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25 Jun 2007

Volume 90, Issue 26, Articles (26xxxx)

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Appl. Phys. Lett. 90, 262501 (2007); http://dx.doi.org/10.1063/1.2752015 (3 pages)

Ian Appelbaum and Douwe J. Monsma
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Optically trapped and controlled microapertures for studies of spatial coherence in an arbitrary light field

W. M. Lee and K. Dholakia

Appl. Phys. Lett. 90, 261101 (2007); http://dx.doi.org/10.1063/1.2751590 (3 pages)

Online Publication Date: 25 June 2007

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By controlling the rotation rate of a trapped birefringent particle with an optically applied torque, the authors introduce a miniscule wave front deformation at a specific location within an arbitrary light field, with the particle acting as an optical microdiffuser. A trapped birefringent particle and a trapped silica microsphere are positioned to form Young’s double slit experiment within a probe light field. The far-field interference from the diffracted optical fields from these particles enable the authors to infer the relative spatial coherence between these local sampling points. With multiple trapped particles, the authors may perform multipoint coherence analysis of a light field.
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42.25.Kb Coherence
37.10.Vz Mechanical effects of light on atoms, molecules, and ions

Patterning of indium tin oxide by projection photoablation and lift-off process for fabrication of flat-panel displays

Junghun Chae, Sreeram Appasamy, and Kanti Jain

Appl. Phys. Lett. 90, 261102 (2007); http://dx.doi.org/10.1063/1.2751594 (3 pages) | Cited 13 times

Online Publication Date: 25 June 2007

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Indium tin oxide (ITO), an important material used as a transparent conductive oxide in thin-film transistor liquid-crystal display fabrication, was patterned by a nonlithographic process. First, a Si3N4 substrate coated with photoresist was patterned by a projection photoablation process using 248 nm wavelength KrF excimer laser radiation. ITO was then deposited by sputtering and patterned by lift-off. The resulting ITO pattern was clean even though it was patterned without the conventional steps of photoresist development and ITO etching. This process technology provides a faster and more economical patterning capability compared to conventional photolithography and etch processes used in the display industry.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Sz Deposition technology

Optically switchable biphotonic gratings based on dye-doped cholesteric liquid crystal films

H.-C. Yeh, G.-H. Chen, C.-R. Lee, and T.-S. Mo

Appl. Phys. Lett. 90, 261103 (2007); http://dx.doi.org/10.1063/1.2752110 (3 pages) | Cited 10 times

Online Publication Date: 25 June 2007

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This study elucidates optically switchable gratings (BGs) based on biphotonic effect in dye-doped cholesteric liquid crystal films. When one circularly polarized green beam is switched on (off), the gratings can be turned on (off) by illumination with an interference field generated by two linearly polarized red beams. The biphotonic gratings are formed by two mechanisms—green-beam-induced dye reorientation through trans-cis isomerization and red-beam-induced suppression of dye reorientation by cis-trans back isomerization. These mechanisms result in a spatially periodic distribution with homeotropiclike and planarlike structures, respectively, in dark and bright regions of the interference field, generating the BGs.
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42.79.Dj Gratings
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.70.Df Liquid crystals
61.30.-v Liquid crystals

Enhancement of two-color high harmonic by using two compound strong ionic transitions in double-target scheme

Masayuki Suzuki, Rashid A. Ganeev, Tsuneyuki Ozaki, Motoyoshi Baba, and Hiroto Kuroda

Appl. Phys. Lett. 90, 261104 (2007); http://dx.doi.org/10.1063/1.2752112 (3 pages) | Cited 5 times

Online Publication Date: 25 June 2007

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The authors generated high-order harmonics by using the two-component laser-ablation plumes, which were irradiated by a femtosecond laser pulse. The harmonic spectra from double-target schemes comprised those obtained from separate targets. For indium/chromium plumes, the enhancement of two harmonics (13th and 29th orders) was obtained at the wavelengths of 61.15 and 27.41 nm, respectively. The conversion efficiencies of these two harmonics were estimated to be 10−5. The authors attribute the enhancement of 13th and 29th harmonics to the multiphoton resonances with the strong radiative transitions of ions in indium and chromium plumes, respectively.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
52.38.Mf Laser ablation
52.38.-r Laser-plasma interactions
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
32.80.Rm Multiphoton ionization and excitation to highly excited states

