelength-diameter waist of a short biconical optical fiber taper. The loop length was chosen so that the free spectrum range of the resonator was ∼ 100 GHz at the optical communication wavelengths near 1.5 μm. In order to change and optimize the spectral characteristics such as the effect of birefringence, the shape of resonances, and the free spectrum range, we manually varied the microfiber self-coupling by alignment of the input and output ends of the loop, which were attached to each other by Van der Waals and electrostatic forces. In particular, we tuned the microfiber loop resonator to exhibit resonances with a Q-factor exceeding 15 000 (finesse ≈ 10) and, also, to the regime of critical coupling with the extinction ratio of transmission oscillations exceeding 34 dB. This paper was in press when we achieved the values of 95 000 and 630 000 for the loaded and intrinsic Q-factor, respectively (see note added in proof). We believe that the demonstrated Q-factor can be significantly enhanced with the more uniform microfiber.
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42.81.Wg Other fiber-optical devices
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.81.Cn Fiber testing and measurement of fiber parameters
42.81.Gs Birefringence, polarization
42.81.Qb Fiber waveguides, couplers, and arrays

Tellurite glasses for ultrabroadband fiber Raman amplifiers

G. Senthil Murugan, Takenobu Suzuki, and Yasutake Ohishi

Appl. Phys. Lett. 86, 161109 (2005); http://dx.doi.org/10.1063/1.1906323 (3 pages) | Cited 25 times

Online Publication Date: 13 April 2005

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Tellurite glasses optimized for higher Raman gain and broad bandwidth have been realized. These glasses were found to have improved thermal stabilities, which make them suitable for fiber devices applications. While maintaining the Raman gains at higher values, the Raman bandwidths could be broadened by proper addition of alkaline earth oxides and heavy metal oxides in to the tellurite glasses. The relative Raman gain and Raman cross sections of the present glasses are better than the tellurite-based glasses reported earlier. Thus, higher Raman gain and much broader Raman amplifications could be possible by using this tellurite glass system as a gain medium compared with the conventional tellurite-based fiber Raman amplifiers.
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42.55.Wd Fiber lasers
42.55.Ye Raman lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.70.Ce Glasses, quartz

Out-of-plane microlens array fabricated using ultraviolet lithography

Ren Yang, Wanjun Wang, and Steven A. Soper

Appl. Phys. Lett. 86, 161110 (2005); http://dx.doi.org/10.1063/1.1901829 (3 pages) | Cited 12 times

Online Publication Date: 13 April 2005

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This letter describes a three-dimensional ultraviolet-lithography (UV-lithography) process for fabricating an out-of-plane microlens array that can be prealigned with other optical components in an integrated optical bench or easily integrated into microfluidic devices. This microlens array is fabricated with a unique UV-lithography technique, and the desired surface profiles are obtained from top rows to lower rows. The microlens’ focal lengths, diameters of focal pads, depths of focus, and surface profiles are measured and reported herein. This microlens array can be prealigned with another microlens array or other optical components on the same substrate to obtain a truly integrated free-space optical bench. In addition, the fill factor of this microlens array approaches 100%.
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42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Et Waveguides, couplers, and arrays

Ultrafast optical switching with CdTe nanocrystals in a glass matrix

L. A. Padilha, A. A. R. Neves, E. Rodriguez, C. L. Cesar, L. C. Barbosa, and C. H. Brito Cruz

Appl. Phys. Lett. 86, 161111 (2005); http://dx.doi.org/10.1063/1.1905805 (3 pages) | Cited 13 times

Online Publication Date: 14 April 2005

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This letter describes a principle demonstration of an ultrafast optical switch operating at 1 Tbit/s using CdTe-quantum-dots-doped glasses. Using a three-beam pump and probe experiment, we showed that thermal effects are responsible for a baseline in the pump and probe graphs and the nonexistence of carrier accumulation effects. After eliminating the thermal effects, we showed that, when two pump pulses are delayed by 1 ps, each pump pulse modulates the probe pulse independently, making this material highly promising for ultrafast all optical switching.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.70.Ce Glasses, quartz
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Near-field and far-field dynamics of (Al,In)GaN laser diodes

Ulrich T. Schwarz, Markus Pindl, Werner Wegscheider, Christoph Eichler, Ferdinand Scholz, Michael Furitsch, Andreas Leber, Stephan Miller, Alfred Lell, and Volker Härle

Appl. Phys. Lett. 86, 161112 (2005); http://dx.doi.org/10.1063/1.1900304 (3 pages) | Cited 13 times

