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1 Sep 2008

Volume 93, Issue 9, Articles (09xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 93, 091901 (2008); http://dx.doi.org/10.1063/1.2976330 (3 pages)

Fang-Fang Ren, M. B. Yu, J. D. Ye, Q. Chen, S. T. Tan, G. Q. Lo, and D. L. Kwong
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Room temperature midinfrared electroluminescence from InSb/InAs quantum dot light emitting diodes

P. J. Carrington, V. A. Solov'ev, Q. Zhuang, A. Krier, and S. V. Ivanov

Appl. Phys. Lett. 93, 091101 (2008); http://dx.doi.org/10.1063/1.2976551 (3 pages) | Cited 12 times

Online Publication Date: 2 September 2008

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Self-assembled InSb submonolayer quantum dots (QDs) in an InAs matrix have been grown by molecular beam epitaxy using Sb2 and As2 fluxes. The structures exhibit bright midinfrared photoluminescence up to room temperature. Intense room temperature electroluminescence with a peak at wavelength near 3.8 μm was observed from p-i-n light emitting diode structures containing ten InSb submonolayer QD sheets inserted within the InAs active region.
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78.60.Fi Electroluminescence
85.60.Jb Light-emitting devices
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.65.Hb Quantum dots (patterned in quantum wells)

Mercury Bromide (HgBr2): A promising nonlinear optical material in IR region with a high laser damage threshold

T. Liu, J. Qin, G. Zhang, T. Zhu, F. Niu, Y. Wu, and C. Chen

Appl. Phys. Lett. 93, 091102 (2008); http://dx.doi.org/10.1063/1.2969059 (3 pages) | Cited 6 times

Online Publication Date: 2 September 2008

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Nonlinear optical (NLO) crystals have played a key role in laser technology, and the existing materials for the IR range showed relatively low laser damage threshold in common. A NLO material HgBr2 is presented here. It shows a powder second harmonic generation about ten times as large as that of KH2PO4, a wide transparency in whole mid-IR region (from 2.5 to 25 μm), and a good stability to the environment. Most importantly it exhibits a high laser damage threshold of about 0.3 GW/cm2. Therefore, it is believed that HgBr2 is a promising candidate for NLO materials in the IR region.
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42.70.Mp Nonlinear optical crystals
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Electric control of spatial beam position based on the Goos–Hänchen effect

Yi Wang, Zhuangqi Cao, Honggen Li, Jun Hao, Tianyi Yu, and Qishun Shen

Appl. Phys. Lett. 93, 091103 (2008); http://dx.doi.org/10.1063/1.2977873 (3 pages) | Cited 10 times

Online Publication Date: 2 September 2008

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A structure of symmetrical metal-cladding waveguide, which contains optically nonlinear material in the guiding layer, is proposed to control the lateral shift of the reflected beam via an external electric field. Owing to the high sensitivity of ultrahigh-order modes, any minute index change of the waveguide will lead to a dramatic variation of the resonance condition, which gives rise to a change of the lateral beam displacement. Experimental result shows that the electric control of the lateral beam shift is realized in a range of 720 μm.
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42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers

Inhomogeneous origin of the interface roughness broadening of intersubband transitions

Jacob B. Khurgin

Appl. Phys. Lett. 93, 091104 (2008); http://dx.doi.org/10.1063/1.2977994 (3 pages) | Cited 10 times

Online Publication Date: 2 September 2008

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The impact of the interface roughness on intersubband transitions (ISTs) in quantum wells is analyzed as an inhomogeneous broadening due to localization rather than a traditional scattering process. The results offer simple explanation for the temperature dependent spectra of gain and absorption in quantum cascade lasers and also for the strong IST polariton phenomena.
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73.21.Fg Quantum wells

Ultrafast probing of light-matter interaction in a midinfrared quantum cascade laser

Wolfgang Parz, Thomas Müller, Juraj Darmo, Karl Unterrainer, Max Austerer, Gottfried Strasser, Luke R. Wilson, John W. Cockburn, Andrey B. Krysa, and John S. Roberts

Appl. Phys. Lett. 93, 091105 (2008); http://dx.doi.org/10.1063/1.2970046 (3 pages) | Cited 7 times

