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24 Jan 2005

Volume 86, Issue 4, Articles (04xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 86, 043106 (2005); http://dx.doi.org/10.1063/1.1853514 (3 pages)

William L. Hughes and Zhong L. Wang
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Frequency beating between monolithically integrated semiconductor ring lasers

Hongjun Cao, Chiyu Liu, Hai Ling, Hui Deng, Marcita Benavidez, Vladimir A. Smagley, Robert B. Caldwell, Gregory M. Peake, Gennady A. Smolyakov, Petr G. Eliseev, and Marek Osiński

Appl. Phys. Lett. 86, 041101 (2005); http://dx.doi.org/10.1063/1.1853532 (3 pages) | Cited 8 times

Online Publication Date: 18 January 2005

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Optoelectronic integrated circuits incorporating a pair of optically independent large-cavity semiconductor ring lasers (SRLs), directional couplers, waveguides, Y-junction mixer, and photodetectors are demonstrated. Counterclockwise and clockwise output beams from the two SRLs are collected separately and mixed prior to detection. Frequency beating between modes of two SRLs is measured. The beat frequency is fine-tuned by an integrated Joule heater, designed for thermal control of the lasing wavelength. No signs of frequency lock-in in the vicinity of zero detuning are observed, which makes this structure a promising candidate for applications in ring laser gyros and optical rotation sensors.
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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
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
73.50.Pz Photoconduction and photovoltaic effects
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
85.60.Bt Optoelectronic device characterization, design, and modeling

Quantum-transfer-efficiency excitation spectroscopy: Application to direct observation of yellow luminescent level of GaN

Tianshu Lai, Jinhui Wen, and Weizhu Lin

Appl. Phys. Lett. 86, 041102 (2005); http://dx.doi.org/10.1063/1.1854201 (3 pages)

Online Publication Date: 18 January 2005

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A quantum-transfer-efficiency excitation spectroscopy (QTEES) is developed. It measures the quantum transfer efficiency from the photoexcited level to the initial level of the luminescence measured. It is self-normalized and based on the relative measurement of photoluminescence intensity. The initial level of the luminescence detected corresponds to the position of the strongest excitation peak in a QTEES spectrum. An experiment of QTEES on an undoped GaN film is carried out, and the initial level of the yellow luminescence is obtained directly from the QTEES spectrum. The initial level measured is very close to the bottom of the conduction band, which provides direct evidence to support shallow donor–deep acceptor recombination of the yellow luminescence in the GaN film. QTEES spectra have the advantages of easy explanation and clear physical meanings. It is also found that the conventional photoluminescence excitation spectra need to be corrected by a factor of the energy of the excitation photon.
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78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Optical properties of stoichiometric LiNbO3 waveguides formed by low-dose oxygen ion implantation

Xue-Lin Wang, Ke-Ming Wang, Feng Chen, Gang Fu, Shi-Ling Li, Hong Liu, Lei Gao, Ding-Yu Shen, Hong-Ji Ma, and Rui Nie

Appl. Phys. Lett. 86, 041103 (2005); http://dx.doi.org/10.1063/1.1854202 (3 pages) | Cited 15 times

Online Publication Date: 18 January 2005

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The planar waveguides in z-cut stoichiometric LiNbO3 crystal have been fabricated by 3.0 MeV oxygen ion implantation with the dose of 6×1014 ions/cm2 at room temperature. The modes of the waveguides were measured by the prism-coupling method with the wavelength 633 and 1539 nm, respectively. The refractive index profiles of the waveguides were reconstructed using reflectivity calculation method. The Rutherford backscattering/channeling technique was used to investigate the damage produced by the ion implantation, the minimum yield of the spectra was 4.52%. The propagation loss of waveguide was 0.61 dB/cm obtained by fiber probe technique. It was found that positive changes of extraordinary refractive indices happened in the guiding regions, and such change increased after the annealing treatment at 260 °C for 60 min.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
61.72.up Other materials
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)
61.80.Jh Ion radiation effects
61.82.Ms Insulators
81.40.Gh Other heat and thermomechanical treatments

