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24 May 2010

Volume 96, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 96, 213701 (2010); http://dx.doi.org/10.1063/1.3431628 (3 pages)

Satish Rao, Saurabh Raj, Stefan Balint, Carlota Bardina Fons, Susana Campoy, Montserrat Llagostera, and Dmitri Petrov
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Operating quantum waveguide circuits with superconducting single-photon detectors

C. M. Natarajan, A. Peruzzo, S. Miki, M. Sasaki, Z. Wang, B. Baek, S. Nam, R. H. Hadfield, and J. L. O’Brien

Appl. Phys. Lett. 96, 211101 (2010); http://dx.doi.org/10.1063/1.3413948 (3 pages) | Cited 12 times

Online Publication Date: 24 May 2010

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Advanced quantum information science and technology (QIST) applications place exacting demands on optical components. Quantum waveguide circuits offer a route to scalable QIST on a chip. Superconducting single-photon detectors (SSPDs) provide infrared single-photon sensitivity combined with low dark counts and picosecond timing resolution. In this study, we bring these two technologies together. Using SSPDs we observe a two-photon interference visibility of 92.3±1.0% in a silica-on-silicon waveguide directional coupler at λ = 804 nm—higher than that measured with silicon detectors (89.9±0.3%). We further operated controlled-NOT gate and quantum metrology circuits with SSPDs. These demonstrations present a clear path to telecom-wavelength quantum waveguide circuits.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.40.Az Waveguides, transmission lines, striplines
85.25.Oj Superconducting optical, X-ray, and γ-ray detectors (SIS, NIS, transition edge)
29.40.Wk Solid-state detectors

Photoacoustic measurement of liquid viscosity

Cunguang Lou and Da Xing

Appl. Phys. Lett. 96, 211102 (2010); http://dx.doi.org/10.1063/1.3435462 (3 pages) | Cited 4 times

Online Publication Date: 24 May 2010

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In this letter, we report on the use of photoacoustic method to measure the viscosity of viscous liquids. The theoretical and experimental study was performed on the influence of viscosity effects on photoacoustic generation. We provide evidence that the frequency spectrum of photoacoustic signal is precisely related to the viscosity. Measurements are validated on different water–glycerol mixtures. Good agreement between theoretical and experimental results is obtained. This present method provides an insight into in situ viscosity measurements, which has potential for noninvasive detection of blood viscosity.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
47.55.-t Multiphase and stratified flows
78.20.H- Piezo-, elasto-optical effects
66.20.-d Viscosity of liquids; diffusive momentum transport

An all optically driven integrated deformable mirror device

V. Mathur, S. R. Vangala, X. Qian, W. D. Goodhue, B. Haji-Saeed, and J. Khoury

Appl. Phys. Lett. 96, 211103 (2010); http://dx.doi.org/10.1063/1.3430568 (3 pages)

Online Publication Date: 24 May 2010

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We demonstrate a technique for actuating micromirrors vertically cascaded on wafer fused GaAs-GaP photodiodes. Unlike traditional actuation schemes, the electrostatic drive of the individual capacitive actuators is addressed optically in this device. Vertical mirror displacements of up to 500 nm were observed using interferometry while addressing the photodetectors with a 5 mW optical signal. Microlenses were used to address a 900 pixel device with patterned conductive pillars and thin film load resistors for each actuator-detector element. This approach can enable realization of faster and denser adaptive optics wave front corrector arrays.
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42.79.Bh Lenses, prisms and mirrors

Dependence of emission of terahertz radiation on geometrical parameters of dipole photoconductive antennas

Fumiaki Miyamaru, Yu Saito, Kohji Yamamoto, Takashi Furuya, Seizi Nishizawa, and Masahiko Tani

Appl. Phys. Lett. 96, 211104 (2010); http://dx.doi.org/10.1063/1.3436724 (3 pages) | Cited 7 times

Online Publication Date: 24 May 2010

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The dependence of the emission spectrum of terahertz (THz) radiation on the geometrical parameters of the dipole antenna, and the relationship between these parameters and the temporal characteristics of the transient current that generate THz radiation, is reported. The emission intensity and the peak frequency strongly depend on these geometrical parameters. This dependence varies significantly with changes in the temporal characteristics of the transient current. We have also found that the emission efficiency can be increased by increasing the aspect ratio for the dipole.
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84.40.Ba Antennas: theory, components and accessories

