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4 Jul 2011

Volume 99, Issue 1, Articles (01xxxx)

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Appl. Phys. Lett. 99, 011107 (2011); http://dx.doi.org/10.1063/1.3606505 (3 pages)

Kosei Ueno, Satoaki Takabatake, Ko Onishi, Hiroko Itoh, Yoshiaki Nishijima, and Hiroaki Misawa
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Microbubbles as contrast agent for in-line x-ray phase-contrast imaging

Yan Xi, Rongbiao Tang, Yujie Wang, and Jun Zhao

Appl. Phys. Lett. 99, 011101 (2011); http://dx.doi.org/10.1063/1.3607292 (3 pages) | Cited 3 times

Online Publication Date: 5 July 2011

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In the present study, we investigated the potential of gas-filled microbubbles as contrast agents for in-line x-ray phase-contrast imaging (PCI) in biomedical applications. When imaging parameters are optimized, the microbubbles function as microlenses that focus the incoming x-rays to form bright spots, which can significantly enhance the image contrast. Since microbubbles have been shown to be safe contrast agents in clinical ultrasonography, this contrast-enhancement procedure for PCI may have promising utility in biomedical applications, especially when the dose of radiation is a serious concern. In this study, we performed both numerical simulations and ex vivo experiments to investigate the formation of the contrast and the effectiveness of microbubbles as contrast agents in PCI.
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87.59.B- Radiography
02.60.Cb Numerical simulation; solution of equations

Dopant profile control of epitaxial emitter for silicon solar cells by low temperature epitaxy

Donny Lai, Yew Heng Tan, Oki Gunawan, Lining He, and Chuan Seng Tan

Appl. Phys. Lett. 99, 011102 (2011); http://dx.doi.org/10.1063/1.3607303 (3 pages) | Cited 1 time

Online Publication Date: 5 July 2011

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We report an alternative approach to grow phosphorus-doped epitaxial silicon emitter by rapid thermal chemical vapor deposition at low temperature (T ≥ 700 °C). A power conversion efficiency (PCE) of (6.6 ± 0.3)% and a pseudo PCE of (10.2 ± 0.2)% has been achieved for the solar cell with epi-emitter grown at 700 °C, in the absence of surface texturization, antireflective coating, and back surface field enhancement, without considering front contact shading. Secondary ion mass spectroscopy revealed that lower temperature silicon epitaxy yields a more abrupt p-n junction, suggesting potential applications for radial p-n junction wire array solar cells.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.ag Semiconductors
88.40.H- Solar cells (photovoltaics)
88.40.jj Silicon solar cells
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Electrically pumped heterogeneously integrated Si/III-V evanescent lasers with micro-loop mirror reflector

Yunan Zheng, Doris Keh-Ting Ng, Yongqiang Wei, Wang Yadong, Yingyan Huang, Yongming Tu, Chee-Wei Lee, Boyang Liu, and Seng-Tiong Ho

Appl. Phys. Lett. 99, 011103 (2011); http://dx.doi.org/10.1063/1.3607309 (3 pages) | Cited 2 times

Online Publication Date: 5 July 2011

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An electrically pumped heterogeneously integrated Si/AlGaInAs evanescent laser with micro-loop mirror (MLM) as high reflectors at both ends is experimentally demonstrated. Finite-difference time-domain simulation shows that 98% reflectivity can be achieved with micro-loop mirror formed by single-mode silicon-on-insulator (SOI) waveguides. The laser based on a Si/III-V hybrid gain waveguide and passive SOI MLM reflectors is fabricated and single-mode continuous-wave (CW) lasing is achieved at room temperature with a lasing threshold current density of 2.5 kA/cm2.
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42.55.Px Semiconductor lasers; laser diodes
42.70.Hj Laser materials
42.82.-m Integrated optics
02.70.Bf Finite-difference methods

Bistability in an injection locked two color laser with dual injection

Patrycja Heinricht, Benjamin Wetzel, Stephen O’Brien, Andreas Amann, and Simon Osborne

Appl. Phys. Lett. 99, 011104 (2011); http://dx.doi.org/10.1063/1.3605584 (3 pages) | Cited 5 times

Online Publication Date: 5 July 2011

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A two color Fabry-Pérot laser subjected to optical injection in both modes is examined experimentally and theoretically. The theoretical analysis predicts a bistability between locked states due to a swallow-tail bifurcation, which is unique to the dual injection system. This bistability is confirmed experimentally and used as the basis for an all optical memory element with switching times below 500 ps.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.55.Px Semiconductor lasers; laser diodes
05.45.-a Nonlinear dynamics and chaos

Rapid adiabatic passage in quantum dots: Influence of scattering and dephasing

K. Schuh, F. Jahnke, and M. Lorke

Appl. Phys. Lett. 99, 011105 (2011); http://dx.doi.org/10.1063/1.3609016 (3 pages) | Cited 1 time

