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21 Mar 2011

Volume 98, Issue 12, Articles (12xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 98, 123101 (2011); http://dx.doi.org/10.1063/1.3567492 (3 pages)

Linus C. Chuang, Michael Moewe, Kar Wei Ng, Thai-Truong D. Tran, Shanna Crankshaw, Roger Chen, Wai Son Ko, and Connie Chang-Hasnain
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Enhanced electron-hole plasma stimulated emission in optically pumped gallium nitride nanopillars

M.-H. Lo, Y.-J. Cheng, H.-C. Kuo, and S.-C. Wang

Appl. Phys. Lett. 98, 121101 (2011); http://dx.doi.org/10.1063/1.3570634 (3 pages) | Cited 1 time

Online Publication Date: 21 March 2011

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An enhanced stimulated emission was observed in optically pumped GaN nanopillars. The nanopillars were fabricated from an epitaxial wafer by patterned pillar etching followed by crystalline regrowth. Under optical excitation, a strong redshifted stimulated emission peak emerged from a broad spontaneous emission background. The emission is attributed to the electron-hole plasma gain at high carrier density. The emission slope efficiency was greatly enhanced by 20 times compared with a GaN substrate under the same pumping condition. The enhancement is attributed to the better photon and gain interaction from the multiple scattering of photons among nanopillars.
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81.05.Ea III-V semiconductors
81.65.Cf Surface cleaning, etching, patterning
78.55.Cr III-V semiconductors
81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.63.Bd Nanocrystalline materials

High performance external cavity InAs/InP quantum dot lasers

P. Chen, Q. Gong, C. F. Cao, S. G. Li, Y. Wang, Q. B. Liu, L. Yue, Y. G. Zhang, S. L. Feng, C. H. Ma, and H. L. Wang

Appl. Phys. Lett. 98, 121102 (2011); http://dx.doi.org/10.1063/1.3569819 (3 pages) | Cited 3 times

Online Publication Date: 21 March 2011

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We report on high performance InAs/InP quantum dot tunable external cavity lasers (ECLs) operating in continuous-wave mode at room temperature. A tuning range of 70 nm has been achieved, covering the wavelengths from 1563 to 1633 nm. The threshold current densities are lower than 1625 A/cm2 in the tuning range. More than 23 mW output power was obtained at lasing wavelength of 1594 nm with an external differential quantum efficiency of 10.3%. An even wider tuning range of 98 nm has been obtained from the ECL based on the QD laser lasing in a longer wavelength.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Deterministic integrated tuning of multicavity resonances and phase for slow-light in coupled photonic crystal cavities

T. Gu, S. Kocaman, X. Yang, J. F. McMillan, M. B. Yu, G.-Q. Lo, D.-L. Kwong, and C. W. Wong

Appl. Phys. Lett. 98, 121103 (2011); http://dx.doi.org/10.1063/1.3571283 (3 pages) | Cited 3 times

Online Publication Date: 22 March 2011

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We present the integrated chip-scale tuning of multiple photonic crystal cavities. The optimized implementation allows effective and precise tuning of multiple cavity resonances (up to ∼ 1.60 nm/mW) and intercavity phase ( ∼ 0.038 π/mW) by direct local temperature tuning on suspended silicon nanomembranes. Through designing the serpentine metal electrodes and careful electron-beam alignment to avoid cavity mode overlap, the coupled photonic crystal L3 cavities preserve their high quality factors. The deterministic resonance and phase control enables switching between the all-optical analog of electromagnetically-induced-transparency to flat-top filter lineshapes, with future applications of trapping photons and optoelectronic modulators.
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42.70.Qs Photonic bandgap materials
42.15.Eq Optical system design
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.79.Ci Filters, zone plates, and polarizers
42.82.-m Integrated optics

Direct probing of evanescent field for characterization of porous terahertz fibers

Shaghik Atakaramians, Shahraam Afshar V., Michael Nagel, Henrik K. Rasmussen, Ole Bang, Tanya M. Monro, and Derek Abbott

