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15 Oct 2012

Volume 101, Issue 16, Articles (16xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 101, 161105 (2012); http://dx.doi.org/10.1063/1.4744947 (4 pages)

Nan Niu, Tsung-Li Liu, Igor Aharonovich, Kasey J. Russell, Alexander Woolf, Thomas C. Sadler, Haitham A. R. El-Ella, Menno J. Kappers, Rachel A. Oliver, and Evelyn L. Hu
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From fabrication to mode mapping in silicon nitride microdisks with embedded colloidal quantum dots

Bram De Geyter, Katarzyna Komorowska, Edouard Brainis, Philippe Emplit, Pieter Geiregat, Antti Hassinen, Zeger Hens, and Dries Van Thourhout

Appl. Phys. Lett. 101, 161101 (2012); http://dx.doi.org/10.1063/1.4758990 (4 pages)

Online Publication Date: 15 October 2012

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We report on the fabrication of free-standing and optically active microdisks with cadmium-based colloidal quantum dots embedded directly into silicon nitride. We show that the process optimization results in low-loss silicon nitride microdisks. The Si3N4 matrix provides the stability necessary to preserve the optical properties of the quantum dots and observe efficient coupling of the photoluminescence to the resonating microdisk modes. Using a spectrally and spatially resolved microphotoluminescence measurement, we map the emission pattern from the microdisk. This technique allows us to identify the resonant modes. The results show good agreement with numerical mode simulations.
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68.65.Hb Quantum dots (patterned in quantum wells)
78.55.Hx Other solid inorganic materials
82.70.Dd Colloids
72.80.Jc Other crystalline inorganic semiconductors
78.67.Hc Quantum dots

Electron dynamics and transverse-kick elimination in a high-field short-period helical microwave undulator

C. Chang, M. Shumail, S. Tantawi, J. Neilson, and C. Pellegrini

Appl. Phys. Lett. 101, 161102 (2012); http://dx.doi.org/10.1063/1.4759002 (4 pages)

Online Publication Date: 15 October 2012

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Single electron dynamics for a circular polarized standing wave (CPSW) undulator synthesized from a corrugated cavity operating with a very low-loss HE11 mode are analyzed. The mechanism of the transverse drift of the CPSW undulator and its elimination are researched, and the tapered-field ends are found effectively to suppress the kick. A prototype of the CPSW undulator with the characters of short undulating-period 1.4 cm, high field K ∼ 1, large aperture ∼ 5 cm, and variable polarization is designed and modeled, whose 3-dimensional electromagnetic fields are used to research the suppression of the transverse kick.
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41.60.Cr Free-electron lasers

Enhancement of photocurrent in ultrathin active-layer photodetecting devices with photonic crystals

Hiroaki Shigeta, Masayuki Fujita, Yoshinori Tanaka, Ardavan Oskooi, Hiroyuki Ogawa, Yusuke Tsuda, and Susumu Noda

Appl. Phys. Lett. 101, 161103 (2012); http://dx.doi.org/10.1063/1.4759149 (4 pages)

Online Publication Date: 15 October 2012

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We demonstrate an enhancement of the photoelectric-conversion efficiency of an ultrathin (50 nm) silicon active-layer photodetecting device using a two-dimensional photonic crystal positioned nearby to boost the optical absorption. We show both experimentally and with simulations that the incident-light absorption within the active layer is enhanced by optical-resonance effects at the photonic band edge. We also find that a photonic crystal with deeper holes can lead to an even larger absorption enhancement due to better quality (Q)-factor matching between the photonic band-edge modes and the intrinsic material absorption. The experimentally observed photocurrent of the fabricated photonic-crystal sample is increased by a factor of ∼20 at the photonic band-edge wavelength relative to that of a control sample without the photonic crystal which is attributed to the improved Q matching.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.70.Qs Photonic bandgap materials

Verification of the physical mechanism of THz generation by dual-color ultrashort laser pulses