Online Publication Date: 2 September 2008

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In this work, we study the interaction of ultrashort midinfrared pulses with the active medium of an InGaAs/InAlAs/InP quantum cascade laser emitting at an 11.7 μm wavelength. Applying an electro-optic sampling technique allowed us to measure the complete phase resolved transmission spectra at operating conditions below and above lasing threshold in a spectral range much broader than the gain band width. Far below threshold, we locate broadband resonant absorption, which spectrally overlaps with the electrically induced gain, forming areas of net absorption and net gain. Above threshold, gain clamping is seen, and it is found that echoes delayed by the round trip time experience spectral pulse shaping converging toward the emission spectrum.
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42.55.Px Semiconductor lasers; laser diodes
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Terahertz emission from black silicon

P. Hoyer, M. Theuer, R. Beigang, and E.-B. Kley

Appl. Phys. Lett. 93, 091106 (2008); http://dx.doi.org/10.1063/1.2978096 (3 pages) | Cited 16 times

Online Publication Date: 3 September 2008

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We report on a terahertz emitter made out of black silicon. The black surface structure absorbs the whole optical pump power in the very surface. In contrast to expectations for indirect semiconductors, the black structure shows an emission in the terahertz range. The emitted radiation of the black silicon crystal is characterized for different parameters using terahertz time-domain spectroscopy.
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78.70.Gq Microwave and radio-frequency interactions
68.35.bg Semiconductors
78.47.D- Time resolved spectroscopy (>1 psec)

Nanoparticle-induced light scattering for improved performance of quantum-well solar cells

D. Derkacs, W. V. Chen, P. M. Matheu, S. H. Lim, P. K. L. Yu, and E. T. Yu

Appl. Phys. Lett. 93, 091107 (2008); http://dx.doi.org/10.1063/1.2973988 (3 pages) | Cited 43 times

Online Publication Date: 3 September 2008

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We report on the improved performance of InP/InGaAsP quantum-well waveguide solar cells via light scattering from deposited dielectric or metal nanoparticles. The integration of metal or dielectric nanoparticles above the quantum-well solar cell device is shown to couple normally incident light into lateral optical propagation paths, with optical confinement provided by the refractive index contrast between the quantum-well layers and surrounding material. With minimal optimization, short-circuit current density increases of 12.9% and 7.3% and power conversion efficiency increases of 17% and 1% are observed for silica and Au nanoparticles, respectively.
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84.60.Jt Photoelectric conversion
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Compact high power broadband Er3+−Yb3+-codoped superfluorescent fiber source

Feng Song, Zhenzhou Cheng, Changguang Zou, Lin Han, Xiaochen Yu, Jiaxiang Zhang, Xueping Jiang, Peize Han, and Jianguo Tian

Appl. Phys. Lett. 93, 091108 (2008); http://dx.doi.org/10.1063/1.2976664 (3 pages) | Cited 3 times

Online Publication Date: 3 September 2008

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Compact high power broadband superfluorescent fiber source has been demonstrated using an ultrashort Er3+−Yb3+-codoped phosphate glass fiber. The fiber is 10.4-cm-long and at 1.68 W pump power, an output power of 16.85 mW, a mean wavelength of 1540.9 nm, a bandwidth of 18.4 nm, and a slope efficiency of 18.6% have been obtained. The dependence of output power, mean wavelength, and bandwidth stability on pump power and fiber length are also studied, and there is an excellent agreement between the theoretical results and experimental data.
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42.81.-i Fiber optics
78.45.+h Stimulated emission
42.70.Ce Glasses, quartz

High-power AlInGaN-based violet laser diodes with InGaN optical confinement layers

Sung-Nam Lee, J. K. Son, H. S. Paek, Y. J. Sung, K. S. Kim, H. K. Kim, H. Kim, T. Sakong, Y. Park, K. H. Ha, and O. H. Nam

Appl. Phys. Lett. 93, 091109 (2008); http://dx.doi.org/10.1063/1.2965113 (3 pages) | Cited 4 times

Online Publication Date: 3 September 2008

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InGaN optical confinement layers (OCLs) were introduced into blue-violet AlInGaN-based laser diodes (LDs), resulting in the drastic improvements of lasing performance. Comparing with conventional LD structure, the lowest threshold current density of 2.3 kA/cm2 has been achieved by adding 100-nm-thick InGaN OCLs which represented maximum optical confinement factor. Additionally, we observed the high quantum efficiency and the uniform emission intensity distribution of InGaN quantum wells grown on lower InGaN OCL than on typical GaN layer. Upper InGaN OCL can reduce Mg diffusion from p-type layers to InGaN active region by separating the distance between InGaN quantum wells and p-type layers.
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42.55.Px Semiconductor lasers; laser diodes
81.05.Ea III-V semiconductors
78.67.De Quantum wells