High transmission nanoscale bowtie-shaped aperture probe for near-field optical imaging

Liang Wang and Xianfan Xu

Appl. Phys. Lett. 90, 261105 (2007); http://dx.doi.org/10.1063/1.2752542 (3 pages) | Cited 37 times

Online Publication Date: 25 June 2007

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A near-field scanning optical microscope probe integrated with nanoscale bowtie aperture for enhanced optical transmission is demonstrated. The bowtie-shape aperture allows a propagating mode in the bowtie gap region, which enables simultaneous nanoscale optical resolution and enhanced optical transmission. The optical characteristics of the bowtie aperture are demonstrated by measuring the optical near fields produced by the aperture. It is shown that bowtie aperture probes have one order of magnitude increase in transmission over probes with a regular shape aperture of the same resolution. The imaging results using bowtie aperture are in agreement with those obtained from numerical calculations.
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07.79.Fc Near-field scanning optical microscopes

Deformation corrected real-time terahertz imaging

Toshiaki Hattori and Masaya Sakamoto

Appl. Phys. Lett. 90, 261106 (2007); http://dx.doi.org/10.1063/1.2752543 (3 pages) | Cited 5 times

Online Publication Date: 25 June 2007

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The authors have developed a method of real-time terahertz imaging in which image deformation due to nonuniformity of residual birefringence in the electro-optic (EO) sampling crystal is corrected. Real-time terahertz imaging using intense terahertz pulses and two-dimensional EO sampling can suffer from birefringence nonuniformity of the EO crystal since the birefringence is explicitly used for the linear detection of the terahertz field. In the proposed method, the distribution of the residual birefringence of the EO crystal is measured and used for image correction. Deformation-free images of the spatial profile of a focused terahertz pulse were obtained.
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07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
78.20.Fm Birefringence
78.20.Jq Electro-optical effects

Direct measurement of the group index of photonic crystal waveguides via Fourier transform spectral interferometry

Alvaro Gomez-Iglesias, David O’Brien, Liam O’Faolain, Alan Miller, and Thomas F. Krauss

Appl. Phys. Lett. 90, 261107 (2007); http://dx.doi.org/10.1063/1.2752761 (3 pages) | Cited 25 times

Online Publication Date: 25 June 2007

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The authors report a direct, single-shot measurement of the group index profile of photonic crystal waveguides, combining spectral interferometry with Fourier transform analysis. This technique’s versatility allows them to resolve subtle changes in dispersion and to quantify the “slow light” effect at the photonic crystal waveguide mode cutoff. For a waveguide 99 μm long, they measure a group index up to 85, whereas for lengths of 397 and 695 μm, they measure maximum values of 30 and 25, respectively. These results show the relationship between transmission characteristics and the maximum group delay observed in photonic crystals.
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07.60.Ly Interferometers
07.60.Hv Refractometers and reflectometers
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
42.30.Kq Fourier optics

Defect mode lasing from a double-layered dye-doped polymeric cholesteric liquid crystal films with a thin rubbed defect layer

Soon Moon Jeong, Na Young Ha, Yoichi Takanishi, Ken Ishikawa, Hideo Takezoe, Suzushi Nishimura, and Goro Suzaki

Appl. Phys. Lett. 90, 261108 (2007); http://dx.doi.org/10.1063/1.2752017 (3 pages) | Cited 16 times

Online Publication Date: 26 June 2007

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The authors have demonstrated defect mode lasing emission from a spin-coated double-layered dye-doped polymeric cholesteric liquid crystal (PCLC) films with a thin rubbed isotropic layer in between. The rubbed layer acts not only as an alignment layer for the second PCLC layer but also as an isotropic defect layer breaking periodicity of PCLC films. All the processes can be achieved in a wet process. Because of the process, the present polymeric solid-state laser is available as a freestanding thin film of only 5.5 μm in thickness and an almost limitless large area, which enable one to use it as a disposable laser chip of any shapes.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.55.Mv Dye lasers

Voltage-tuned resonant reflectance optical filter for visible wavelengths fabricated by nanoreplica molding

Fuchyi Yang, Gary Yen, and Brian T. Cunningham

Appl. Phys. Lett. 90, 261109 (2007); http://dx.doi.org/10.1063/1.2752128 (3 pages) | Cited 10 times