Appl. Phys. Lett. 98, 121104 (2011); http://dx.doi.org/10.1063/1.3568892 (3 pages) | Cited 10 times

Online Publication Date: 22 March 2011

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We develop a technique based on a micromachined photoconductive probe-tip to characterize a terahertz (THz) porous fiber. Losses less than 0.08 cm−1 are measured in the frequency range from 0.2 to 0.35 THz, with the minimum of 0.003 cm−1 at 0.24 THz. Normalized group velocity greater than 0.8, which corresponds to dispersion values in between −1.3 and −0.5 ps/m/μm for 0.2<f<0.35 THz are obtained. Moreover, we directly measure the evanescent electric field as a function of frequency. Good agreement between the measured curves and expected theoretical values indicates the low invasiveness of the applied probe-tip.
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42.81.Cn Fiber testing and measurement of fiber parameters
42.81.Dp Propagation, scattering, and losses; solitons

Single-shot nanometer-scale holographic imaging with laser-driven x-ray laser

H. T. Kim, I J. Kim, C. M. Kim, T. M. Jeong, T. J. Yu, S. K. Lee, J. H. Sung, J. W. Yoon, H. Yun, S. C. Jeon, I. W. Choi, and J. Lee

Appl. Phys. Lett. 98, 121105 (2011); http://dx.doi.org/10.1063/1.3560466 (3 pages) | Cited 3 times

Online Publication Date: 22 March 2011

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Single-shot nanometer-scale imaging techniques have become important because of their potential application in observing the structural dynamics of nanomaterials. We report here the image reconstruction results obtained using single-shot Fourier transform x-ray holography with an x-ray laser driven by a table top laser system. A minimum resolution of 87 nm was obtained from the reconstructed image. We could also discriminate the aggregates of carbon nanotubes, which shows the feasibility of single-exposure nanoimaging for real specimens using a laser-driven x-ray laser.
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42.40.My Applications
42.55.Vc X- and γ-ray lasers
07.85.-m X- and γ-ray instruments
42.30.Wb Image reconstruction; tomography
42.30.Kq Fourier optics

Three color infrared detector using InAs/GaSb superlattices with unipolar barriers

N. Gautam, M. Naydenkov, S. Myers, A. V. Barve, E. Plis, T. Rotter, L. R. Dawson, and S. Krishna

Appl. Phys. Lett. 98, 121106 (2011); http://dx.doi.org/10.1063/1.3570687 (3 pages) | Cited 2 times

Online Publication Date: 23 March 2011

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We report on a three color heterojunction band gap engineered type-II InAs/GaSb strained-layer superlattice photodiode for short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) detection. The reported structure is a three contact device with nBn architecture for SWIR and MWIR and heterojunction PIbN architecture for LWIR detection. At 77 K, the cutoff wavelength for SWIR, MWIR, and LWIR regions are 3.0 μm, 4.7 μm, and 10.1 μm, respectively. The reported architecture can be used for simultaneous detection in the LWIR/MWIR and LWIR/SWIR bands as well as sequential detection in the MWIR/SWIR bands by switching the polarity of the applied bias.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Terahertz-frequency photoconductive detectors fabricated from metal-organic chemical vapor deposition-grown Fe-doped InGaAs

O. Hatem, J. Cunningham, E. H. Linfield, C. D. Wood, A. G. Davies, P. J. Cannard, M. J. Robertson, and D. G. Moodie

Appl. Phys. Lett. 98, 121107 (2011); http://dx.doi.org/10.1063/1.3571289 (3 pages) | Cited 2 times

Online Publication Date: 23 March 2011

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We report the detection of terahertz frequency radiation using photoconductive antennas fabricated from Fe-doped InGaAs, grown by metal-organic chemical vapor deposition. Coherent photoconductive detection is demonstrated using femtosecond laser pulses centered at either an 800 or a 1550 nm wavelength. The InGaAs resistivity and the sensitivity of photoconductive detection are both found to depend on the Fe-doping level. We investigate a wide range of probe laser powers, finding a peak in detected signal for ∼ 5 mW probe power, followed by a reduction at larger powers, attributed to screening of the detected THz field by photo-generated carriers in the material. The measured signal from Fe:InGaAs photoconductive detectors excited at 800 nm is four times greater than that from a low-temperature-grown GaAs photodetector with identical antenna design, despite the use of a ten times smaller probe power.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
84.40.Ba Antennas: theory, components and accessories