Min Li, Wenxue Li, Yi Shi, Peifen Lu, Haifeng Pan, and Heping Zeng

Appl. Phys. Lett. 101, 161104 (2012); http://dx.doi.org/10.1063/1.4759268 (3 pages) | Cited 2 times

Online Publication Date: 15 October 2012

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We experimentally verified the physical mechanism of the dual-color ultrashort laser-driven THz wave generation in air by measuring its dependence on the dual-color field phase difference. Our results evidenced that the THz generation from the laser-induced plasma is dominated by the photo-current mechanism. A continuous rotation of THz polarization was observed by changing the dual-color phase difference, facilitating coherent control of the THz intensity and polarization.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

A full free spectral range tuning of p-i-n doped gallium nitride microdisk cavity

Nan Niu, Tsung-Li Liu, Igor Aharonovich, Kasey J. Russell, Alexander Woolf, Thomas C. Sadler, Haitham A. R. El-Ella, Menno J. Kappers, Rachel A. Oliver, and Evelyn L. Hu

Appl. Phys. Lett. 101, 161105 (2012); http://dx.doi.org/10.1063/1.4744947 (4 pages)

Online Publication Date: 15 October 2012

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Effective, permanent tuning of the whispering gallery modes (WGMs) of p-i-n doped GaN microdisk cavity with embedded InGaN quantum dots over one free spectral range is demonstrated by irradiating the microdisks with a ultraviolet laser (380 nm) in DI water. For incident laser powers between 150 and 960 nW, the tuning rate varies linearly. Etching of the top surface of the cavity is proposed as the driving force for the observed shift in WGMs and is supported by experiments. The tuning for GaN/InGaN microdisk cavities is an important step for deterministically realizing nanophotonic devices for studying cavity quantum electrodynamics.
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78.55.Cr III-V semiconductors
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.65.Cf Surface cleaning, etching, patterning
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

Intermodal four-wave mixing in a higher-order-mode fiber

Ji Cheng, Martin E. V. Pedersen, Kriti Charan, Ke Wang, Chris Xu, Lars Grüner-Nielsen, and Dan Jakobsen

Appl. Phys. Lett. 101, 161106 (2012); http://dx.doi.org/10.1063/1.4759038 (4 pages) | Cited 1 time

Online Publication Date: 16 October 2012

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We demonstrate a high-efficiency intermodal four-wave-mixing process in an all-fiber system, comprising a picosecond fiber laser and a high-order-mode (HOM) fiber. Two pump photons in the LP01 mode of the fiber can generate an anti-Stokes photon in the LP01 mode and a Stokes photon in the LP02 mode. The wavelength dependent mode profiles of the HOM fiber produce significant spatial overlap between the modes involved. The anti-Stokes wave at 941 nm is generated with 20% conversion efficiency with input pulse energy of 20 nJ. The guidance of the anti-Stokes and Stokes waves in the HOM fiber enhances system stability.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.81.Wg Other fiber-optical devices
42.55.Wd Fiber lasers

Anomalous dip observed in intensity autocorrelation function as an inherent nature of single-photon emitters

H. Nakajima, H. Kumano, H. Iijima, and I. Suemune

Appl. Phys. Lett. 101, 161107 (2012); http://dx.doi.org/10.1063/1.4760222 (4 pages) | Cited 1 time

Online Publication Date: 16 October 2012

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We report the observation of an anomalous antibunching dip in intensity autocorrelation function with photon correlation measurements on a single-photon emitter (SPE). We show that the anomalous dip observed is a manifestation of quantum nature of SPEs. Taking population dynamics in a quantum two-level system into account correctly, we redefine intensity autocorrelation function. This is of primary importance for precisely evaluating the lowest-level probability of multiphoton generation in SPEs toward realizing versatile pure SPEs for quantum information and communication.
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42.50.-p Quantum optics
42.30.-d Imaging and optical processing

Optical phase conjugation in azo-dye doped chiral liquid crystal

Pawel Karpinski and Andrzej Miniewicz

Appl. Phys. Lett. 101, 161108 (2012); http://dx.doi.org/10.1063/1.4760227 (4 pages)