Sub-100 attoseconds stability optics-to-microwave synchronization

W. Zhang, Z. Xu, M. Lours, R. Boudot, Y. Kersalé, G. Santarelli, and Y. Le Coq

Appl. Phys. Lett. 96, 211105 (2010); http://dx.doi.org/10.1063/1.3431299 (3 pages) | Cited 9 times

Online Publication Date: 24 May 2010

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We use two fiber-based femtosecond frequency combs and a low-noise carrier suppression phase detection system to characterize the optical to microwave synchronization achievable with such frequency divider systems. By applying specific noise reduction strategies, a residual phase noise as low as −120 dBc/Hz at 1 Hz offset frequency from a 11.55 GHz carrier is measured. The fractional frequency instability from a single optical-to-microwave frequency divider is 1.1×10−16 at 1 s averaging down to below 2×10−19 after only 1000 s. The corresponding rms time deviation is lower than 100 attoseconds up to 1000 s averaging duration.
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05.45.Xt Synchronization; coupled oscillators
84.40.-x Radiowave and microwave (including millimeter wave) technology
72.70.+m Noise processes and phenomena

Broadband quantum cascade laser gain medium based on a “continuum-to-bound” active region design

Yu Yao, William O. Charles, Tracy Tsai, Jianxin Chen, Gerard Wysocki, and Claire F. Gmachl

Appl. Phys. Lett. 96, 211106 (2010); http://dx.doi.org/10.1063/1.3431577 (3 pages) | Cited 9 times

Online Publication Date: 24 May 2010

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We present quantum cascade laser designs at 7–9 μm with two lower injector states strongly coupled with the upper laser state at the operating electric fields. Optical transitions from these three coupled states contribute to a large gain spectrum width ( ∼ 250 cm−1 full width at half maximum), which enables external cavity tuning of the lasers over 200 cm−1. Lasers show comparable performance to the conventional narrow band design at a similar wavelength with a peak modal gain coefficient of ∼ 10 kA/cm, a slope efficiency ∼ 1 W/A, and good temperature performance (T0 = 170 K) in pulsed mode operation at 295 K.
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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

Electrically enhanced infrared photoluminescence in Cr:ZnSe

Julien Jaeck, Riad Haidar, Fabrice Pardo, Jean-Luc Pelouard, and Emmanuel Rosencher

Appl. Phys. Lett. 96, 211107 (2010); http://dx.doi.org/10.1063/1.3431663 (3 pages)

Online Publication Date: 24 May 2010

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A sixfold enhancement of infrared (IR) photoluminescence (PL) from thick single crystal Cr:ZnSe under electrical excitation is reported. The baseline PL signal is obtained under a charge-transfer band optical seeding. The electrically enhanced IR signal is localized in the vicinity of the cathode and is shown to be likely related to hole concentration. The various mechanisms involved in this IR light emission will be discussed.
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78.55.Et II-VI semiconductors
81.05.Dz II-VI semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Hf II-VI semiconductors

Strain-enhanced photoluminescence from Ge direct transition

T.-H. Cheng, K.-L. Peng, C.-Y. Ko, C.-Y. Chen, H.-S. Lan, Y.-R. Wu, C. W. Liu, and H.-H. Tseng

Appl. Phys. Lett. 96, 211108 (2010); http://dx.doi.org/10.1063/1.3429085 (3 pages) | Cited 16 times

Online Publication Date: 24 May 2010

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Strong enhancement of Ge direct transition by biaxial-tensile strain was observed. The reduction in band gap difference between the direct and indirect valleys by biaxial tensile strain increases the electron population in the direct valley, and enhances the direct transition. The band gap reduction in the direct and indirect valleys can be extracted from the photoluminescence spectra and is consistent with the calculations using k⋅p and deformation potential methods for conduction bands and valence bands, respectively.
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78.55.Ap Elemental semiconductors
78.60.Mq Sonoluminescence, triboluminescence
71.20.Mq Elemental semiconductors
71.15.-m Methods of electronic structure calculations