Surface segregation effects of erbium in GaAs growth and their implications for optical devices containing ErAs nanostructures

Adam M. Crook, Hari P. Nair, and Seth R. Bank

Appl. Phys. Lett. 98, 121108 (2011); http://dx.doi.org/10.1063/1.3565168 (3 pages) | Cited 3 times

Online Publication Date: 23 March 2011

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We report on the integration of semimetallic ErAs nanoparticles with high optical quality GaAs-based semiconductors, grown by molecular beam epitaxy. Secondary ion mass spectrometry and photoluminescence measurements provide evidence of surface segregation and incorporation of erbium into layers grown with the erbium cell hot, despite the closed erbium source shutter. We establish the existence of a critical areal density of the surface erbium layer, below which the formation of ErAs precipitates is suppressed. Based upon these findings, we demonstrate a method for overgrowing ErAs nanoparticles with III-V layers of high optical quality, using subsurface ErAs nanoparticles as a sink to deplete the surface erbium concentration. This approach provides a path toward realizing optical devices based on plasmonic effects in an epitaxially-compatible semimetal/semiconductor system.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
68.35.Dv Composition, segregation; defects and impurities
78.66.Fd III-V semiconductors
81.16.-c Methods of micro- and nanofabrication and processing

Large optical Stark shifts in semiconductor quantum dots coupled to photonic crystal cavities

R. Bose, D. Sridharan, G. S. Solomon, and E. Waks

Appl. Phys. Lett. 98, 121109 (2011); http://dx.doi.org/10.1063/1.3571446 (3 pages) | Cited 4 times

Online Publication Date: 23 March 2011

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We demonstrate large cavity-enhanced optical Stark shifts for a single quantum dot (QD) coupled to a photonic crystal cavity. A maximum Stark shift of 20 GHz is observed for a QD detuned by 104 GHz from the cavity mode. These Stark shifts are attained with extremely low cavity field energies of only ten photons. The changes in the QD emission wavelength are monitored via nonresonant transfer between the QD and cavity mode. Experimental results are compared to theoretical predictions based on the solution to the full master equation and found to be in excellent agreement.
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78.66.Fd III-V semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
78.20.Jq Electro-optical effects
02.30.-f Function theory, analysis

Experimental observation of a traveling plasma grating formed by two crossing filaments in gases

Magali Durand, Yi Liu, Benjamin Forestier, Aurélien Houard, and André Mysyrowicz

Appl. Phys. Lett. 98, 121110 (2011); http://dx.doi.org/10.1063/1.3568888 (3 pages) | Cited 1 time

Online Publication Date: 23 March 2011

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The spatial motion and effective duration of a traveling plasma grating formed by two interfering femtosecond laser filaments in gases is characterized by its Doppler effect imparted on a probe pulse. The shift velocity determined experimentally agrees with the theoretical calculations.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.25.Fx Diffraction and scattering
42.25.Hz Interference
52.38.Hb Self-focussing, channeling, and filamentation in plasmas
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Permanent tuning of quantum dot transitions to degenerate microcavity resonances

Jan Gudat, Cristian Bonato, Evert van Nieuwenburg, Susanna Thon, Hyochul Kim, Pierre M. Petroff, Martin P. van Exter, and Dirk Bouwmeester

Appl. Phys. Lett. 98, 121111 (2011); http://dx.doi.org/10.1063/1.3569587 (3 pages) | Cited 1 time