Online Publication Date: 14 April 2005

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Near- and far-field dynamics of edge-emitting (Al,In)GaN laser diodes are measured simultaneously with a 100 nm spatial and a 5 ns temporal resolution using a scanning near-field microscope. We reconstruct the phase distribution at the laser diode facet. Beam steering and near-field mode dynamics are interpreted in terms of thermal and carrier induced change of refractive index in the waveguide.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
68.37.Uv Near-field scanning microscopy and spectroscopy

Nanoimprinted strain-controlled elastomeric gratings for optical wavelength tuning

Yi-Chung Tung and Katsuo Kurabayashi

Appl. Phys. Lett. 86, 161113 (2005); http://dx.doi.org/10.1063/1.1900923 (3 pages) | Cited 18 times

Online Publication Date: 14 April 2005

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We demonstrate strain-controlled gratings made of an organic elastomer, polydimethylsiloxane (PDMS), which can achieve optical wavelength tuning by varying their spatial periods. The whole device structure presented in this work incorporates a nanoimprinted PDMS grating integrated with electrostatic microelectromechanical systems actuators on a silicon chip. The fabrication of the device combines polymer soft lithography, nanoimprint lithography, and silicon micromachining across multiscale dimensions ranging from a few hundred nanometers to a few millimeters. The fine tuning capability with fast dynamic response of our PDMS/silicon hybrid optical grating device makes it attractive for use in various micro-optical instruments.
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42.79.Dj Gratings
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
81.16.Nd Micro- and nanolithography
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.82.Fv Hybrid systems
78.40.Me Organic compounds and polymers
78.40.Fy Semiconductors

Quantum-cascade lasers without injector regions operating above room temperature

Andrea Friedrich, Gerhard Boehm, Markus Christian Amann, and Giuseppe Scarpa

Appl. Phys. Lett. 86, 161114 (2005); http://dx.doi.org/10.1063/1.1906302 (2 pages) | Cited 2 times

Online Publication Date: 14 April 2005

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We present above-room-temperature operation of an injectorless quantum-cascade (QC) laser. The active region is designed as a four-level staircase and has been realized in the strain-compensated material system Ga0.4In0.6As/Al0.56In0.44As based on InP. In pulsed operation the lasers work up to a heat-sink temperature of 340 K, the highest temperature achieved so far with injectorless QC lasers. A large wavelength shift is observed for higher bias fields and (therefore) at high temperatures (10 μm at 77 K and 8.4 μm at 300 K).
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes

Lithium niobate ridge waveguides and modulators fabricated using smart guide

Payam Rabiei and William H. Steier

Appl. Phys. Lett. 86, 161115 (2005); http://dx.doi.org/10.1063/1.1906311 (3 pages) | Cited 33 times

Online Publication Date: 14 April 2005

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Ridge waveguides are fabricated using submicron thin films of lithium niobate prepared by crystal ion slicing and wafer bonding (“smart guide”). The waveguides are made by physical etching the lithium niobate thin film using ion beam milling. The waveguides are low loss. An electro-optic polarization modulator with VπL of 15 V cm at λ = 1.55 μm is demonstrated using the waveguides.
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42.79.Gn Optical waveguides and couplers
42.79.Hp Optical processors, correlators, and modulators
42.70.Mp Nonlinear optical crystals
42.86.+b Optical workshop techniques

9.2‐W diode–end–pumped Yb:Y2O3 ceramic laser

J. Kong, D. Y. Tang, B. Zhao, J. Lu, K. Ueda, H. Yagi, and T. Yanagitani

Appl. Phys. Lett. 86, 161116 (2005); http://dx.doi.org/10.1063/1.1914958 (3 pages) | Cited 26 times

Online Publication Date: 14 April 2005

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We report on a high-power diode–end–pumped polycrystalline Yb:Y2O3 ceramic laser. Under the pump power of 27 W, continuous-wave output power of 9.2 W at 1078 nm has been obtained by using an output coupler of R = 96%. The laser had a threshold of 3.1 W and a slope efficiency of 41%. Comparative studies on the laser performance between the Yb:Y2O3 ceramic and the Yb:yttrium aluminum garnet (YAG) single crystal show that at the same doping concentration of 8 at. %, higher laser efficiency can be obtained in the Yb:Y2O3 ceramic laser than in the Yb:YAG single crystal laser.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.70.Hj Laser materials

Intracavity grating-confined all-epitaxial vertical-cavity surface-emitting laser based on selective interface Fermi-level pinning

D. Gazula, J. Ahn, D. Lu, H. Huang, and D. G. Deppe

Appl. Phys. Lett. 86, 161117 (2005); http://dx.doi.org/10.1063/1.1897049 (3 pages)