Resonance behavior of single ultrathin slot antennas on finite dielectric substrates in terahertz regime

H. R. Park, S. M. Koo, O. K. Suwal, Y. M. Park, J. S. Kyoung, M. A. Seo, S. S. Choi, N. K. Park, D. S. Kim, and K. J. Ahn

Appl. Phys. Lett. 96, 211109 (2010); http://dx.doi.org/10.1063/1.3437091 (3 pages) | Cited 5 times

Online Publication Date: 25 May 2010

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We investigate resonance behaviors of optically thin metallic slot antennas on finite substrates in terahertz frequency regime. By carefully analyzing theoretical and experimental results, we observe that slot antennas fabricated in a gold film with a thickness below the skin depth of gold show blueshifted resonance frequencies for the increasing slot width, while the opposite resonance behaviors appear when the slot antennas are perforated in perfectly electric conductor. In addition, we find that for slot antenna sustained by a finite substrate its thickness and the slot width are additional crucial factors determining the resonance frequency of slot antennas.
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84.40.Ba Antennas: theory, components and accessories

Pulse width narrowing due to dual ground state emission in quantum dot passively mode locked lasers

Charis Mesaritakis, Christos Simos, Hercules Simos, Spiros Mikroulis, Igor Krestnikov, and Dimitris Syvridis

Appl. Phys. Lett. 96, 211110 (2010); http://dx.doi.org/10.1063/1.3432076 (3 pages) | Cited 4 times

Online Publication Date: 25 May 2010

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We present an experimental investigation of the emission properties of a multisection InGaAs quantum dot passively mode locked laser under dual waveband emission from the ground state (GS). A mode locking regime directly related to the GS splitting has been depicted. It is related to significant pulse width decrease with increasing injection current under dual peak emission from the GS, leading to generation of pulses with increased peak power with respect to the usual device operation.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Particle-size effects on the terahertz transmittance of metallic particle ensembles: Comparison with effective medium theory

Y. Zheng, A. Johnson, E. Pyde, and K. J. Chau

Appl. Phys. Lett. 96, 211111 (2010); http://dx.doi.org/10.1063/1.3430547 (3 pages) | Cited 1 time

Online Publication Date: 25 May 2010

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We investigate the transmittance of fixed-length ensembles of spherical particles having average radii ranging over two orders of magnitude. The transmittance is interrogated at discrete frequencies in the terahertz regime where the particle radius is subwavelength by at least an order of magnitude. A nonmonotonic dependence of the transmittance on particle radius is observed. As a function of increasing particle size, the transmittance increases to a peak value and then decreases toward zero. Calculations of the complex effective permittivity of the ensemble yield predicted transmittance curves that accurately describe the transmittance decrease as a function of increasing particle size.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.25.Bs Wave propagation, transmission and absorption

Storing light in active optical waveguides with single-negative materials

W. T. Lu (陆文韬), Y. J. Huang (黄永坚), B. D. F. Casse, R. K. Banyal, and S. Sridhar

Appl. Phys. Lett. 96, 211112 (2010); http://dx.doi.org/10.1063/1.3431574 (3 pages) | Cited 10 times

Online Publication Date: 25 May 2010

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We show that a nonresonant planar waveguide consisting of conventional dielectric cladded with single-negative materials supports degenerate propagating modes for which the group velocity and total energy flow can be zero if the media are lossless. Absorptive losses will destroy the zero-group velocity condition for real frequency/complex wave vector modes. We show that by incorporating gain G into the core dielectric, there exists a critical gain value Gc at which we can recover the condition of zero group velocity, so that light pulses can be stopped and stored. This structure is simpler to achieve than double-negative metamaterials, has small footprint, and can be incorporated into ultracompact on-chip optoelectronics.
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42.79.Gn Optical waveguides and couplers
42.25.Bs Wave propagation, transmission and absorption
42.70.-a Optical materials

Terahertz emission from a dc-biased two-color femtosecond laser-induced filament in air

Tie-Jun Wang, Claude Marceau, Yanping Chen, Shuai Yuan, Francis Théberge, Marc Châteauneuf, Jacques Dubois, and See Leang Chin