Online Publication Date: 23 March 2011

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We demonstrate a technique for achieving spectral resonance between a polarization-degenerate micropillar cavity mode and an embedded quantum dot transition. Our approach is based on a combination of isotropic and anisotropic tensile strain effected by laser-induced surface defects, thereby providing permanent tuning. Such a technique is a prerequisite for the implementation of scalable quantum information schemes based on solid-state cavity quantum electrodynamics.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
42.79.Bh Lenses, prisms and mirrors
42.60.Fc Modulation, tuning, and mode locking

Band structures and optical gain of strained GaAsxP1−x−yNy/GaP quantum wells

Yuan-Hui Zhu, Hong-Yu Yu, and Wei-Jun Fan

Appl. Phys. Lett. 98, 121112 (2011); http://dx.doi.org/10.1063/1.3570630 (3 pages) | Cited 1 time

Online Publication Date: 24 March 2011

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In the framework of effective mass Hamiltonian of semiconductor quantum well structures and band anticrossing model, we investigated the band structures of fully strained GaAsxP1−x−yNy/GaP quantum wells. The GaAsxP1−x−yNy could be widely modified to be direct-band gap or indirect-band gap by changing the mole fraction of As and N in the well layer. We found that an increase in the N mole fraction in the well layer increases the TE mode optical gain very slightly.
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73.21.Fg Quantum wells
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
78.67.De Quantum wells

Electroluminescence from a suspended tip-synthesized nano ZnO dot

Jun Hyun Han, Norimasa Yoshimizu, Cheng Jiang, Amit Lal, and Chung Hoon Lee

Appl. Phys. Lett. 98, 121113 (2011); http://dx.doi.org/10.1063/1.3570642 (3 pages) | Cited 2 times

Online Publication Date: 24 March 2011

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Electroluminescence (EL) from a laterally suspended nano ZnO dot (LSNZD) integrated between two microfabricated atomically sharp probe-tips is presented. When driven by 1 μA of bias current, the LSNZD emitted light, which was easily observed by the naked eye at room temperature. The minimum number of photons emitted per a second from the LSNZD was ∼ 9000/s at 100 nA of current, when driven by 12.5 V. The light emission mechanism and electrical characteristics of the LSNZD are explained with a metal-semiconductor-metal model. An optical wavelength spectrum of the emitted light shows major bands of emitted photons between 580 and 750 nm, which indicates the electron transitions from defects in the ZnO band gap. The device fabrication is compatible with typical integrated circuit processes and is suitable for chip- scale optoelectronics.
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78.60.Fi Electroluminescence
73.21.La Quantum dots
73.63.Kv Quantum dots
78.67.Hc Quantum dots

Modulating the fundamental inductive-capacitive resonance in asymmetric double-split ring terahertz metamaterials

Yuanmu Yang, Ran Huang, Longqing Cong, Zhihua Zhu, Jianqiang Gu, Zhen Tian, Ranjan Singh, Shuang Zhang, Jiaguang Han, and Weili Zhang

Appl. Phys. Lett. 98, 121114 (2011); http://dx.doi.org/10.1063/1.3571288 (3 pages) | Cited 8 times

Online Publication Date: 24 March 2011

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We investigate resonant transmission of planar asymmetric metamaterials made from double split-ring resonators. As the symmetry of the unit cell resonator is broken by displacing the two gaps away from the center in opposite directions, a giant amplitude modulation is observed at the fundamental inductive-capacitive resonance due to strong polarization conversion. The modulation is nearly absent when the gaps are moved together in the same direction. This effect persists in metamaterials with different structural designs. These asymmetric metamaterials may open up new avenues toward the control of terahertz waves and the development of modulator and polarizer based terahertz devices.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.-e Optical elements, devices, and systems
84.40.-x Radiowave and microwave (including millimeter wave) technology

The effect of trimethylgallium flows in the AlInGaN barrier on optoelectronic characteristics of near ultraviolet light-emitting diodes grown by atmospheric pressure metalorganic vapor phase epitaxy

Yi-Keng Fu, Ren-Hao Jiang, Yu-Hsuan Lu, Bo-Chun Chen, Rong Xuan, Yen-Hsiang Fang, Chia-Feng Lin, Yan-Kuin Su, and Jenn-Fang Chen

