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14 Jul 2008

Volume 93, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 023303 (2008); http://dx.doi.org/10.1063/1.2953179 (3 pages)

Takafumi Kawanishi, Takaaki Fujiwara, Megumi Akai-Kasaya, Akira Saito, Masakazu Aono, Junichi Takeya, and Yuji Kuwahara
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Dynamic properties of InAs/InP (311)B quantum dot Fabry–Perot lasers emitting at 1.52 μm

A. Martinez, K. Merghem, S. Bouchoule, G. Moreau, A. Ramdane, J.-G. Provost, F. Alexandre, F. Grillot, O. Dehaese, R. Piron, and S. Loualiche

Appl. Phys. Lett. 93, 021101 (2008); http://dx.doi.org/10.1063/1.2957479 (3 pages) | Cited 7 times

Online Publication Date: 14 July 2008

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Dynamic properties of truly three-dimensional-confined InAs/InP quantum dot (QD) lasers obtained by molecular beam epitaxy growth on a (311)B oriented substrate are reported. The relative intensity noise and small signal modulation bandwidth experiments evidence maximum relaxation frequency of 3.8 GHz with a clear relaxation oscillation peak, indicating less damping than InAs/GaAs QD lasers. The Henry factor amounts to ∼ 1.8 below threshold and increases to ∼ 6 above threshold, which is attributed to band filling of the thick wetting layer.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Barrier effect on hole transport and carrier distribution in InGaN/GaN multiple quantum well visible light-emitting diodes

J. P. Liu, J.-H. Ryou, R. D. Dupuis, J. Han, G. D. Shen, and H. B. Wang

Appl. Phys. Lett. 93, 021102 (2008); http://dx.doi.org/10.1063/1.2957667 (3 pages) | Cited 29 times

Online Publication Date: 14 July 2008

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Carrier distributions governed by hole transport in InGaN/GaN multiple quantum well (MQW) visible light-emitting diodes (LEDs) were investigated using conventional blue LEDs and dual-wavelength blue-green LEDs. It was found that holes were dominantly distributed in the QW close to the p-GaN layer in LEDs with conventional MQW active regions at a current of 20 mA. A decrease in the thickness or the height of the quantum-well potential barrier enhanced hole injection into the MQWs located near the n-GaN layer. Reducing the thickness of a GaN quantum-well barrier between the blue QW and green QW did not degrade the electroluminescence (EL) intensity of the LED. In contrast, reducing the potential height of the barrier with material of possibly compromised quality resulted in a degradation of the EL intensity of the LED.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.63.Hs Quantum wells
78.60.Fi Electroluminescence

Room temperature continuous wave operation of quantum cascade lasers with 12.5% wall plug efficiency

Y. Bai, S. Slivken, S. R. Darvish, and M. Razeghi

Appl. Phys. Lett. 93, 021103 (2008); http://dx.doi.org/10.1063/1.2957673 (3 pages) | Cited 66 times

Online Publication Date: 14 July 2008

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An InP based quantum cascade laser heterostructure emitting at 4.6 μm was grown with gas-source molecular beam epitaxy. The wafer was processed into a conventional double-channel ridge waveguide geometry with ridge widths of 19.7 and 10.6 μm without semi-insulating InP regrowth. An uncoated, narrow ridge device with a 4.8 mm cavity length was epilayer down bonded to a diamond submount and exhibits 2.5 W maximum output power with a wall plug efficiency of 12.5% at room temperature in continuous wave operation.
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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

Gain and continuous-wave laser oscillation on the 1315 nm atomic iodine transition pumped by an air-helium electric discharge

B. S. Woodard, J. W. Zimmerman, G. F. Benavides, D. L. Carroll, J. T. Verdeyen, A. D. Palla, T. H. Field, W. C. Solomon, S. J. Davis, W. T. Rawlins, and S. Lee

Appl. Phys. Lett. 93, 021104 (2008); http://dx.doi.org/10.1063/1.2957678 (3 pages) | Cited 4 times

Online Publication Date: 14 July 2008

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Herein the authors report on the demonstration of gain and a continuous-wave laser on the 1315 nm transition of atomic iodine using the energy transferred to I(2P1/2) from O2(a1Δ) produced by a radio-frequency-excited electric discharge sustained in a dry air-He–NO gas mixture. Active oxygen and nitrogen species were observed downstream of the discharge region. Downstream of the discharge, cold gas injection was employed to raise the gas density and lower the temperature of the continuous gas flow. Gain of 0.0062% cm−1 was obtained and the laser output power was 32 mW in a supersonic flow cavity.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems

Uncooled infrared detectors for 3–5 μm and beyond

P. V. V. Jayaweera, S. G. Matsik, A. G. U. Perera, H. C. Liu, M. Buchanan, and Z. R. Wasilewski

Appl. Phys. Lett. 93, 021105 (2008); http://dx.doi.org/10.1063/1.2959060 (3 pages) | Cited 14 times

Online Publication Date: 15 July 2008

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Avoiding cryogenic cooling not only reduces the cost and weight but also simplifies the infrared detector system allowing widespread usage. Here an uncooled infrared detection using intravalence bands is reported. A set of three p-GaAs/AlxGa1−xAs multiple heterojunction detector structures were used to demonstrate the concept experimentally. A preliminary detector showed peak responsivity of 0.29 mA/W at 2.5 μm at 300 K. The intravalence band approach can be used to cover various wavelength ranges by using different material systems giving rise to the possibilities of a dual band detector operating in atmospheric windows.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Highly sensitive coherent detection of terahertz waves at room temperature using a parametric process

Ruixiang Guo, Seigo Ohno, Hiroaki Minamide, Tomofumi Ikari, and Hiromasa Ito

Appl. Phys. Lett. 93, 021106 (2008); http://dx.doi.org/10.1063/1.2953452 (3 pages) | Cited 9 times

Online Publication Date: 15 July 2008

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We report the experimental results of coherent detection of narrow-linewidth nanosecond terahertz radiation at room temperature using frequency conversion in a nonlinear MgO:LiNbO3 crystal. Mixing the terahertz radiation with a near-infrared intense pump pulse results in the excitation and amplification of the difference-frequency component, which is detected with an InGaAs-based photodiode. We demonstrate this method in a fast and very sensitive terahertz wave detector. The detector is capable of capturing the temporal profile of terahertz pulses with nanosecond resolution, and is at least one order more sensitive than a typical liquid-He-cooled Si bolometer for detecting nanosecond pulsed terahertz wave beams.
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42.70.Mp Nonlinear optical crystals
42.65.-k Nonlinear optics
42.79.Pw Imaging detectors and sensors
78.30.-j Infrared and Raman spectra
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

Observation of spectral drift in engineered quadratic nonlinear media

M. Marangoni, G. Sanna, D. Brida, M. Conforti, G. Cirmi, C. Manzoni, F. Baronio, P. Bassi, C. De Angelis, and G. Cerullo

Appl. Phys. Lett. 93, 021107 (2008); http://dx.doi.org/10.1063/1.2955529 (3 pages) | Cited 2 times

Online Publication Date: 15 July 2008

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Spectral blueshifts of femtosecond pulses induced by quadratic cascaded nonlinearities are experimentally studied in an engineered aperiodically poled stoichiometric lithium tantalate crystal with optimized nonlinear pattern and chirp of the input pump pulses. Starting from nearly Gaussian input pulses centered at 1420 nm with 70 nm spectral width, spectral shifts as high as 40 nm were obtained in combination with an almost unaltered spectral shape and a transform-limited pulse duration.
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78.20.-e Optical properties of bulk materials and thin films
78.47.J- Ultrafast spectroscopy (<1 psec)

Full-field particle velocimetry with a photorefractive optical novelty filter

Mike Woerdemann, Frank Holtmann, and Cornelia Denz

Appl. Phys. Lett. 93, 021108 (2008); http://dx.doi.org/10.1063/1.2955842 (3 pages) | Cited 6 times

Online Publication Date: 15 July 2008

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We utilize the finite time constant of a photorefractive optical novelty filter microscope to access full-field velocity information of fluid flows on microscopic scales. In contrast to conventional methods such as particle image velocimetry and particle tracking velocimetry, not only image acquisition of the tracer particle field but also evaluation of tracer particle velocities is done all-optically by the novelty filter. We investigate the velocity dependent parameters of two-beam coupling based optical novelty filters and demonstrate calibration and application of a photorefractive velocimetry system. Theoretical and practical limits to the range of accessible velocities are discussed.
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42.79.Ci Filters, zone plates, and polarizers
06.30.Gv Velocity, acceleration, and rotation
07.60.Pb Conventional optical microscopes