Appl. Phys. Lett. 96, 211113 (2010); http://dx.doi.org/10.1063/1.3441004 (3 pages) | Cited 6 times

Online Publication Date: 26 May 2010

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The generation of terahertz (THz) emission from a dc-biased two-color femtosecond laser-induced filament in air was systematically investigated. A polarization analysis demonstrated that the THz emission could be the sum of two components: one generated by two-color laser-induced filamentation and the second induced by the external dc electric field. The first component is mostly from four-wave mixing process and a transient transverse electric current under the action of the external dc field could be responsible for the second THz emission.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.25.Ja Polarization
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Terahertz chemical microscope for label-free detection of protein complex

Toshihiko Kiwa, Yousuke Kondo, Yuji Minami, Iwao Kawayama, Masayoshi Tonouchi, and Keiji Tsukada

Appl. Phys. Lett. 96, 211114 (2010); http://dx.doi.org/10.1063/1.3441408 (3 pages) | Cited 7 times

Online Publication Date: 26 May 2010

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A terahertz (THz) chemical microscope (TCM) has been proposed and developed for label-free analysis of the interactions of proteins, including immune reactions. A SiO2/Si/sapphire plate was fabricated and emitted THz pulses from the sapphire side using a femtosecond laser. The amplitude of a THz pulse depends on the chemical potential of the SiO2 surface. As an initial demonstration, a biotin–avidin complex was analyzed using TCM. Results indicate that biotin concentrations of up to 10−12 mol/l could be detected, suggesting that a high sensitivity immunoassay system can be realized using this method. The distribution of the THz peak amplitude was measured, reflecting the distribution of the biotin–avidin complex on the plate.
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87.80.Un Proteomic techniques
87.15.R- Reactions and kinetics
07.60.Pb Conventional optical microscopes
87.18.Xr Proteomics
87.14.E- Proteins

Electric field control of a quantum dot molecule through optical excitation

Mauricio Garrido, Kushal C. Wijesundara, Swati Ramanathan, E. A. Stinaff, A. S. Bracker, and D. Gammon

Appl. Phys. Lett. 96, 211115 (2010); http://dx.doi.org/10.1063/1.3430506 (3 pages)

Online Publication Date: 26 May 2010

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Nonresonant optical excitation of a coupled quantum dot system was seen to generate a shift in the electric-field-dependent photoluminescence spectra. By monitoring the interdot recombination associated with an electron and hole in different dots we were able to precisely monitor the internal electric field generated. Power, wavelength, and applied field dependence of the charging was studied. Such an optically generated electric field may provide a means for applying local oscillating voltages, allowing for optical tuning of the device parameters.
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78.67.Hc Quantum dots
73.63.Kv Quantum dots
73.21.La Quantum dots
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Cr III-V semiconductors

Extraordinary transmission from high-gain nanoaperture antennas

Edward C. Kinzel, Pornsak Srisungsitthisunti, Yan Li, Arvind Raman, and Xianfan Xu

Appl. Phys. Lett. 96, 211116 (2010); http://dx.doi.org/10.1063/1.3436726 (3 pages) | Cited 6 times

Online Publication Date: 26 May 2010

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This letter describes a bowtie nanoaperture antenna for coupling light to a subdiffraction limited near-field spot (<λ/8). The gain of the antenna is increased using a concentric grating structure to coherently diffract normally incident light toward the aperture. We experimentally demonstrate that the addition of the grating structure enhances the far-field transmission through the aperture by 6.9 times while the intensity at the near-field is increased more than 15 times. The nanoantenna is useful for applications including nanolithography and data storage.
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84.40.Ba Antennas: theory, components and accessories

Single photon emission from positioned GaAs/AlGaAs photonic nanowires

J. Heinrich, A. Huggenberger, T. Heindel, S. Reitzenstein, S. Höfling, L. Worschech, and A. Forchel

Appl. Phys. Lett. 96, 211117 (2010); http://dx.doi.org/10.1063/1.3440967 (3 pages) | Cited 14 times