Online Publication Date: 26 June 2007

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A guided-mode resonant filter incorporating an electro-optically tunable liquid crystal refractive index is demonstrated at a wavelength of 655 nm and a tuning range of 4 nm. Rigorous coupled wave analysis and finite difference time domain analysis are used to simulate the characteristics of the filter during liquid crystal reorientation. Tuning performance is demonstrated that is consistent with the device simulations. Tunable filters in the visible wavelength range that are inexpensively fabricated over large surface areas are expected to find applications in optical limiting and video display.
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42.79.Ci Filters, zone plates, and polarizers
42.70.Df Liquid crystals
81.16.Nd Micro- and nanolithography

Ultrabroadband near-infrared emission from a colorless bismuth-doped glass

Yusuke Arai, Takenobu Suzuki, Yasutake Ohishi, Shigeki Morimoto, and Sasithorn Khonthon

Appl. Phys. Lett. 90, 261110 (2007); http://dx.doi.org/10.1063/1.2752539 (3 pages) | Cited 39 times

Online Publication Date: 26 June 2007

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The characteristics of bismuth-doped glasses were investigated as colorless ultrabroadband near-infrared gain media. The colorless Bi-doped soda-lime-silicate glass was prepared under controlled redox conditions, and it realized the broadest near-infrared emission of about 600 nm in full width at half maximum, centered at 1000 nm, under 720 nm excitation. The emission band extended toward shorter wavelengths compared with the shortest wavelength for the Bi-doped glass ever reported. The colorless Bi-doped glass developed in this work has a good potential for the broadband gain media for amplifiers and tunable lasers.
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42.70.Hj Laser materials
42.70.Ce Glasses, quartz
78.55.Hx Other solid inorganic materials
42.55.Rz Doped-insulator lasers and other solid state lasers

Molding light flow from photonic band gap circuits to microstructured fibers

James Bauer and Sajeev John

Appl. Phys. Lett. 90, 261111 (2007); http://dx.doi.org/10.1063/1.2752732 (3 pages) | Cited 4 times

Online Publication Date: 26 June 2007

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The authors demonstrate nearly lossless, broadband coupling of light between photonic band gap (PBG) circuits and photonic crystal fibers (PCFs) using two-dimensional design paradigms. A hollow-core PBG fiber yields a coupling efficiency of better than 94% over a bandwidth of 25% of the center frequency, with peak transmittance exceeding 98%. A small-mode-area PCF consisting of a subwavelength solid core with nonadiabatic taper, combined with a PBG beam collimator at the air-waveguide exit port, yields over 98% coupling efficiency over a bandwidth of 135 nm centered at a wavelength of 1.5 μm.
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42.81.Wg Other fiber-optical devices
42.81.Dp Propagation, scattering, and losses; solitons
42.82.Et Waveguides, couplers, and arrays

Above room-temperature operation of InAs/AlGaSb superlattice quantum cascade lasers emitting at 12 μm

K. Ohtani, Y. Moriyasu, H. Ohnishi, and H. Ohno

Appl. Phys. Lett. 90, 261112 (2007); http://dx.doi.org/10.1063/1.2752771 (3 pages) | Cited 2 times

Online Publication Date: 27 June 2007

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The authors report on above-room-temperature operation of InAs/AlGaSb quantum cascade lasers emitting at 12 μm. The laser structures are grown on a n-InAs (100) substrate using solid-source molecular beam epitaxy. An InAs/AlGaSb superlattice is used as an active part and an InAs double plasmon waveguide is used for optical confinement. Results show that increased doping concentration in the injection part of the active region expands the current operation range of the devices, allowing laser operation at and above room temperature. The observed threshold current density is 4.0 kA/cm2 at 300 K; the maximum operation temperature is 340 K.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

White light emitting diode by using α-Ca2P2O7:Eu2+, Mn2+ phosphor

Zhendong Hao, Jiahua Zhang, Xia Zhang, Xiaoyuan Sun, Yongshi Luo, Shaozhe Lu, and Xiao-jun Wang

Appl. Phys. Lett. 90, 261113 (2007); http://dx.doi.org/10.1063/1.2752725 (3 pages) | Cited 53 times