Appl. Phys. Lett. 98, 121115 (2011); http://dx.doi.org/10.1063/1.3571440 (3 pages) | Cited 3 times

Online Publication Date: 24 March 2011

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The letter reports a theoretical and experimental study on the device performance of near ultraviolet light-emitting diodes (LEDs) with quaternary AlInGaN quantum barrier (QB). The indium mole fraction of AlInGaN QB could be enhanced as we increased the trimethylgallium flow rate. It was found the AlInGaN/InGaN LEDs can reduce forward voltage and improve light output power, compared with conventional GaN QB. By using advanced device simulation, it should be attributed to a reduction in lattice mismatch induced polarization mismatch in the active layer, which results in the suppression of electron overflow.
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85.60.Jb Light-emitting devices
85.30.Kk Junction diodes

Angle and polarization independent narrow-band thermal emitter made of metallic disk on SiO2

Mohammed Nadhim Abbas, Cheng-Wen Cheng, Yia-Chung Chang, Min-Hsiung Shih, Hung-Hsin Chen, and Si-Chen Lee

Appl. Phys. Lett. 98, 121116 (2011); http://dx.doi.org/10.1063/1.3571442 (3 pages) | Cited 2 times

Online Publication Date: 24 March 2011

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It is shown that the metallic disk structure can be used as an efficient narrow-band thermal emitter in the IR region. The absorption spectra of such structure are investigated both theoretically and experimentally. Calculations of thermal radiation properties of the metallic disk show that the metallic disk is a perfect emitter at a specific wavelength, which can be tuned by varying the diameter of the disk. The metallic disk exhibits only one significant localized surface plasmon polariton (LSPP) mode for both TM and TE polarizations simultaneously. The LSPP mode can be tuned by either varying the disk diameter or the spacer (made of SiO2).
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07.20.-n Thermal instruments and apparatus

Improved performance of GaN metal-semiconductor-metal ultraviolet detectors by depositing SiO2 nanoparticles on a GaN surface

Xiaojuan Sun, Dabing Li, Hong Jiang, Zhiming Li, Hang Song, Yiren Chen, and Guoqing Miao

Appl. Phys. Lett. 98, 121117 (2011); http://dx.doi.org/10.1063/1.3567943 (3 pages) | Cited 3 times

Online Publication Date: 24 March 2011

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GaN metal-semiconductor-metal (MSM) ultraviolet detectors were investigated by depositing different density of SiO2 nanoparticles (SNPs) on the GaN. It was shown that the dark current of the detectors with SNPs was more than one order of magnitude lower than that without SNPs and the peak responsivity was enhanced after deposition of the SNPs. Atomic force microscopy observations indicated that the SNPs usually formed at the termination of screw and mixed dislocations, and further current-voltage measurements showed that the leakage of the Schottky contact for the GaN MSM detector decreased with deposited the SNPs. Moreover, the leakage obeyed the Frenkel–Poole emission model, which meant that the mechanism for improving the performance is the SNPs passivation of the dislocations followed by the reduction in the dark current.
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73.40.Sx Metal-semiconductor-metal structures
72.40.+w Photoconduction and photovoltaic effects
72.20.Ht High-field and nonlinear effects
73.30.+y Surface double layers, Schottky barriers, and work functions
85.60.Gz Photodetectors (including infrared and CCD detectors)

Guided Bloch surface wave polaritons

Marco Liscidini, Dario Gerace, Daniele Sanvitto, and Daniele Bajoni

Appl. Phys. Lett. 98, 121118 (2011); http://dx.doi.org/10.1063/1.3571285 (3 pages) | Cited 7 times