Online Publication Date: 6 July 2011

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Theoretical investigations for the realization of population inversion of semiconductor quantum dot ground-state transitions by means of adiabatic passage with chirped optical pulses are presented. While the inversion due to Rabi oscillations depends sensitively on the resonance condition, the pulse area, as well as on the absence of carrier scattering and dephasing, we find that adiabatic passage is surprisingly insensitive to the excitation conditions and carrier scattering effects. Quantum kinetic models for the interaction of quantum-dot carriers with longitudinal optical phonons are used to describe carrier scattering and dephasing in the corresponding simulations and allow to quantify the conditions to simultaneously invert an ensamble of quantum dots.
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73.25.+i Surface conductivity and carrier phenomena
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)

Retrieval of terahertz spectra through ultrafast electro-optic modulation

Z. Chen, Y. Gao, and M. F. DeCamp

Appl. Phys. Lett. 99, 011106 (2011); http://dx.doi.org/10.1063/1.3607486 (3 pages) | Cited 1 time

Online Publication Date: 6 July 2011

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Ultrafast electro-optic modulation on a narrow band optical pulse is utilized to spectrally resolve coherent terahertz radiation. This technique requires no moving parts and has the potential to measure THz spectra with a resolution better than 10 GHz, limited by the bandwidth of the optical probe field or optical spectrometer. The dynamic range of this device is limited by the detection capabilities of an optical spectrometer, providing a highly efficient method of spectral reconstruction of both narrow band and broadband terahertz radiation.
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42.79.Hp Optical processors, correlators, and modulators
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Homogeneous nano-patterning using plasmon-assisted photolithography

Kosei Ueno, Satoaki Takabatake, Ko Onishi, Hiroko Itoh, Yoshiaki Nishijima, and Hiroaki Misawa

Appl. Phys. Lett. 99, 011107 (2011); http://dx.doi.org/10.1063/1.3606505 (3 pages) | Cited 13 times

Online Publication Date: 6 July 2011

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We report an innovative lithography system appropriate for fabricating sharp-edged nanodot patterns with nanoscale accuracy using plasmon-assisted photolithography. The key technology is two-photon photochemical reactions of a photoresist induced by plasmonic near-field light and the scattering component of the light in a photoresist film. The scattering component of the light is a radiation mode from higher order localized surface plasmon resonances scattered by metallic nanostructures.
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81.16.Rf Micro- and nanoscale pattern formation
82.50.Hp Processes caused by visible and UV light
81.16.Nd Micro- and nanolithography

Temporal and phase measurements of ultraviolet femtosecond pulses at 200 nm by molecular alignment based frequency resolved optical gating

Hao Li, Jia Liu, Yahui Feng, Cheng Chen, Haifeng Pan, Jian Wu, and Heping Zeng

Appl. Phys. Lett. 99, 011108 (2011); http://dx.doi.org/10.1063/1.3609238 (3 pages) | Cited 4 times

Online Publication Date: 8 July 2011

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We demonstrate that the temporal profile and phase of a weak ultraviolet femtosecond pulse around 200 nm can be measured by molecular alignment based cross-correlation frequency resolved optical gating technique. This technique employs the impulsive alignment of gaseous molecules as gate function and exhibits the advantage of no phase-matching constraint and applicability to pulses at various wavelengths. Simultaneous measurements of near-infrared and ultraviolet pulses are demonstrated. Its agreements with the independent spectral phase interferometry for direct electric field reconstruction and second-order auto-correlation measurements confirm that the molecular alignment gating is a robust technique for ultrashort pulse diagnosis.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.-e Optical elements, devices, and systems
07.68.+m Photography, photographic instruments; xerography
07.60.-j Optical instruments and equipment

Strain-balanced InAs/GaSb type-II superlattice structures and photodiodes grown on InAs substrates by metalorganic chemical vapor deposition

Yong Huang, Jae-Hyun Ryou, Russell D. Dupuis, Daniel Zuo, Benjamin Kesler, Shun-Lien Chuang, Hefei Hu, Kyou-Hyun Kim, Yen Ting Lu, K. C. Hsieh, and Jian-Min Zuo

Appl. Phys. Lett. 99, 011109 (2011); http://dx.doi.org/10.1063/1.3609240 (3 pages)

Online Publication Date: 8 July 2011

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We propose and demonstrate strain-balanced InAs/GaSb type-II superlattices (T2SLs) grown on InAs substrates employing GaAs-like interfacial (IF) layers by metalorganic chemical vapor deposition (MOCVD) for effective strain management, simplified growth scheme, improved materials crystalline quality, and reduced substrate absorption. The in-plane compressive strain from the GaSb layers in the T2SLs on the InAs was completely balanced by the GaAs-like IF layers formed by controlled precursor carry-over and anion exchange effects, avoiding the use of complicated IF layers and precursor switching schemes that were used for the MOCVD growth of T2SLs on GaSb. An infrared (IR) p-i-n photodiode structure with 320-period InAs/GaSb T2SLs on InAs was grown and the fabricated devices show improved performance characteristics with a peak responsivity of ∼1.9 A/W and a detectivity of ∼6.78 × 109 Jones at 8 μm at 78 K. In addition, the InAs buffer layer and substrate show a lower IR absorption coefficient than GaSb substrates in most of the mid- and long-IR spectral range.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
82.39.Wj Ion exchange, dialysis, osmosis, electro-osmosis, membrane processes
85.60.Dw Photodiodes; phototransistors; photoresistors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Fs III-V and II-VI semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