Online Publication Date: 16 October 2012

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We report on optical phase conjugation phenomenon observed in chiral nematic liquid crystal showing band gap type Bragg reflection. The phase conjugate to the signal beam is observable only in the small temperature interval when the Bragg condition is fulfilled and only for circularly polarized light. The optical phase conjugation signals were observed at low cw laser light intensities (<100 mW/cm2, λ = 532 nm). Estimated value of third order optical susceptibility χ(3) = 2.8 × 10−17 m2/V2 is attributed to enhancement due to photoisomerisation of azo-dye (disperse red 1) inducing molecular reorientation process of liquid crystal molecules.
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42.70.Df Liquid crystals
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.79.Dj Gratings
42.81.-i Fiber optics
82.30.Qt Isomerization and rearrangement
82.50.-m Photochemistry
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High-speed plasmonic nanolithography with a solid immersion lens-based plasmonic optical head

Taeseob Kim, Won-Sup Lee, Hang-Eun Joe, Geon Lim, Guk-Jong Choi, Myeong-Gu Gang, Sung-Mook Kang, Kyoung-Su Park, Byung-Kwon Min, Young-Pil Park, and No-Cheol Park

Appl. Phys. Lett. 101, 161109 (2012); http://dx.doi.org/10.1063/1.4760263 (4 pages)

Online Publication Date: 16 October 2012

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This letter describes the use of a plasmonic optical head to achieve high-speed nanopatterning. A plasmonic optical head employs both a sharp-ridged nanoaperture and a nanogap control to maintain the nanogap required for near-field nanolithography. The nanogap control uses a gap error signal produced by evanescent coupling through the air-gap. We demonstrate that a plasmonic optical head achieves a patterning resolution of 70 nm and a patterning speed of 100 mm/s. The proposed combination of a surface plasmon nanoaperture and a nanogap servo system is one of the strategies used to achieve high-speed, high-resolution nanolithography.
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81.16.Nd Micro- and nanolithography
85.40.Hp Lithography, masks and pattern transfer
42.79.Bh Lenses, prisms and mirrors
81.16.Rf Micro- and nanoscale pattern formation
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Efficiency droop due to electron spill-over and limited hole injection in III-nitride visible light-emitting diodes employing lattice-matched InAlN electron blocking layers

Suk Choi, Mi-Hee Ji, Jeomoh Kim, Hee Jin Kim, Md. M. Satter, P. D. Yoder, Jae-Hyun Ryou, Russell D. Dupuis, Alec M. Fischer, and Fernando A. Ponce

Appl. Phys. Lett. 101, 161110 (2012); http://dx.doi.org/10.1063/1.4759044 (5 pages)

Online Publication Date: 17 October 2012

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Data and analysis are presented for the study of efficiency droop in visible III-nitride light-emitting diodes (LEDs) considering the effects of both electron spill-over out of active region and hole injection into the active region. Performance characteristics of blue LEDs with lattice-matched In0.18Al0.82N electron-blocking layers (EBLs) with different thicknesses were measured in order to exclude the effects of strain and doping efficiency of the EBL, and the quantum efficiencies were analyzed taking account of the electron spill-over current and the relative hole concentration. The results suggest that the highest efficiency in LEDs with a 15-nm In0.18Al0.82N EBL is due to relatively lower hole-blocking effect, hence higher hole injection than in LEDs with a 20-nm EBL, while providing a higher potential barrier for reduced electron spill-over than in LEDs with thinner EBLs. This study suggests that the EBL hole-blocking and electron-confinement effects should be considered in order to achieve higher light output power and reduced efficiency droop at high currents.
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85.60.Jb Light-emitting devices

Detection of virus-like nanoparticles via scattering using a chip-scale optical biosensor

Rongjin Yan, N. Scott Lynn, Luke C. Kingry, Zhangjing Yi, Tim Erickson, Richard A. Slayden, David S. Dandy, and Kevin L. Lear