Microlens coupled interdigital photoconductive switch

Gabor Matthäus, Stefan Nolte, Rico Hohmuth, Martin Voitsch, Wolfgang Richter, Boris Pradarutti, Stefan Riehemann, Gunther Notni, and Andreas Tünnermann

Appl. Phys. Lett. 93, 091110 (2008); http://dx.doi.org/10.1063/1.2976162 (3 pages) | Cited 12 times

Online Publication Date: 3 September 2008

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A large-area terahertz emitter based on an interdigital finger electrode photoconductive switch on low-temperature grown GaAs attached to a hexagonal microlens array is demonstrated. The hexagonal arranged microlenses direct the incident IR excitation pulses into specified electrode gaps, resulting in constructive interference in the terahertz far field. Using a Ti:sapphire oscillator running at 80 MHz with 150 fs pulses, 6.5 μm THz average power at 540 mW optical excitation is obtained. The maximum IR-to-terahertz conversion efficiency achieved is ≥ 1.35×10−5.
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84.30.Ng Oscillators, pulse generators, and function generators
85.60.-q Optoelectronic devices
81.05.Ea III-V semiconductors

In situ tuning of a photonic band gap with laser pulses

A. Pasquazi, S. Stivala, G. Assanto, V. Amendola, M. Meneghetti, M. Cucini, and D. Comoretto

Appl. Phys. Lett. 93, 091111 (2008); http://dx.doi.org/10.1063/1.2977998 (3 pages) | Cited 3 times

Online Publication Date: 3 September 2008

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We report on light-induced optical tuning of colloidal photonic crystals doped with gold nanoparticles (Au-nps). By resonantly exciting the Au-np surface plasmon absorption with picosecond pulses at 0.53 μm in a standard pump-probe setup, we observed permanent changes in the stop band resonance around 1.7 μm, with blue wavelength shifts as large as 30 nm and associated to a nanoparticle reshaping. Fine tuning was achieved by controlling either the pulse energy or the irradiation time.
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82.70.Dd Colloids
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
42.70.Qs Photonic bandgap materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.65.-k Nonlinear optics
78.66.Bz Metals and metallic alloys

Anisotropic optical gain in m-plane InxGa1−xN/GaN multiple quantum well laser diode wafers fabricated on the low defect density freestanding GaN substrates

T. Onuma, K. Okamoto, H. Ohta, and S. F. Chichibu

Appl. Phys. Lett. 93, 091112 (2008); http://dx.doi.org/10.1063/1.2978242 (3 pages) | Cited 16 times

Online Publication Date: 4 September 2008

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The threshold power density for the stimulated emission (SE) at 400 nm of m-plane In0.05Ga0.95N/GaN multiple quantum well (QW) laser diode (LD) wafer excited with a stripe along the c-axis was found to be lower than along the a-axis, although the SEs exhibited transverse electric field mode for both configurations. The result was explained according to the polarization selection rules for the lowest and the second lowest energy interband transitions in anisotropically strained m-plane InGaN QWs. In case of the LD wafer lased at 426 nm, SE was observed only along the c-axis, where pronounced broadening of the gain spectrum was found. Because the equivalent internal quantum efficiency was only 44%, further reductions in nonradiative defect density and the width of gain spectrum are essential to realize longer wavelength LDs.
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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.)

Quantitative differential interference contrast microscopy based on structured-aperture interference

Xiquan Cui, Matthew Lew, and Changhuei Yang

Appl. Phys. Lett. 93, 091113 (2008); http://dx.doi.org/10.1063/1.2977870 (3 pages) | Cited 9 times

Online Publication Date: 4 September 2008

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We report a quantitative differential interference contrast (DIC) microscope based on a structured-aperture (SA) wavefront sensor. Unlike a conventional DIC microscope, the SA-DIC microscope can separate the amplitude and the phase gradient information of the image wavefront, and form quantitative intensity and DIC images of the sample with good resolution; our prototype achieved resolution ∼ 2 μm. Furthermore, due to the nonpolarization nature of the microscope, we were able to image birefringent samples without artifacts.
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07.60.Pb Conventional optical microscopes
42.79.Pw Imaging detectors and sensors
42.30.Va Image forming and processing