Rendering a color palette by light-emitting diodes

A. Žukauskas, R. Vaicekauskas, F. Ivanauskas, H. Vaitkevičius, and M. S. Shur

Appl. Phys. Lett. 93, 021109 (2008); http://dx.doi.org/10.1063/1.2955843 (3 pages) | Cited 10 times

Online Publication Date: 15 July 2008

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We present a new approach to the optimization of sources of white light based on colored light-emitting diodes (LEDs) and show that a pentachromatic source composed of LEDs with the equidistant peak wavelengths at about 450, 500, 550, 600, and 650 nm renders all 1269 colors of the Munsell palette almost indistinguishably from daylight.
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85.60.Jb Light-emitting devices

Manipulating optical rotation in extraordinary transmission by hybrid plasmonic excitations

Tao Li, Hui Liu, Shu-Ming Wang, Xiao-Gang Yin, Fu-Ming Wang, Shi-Ning Zhu, and Xiang Zhang

Appl. Phys. Lett. 93, 021110 (2008); http://dx.doi.org/10.1063/1.2958214 (3 pages) | Cited 20 times

Online Publication Date: 15 July 2008

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Polarized optical transmission properties through the L-shaped holes array in silver film was investigated at near infrared wavelength. Besides the enhanced transmission due to the combined plasmonic excitations, strong optical rotation was definitely observed at specific polarized incidences. After elaborate analyses, two eigenmodes were clearly characterized as the results of the hybrid localized plasmon resonances. Any polarization states from the incidences will degenerate into these two eigenstates after transmissions, suggesting a practical method to manipulate the polarization of light. Our result demonstrates the giant rotation rate achieved by the nanothin sample, indicating potential applications in the micro-optical devices.
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78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.79.Wc Optical coatings
78.30.Er Solid metals and alloys

Transistor laser with emission wavelength at 1544 nm

F. Dixon, M. Feng, N. Holonyak, Jr., Yong Huang, X. B. Zhang, J. H. Ryou, and R. D. Dupuis

Appl. Phys. Lett. 93, 021111 (2008); http://dx.doi.org/10.1063/1.2958228 (3 pages) | Cited 7 times

Online Publication Date: 15 July 2008

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Data are presented demonstrating continuous wave laser operation at −185 °C of an InP–InAlGaAs–InAlAs double heterojunction bipolar transistor with strained InGaAs quantum wells incorporated in the p-type base region. The laser exhibits a peak wavelength λ ∼ 1544 nm when biased in the forward active mode in the common-emitter configuration. A threshold current IB = 10 mA is observed.
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85.30.Pq Bipolar transistors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.30.De Semiconductor-device characterization, design, and modeling
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Emission properties of high-Q silicon nitride photonic crystal heterostructure cavities

Michael Barth, Nils Nüsse, Johannes Stingl, Bernd Löchel, and Oliver Benson

Appl. Phys. Lett. 93, 021112 (2008); http://dx.doi.org/10.1063/1.2958346 (3 pages) | Cited 23 times

Online Publication Date: 15 July 2008

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We report on the fabrication and optical characterization of photonic crystal (PC) double-heterostructure cavities made from silicon nitride (SiN). The intrinsic luminescence of the SiN membranes was used as an internal light source in the visible wavelength range (600–700 nm) to study the quality factor and polarization properties of the cavity modes. Quality factors of up to 3400 were found experimentally, which represents the highest value reported so far in low-index PCs. These results highlight the role of SiN as a promising material system for PC devices in the visible.
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78.55.Hx Other solid inorganic materials

Photoluminescence from localized states in disordered indium nitride

Bhavtosh Bansal, Abdul Kadir, Arnab Bhattacharya, and V. V. Moshchalkov

Appl. Phys. Lett. 93, 021113 (2008); http://dx.doi.org/10.1063/1.2959185 (3 pages) | Cited 4 times