Online Publication Date: 15 April 2005

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An all-epitaxial GaAs-based vertical-cavity surface-emitting laser is demonstrated with an intracavity mode and current-confining grating. The grating uses selective Fermi-level pinning at a heterointerface to confine the current to the same regions as the optical mode. Despite the grating’s “coarseness,” an increase of efficiency is obtained in side-by-side comparison with devices that lack the grating.
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42.55.Px Semiconductor lasers; laser diodes
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Short pitch cholesteric electro-optical device stabilized by nonuniform polymer network

Sang Hwa Kim, Liang-Chy Chien, and Lachezar Komitov

Appl. Phys. Lett. 86, 161118 (2005); http://dx.doi.org/10.1063/1.1897057 (3 pages) | Cited 13 times

Online Publication Date: 15 April 2005

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We have developed a method for stabilization of the uniform lying helix (ULH) texture of short pitch cholesterics in an electro-optical device, based on the flexoelectro-optic effect in such a texture. By using a small concentration of photoreactive liquid crystal monomer (less than 5 wt. %) and selecting the illumination conditions, we were able to create a nonuniform polymeric network in the liquid crystal bulk (localized essentially at both substrate surfaces) which stabilized efficiently the amplitude and the phase modulation modes of the device. Most importantly, the effect of the residual birefringence of the polymeric network in the field-unwound state of the device was eliminated resulting thus in a substantial improvement of device performance.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Kr Display devices, liquid-crystal devices
42.70.Df Liquid crystals
61.30.Vx Polymer liquid crystals

Single polarized Tm3+ laser in Zn-diffused LiNbO3 channel waveguides

E. Cantelar, J. A. Sanz-García, G. Lifante, F. Cussó, and P. L. Pernas

Appl. Phys. Lett. 86, 161119 (2005); http://dx.doi.org/10.1063/1.1887813 (3 pages) | Cited 22 times

Online Publication Date: 15 April 2005

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In this work, laser operation at 1.76 μm in Tm3+:LiNbO3 Zn-diffused channel waveguides is reported. The laser emission is single polarized with the electric field parallel to the optic axis(π-polarization) and operates in continuous-wave regime, at room temperature. The threshold of laser oscillation is in the range of 40 mW, the slope efficiency is around 1%, and both magnitudes are dependent on the channel width, in accordance with the mode overlap between the pump and signal modes within the waveguides.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Pk Continuous operation

Cholesteric liquid crystal laser with wide tuning capability

Tsung-Hsien Lin, Yi-Jan Chen, Chun-Hui Wu, Andy Y.-G. Fuh, J.-H. Liu, and P.-C. Yang

Appl. Phys. Lett. 86, 161120 (2005); http://dx.doi.org/10.1063/1.1897439 (3 pages) | Cited 52 times

Online Publication Date: 15 April 2005

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This letter examines a planar cholesteric cell (CLC) doped with two collocated laser dyes as a one-dimensional photonic crystal. Adding phototunable chiral material (AzoB) allows the CLC photonic crystal to be lased at the band edges of the photonic band gap with a tuning range of over 100 nm. Tuning is performed by irradiating the chiral AzoB material with UV light, causing the material to undergo trans-cis isomerization in the CLC film. The tuning range is the visible region from 563 to 667 nm. Moreover, the tuning is reversible.
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42.55.Tv Photonic crystal lasers and coherent effects
42.55.Mv Dye lasers
42.60.Fc Modulation, tuning, and mode locking
42.70.Df Liquid crystals
42.70.Hj Laser materials
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Direct measurement of electron density in microdischarge at atmospheric pressure by Stark broadening

Lifang Dong, Junxia Ran, and Zhiguo Mao

Appl. Phys. Lett. 86, 161501 (2005); http://dx.doi.org/10.1063/1.1906299 (3 pages) | Cited 20 times

Online Publication Date: 14 April 2005

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We present a method and results for measurement of electron density in atmospheric-pressure dielectric barrier discharge. The electron density of microdischarge in atmospheric pressure argon is measured by using the spectral line profile method. The asymmetrical deconvolution is used to obtain Stark broadening. The results show that the electron density in single filamentary microdischarge at atmospheric pressure argon is 3.05×1015 cm−3 if the electron temperature is 10 000 K. The result is in good agreement with the simulation. The electron density in dielectric barrier discharge increases with the increase of applied voltage.
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52.80.Tn Other gas discharges
52.70.−m
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
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Effect of gold coating on local oxidation using an atomic force microscope