Limiting nature of continuum generation in silicon

Prakash Koonath, Daniel R. Solli, and Bahram Jalali

Appl. Phys. Lett. 93, 091114 (2008); http://dx.doi.org/10.1063/1.2977872 (3 pages) | Cited 11 times

Online Publication Date: 4 September 2008

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Spectral broadening in silicon through self-phase modulation is studied numerically and experimentally in the normal dispersion regime. Temporal dynamics of the free carriers generated during the propagation of optical pulses, through the process of two-photon absorption, affect the amplitude and phase of the optical pulses, thereby determining the nature and extent of the generated spectral continuum. Experimental results are obtained by propagating picosecond optical pulses in a silicon waveguide for intensities that span two orders of magnitude (1–150 GW/cm2). These results validate the conclusions drawn from numerical simulations that the continuum generation has a self-limiting nature in silicon.
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42.82.-m Integrated optics
42.79.Gn Optical waveguides and couplers
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Single-laser-shot detection of nitric oxide in reacting flows using electronic resonance enhanced coherent anti-Stokes Raman scattering

Ning Chai, Sameer V. Naik, Normand M. Laurendeau, Robert P. Lucht, Sukesh Roy, and James R. Gord

Appl. Phys. Lett. 93, 091115 (2008); http://dx.doi.org/10.1063/1.2973166 (3 pages) | Cited 4 times

Online Publication Date: 4 September 2008

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Single-laser-shot electronic resonance enhanced coherent anti-Stokes Raman scattering (ERE-CARS) spectra of nitric oxide (NO) were generated using the 532 nm output of an injection-seeded Nd:YAG (yttrium aluminum garnet) laser as the pump beam, a broadband dye laser at approximately 591 nm as the Stokes beam, and a 236 nm narrowband ultraviolet probe beam. Single-laser-shot ERE-CARS spectra of NO were acquired in an atmospheric-pressure hydrogen/air counterflow diffusion flame. The single-shot detection limit in this flame was found to be approximately 30 ppm, and the standard deviation of the measured NO concentration was found to be approximately 20% of the mean.
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42.65.Dr Stimulated Raman scattering; CARS
42.65.Es Stimulated Brillouin and Rayleigh scattering
42.55.Rz Doped-insulator lasers and other solid state lasers
42.55.Tv Photonic crystal lasers and coherent effects

Variable optical delays at 1.55 μm using fast light in an InAs/InP quantum dash based semiconductor optical amplifier

A. Martinez, G. Aubin, F. Lelarge, R. Brenot, J. Landreau, and A. Ramdane

Appl. Phys. Lett. 93, 091116 (2008); http://dx.doi.org/10.1063/1.2973168 (3 pages) | Cited 1 time

Online Publication Date: 4 September 2008

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Room temperature optical variable delays are demonstrated using InAs/InP quantum dash semiconductor optical amplifiers (SOAs) at 1.55 μm. A microwave frequency modulated single optical beam allows to demonstrate fast light through the achievement of maximum optical delays of 136 ps at 250 MHz and ∼ 55 ps at 2 GHz by means of electrical control of the SOA bias current. The group index variation is attributed to enhanced nearly degenerate four wave mixing of this material system as well as population pulsation.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Hybrid metamaterials enable fast electrical modulation of freely propagating terahertz waves

Hou-Tong Chen, Sabarni Palit, Talmage Tyler, Christopher M. Bingham, Joshua M. O. Zide, John F. O’Hara, David R. Smith, Arthur C. Gossard, Richard D. Averitt, Willie J. Padilla, Nan M. Jokerst, and Antoinette J. Taylor

Appl. Phys. Lett. 93, 091117 (2008); http://dx.doi.org/10.1063/1.2978071 (3 pages) | Cited 29 times

Online Publication Date: 4 September 2008

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We demonstrate fast electrical modulation of freely propagating terahertz waves at room temperature using hybrid metamaterial devices. The devices are planar metamaterials fabricated on doped semiconductor epitaxial layers, which form hybrid metamaterial—Schottky diode structures. With an applied ac voltage bias, we show modulation of terahertz radiation at inferred frequencies over 2 MHz. The modulation speed is limited by the device depletion capacitance which may be reduced for even faster operation.
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85.30.Kk Junction diodes
85.30.Hi Surface barrier, boundary, and point contact devices

Polarization-switchable single photon source using the Stark effect

M. T. Rakher, N. G. Stoltz, L. A. Coldren, P. M. Petroff, and D. Bouwmeester

Appl. Phys. Lett. 93, 091118 (2008); http://dx.doi.org/10.1063/1.2978396 (3 pages) | Cited 6 times