Online Publication Date: 27 June 2007

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The α-Ca2P2O7:Eu2+, Mn2+ phosphors show two emission bands peaking at around 416 (blue) and 600 nm (orange), originating from the allowed f-d transition of Eu2+ and the forbidden 4T1-6A1 transition of Mn2+, respectively, under near ultraviolet (UV) excitation at 400 nm. Spectroscopy and fluorescence lifetime measurements demonstrate that energy transfer from Eu2+ to Mn2+ performs with transfer efficiency as high as 65% for Mn2+ concentration of 12 mol %. The authors have fabricated a white light emitting diode (LED) through the integration of GaN near-UV chip and two phosphor blends (α-Ca2P2O7:Eu2+, Mn2+ blue-orange phosphor and Ba2SiO4:Eu2+ green phosphor) into a single package. The white LED shows color rendering index of 78, luminescent efficiency of 9 lm/W, and low color point variation against forward-bias currents.
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85.60.Jb Light-emitting devices

How to create and detect N-dimensional entangled photons with an active phase hologram

Martin Stütz, Simon Gröblacher, Thomas Jennewein, and Anton Zeilinger

Appl. Phys. Lett. 90, 261114 (2007); http://dx.doi.org/10.1063/1.2752728 (3 pages) | Cited 22 times

Online Publication Date: 28 June 2007

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The experimental realization of multidimensional quantum states may lead to unexplored and interesting physics, as well as advanced quantum communication protocols. The orbital angular momentum of photons is a well suitable discrete degree of freedom for implementing high-dimensional quantum systems. The standard method to generate and manipulate such photon modes is to use bulk and fixed optics. Here the authors demonstrate the utilization of a spatial light modulator to manipulate the orbital angular momentum of entangled photons generated in spontaneous parametric downconversion. They show that their setup allows them to realize photonic entanglement of up to 21 dimensions, which in principle can be extended to even larger dimensions.
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42.50.Dv Quantum state engineering and measurements
42.65.Lm Parametric down conversion and production of entangled photons
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.40.My Applications

Lasing characteristics of GaSb/GaAs self-assembled quantum dots embedded in an InGaAs quantum well

J. Tatebayashi, A. Khoshakhlagh, S. H. Huang, G. Balakrishnan, L. R. Dawson, D. L. Huffaker, D. A. Bussian, H. Htoon, and V. Klimov

Appl. Phys. Lett. 90, 261115 (2007); http://dx.doi.org/10.1063/1.2752018 (3 pages) | Cited 17 times

Online Publication Date: 28 June 2007

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The authors report the optical characteristics of GaSb/GaAs self-assembled quantum dots (QDs) embedded in an InGaAs quantum well (QW). Variations in the In composition of the QW can significantly alter the emission wavelength up to 1.3 μm and emission efficiency. Lasing operation at room temperature is obtained from a 2-mm-long device containing five stacked GaSb QDs in In0.13Ga0.87As QWs at 1.026 μm with a threshold current density of 860 A/cm2. The probable lasing transition involves electrons and holes confined in the QW and QDs, respectively, resulting in a large peak modal gain of 45 cm−1. A significant blueshift of the electroluminescence peak is observed with increased injection current and suggests a type-II band structure.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Continuous-wave operation of electrically pumped, single-mode, edge-emitting photonic crystal Bragg lasers

Lin Zhu, Xiankai Sun, Guy A. DeRose, Axel Scherer, and Amnon Yariv

Appl. Phys. Lett. 90, 261116 (2007); http://dx.doi.org/10.1063/1.2752124 (3 pages) | Cited 3 times

Online Publication Date: 28 June 2007

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The authors demonstrate an electrically pumped, single-mode, large-area, edge-emitting InGaAsP/InP two dimensional photonic crystal Bragg laser operating in continuous-wave condition. The laser uses a weak index perturbed, polymer-planarized, surface photonic crystal structure to control the optical mode in the wafer plane. They find that the laser operates in single transverse and longitudinal modes. They compare the performance of the photonic crystal Bragg laser with a broad-area laser fabricated from the same wafer and the comparison shows that the performance penalty incurred by the photonic crystal is small.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Effect of periodic deflector embedded in InGaN/GaN light emitting diode

Hyung Gu Kim, Min Gyu Na, Hyun Kyu Kim, Hee Yun Kim, Jae Hyoung Ryu, Tran Viet Cuong, and Chang-Hee Hong

Appl. Phys. Lett. 90, 261117 (2007); http://dx.doi.org/10.1063/1.2752777 (3 pages) | Cited 21 times