Online Publication Date: 27 May 2010

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Positioned AlGaAs nanowires with an embedded axial heterostructure GaAs quantum dot (QD) on a prepatterned substrate have been grown. The geometry of the nanowires allows for an outcoupling of the emitted light through the nanowire tip and thereby to probe a single nanowire directly on the growth substrate. Single QD linewidths as small as 95 μeV and photon antibunching were observed at continuous wave laser excitation with a second order autocorrelation function g(2)(0) = 0.46. The results represent an attractive bottom-up fabrication approach for the realization of high efficiency photonic wire based single photon sources.
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81.07.Gf Nanowires
81.05.Ea III-V semiconductors
78.67.Uh Nanowires
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
42.70.Qs Photonic bandgap materials

Terahertz photoluminescence from GaAs doped with shallow donors at interband excitation

A. O. Zakhar’in, A. V. Andrianov, A. Yu. Egorov, and N. N. Zinov’ev

Appl. Phys. Lett. 96, 211118 (2010); http://dx.doi.org/10.1063/1.3441401 (3 pages)

Online Publication Date: 27 May 2010

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We report on the observation of efficient generation of terahertz radiation at continuous-wave interband excitation of n-GaAs at low temperatures. The radiative transitions, accompanying relaxation and trapping of photoexcited electrons to localized donor states or to empty states in impurity subband, lead to the emission of terahertz photons with a relatively high external quantum yield up to 0.3%.
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78.70.Gq Microwave and radio-frequency interactions
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors

Oscillator-free atomic clock using a multimode laser

Sin Hyuk Yim and D. Cho

Appl. Phys. Lett. 96, 211119 (2010); http://dx.doi.org/10.1063/1.3435474 (3 pages)

Online Publication Date: 27 May 2010

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We developed an atomic clock using two modes from a single extended-cavity diode laser in multimode operation. The two modes are phase locked with reference to a dispersion signal from a coherent population trapping (CPT) resonance of 85Rb at 3.036 GHz. The design is in principle free from an oscillator and a modulator and it is a significant simplification over a conventional CPT-based atomic clock. Allan deviation of the beat frequency is 1×10−10 at 200 s integration time.
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42.55.Px Semiconductor lasers; laser diodes
42.50.Wk Mechanical effects of light on material media, microstructures and particles

Modulation of 1.5 μm dislocation-related luminescence emitted from a direct silicon bonded interface by external bias

Xuegong Yu, Lihui Song, Deren Yang, Martin Kittler, and George A. Rozgonyi

Appl. Phys. Lett. 96, 211120 (2010); http://dx.doi.org/10.1063/1.3431580 (3 pages) | Cited 2 times

Online Publication Date: 27 May 2010

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Interfacial dislocation networks were formed in silicon by direct bonding technology. Cathodoluminescence and deep level transient spectroscopy measurements verified that the D1 luminescence at 1.5 μm is associated with carrier transitions via a dislocation-related deep level at 0.35 eV. Both the experiment and theoretical calculations demonstrate that application of an external bias voltage on the bonding interface increases the majority carrier density at this deep level, thereby enhancing the local dislocation-related luminescence. However, beyond a critical voltage, corresponding to saturation of the majority carrier occupancy, the luminescence intensity decreases, due to the reduction in minority carrier density.
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78.60.Hk Cathodoluminescence, ionoluminescence
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
73.20.At Surface states, band structure, electron density of states
68.35.Ct Interface structure and roughness
72.20.Ee Mobility edges; hopping transport
71.55.Cn Elemental semiconductors

Experimental observation of the trapped rainbow

Vera N. Smolyaninova, Igor I. Smolyaninov, Alexander V. Kildishev, and Vladimir M. Shalaev

Appl. Phys. Lett. 96, 211121 (2010); http://dx.doi.org/10.1063/1.3442501 (3 pages) | Cited 16 times

Online Publication Date: 28 May 2010

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We report on the experimental demonstration of the broadband “trapped rainbow” in the visible frequency range using an adiabatically tapered optical nano waveguide. Being a distinct case of the slow light phenomenon, the trapped rainbow effect could be applied to optical computing and signal processing, such as spectroscopy on a chip, and to providing enhanced light-matter interactions.
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42.50.Wk Mechanical effects of light on material media, microstructures and particles
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Radiative and nonradiative recombination in an ultraviolet GaN/AlGaN multiple-quantum-well laser diode