Online Publication Date: 5 September 2008

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A polarization-switchable single photon source is demonstrated by embedding a self-assembled quantum dot in a high-quality, electrically gated, oxide-apertured micropillar cavity. Due to the noncircular aperture, the polarization degeneracy of the fundamental cavity mode is lifted, leaving two linearly polarized Q ≈ 20 000 modes separated by 194 μeV. An intracavity electric field generated by an applied bias enables Stark shift tuning of the quantum dot emission over a frequency range containing both polarization modes, switching the dominant single photon polarization through the Purcell effect. We measure polarization switching up to 300 kHz, limited by the RC time constant of the device.
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78.67.Hc Quantum dots
78.20.Jq Electro-optical effects
68.65.Hb Quantum dots (patterned in quantum wells)

Carrier dynamics and erbium sensitization in silicon-rich nitride nanocrystals

R. Li, J. R. Schneck, J. Warga, L. D. Ziegler, and L. Dal Negro

Appl. Phys. Lett. 93, 091119 (2008); http://dx.doi.org/10.1063/1.2978069 (3 pages) | Cited 17 times

Online Publication Date: 5 September 2008

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Ultrafast two-color pump-probe measurements, time-resolved photoluminescence (TRPL), and photoluminescence excitation measurements were performed on Si-rich nitride (SRN) and Er doped SRN (Er:SRN) nanocrystals samples. Transient absorption data were compared with picosecond TRPL and excited state absorption cross (ESA) sections σ were measured at different wavelengths. Our data show that σ in Er:SRN, which is approximately 10−19 cm2 at 1.54 μm, does not scale with the ∼ λ2 behavior predicted by simple free carrier absorption models. Finally, our data demonstrate that in Er:SRN efficient energy transfer to Er ions occurs on the nanosecond time scale with reduced ESA compared to Er-doped oxide-based systems.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.55.Hx Other solid inorganic materials
78.47.J- Ultrafast spectroscopy (<1 psec)
78.47.D- Time resolved spectroscopy (>1 psec)
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Theoretical investigation of sheath expansion and implant fluence uniformity in enhanced glow discharge plasma immersion ion implantation

Dixon T. K. Kwok, Qiu Yuan Lu, Liu He Li, Ricky K. Y. Fu, and Paul K. Chu

Appl. Phys. Lett. 93, 091501 (2008); http://dx.doi.org/10.1063/1.2977962 (3 pages) | Cited 4 times

Online Publication Date: 2 September 2008

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In enhanced glow discharge plasma immersion ion implantation that involves a small-pointed anode and large area tabular cathode, the high negative substrate bias acts as the plasma producer and supplies the implantation voltage. An electric field is created to focus the electrons and the electron-focusing field in turn enhances the glow discharge process. The sheath physics is theoretically investigated using numerical simulation based on the multiple-grid particle-in-cell code. Electron focusing is corroborated and the plasma sheath has enough expansion when t = 40 μs so that a uniform distribution of the incident ion fluence is attained.
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52.40.Kh Plasma sheaths
52.25.Fi Transport properties
52.65.Rr Particle-in-cell method
52.77.Dq Plasma-based ion implantation and deposition
52.80.Hc Glow; corona

Laser wavelength dependence of extreme ultraviolet light and particle emissions from laser-produced lithium plasmas

Akihisa Nagano, Takayasu Mochizuki, Shuji Miyamoto, and Sho Amano

Appl. Phys. Lett. 93, 091502 (2008); http://dx.doi.org/10.1063/1.2975180 (3 pages) | Cited 4 times

Online Publication Date: 4 September 2008

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Maximum extreme ultraviolet (EUV) conversion efficiencies (CEs) of 2.3% and 1.8% were achieved in planar Li targets by using pulsed 2ω and 1ω Nd:YAG laser irradiation, respectively. In a forced recombination scheme, the total CE can be expected to be about 4%. The maximum kinetic energy of the lithium ion debris was found to be less than 1 keV, indicating that mirror damage caused by lithium ion debris is more easily mitigated by using a magnetic field than for tin ions. These results suggest that a Li target is a reasonable candidate for an EUV lithography source.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.25.Tx Emission, absorption, and scattering of particles
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Highly efficient electron beam generation in a wide-aperture discharge in helium

E. V. Belskaya, P. A. Bokhan, and Dm. E. Zakrevsky

Appl. Phys. Lett. 93, 091503 (2008); http://dx.doi.org/10.1063/1.2978350 (3 pages) | Cited 2 times