Online Publication Date: 16 July 2008

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Photoluminescence spectra from disordered InN were studied in very high magnetic fields. The samples had Gaussian spectra with low temperature emission peaks at 0.82 and 0.98 eV, respectively. The average spatial extent of the excitonic wave functions, inferred from the diamagnetic shift, is only 2–3 nm. This shows that the recombination is from an ensemble of highly localized states within a landscape of a smooth (classical) disorder potential of strength of the order of 10 meV. The anomalies in the temperature dependence of the photoluminescence peak and linewidth give further support to the picture of trapped photoexcited carriers.
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78.55.Cr III-V semiconductors
71.55.Jv Disordered structures; amorphous and glassy solids
71.35.Ji Excitons in magnetic fields; magnetoexcitons

Multiphoton microscopy based on four-wave mixing of colloidal quantum dots

Francesco Masia, Wolfgang Langbein, and Paola Borri

Appl. Phys. Lett. 93, 021114 (2008); http://dx.doi.org/10.1063/1.2959737 (3 pages) | Cited 5 times

Online Publication Date: 16 July 2008

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We demonstrate a novel multiphoton imaging modality based on the detection of four-wave mixing (FWM) from colloidal nanoparticles. This third-order signal is excited and detected in resonance with the ground-state excitonic transition of CdSe/ZnS quantum dots. We measure transversal and axial resolutions of 140 and 590 nm, respectively, significantly improved compared to the one-photon diffraction limit. The coherent FWM signal is detected using a heterodyne technique which rejects incoherent background for improved image contrast compared to fluorescence methods. As sensitivity limit, we estimate a minimum number of 10 dots/math detectable in the focal volume.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
07.60.Pb Conventional optical microscopes
82.70.Dd Colloids
78.67.Hc Quantum dots
71.35.-y Excitons and related phenomena

Method to measure spatial coherence of subangstrom electron beams

Christian Dwyer, Rolf Erni, and Joanne Etheridge

Appl. Phys. Lett. 93, 021115 (2008); http://dx.doi.org/10.1063/1.2957648 (3 pages) | Cited 18 times

Online Publication Date: 16 July 2008

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A method is described for measuring the intensity distribution of the electron source in a scanning transmission electron microscope (STEM) fitted with an objective lens aberration corrector. The method is applied to a Cs-corrected 300 kV field emission gun TEM/STEM, which is found to have an effective source size of 0.56 Å full width at half maximum (FWHM) under optical conditions suitable for high resolution STEM imaging. This corresponds to a probe intensity distribution at the specimen plane of 0.72 Å FWHM using a probe-forming aperture of 25 mrad and including the measured residual lens aberrations.
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41.75.Fr Electron and positron beams
41.85.-p Beam optics
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Ultraviolet electroluminescence from controlled arsenic-doped ZnO nanowire homojunctions

Jun-Yan Zhang, Ping-Jian Li, Hui Sun, Xin Shen, Tian-Song Deng, Kong-Tao Zhu, Qi-Feng Zhang, and Jin-Lei Wu

Appl. Phys. Lett. 93, 021116 (2008); http://dx.doi.org/10.1063/1.2958230 (3 pages) | Cited 20 times

Online Publication Date: 16 July 2008

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ZnO nanowire arrays were grown on semi-insulating intrinsic GaAs substrates, and controlled arsenic-doping process was carried out to realize the n-ZnO/p-ZnO nanowire array/GaAs structures. The constructed ZnO nanowire homojunctions demonstrated a clear rectifying behavior and the turn-on voltage was above 4.0 V. The corresponding ultraviolet electroluminescence spectra were obtained for the applied forward voltage above 30 V (20 mA). The distinct ultraviolet electroluminescence peak, centered at 382 nm, is nonlinearly enhanced with an increase in the applied forward voltage. The origin of the strong ultraviolet electroluminescence was discussed in terms of the controlled arsenic-doping process.
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78.66.Fd III-V semiconductors
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
78.60.Fi Electroluminescence
78.40.Fy Semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.65.La Quantum wires (patterned in quantum wells)

Room temperature electrical spin injection in remanence

S. Hövel, N. C. Gerhardt, M. R. Hofmann, F.-Y. Lo, A. Ludwig, D. Reuter, A. D. Wieck, E. Schuster, H. Wende, W. Keune, O. Petracic, and K. Westerholt

Appl. Phys. Lett. 93, 021117 (2008); http://dx.doi.org/10.1063/1.2957469 (3 pages) | Cited 14 times