Online Publication Date: 29 June 2007

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This letter proposes a concept of InGaN/GaN light emitting diodes with periodic deflector embedded structure (PDE-LED). The PDE-LED was grown on a sapphire substrate with SiO2 hexagonal patterned mask using selective metal-organic chemical deposition. More than 200 artificial inverted polygonal pyramids (AIPPs), which included six R planes and six N planes deflectors with inclined angles of 57° and 61°, respectively, were formed and periodically distributed on masked area. These AIPP deflectors revealed a superior capability of enhancing light extraction efficiency mainly because the AIPP deflector structure could provide multiple chances for photons to escape from the LED sidewall as opposed to a rectangular conventional LED. Thus, the light output power of the PDE-LED was 1.51 times higher than that of a conventional LED at an injection current of 20 mA, while forward bias voltage and leakage current were compatible to those of conventional LEDs.
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85.60.Jb Light-emitting devices

Discrete diffraction in waveguide arrays: A quantitative analysis by tunneling optical microscopy

Giuseppe Della Valle, Stefano Longhi, Paolo Laporta, Paolo Biagioni, Lamberto Duò, and Marco Finazzi

Appl. Phys. Lett. 90, 261118 (2007); http://dx.doi.org/10.1063/1.2753099 (3 pages) | Cited 7 times

Online Publication Date: 29 June 2007

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The authors report on a quantitative measurement of discrete diffraction in an array of tunneling-coupled optical waveguides using scanning tunneling optical microscopy performed with a cantilevered hollow pyramid tip. The impulse response of the array in terms of Bessel functions is reproduced with excellent accuracy, proving that photon transport in the array is fully analogous to the ballistic motion of electrons in a tight-binding lattice without disorder.
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42.79.Gn Optical waveguides and couplers
05.60.Gg Quantum transport
07.79.Cz Scanning tunneling microscopes
07.60.Pb Conventional optical microscopes

Effective tuning of exciton polarization splitting in coupled quantum dots

Jia-Lin Zhu and Dong Xu

Appl. Phys. Lett. 90, 261119 (2007); http://dx.doi.org/10.1063/1.2753116 (3 pages) | Cited 7 times

Online Publication Date: 29 June 2007

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The polarization splitting of the exciton ground state in two laterally coupled quantum dots under an in-plane electric field is investigated, and its effective tuning is designed. It is found that there are significant Stark effect and anticrossing in energy levels. Due to the coupling between inter- and intradot states, the absolute value of polarization splitting is significantly reduced, and it could be tuned to zero by the electric field for proper interdot separations. The scheme of the authors is interesting for the research on the quantum dot–based entangled-photon source.
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73.21.La Quantum dots
71.35.-y Excitons and related phenomena
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

High-efficiency and economical solar-energy-pumped laser with Fresnel lens and chromium codoped laser medium

T. Yabe, T. Ohkubo, S. Uchida, K. Yoshida, M. Nakatsuka, T. Funatsu, A. Mabuti, A. Oyama, K. Nakagawa, T. Oishi, K. Daito, B. Behgol, Y. Nakayama, M. Yoshida, S. Motokoshi, et al.

Appl. Phys. Lett. 90, 261120 (2007); http://dx.doi.org/10.1063/1.2753119 (3 pages) | Cited 13 times

Online Publication Date: 29 June 2007

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The authors achieved 11%–14% slope efficiency of solar-pumped laser by Cr-codoped Nd:yttrium aluminum garnet ceramic and Fresnel lens focusing from natural sunlight. The laser output of 24.4 W was achieved with 1.3 m2 Fresnel lens. The maximum output for unit area of sunlight was 18.7 W/m2, which is 2.8 times larger than previous results with mirror collector. The utilization of Cr3+ ion enabled efficient absorption and energy transfer to Nd3+ ion of solar spectrum. The fluorescence yield at 1064 nm for various pumping wavelengths was measured both for Crcodoped and nondoped laser media, and 1.8 times enhancement of laser output from sunlight is predicted.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
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Sterilization of bacterial endospores by an atmospheric-pressure argon plasma jet

Han S. Uhm, Jin P. Lim, and Shou Z. Li

Appl. Phys. Lett. 90, 261501 (2007); http://dx.doi.org/10.1063/1.2747177 (3 pages) | Cited 27 times

Online Publication Date: 27 June 2007

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Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological warfare agents. However, the spore-killing efficiency of the atmospheric-pressure argon-oxygen jet depends very sensitively on the oxygen concentration in the argon gas.
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52.77.-j Plasma applications
52.75.-d Plasma devices