Online Publication Date: 25 March 2011

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The authors report on a theoretical investigation of guided polariton states arising from the strong coupling between quantum-well excitons and a Bloch surface wave confined at the interface between a uniform dielectric medium and a Bragg mirror. It is shown that the exciton–photon coupling is almost doubled as compared to a similar structure made in a conventional planar microcavity. It is also shown that, by simple engineering of the sample surface with silicon oxide deposition, one can efficiently produce one-dimensional polaritons propagating within the structure with extremely low losses. The latter result evidences the usefulness of Bloch surface waves as a key component for the realization of “polaritonic integrated circuits.”
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.21.Fg Quantum wells

Efficient parametric terahertz generation in quasi-phase-matched GaP through cavity enhanced difference-frequency generation

Eliot B. Petersen, Wei Shi, Arturo Chavez-Pirson, N. Peyghambarian, and Adam T. Cooney

Appl. Phys. Lett. 98, 121119 (2011); http://dx.doi.org/10.1063/1.3571550 (3 pages) | Cited 4 times

Online Publication Date: 25 March 2011

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We report an efficient parametric terahertz (THz) source by using bonded quasi-phase-matched (QPM) GaP crystals pumped by the C-band pulsed fiber lasers in a master oscillator power amplifier configuration, based on difference frequency generation (DFG). We observed that the QPM-GaP crystals can effectively increase the THz generation power and efficiency by increasing the number of periods. Moreover, we observed external cavity enhanced THz DFG by placing the QPM-GaP crystal in an external ring cavity. The THz cavity enhancement factor of approximately 250 has been achieved in comparison with a single-pass THz DFG. The maximum THz average power can reach 339 μW, corresponding to a power conversion efficiency of 2.43×10−4 and a quantum efficiency of 3.16%.
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84.40.-x Radiowave and microwave (including millimeter wave) technology
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
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Theoretical discussion for electron-density distribution in multicusp ion source

Hualin Zhan, Chundong Hu, Yahong Xie, Bin Wu, Jinfang Wang, Lizheng Liang, and Jianglong Wei

Appl. Phys. Lett. 98, 121501 (2011); http://dx.doi.org/10.1063/1.3571292 (3 pages) | Cited 2 times

Online Publication Date: 24 March 2011

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By introducing some ideas of magnetohydrodynamics (MHD) and kinetic theories, some useful solutions for electron-density distribution in the radial direction in multicusp ion source are obtained. Therefore, some conclusions are made in this perspective: 1, the electron-density distributions in a specific region in the sheath are the same with or without magnetic field; 2, the influence of magnetic field on the electron density obeys exponential law, which should take into account the collision term as well if the magnetic field is strong; 3, the result derived from the Boltzmann equation is qualitatively consistent with some given experimental results.
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52.25.Dg Plasma kinetic equations
52.35.Bj Magnetohydrodynamic waves (e.g., Alfven waves)
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.40.Kh Plasma sheaths
52.50.Dg Plasma sources
52.25.Fi Transport properties
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Ultrasensitive string-based temperature sensors

T. Larsen, S. Schmid, L. Grönberg, A. O. Niskanen, J. Hassel, S. Dohn, and A. Boisen

Appl. Phys. Lett. 98, 121901 (2011); http://dx.doi.org/10.1063/1.3567012 (3 pages) | Cited 3 times

Online Publication Date: 21 March 2011

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Resonant strings are a promising concept for ultra sensitive temperature detection. We present an analytical model for the sensitivity with which we optimize the temperature response of resonant strings by varying geometry and material. The temperature sensitivity of silicon nitride and aluminum microstrings was measured. The relative change in resonant frequency per temperature change of −1.74±0.04%/°C of the aluminum strings is more than one order of magnitude higher than of the silicon nitride strings and of comparable state-of-the-art AuPd strings.
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07.20.Dt Thermometers

Mechanical properties of ultralow-dielectric-constant mesoporous amorphous silica structures: Effects of pore morphology and loading mode

M. Rauf Gungor, James J. Watkins, and Dimitrios Maroudas

Appl. Phys. Lett. 98, 121902 (2011); http://dx.doi.org/10.1063/1.3567537 (3 pages)