Online Publication Date: 17 July 2008

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We demonstrate electrical spin injection from ferromagnetic Fe/Tb multilayer structures with remanent perpendicular magnetization into GaAs-based light-emitting diodes at room temperature. Using a reverse-biased Schottky contact and a MgO tunnel contact, respectively, we achieve spin injection at remanence. The maximum degree of circular polarization of the emitted light is 3% at room temperature.
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75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
72.25.-b Spin polarized transport
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.60.Jb Light-emitting devices
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields

Degenerate multiwave mixing using Z-scan technique

G. Boudebs, K. Fedus, C. Cassagne, and H. Leblond

Appl. Phys. Lett. 93, 021118 (2008); http://dx.doi.org/10.1063/1.2960336 (3 pages) | Cited 6 times

Online Publication Date: 17 July 2008

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This study deals with a multiwave mixing experiment using Z-scan technique. We show that it is possible to simplify the complex degenerate four-wave mixing (DFWM) experimental setup in order to characterize nonlinear materials. One object composed of three circular apertures is used as an input in a 4f coherent imaging system. When the nonlinear material is moved around the focus, we observe the variations of the forward fourth wave at the output as well as other diffracted waves. Experimental and simulated images are presented here to validate our approach. We show also that this method increases significantly the sensitivity of the measurement compared to DFWM. We provide a simple quadratic relation that allows the characterization of the cubic optical nonlinearity.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

A novel approach to quantitative spectroscopy of atoms in a magnetic field and applications based on an atomic vapor cell with L = λ

A. Sargsyan, G. Hakhumyan, A. Papoyan, D. Sarkisyan, A. Atvars, and M. Auzinsh

Appl. Phys. Lett. 93, 021119 (2008); http://dx.doi.org/10.1063/1.2960346 (3 pages) | Cited 17 times

Online Publication Date: 17 July 2008

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We describe the so-called λ-Zeeman method to investigate individual hyperfine transitions between Zeeman sublevels of atoms in an external magnetic field of 0.1 mT–0.25 T. Atoms are confined in a nanocell with thickness L = λ, where λ is the resonant wavelength (794 or 780 nm for D1 or D2 line, respectively, of Rb). Narrow resonances in the transmission spectrum of the nanocell are split into several components in a magnetic field; their frequency positions and transition probabilities depend on the B field. Possible applications are described, such as magnetometers with nanometric spatial resolution and tunable atomic frequency references.
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32.60.+i Zeeman and Stark effects
32.80.Xx Level crossing and optical pumping
42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption

Electroluminescence efficiency enhancement using metal nanoparticles

J. B. Khurgin, G. Sun, and R. A. Soref

Appl. Phys. Lett. 93, 021120 (2008); http://dx.doi.org/10.1063/1.2957989 (3 pages) | Cited 16 times

Online Publication Date: 17 July 2008

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We apply the “effective mode volume” theory to evaluate enhancement of the electroluminescence efficiency of semiconductor emitters placed in the vicinity of isolated metal nanoparticles and their arrays. Using the example of an InGaN/GaN quantum-well active region positioned in close proximity to Ag nanospheres, we show that while the enhancement due to isolated metal nanoparticles is large, only modest enhancement can be obtained with ordered array of those particles. We further conclude that random assembly of isolated particles holds an advantage over the ordered arrays for light emitting devices of finite area.
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85.60.Jb Light-emitting devices

Enhanced light extraction efficiency in flip-chip GaN light-emitting diodes with diffuse Ag reflector on nanotextured indium-tin oxide

Ja-Yeon Kim, Min-Ki Kwon, Il-Kyu Park, Chu-Young Cho, Seong-Ju Park, Dong-Min Jeon, Je Won Kim, and Yong Chun Kim

Appl. Phys. Lett. 93, 021121 (2008); http://dx.doi.org/10.1063/1.2953174 (3 pages) | Cited 4 times

Online Publication Date: 17 July 2008

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We investigated a flip-chip light emitting diode (FCLED) with a diffuse reflector fabricated by depositing a Ag film on a nanotextured indium-tin oxide (ITO) layer. The FCLED with a diffuse Ag reflector showed remarkably good adhesion and high reflectance than that with a specular Ag reflector deposited on the planar ITO layer. The optical output power of FCLED with the diffuse Ag reflector was enhanced by 161.3% at 300 mA compared to that with the specular Ag reflector.
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85.60.Jb Light-emitting devices

Examining the terahertz signal from a photoexcited biased semiconductor superlattice for evidence of gain