J. S. Hwang, Z. Y. You, S. Y. Lin, Z. S. Hu, C. T. Wu, C. W. Chen, and K. H. Chen

Appl. Phys. Lett. 86, 161901 (2005); http://dx.doi.org/10.1063/1.1901804 (3 pages) | Cited 12 times

Online Publication Date: 11 April 2005

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A simple method to enhance atomic force microscopy local oxidation by coating the substrate with a thin layer of gold is reported. The effect of gold coating is demonstrated experimentally by atomic force microscopy oxidation at various thicknesses of gold on Si and InP. Oxide heights reaching 30 nm are easily achieved on silicon at rates 10 times greater than traditional methods. The gold layer is assumed to increase conductance and current during oxidation, thereby reducing decline in growth rates caused by the increasing resistance of the growing oxide layer itself. Improvement in growth rate and height increases with increasing gold thickness up to a maximum height, but beyond that thickness the heights and rates decrease because the gold layer itself becomes a barrier to the migration of oxyions. The presented method is demonstrated to improve the oxidation rate and height on normal and highly resistive substrates, with lower requirements for applied voltage during oxidation.
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81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
81.05.Ea III-V semiconductors
68.37.Ps Atomic force microscopy (AFM)
73.25.+i Surface conductivity and carrier phenomena

Atomistic modeling of shock-induced void collapse in copper

L. P. Dávila, P. Erhart, E. M. Bringa, M. A. Meyers, V. A. Lubarda, M. S. Schneider, R. Becker, and M. Kumar

Appl. Phys. Lett. 86, 161902 (2005); http://dx.doi.org/10.1063/1.1906307 (3 pages) | Cited 20 times

Online Publication Date: 12 April 2005

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Nonequilibrium molecular-dynamics (MD) simulations show that shock-induced void collapse in copper occurs by emission of shear loops. These loops carry away the vacancies which comprise the void. The growth of the loops continues even after they collide and form sessile junctions, creating a hardened region around the collapsing void. The scenario seen in our simulations differs from current models that assume that prismatic loop emission is responsible for void collapse. We propose a dislocation-based model that gives excellent agreement with the stress threshold found in the MD simulations for void collapse as a function of void radius.
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62.50.-p High-pressure effects in solids and liquids
61.72.Nn Stacking faults and other planar or extended defects
61.72.Bb Theories and models of crystal defects
62.20.F- Deformation and plasticity
61.72.J- Point defects and defect clusters
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Lattice distortion of MnAs nanocrystals embedded in GaAs: Effect on the magnetic properties

M. Moreno, B. Jenichen, L. Däweritz, and K. H. Ploog

Appl. Phys. Lett. 86, 161903 (2005); http://dx.doi.org/10.1063/1.1899767 (3 pages) | Cited 6 times

Online Publication Date: 12 April 2005

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The x-ray coherent scattering in nanosized MnAs crystallites embedded in a GaAs matrix has been detected. The room-temperature interatomic distances along three orthogonal directions of the crystallites are determined. The MnAs nanocrystals are found to exhibit an anisotropically distorted hexagonal structure as compared to unstrained bulk MnAs. Despite the crystallite lattice distortion, the granular GaAs:MnAs material exhibits robust ferromagnetism, with enhanced transition temperature. The observed magnetic behavior is consistently explained by a localized double-exchange model of MnAs ferromagnetism, where magnetic order appears for large enough Mn–As–Mn distances, i.e., for weak enough p-d hybridization.
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75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.20.Ck Nonmetals
75.30.Et Exchange and superexchange interactions
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
78.70.Ck X-ray scattering

THz Sommerfeld wave propagation on a single metal wire

Tae-In Jeon, Jiangquan Zhang, and D. Grischkowsky

Appl. Phys. Lett. 86, 161904 (2005); http://dx.doi.org/10.1063/1.1904718 (3 pages) | Cited 74 times

Online Publication Date: 12 April 2005

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We report an experimental and theoretical study of THz Sommerfeld wave propagation on a single copper wire. THz pulses are optoelectronically generated and launched onto 0.52-mm-diam copper wire, and the guided THz pulses are detected at the end of the wire by a standard photoconductive antenna. Very low attenuation and group velocity dispersion are observed, and the measured radial field amplitude of the Sommerfeld wave is inversely proportional to the radial distance. These results are consistent with theoretical predictions. Experimental results from curved wires show the weakly guiding property of the THz Sommerfeld wave, which will limit its applications.
Show PACS
41.20.Jb Electromagnetic wave propagation; radiowave propagation
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.57.Hm Infrared, submillimeter wave, microwave, and radiowave sources
84.40.Ba Antennas: theory, components and accessories
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