Appl. Phys. Lett. 101, 161111 (2012); http://dx.doi.org/10.1063/1.4758294 (4 pages) | Cited 1 time

Online Publication Date: 17 October 2012

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A local evanescent array coupled biosensor is used to detect spherical polystyrene nanoparticles with diameters of 40 nm and 200 nm, whose sizes and refractive index are similar to virus particles. The sensitivity is ∼1%/particle for 200 nm particles and 0.04%/particle for 40 nm particles. Mie scattering in an evanescent field theory is used to model the scattered light intensity for both sizes of nanoparticles.
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87.85.-d Biomedical engineering

Graphene mode-locked femtosecond Yb:KLuW laser

Elena Ugolotti, Andreas Schmidt, Valentin Petrov, Jun Wan Kim, Dong-Il Yeom, Fabian Rotermund, Sukang Bae, Byung Hee Hong, Antonio Agnesi, Christian Fiebig, Götz Erbert, Xavier Mateos, Magdalena Aguiló, Francesc Diaz, and Uwe Griebner

Appl. Phys. Lett. 101, 161112 (2012); http://dx.doi.org/10.1063/1.4760265 (4 pages) | Cited 2 times

Online Publication Date: 17 October 2012

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Large-area monolayer graphene, synthesized by chemical vapor deposition, was transferred to a 1-in. quartz substrate. The high-quality monolayer graphene has been subject to characterization of the nonlinear properties near 1 μm and was successfully applied as saturable absorber for passive mode-locking of a femtosecond Yb:KLuW laser. The diode-pumped mode-locked Yb:KLuW laser was tunable around 1.04 μm and delivered pulses as short as 160 fs. The maximum output power of 160 mW was demonstrated for 203 fs pulse duration. The mode-locked laser results are comparable to those demonstrated with the same laser gain medium using single-walled carbon nanotubes as saturable absorbers.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Localized surface plasmon resonances in highly doped semiconductors nanostructures

V. N'Tsame Guilengui, L. Cerutti, J.-B. Rodriguez, E. Tournié, and T. Taliercio

Appl. Phys. Lett. 101, 161113 (2012); http://dx.doi.org/10.1063/1.4760281 (4 pages) | Cited 1 time

Online Publication Date: 17 October 2012

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We demonstrate the occurrence of localized surface plasmon resonances (LSPRs) in periodic arrays of highly doped/un-doped InAsSb/GaSb semiconductor nanostructures, where highly doped InAsSb is degenerated and exhibits a metallic behavior while being lattice-matched onto GaSb. Reflectance spectroscopy allows investigating the impact of the geometrical and physical properties of both InAsSb and GaSb materials on the LSPR. Our results show that these InAsSb/GaSb nanostructures form the building blocks of metal-free, all-semiconductor infrared plasmonic devices.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.22.Lp Collective excitations

Long-wave infrared nBn photodetectors based on InAs/InAsSb type-II superlattices

H. S. Kim, O. O. Cellek, Zhi-Yuan Lin, Zhao-Yu He, Xin-Hao Zhao, Shi Liu, H. Li, and Y.-H. Zhang

Appl. Phys. Lett. 101, 161114 (2012); http://dx.doi.org/10.1063/1.4760260 (3 pages)

Online Publication Date: 18 October 2012

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Long-wave infrared InAs/InAsSb type-II superlattice nBn photodetectors are demonstrated on GaSb substrates. The typical device consists of a 2.2 μm thick absorber layer and has a 50% cutoff wavelength of 13.2 μm, a measured dark current density of 5 × 10−4 A/cm2 at 77 K under a bias of −0.3 V, a peak responsivity of 0.24 A/W at 12 μm, and a maximum resistance-area product of 300 Ω cm2 at 77 K. The calculated generation-recombination noise limited specific detectivity (D*) and experimentally measured D* at 12 μm and 77 K are 1 × 1010 cm Hz1/2/W and 1 × 108 cm Hz1/2/W, respectively.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Single-mode quantum cascade lasers employing asymmetric Mach-Zehnder interferometer type cavities