Harumasa Yoshida, Masakazu Kuwabara, Yoji Yamashita, Kazuya Uchiyama, and Hirofumi Kan

Appl. Phys. Lett. 96, 211122 (2010); http://dx.doi.org/10.1063/1.3442918 (3 pages) | Cited 10 times

Online Publication Date: 28 May 2010

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We have experimentally investigated the radiative and nonradiative recombination in a GaN/AlGaN multiple-quantum-well laser diode. The each carrier lifetime has been evaluated based on a rate equation analysis of light output-current characteristics of the laser diode. The estimated nonradiative carrier lifetime is 830 ps, and the Auger recombination is negligibly small at room temperature. At a threshold current density of 8 kA cm−2, the carrier density and the internal quantum efficiency are estimated to be 2.6×1019 cm−3 and 34%, respectively. These results are responsible for experimental and theoretical analysis of optical and electrical properties in AlGaN-based laser diodes.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
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Silicon nanocrystals dispersed in water: Photosensitizers for molecular oxygen

B. Goller, S. Polisski, H. Wiggers, and D. Kovalev

Appl. Phys. Lett. 96, 211901 (2010); http://dx.doi.org/10.1063/1.3432349 (3 pages) | Cited 2 times

Online Publication Date: 24 May 2010

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We report on the synthesis of freestanding silicon spheres having sizes in the range of 3–10 nm. As-prepared luminescent silicon nanocrystals have H-passivated surface. Therefore, energy transfer from excitons confined in Si nanocrystals to oxygen molecules is found to be efficient. It is demonstrated that a termination of silicon nanocrystal H-passivated hydrophobic surface by lipids provides their water solubility. We found that this procedure preserves photosensitizing ability of silicon nanocrystals. Therefore, this material system can potentially be employed for a variety of biomedical applications.
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73.22.-f Electronic structure of nanoscale materials and related systems
61.46.-w Structure of nanoscale materials
33.50.Hv Radiationless transitions, quenching
82.37.Vb Single molecule photochemistry

Hyperfine fields in nanocrystalline Fe–Zr–B probed by 57Fe nuclear magnetic resonance spectroscopy

Marcel Miglierini, Adriana Lančok, and Jaroslav Kohout

Appl. Phys. Lett. 96, 211902 (2010); http://dx.doi.org/10.1063/1.3431612 (3 pages)

Online Publication Date: 24 May 2010

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In nanocrystalline Fe90Zr7B3, hyperfine fields belonging to the amorphous residual matrix are distinguished from those of bcc-Fe nanograins by nuclear magnetic resonance spectroscopy on 57Fe nuclei. With this technique, the nanograins located in magnetic domains can be distinguished from those positioned in domain walls. Structural features of core and surface regions of both types of nanograins are described. Presence of small ( ∼ 0.2%) inclusions of Zr was identified in the core of nanograins.
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71.70.Jp Nuclear states and interactions
76.60.-k Nuclear magnetic resonance and relaxation
75.50.Tt Fine-particle systems; nanocrystalline materials
75.75.Fk Domain structures in nanoparticles
75.60.Ch Domain walls and domain structure

Stress control in polycrystalline thin films—reduction in adatoms diffusion into grain boundaries via surfactants

Yi Yang, Hanchen Huang, S. K. Xiang, and Eric Chason

Appl. Phys. Lett. 96, 211903 (2010); http://dx.doi.org/10.1063/1.3435473 (3 pages) | Cited 2 times

Online Publication Date: 25 May 2010

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The diffusion of adatoms into grain boundaries (GBs) of polycrystalline thin film during vapor deposition affects the stress that develops and the film’s subsequent performance. This Letter reports a proposed mechanism of modifying the stress by controlling adatom diffusion into GBs through the use of surfactants. Based on polycrystalline kinetic Monte Carlo simulations of Cu〈111〉 thin films with In surfactant, the authors demonstrate that the proposed mechanism is feasible. Further, the authors show that the reduction is due to the decrease in effective adatom diffusivity, which dominates over the increase in adatom concentration.
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68.60.Bs Mechanical and acoustical properties
66.30.Lw Diffusion of other defects
61.72.Mm Grain and twin boundaries
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
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