Online Publication Date: 21 March 2011

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We report results for the dependence of the mechanical properties of ordered mesoporous silica structures on the pore diameter based on molecular-dynamics simulations. We examine structures with spherical pores arranged in a simple cubic lattice and cylindrical pores arranged in a square lattice subjected to uniaxial tension and compression; for the structures with cylindrical pores, both radial and axial loading is studied with respect to the pore orientation. Our analysis provides a unifying explanation to the observed mechanical response based on the mechanical loading effects on the pore wall thickness.
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77.22.Ch Permittivity (dielectric function)
61.43.Gt Powders, porous materials
61.43.Bn Structural modeling: serial-addition models, computer simulation
62.20.F- Deformation and plasticity

Photoluminescence characteristics of ZnCdO/ZnO single quantum well grown by pulsed laser deposition

W. F. Yang, L. M. Wong, S. J. Wang, H. D. Sun, C. H. Ge, Alex Y. S. Lee, and H. Gong

Appl. Phys. Lett. 98, 121903 (2011); http://dx.doi.org/10.1063/1.3567549 (3 pages) | Cited 3 times

Online Publication Date: 21 March 2011

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Optical properties of ZnCdO/ZnO single quantum well (SQW) grown on c-sapphire substrate by pulsed laser deposition were investigated. Temperature dependent photoluminescence (PL) measurement was performed from 10 to 300 K to study the carrier localization effect and peak evolution. The LO-phonon replicas up to third order with Huang–Rhys factor of 0.17 were observed. The SQW exhibited very strong PL from the well layer and extremely weak emission from the ZnO barriers, indicating high quality interfaces and highly efficient relaxation.
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78.55.Et II-VI semiconductors
81.15.Fg Pulsed laser ablation deposition
68.65.Fg Quantum wells
81.07.St Quantum wells
81.05.Dz II-VI semiconductors
78.67.De Quantum wells

Controlling elastic waves with isotropic materials

Zheng Chang, Jin Hu, Gengkai Hu, Ran Tao, and Yue Wang

Appl. Phys. Lett. 98, 121904 (2011); http://dx.doi.org/10.1063/1.3569598 (3 pages) | Cited 7 times

Online Publication Date: 21 March 2011

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Design of functional devices with isotropic materials has significant advantages, as regards easy fabrication and broadband application. In this letter, we present a method to derive isotropic transformation material parameters for elastodynamics under local conformal transformation. The transformed material parameters are then applied to design a beam bender, a four-beam antenna and an approximate carpet cloak for elastic wave with isotropic materials, validated by the numerical simulations.
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62.30.+d Mechanical and elastic waves; vibrations
02.60.-x Numerical approximation and analysis

Ultrafast carrier dynamics and saturable absorption of solution-processable few-layered graphene oxide

Xin Zhao, Zhi-Bo Liu, Wei-Bo Yan, Yingpeng Wu, Xiao-Liang Zhang, Yongsheng Chen, and Jian-Guo Tian

Appl. Phys. Lett. 98, 121905 (2011); http://dx.doi.org/10.1063/1.3570640 (3 pages) | Cited 15 times

Online Publication Date: 22 March 2011

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Ultrafast carrier dynamics and saturable absorption of few-layered graphene oxide, well-dispersed in organic solvent, are studied using femtosecond pump-probe and Z-scan techniques. The results demonstrate that few-layered graphene oxide has a fast energy relaxation of hot carriers and strong saturable absorption, which is comparable with that of reduced graphene oxide. Fast carrier relaxation combined with well solution processing capability arises from the large fraction of sp2 carbon atom inside the few-layered graphene oxide sheet together with oxidation mainly existing at the edge areas. This superiority of few-layered graphene oxide will facilitate potential applications of graphene for ultrafast photonics.
Show PACS
78.47.J- Ultrafast spectroscopy (<1 psec)
78.40.Ri Fullerenes and related materials
78.30.Na Fullerenes and related materials
82.30.-b Specific chemical reactions; reaction mechanisms
78.67.Wj Optical properties of graphene
78.55.Hx Other solid inorganic materials
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