A. Lisauskas, M. M. Dignam, N. V. Demarina, E. Mohler, and H. G. Roskos

Appl. Phys. Lett. 93, 021122 (2008); http://dx.doi.org/10.1063/1.2957040 (3 pages) | Cited 4 times

Online Publication Date: 18 July 2008

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We present a careful analysis of the coherent terahertz emission from an undoped biased semiconductor superlattice excited via an ultrashort optical pulse. We use both a semiclassical model and a fully quantum-mechanical model that includes the excitation process and excitonic effects to analyze emission. We conclude that, in contrast to what has recently been claimed, it is not possible to deduce whether there is terahertz gain from the analysis of the emitted coherent terahertz pulse.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.47.-p Spectroscopy of solid state dynamics
78.70.Gq Microwave and radio-frequency interactions

Strain control of the magnetic anisotropy in (Ga,Mn) (As,P) ferromagnetic semiconductor layers

A. Lemaître, A. Miard, L. Travers, O. Mauguin, L. Largeau, C. Gourdon, V. Jeudy, M. Tran, and J.-M. George

Appl. Phys. Lett. 93, 021123 (2008); http://dx.doi.org/10.1063/1.2963979 (3 pages) | Cited 18 times

Online Publication Date: 18 July 2008

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A small fraction of phosphorus (up to 10%) was incorporated in ferromagnetic (Ga,Mn)As epilayers grown on a GaAs substrate. P incorporation allows reducing the epitaxial strain or even change its sign, resulting in strong modifications of the magnetic anisotropy. In particular a reorientation of the easy axis toward the growth direction is observed for high P concentration. It offers an interesting alternative to the metamorphic approach, in particular for magnetization reversal experiments where epitaxial defects strongly affect the domain wall propagation.
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75.30.Gw Magnetic anisotropy
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ch Domain walls and domain structure
75.50.Pp Magnetic semiconductors
61.72.U- Doping and impurity implantation

“Plug and Play” single photons at 1.3 μm approaching gigahertz operation

Xiulai Xu, Frederic Brossard, Kiyotaka Hammura, David A. Williams, B. Alloing, L. H. Li, and Andrea Fiore

Appl. Phys. Lett. 93, 021124 (2008); http://dx.doi.org/10.1063/1.2960549 (3 pages) | Cited 4 times

Online Publication Date: 18 July 2008

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We report a “plug and play” single photon source, fully integrated with an optical fiber, emitting at 1.3 μm. Micropillars were patterned on a single layer InAs quantum dot wafer to guarantee a single pillar per fiber core. The single exciton peak filtered with a tunable optical filter was fed to a Hanbury Brown and Twiss interferometer, and the second order correlation function at zero delay was less than 0.5, indicating single photon emission. The measured decay dynamics under double-pulse excitation show that the single photon device can be operated at speeds greater than 0.5 GHz.
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42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.81.Wg Other fiber-optical devices
42.79.Ci Filters, zone plates, and polarizers
42.82.Cr Fabrication techniques; lithography, pattern transfer
42.50.St Nonclassical interferometry, subwavelength lithography
03.67.Hk Quantum communication

Light extraction enhancement of InGaN light-emitting diode by roughening both undoped micropillar-structure GaN and p-GaN as well as employing an omnidirectional reflector

Ray-Hua Horng, Xinhe Zheng, Chuang-Yu Hsieh, and Dong-Sing Wuu

Appl. Phys. Lett. 93, 021125 (2008); http://dx.doi.org/10.1063/1.2961008 (3 pages) | Cited 10 times

Online Publication Date: 18 July 2008

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Light extraction enhancement of InGaN–GaN light-emitting diode (LED) is demonstrated with double-side roughening both on the p-GaN surface and the micropillar undoped GaN as well as an omnidirectional reflector via patterning sapphire substrate, wafer-bonding, laser lift-off, and chemical wet etching technologies. This device design enhances the light output power up to 77% compared to the conventional LED with a single roughened p-GaN on patterned sapphire substrate at an injection current of 350 mA. Due to the employment of Si carrier, the junction temperature measurement at 350 mA yields a 46.6 °C lower than that of the conventional LEDs.
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85.60.Jb Light-emitting devices
42.62.Cf Industrial applications
81.65.Cf Surface cleaning, etching, patterning
42.79.Bh Lenses, prisms and mirrors
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