Peter Q. Liu, Xiaojun Wang, and Claire F. Gmachl

Appl. Phys. Lett. 101, 161115 (2012); http://dx.doi.org/10.1063/1.4761247 (5 pages)

Online Publication Date: 18 October 2012

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We employ properly designed asymmetric Mach-Zehnder interferometer structures as effective wavelength filters and monolithically integrate them in conventional Fabry-Perot cavities to facilitate single-mode operation of the lasers. With such asymmetric Mach-Zehnder interferometer type laser cavities, continuously tunable single-mode operation of quantum cascade (QC) lasers is achieved in pulsed mode from 80 K up to room temperature and in continuous-wave mode with side-mode suppression ratio up to ∼35 dB. These devices are fabricated with the same process as simple ridge lasers, therefore providing a promising solution to achieving more cost-effective single-mode QC lasers.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
07.60.Ly Interferometers

Quasiresonant excitation of InP/InGaP quantum dots using second harmonic generated in a photonic crystal cavity

Sonia Buckley, Kelley Rivoire, Fariba Hatami, and Jelena Vučković

Appl. Phys. Lett. 101, 161116 (2012); http://dx.doi.org/10.1063/1.4761248 (4 pages)

Online Publication Date: 18 October 2012

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Indistinguishable single photons are necessary for quantum information processing applications. Resonant or quasiresonant excitation of single quantum dots provides greater single photon indistinguishability than incoherent pumping, but is also more challenging experimentally. Here, we demonstrate high signal to noise quasiresonant excitation of InP/InGaP quantum dots. The excitation is provided via second harmonic generated from a telecommunications wavelength laser resonant with the fundamental mode of a photonic crystal cavity, fabricated at twice the quantum dot transition wavelength. The second harmonic is generated using the χ(2) nonlinearity of the InGaP material matrix.
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42.70.Qs Photonic bandgap materials
78.67.Hc Quantum dots
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.82.Cr Fabrication techniques; lithography, pattern transfer

Bistability patterns and nonlinear switching with very high contrast ratio in a 1550 nm quantum dash semiconductor laser

A. Hurtado, M. Nami, I. D. Henning, M. J. Adams, and L. F. Lester

Appl. Phys. Lett. 101, 161117 (2012); http://dx.doi.org/10.1063/1.4761473 (5 pages) | Cited 1 time

Online Publication Date: 18 October 2012

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We report on the experimental observation of optical bistability (OB) and nonlinear switching (NS) in a nanostructure laser; specifically a 1550 nm quantum dash Fabry-Perot laser subject to external optical injection and operated in reflection. Different shapes of optical bistability and nonlinear switching, anticlockwise and clockwise, with very high on-off contrast ratio (up to 180:1) between output states were experimentally measured. These results added to the potential of nanostructure lasers for enhanced performance offer promise for use in fast all-optical signal processing applications in optical networks.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Pc Optical bistability, multistability, and switching, including local field effects

Experimental observation of frequency up-conversion by flash ionization

A. Nishida, N. Yugami, T. Higashiguchi, T. Otsuka, F. Suzuki, M. Nakata, Y. Sentoku, and R. Kodama

Appl. Phys. Lett. 101, 161118 (2012); http://dx.doi.org/10.1063/1.4755843 (3 pages)

Online Publication Date: 18 October 2012

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We have demonstrated frequency up-conversion in the terahertz (THz) region by flash ionization, which occurs due a terahertz wave interacting with a plasma created by an ultrashort laser pulse. The upshift frequency is controlled by the plasma density. We performed a proof-of-principle experiment with a plasma creation time scale much shorter than the period of the electromagnetic wave and a plasma length longer than its wavelength. We upshifted the frequency from 0.35 to 3.5 THz by irradiating a ZnSe crystal with a Ti:sapphire laser pulse.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.-v Laser optical systems: design and operation
42.60.By Design of specific laser systems