Prepulse effect on laser-induced water-window radiation from a liquid nitrogen jet

J. Son, M. Cho, D. Kim, B. Ahn, and J. Kim

Appl. Phys. Lett. 90, 261502 (2007); http://dx.doi.org/10.1063/1.2751581 (3 pages) | Cited 2 times

Online Publication Date: 29 June 2007

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The authors show the prepulse effect on the conversion efficiency of a visible laser into water-window (λ = 2.3–4.4 nm) x ray from a liquid nitrogen jet. It is observed that a prepulse of only 2 mJ enhances the conversion efficiency by 10–15 times for the main pulse of 15–60 mJ at a delay of 3–6 ns. The photon flux is ∼ 1.2×1012 photons/pulse sr at a delay of 4 ns for a main pulse of 60 mJ with a prepulse of 4–8 mJ. It is noticed that the conversion efficiency increases with the delay up to 3 ns and is then saturated.
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52.38.Ph X-ray, γ-ray, and particle generation
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.70.La X-ray and γ-ray measurements
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Superior mechanical properties of FeCrMoVC

U. Kühn, N. Mattern, T. Gemming, U. Siegel, K. Werniewicz, and J. Eckert

Appl. Phys. Lett. 90, 261901 (2007); http://dx.doi.org/10.1063/1.2751577 (3 pages) | Cited 9 times

Online Publication Date: 25 June 2007

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This work presents results on the microstructure and mechanical properties of the steel composition Fe84.3Cr4.3Mo4.6V2.2C4.6 subjected to preparation conditions typically used for manufacturing of bulk metallic glasses. Thermodynamical aspects and kinetic limitations on the specific solidification process of phase formation, particularly those, which are strongly dominated by diffusion controlled mechanisms, promote the formation of nonequilibrium phases, such as martensite and complex carbide structures already in the as-cast state. This combination of high strength phases yields material with highly desirable properties, such as an engineering compression strength of more than 4000 MPa surprisingly combined with a fracture strain of about 12%.
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81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Lm Deformation, plasticity, and creep
81.30.Fb Solidification
81.30.Bx Phase diagrams of metals, alloys, and oxides
62.20.M- Structural failure of materials
62.20.F- Deformation and plasticity

Solitary and shock waves in discrete strongly nonlinear double power-law materials

E. B. Herbold and V. F. Nesterenko

Appl. Phys. Lett. 90, 261902 (2007); http://dx.doi.org/10.1063/1.2751592 (3 pages) | Cited 6 times

Online Publication Date: 25 June 2007

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A laminar metamaterial supporting strongly nonlinear solitary and shock waves with impact energy mitigating capabilities is presented. It consists of steel plates with intermittent polymer toroidal rings acting as strongly nonlinear springs with large allowable strain. The force-displacement relationship of a compressed o-ring is described by the addition of two power-law relationships resulting in a solitary wave speed and width depending on the amplitude. This double nonlinearity allows splitting of an initial impulse into three separate strongly nonlinear solitary wave trains. Solitary and shock waves are observed experimentally and analyzed numerically in an assembly with Teflon o-rings.
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46.40.-f Vibrations and mechanical waves

Structural and optical properties of nanocrystalline Zn1−xMnxO

K. Samanta, S. Dussan, R. S. Katiyar, and P. Bhattacharya

Appl. Phys. Lett. 90, 261903 (2007); http://dx.doi.org/10.1063/1.2751593 (3 pages) | Cited 45 times

Online Publication Date: 25 June 2007

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The multi phonon Raman scattering in Mn doped (1%–10%) ZnO was observed at room temperature using 514.5 nm Ar+ laser. The additional optical modes at 327, 332, 482, 532, and 680 cm−1 in Zn1−xMnxO targets were identified as the second order Raman modes in the disordered lattice and the precipitation of the secondary phase ZnMn2O4. The crystalline grain sizes of 1%, 3%, 5%, and 10% Mn doped ZnO samples were calculated by phonon confinement model as 31.8, 18.3, 15.9, and 14.1 nm, respectively. The optical band gap was found to be increased (3.27–3.41 eV) due to the Mn doping.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.30.Fs III-V and II-VI semiconductors
61.46.Hk Nanocrystals
61.72.uj III-V and II-VI semiconductors
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