Realization of a nonlinear interferometer with parametric amplifiers

Jietai Jing, Cunjin Liu, Zhifan Zhou, Z. Y. Ou, and Weiping Zhang

Appl. Phys. Lett. 99, 011110 (2011); http://dx.doi.org/10.1063/1.3606549 (3 pages) | Cited 7 times

Online Publication Date: 8 July 2011

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We construct an interferometer with parametric amplifiers as beam splitters. Because of the gain in the parametric amplifiers, the maximum output intensity of the interferometer can be much bigger than the input intensity as well as the intensity inside the interferometer (the phase sensing intensity). We find that the fringe intensity depends quadratically on the intensity of the phase sensing field at high gain. This type of nonlinear interferometer has better sensitivity than the traditional linear interferometer made of beam splitters with the same phase sensing intensity.
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07.60.Ly Interferometers
84.30.Le Amplifiers

Faraday rotator properties of {Tb3}[Sc1.95Lu0.05](Al3)O12, a highly transparent terbium-garnet for visible-infrared optical isolators

Encarnación G. Víllora, Pablo Molina, Masaru Nakamura, Kiyoshi Shimamura, Tsubasa Hatanaka, Akiharu Funaki, and Kunihiro Naoe

Appl. Phys. Lett. 99, 011111 (2011); http://dx.doi.org/10.1063/1.3609245 (3 pages) | Cited 7 times

Online Publication Date: 8 July 2011

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The optical and magneto-optical properties of the {Tb3}[Sc1.95Lu0.05](Al3)O12 garnet (TSLAG) crystal are analyzed in detailed and compared with those of the reference compound Tb3Ga5O12 (TGG). TSLAG presents a very high transmittance, particularly higher than that of TGG in the visible region, and its Verdet constant is 20% larger at any wavelength. The figure of merit and extinction features point out the superior characteristics of TSLAG respect to TGG. A prototype, polarization independent optical isolator based on a TSLAG rotator is demonstrated at 1080 nm. Its performance confirms the high optical quality of this crystal, indicating its mature development for Faraday rotator applications.
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42.79.-e Optical elements, devices, and systems
75.50.Gg Ferrimagnetics
78.20.Ls Magneto-optical effects

Microwave frequency-comb generation in a tunneling junction by intermode mixing of ultrafast laser pulses

Mark J. Hagmann, Anatoly Efimov, Antoinette J. Taylor, and Dzmitry A. Yarotski

Appl. Phys. Lett. 99, 011112 (2011); http://dx.doi.org/10.1063/1.3607482 (3 pages) | Cited 3 times

Online Publication Date: 8 July 2011

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We present a method for hyper-spectral characterization of the nonlinear effects in a tunneling junction. Harmonics up to 1 GHz were measured in a frequency comb in the tunneling current when 15-fs laser pulses at a repetition rate of 74.25 MHz were focused on the tunneling junction of a scanning tunneling microscope. The typical output power is −120 dBm at the fundamental frequency, which is the pulse repetition rate and decreases by several dB for the higher harmonics. The observed square-law dependence of the signal power on the tunneling current and incident laser power is in good agreement with theoretical predictions.
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73.40.Gk Tunneling
79.20.Ds Laser-beam impact phenomena
61.82.Bg Metals and alloys
72.30.+q High-frequency effects; plasma effects

Laser-induced radial birefringence and spin-to-orbital optical angular momentum conversion in silver-doped glasses

Jafar Mostafavi Amjad, Hamid Reza Khalesifard, Sergei Slussarenko, Ebrahim Karimi, Lorenzo Marrucci, and Enrico Santamato

Appl. Phys. Lett. 99, 011113 (2011); http://dx.doi.org/10.1063/1.3610474 (3 pages) | Cited 3 times

Online Publication Date: 8 July 2011

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Samples of Ag+/Na+ ion-exchanged glass that have been subject to intense laser irradiation may develop novel optical properties, as a consequence of the formation of patterns of silver nanoparticles and other structures. Here, we report the observation of a laser-induced permanent transverse birefringence, with the optical axis forming a radial pattern, as revealed by the spin-to-orbital angular momentum conversion occurring in a probe light beam. The birefringence pattern can be modeled well as resulting from thermally-induced stresses arising in the silver-doped glass during laser exposure, although the actual mechanism leading to the permanent anisotropy is probably more complex.
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78.20.Fm Birefringence
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
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