Ultrasmall radial polarizer array based on patterned plasmonic nanoslits

Kentaro Iwami, Miho Ishii, Yuzuru Kuramochi, Kenichi Ida, and Norihiro Umeda

Appl. Phys. Lett. 101, 161119 (2012); http://dx.doi.org/10.1063/1.4761943 (4 pages)

Online Publication Date: 19 October 2012

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We developed an ultrasmall radial or azimuthal polarization converter of size ranged from 10 to 100 μm. The converter consists of a half-wave plate divided into four quadrants, each of which is made of periodic gold nanoslits at different orientations in steps of 45°. The converter and its array were fabricated and followed by an evaluation with the Sénarmont method and the polarization microscopy. Due to the giant birefringence of the gold nanoslits, each slit segment achieved 180° retardation at the wavelength of 633 nm, and the conversion from linear to radial polarization was demonstrated.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Fm Birefringence
81.16.Rf Micro- and nanoscale pattern formation
42.79.Ci Filters, zone plates, and polarizers
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Molecular orientation change during adsorption of NO and N2O on Ir(111) observed by real-time wavelength-dispersive x-ray absorption spectroscopy with polarization switching

Kenta Amemiya, Masako Sakamaki, Shuichi Nakamoto, Masaaki Yoshida, Kazuma Suzuki, Hiroshi Kondoh, Tsuneharu Koide, Kenji Ito, Kimichika Tsuchiya, Kentaro Harada, Hiroyuki Sasaki, Tomohiro Aoto, Tatsuro Shioya, Takashi Obina, Shigeru Yamamoto, et al.

Appl. Phys. Lett. 101, 161601 (2012); http://dx.doi.org/10.1063/1.4759114 (4 pages)

Online Publication Date: 15 October 2012

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The molecular orientation of NO and N2O during adsorption on Ir(111) is observed by combining the wavelength-dispersive x-ray absorption spectroscopy with 1 Hz switching between the vertical and horizontal linear polarizations. It is revealed that NO adsorbs keeping its molecular axis at ∼ 20° from surface normal. In contrast, N2O rapidly adsorbs up to 2/3 of the saturation coverage with an orientation angle of ∼ 35°, then turns to a slow adsorption phase with larger orientation angles, and gradually reaches its saturation with an average orientation angle of ∼ 45°. Such a complicated behavior is interpreted by assuming different adsorption sites.
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68.43.Mn Adsorption kinetics
78.70.Dm X-ray absorption spectra

Thermal annealing influence on poly(3-hexyl-thiophene)/phenyl-C61-butyric acid methyl ester-based solar cells with anionic conjugated polyelectrolyte as cathode interface layer

Ting Shi, Xiaoguang Zhu, Dong Yang, Yanhua Xie, Jian Zhang, and Guoli Tu

Appl. Phys. Lett. 101, 161602 (2012); http://dx.doi.org/10.1063/1.4759148 (4 pages) | Cited 1 time

Online Publication Date: 16 October 2012

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Thermal annealing dependent performance was demonstrated in poly(3-hexyl-thiophene):phenyl-C61-butyric acid methyl ester based organic photovoltaics with anionic conjugated polyelectrolyte (PFEOSO3Na) as the cathode interface layer. The best performance can be achieved when the device based PFEOSO3Na was treated by post-annealing, exhibiting about 20% higher power conversion efficiency than the control device. Atomic force microscopy studies showed that the morphology of interface layers changed under different device treatment processes, leading to various electron extraction efficiencies. Compared with different interface materials, it further demonstrated the best charge extraction efficiency in the device with PFEOSO3Na layer, due to its stronger interface dipole.
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88.40.jr Organic photovoltaics
88.40.hj Efficiency and performance of solar cells
82.47.Nj Polymer-electrolyte fuel cells (PEFC)

Polarization dependant scattering as a tool to retrieve the buried phase information of surface plasmon polaritons