Online Publication Date: 5 September 2008

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The paper deals with a gas discharge having electron beam generation efficiency η ≃ 100% at a voltage U>300 V. The discharge has been realized in helium in a cell with a cathode diameter of 19.5 cm. The discharge features are a higher η as compared to other discharges, the presence of reverse bends in the voltage-current characteristics including the occurrence of a falling section, and nonmonotony in η(U) and its growth with increasing He pressure. The discharge peculiarities are explained by its photoemissive nature. The basic contribution to the photoemission is made by the emission from the resonance state excited in the secondary processes.
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52.80.Hc Glow; corona
41.75.Fr Electron and positron beams
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Strong vertical light output from thin silicon rich oxide/SiO2 multilayers via in-plane modulation of photonic crystal patterns

Fang-Fang Ren, M. B. Yu, J. D. Ye, Q. Chen, S. T. Tan, G. Q. Lo, and D. L. Kwong

Appl. Phys. Lett. 93, 091901 (2008); http://dx.doi.org/10.1063/1.2976330 (3 pages) | Cited 4 times

Online Publication Date: 2 September 2008

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Three-dimensional-confined structures with triangular-lattice air-hole photonic crystal patterns were fabricated to enhance the light output from silicon rich oxide/SiO2 multilayer stack. The intensity and profile of spontaneous emission were found to be efficiently modulated by controlling the optical modes of the periodic arrays via varying their structural parameters. With lattice constant/radius of 700 nm/280 nm, the photoluminescence intensity was found to be enhanced by nearly nine times in the vertical direction. The mechanisms for different enhancement features have been theoretically analyzed based on coherent scattering and quantum electrodynamic effects, well supporting the experimental observation.
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78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
68.65.Ac Multilayers
42.79.Wc Optical coatings

Enhancement in middle-ultraviolet emission in a surface-plasmon-assisted coaxial nanocavity

Qingrui Zhuang, Xia Feng, Zhilin Yang, Junyong Kang, and Xiaoli Yuan

Appl. Phys. Lett. 93, 091902 (2008); http://dx.doi.org/10.1063/1.2973159 (3 pages) | Cited 3 times

Online Publication Date: 2 September 2008

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Cathodoluminescence spectrum of a single Zn–Zn2SiO4 core-shell nanocable exhibits a strong emission at 293 nm accompanied with a weaker splitting peak at its long wavelength side. Experiment and ab initio calculation results indicate that the UV emissions are associated with the Zn2SiO4 surface states. Finite-difference time-domain simulations show that a surface-plasmon-assisted nanocavity can selectively confine and enhance the electric field energy of the 293 nm light due to the smallest mode volume and the highest finesse among surface plasmon resonance, whispering gallery, and waveguide modes. Further temperature dependence experiment and correlative theoretical derivation suggest that the splitting is associated with a strong coupling between the nanocavity and the emitter.
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78.60.Hk Cathodoluminescence, ionoluminescence
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.15.-m Methods of electronic structure calculations
73.20.At Surface states, band structure, electron density of states
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
73.40.Ns Metal-nonmetal contacts

Ultrafast electron dynamics and cubic optical nonlinearity of freestanding thin film of double walled carbon nanotubes

N. Kamaraju, Sunil Kumar, B. Karthikeyan, Alexander Moravsky, R. O. Loutfy, and A. K. Sood

Appl. Phys. Lett. 93, 091903 (2008); http://dx.doi.org/10.1063/1.2977463 (3 pages) | Cited 3 times

Online Publication Date: 3 September 2008

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Ultrafast degenerate pump-probe experiments performed on a freestanding film of double walled carbon nanotubes near the first metallic transition energy of outer tube show ultrafast (97 fs) photobleaching followed by a photoinduced absorption with a slow relaxation of 1.8 ps. Femtosecond closed and open aperture z-scan experiments carried out at the same excitation energy show saturation absorption and negative cubic nonlinearity. From these measurements, real and imaginary part of the third order nonlinear susceptibility are estimated to be Re(χ(3)) ∼ −2.2×10−9 esu and Im(χ(3)) ∼ 4.5×10−11 esu.
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78.47.J- Ultrafast spectroscopy (<1 psec)
68.55.-a Thin film structure and morphology
42.65.An Optical susceptibility, hyperpolarizability
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
78.67.Ch Nanotubes
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