S. Crosbie, É. McClean, and D. Zerulla

Appl. Phys. Lett. 101, 161603 (2012); http://dx.doi.org/10.1063/1.4761476 (4 pages)

Online Publication Date: 17 October 2012

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We report on an experimental and theoretical study demonstrating that the phase information of a surface plasmon polariton (SPP) can be retrieved by investigating the cross polarized scattered components in the SPP reflection channel. The method does not require traditional interferometric techniques, optical heterodyning, or polarimetry, instead the method is self referencing. Studies are performed for different excitation wavelengths (561 nm and 795 nm), providing an alternative access route to phase information for sensing applications while also offering a deeper understanding of the scattering behavior of SPPs.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
41.20.Jb Electromagnetic wave propagation; radiowave propagation
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing

Measurement of electric-field induced second harmonic generation in hydrogenated amorphous silicon

Long He, James D. Walker, Howard M. Branz, Charles T. Rogers, and Charles W. Teplin

Appl. Phys. Lett. 101, 161604 (2012); http://dx.doi.org/10.1063/1.4761477 (5 pages)

Online Publication Date: 18 October 2012

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We quantitatively separate interface optical second harmonic generation (SHG) and electric-field induced second harmonic generation (EFISH) from hydrogenated amorphous silicon (a-Si:H) interfaces and bulk. Using a 1.51 eV probe laser, we measure SHG signals from indium tin oxide (ITO) ITO/a-Si:H/ITO sandwich structures and vary the electric fields in the a-Si:H layer using an applied voltage bias. The a-Si:H/ITO interfaces form back-to-back diodes. Because of finite optical penetration depth, SHG probes only the front diode. When the front diode is reverse biased, the EFISH contribution dominates the SHG signal and probes the electric field in the ∼30 nm adjacent to the interface. Through fitting of the SHG data, we find that in this near-interface region, the electric field is proportional to the square root of the applied bias. The fitting measures the interfacial ITO/a-Si:H built-in voltage to be ∼0.2 V.
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81.05.Cy Elemental semiconductors
81.05.Gc Amorphous semiconductors
85.30.Kk Junction diodes

Transport characteristics of graphene-metal interfaces

V. Nam Do and H. Anh Le

Appl. Phys. Lett. 101, 161605 (2012); http://dx.doi.org/10.1063/1.4761940 (5 pages) | Cited 1 time

Online Publication Date: 19 October 2012

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A physical model is proposed to clarify the electron transport through graphene-metal interfaces. It is based on an effective description of the coupling between the graphene π-bands and the metal sd- and d-bands. Applying this model to vertically symmetrical metal-graphene-metal structures, we show that the current-voltage characteristics can be either linear or non-linear with a negative or positive differential resistance depending on the dominance of the d-like or s-like electrons in the metal as well as the graphene-metal coupling.
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73.40.Rw Metal-insulator-metal structures
72.20.Ht High-field and nonlinear effects
68.35.Ct Interface structure and roughness
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Dual-band asymmetry chiral metamaterial based on planar spiral structure

Xiaoliang Ma, Cheng Huang, Mingbo Pu, Yanqin Wang, Zeyu Zhao, Changtao Wang, and Xiangang Luo

Appl. Phys. Lett. 101, 161901 (2012); http://dx.doi.org/10.1063/1.4756901 (4 pages)

Online Publication Date: 15 October 2012

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A dual-band asymmetric chiral metamaterial is constructed by using two pairs of planar spiral structures with a certain twisted angle. Numerical simulation results show that when a y-polarized wave is incident on the chiral metamaterial the left circularly polarized wave is emitted at 12.25 GHz and 15.57 GHz, while right circularly polarized wave is excited at 13.9 GHz and 16.86 GHz. The measured transmissions are higher than −2.4 dB, and the absolute values of the transmission differences between the right and left circularly polarized waves exceed 15 dB at the four frequencies, which agree well with the simulated results.
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42.70.-a Optical materials
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