Integrated fluorescent light source for optofluidic applications

Dmitri V. Vezenov, Brian T. Mayers, Daniel B. Wolfe, and George M. Whitesides

Appl. Phys. Lett. 86, 041104 (2005); http://dx.doi.org/10.1063/1.1850610 (3 pages) | Cited 32 times

Online Publication Date: 18 January 2005

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This letter describes a simple fluidic light source for use “on-chip” in integrated microsystems. It demonstrates the feasibility of light sources based on liquid-core, liquid-cladding (L2) microchannel waveguides, with liquid cores containing fluorescent dyes. These fluorescent light sources, using both miscible and two-phase systems, are tunable in terms of the beam size, intensity and spectral content. The observed output intensity from fluorescent L2 light sources is comparable to standard fiber optic spectrophotometer light sources. Integration of fluorescent light sources during device fabrication removes both the need for insertion and alignment of conventional, optical-fiber light sources and the constraints on channel size imposed by fiber optics, albeit at the cost of establishing a microfluidic infrastructure.
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42.82.Et Waveguides, couplers, and arrays
42.72.Bj Visible and ultraviolet sources
42.79.Gn Optical waveguides and couplers
42.81.Bm Fabrication, cladding, and splicing
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
42.82.Bq Design and performance testing of integrated-optical systems

Mechanism of dark-spot degradation of organic light-emitting devices

P. Melpignano, A. Baron-Toaldo, V. Biondo, S. Priante, R. Zamboni, M. Murgia, S. Caria, L. Gregoratti, A. Barinov, and M. Kiskinova

Appl. Phys. Lett. 86, 041105 (2005); http://dx.doi.org/10.1063/1.1852706 (3 pages) | Cited 25 times

Online Publication Date: 18 January 2005

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Using chemically sensitive x-ray photoelectron microscopy, we investigate the mechanism of dark-spot formation and degradation of organic light-emitting devices. The morphological and chemical evolution of the Al cathode surface under operation conditions reveals the formation of “domelike” structures, followed by local disruptions of the cathode, exposing microareas of the underlying indium tin oxide anode. The chemical maps and microspot spectra identify a release of volatile In-, Sn-, and C-containing species, including metallic In, which is clear evidence that the degradation is driven by local decomposition of the anode∕organic interface.
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82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
82.45.Fk Electrodes

Midinfrared luminescence imaging and its application to the optimization of light-emitting diodes

F. Weik, J. W. Tomm, R. Glatthaar, U. Vetter, D. Szewczy, J. Nurnus, A. Lambrecht, L. Mechold, B. Spellenberg, M. Bassler, M. Behringer, and J. Luft

Appl. Phys. Lett. 86, 041106 (2005); http://dx.doi.org/10.1063/1.1855420 (3 pages) | Cited 2 times

Online Publication Date: 18 January 2005

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Midinfrared luminescence imaging spectroscopy is used for evaluating surface structures etched into narrow-gap PbSe films. These structures provide a luminescence enhancement by a factor of 6. On the basis of such structures an optically pumped luminescence device is realized. A maximum cw output power of 0.5 mW and a slope efficiency of 0.2 mW/A are obtained at 25 °C. The power efficiency amounts to 2.3×10−2%. The emission wavelength is 4.2 μm, with a half width of 0.8 μm (50 meV). Such devices are promising light sources for a new generation of gas detection systems.
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85.60.Jb Light-emitting devices
68.55.-a Thin film structure and morphology
78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
68.35.B- Structure of clean surfaces (and surface reconstruction)

Enhanced 1.54 μm photoluminescence from Er-containing ZnO through nitrogen doping

Zhen Zhou, Toshitaka Komori, Masahito Yoshino, Masahiko Morinaga, Noriaki Matsunami, Atsushi Koizumi, and Yoshikazu Takeda

Appl. Phys. Lett. 86, 041107 (2005); http://dx.doi.org/10.1063/1.1856692 (3 pages) | Cited 24 times

Online Publication Date: 19 January 2005

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Nitrogen doping into an erbium (Er)-containing ZnO specimen through the N+ irradiation and the subsequent annealing in air was found to increase the photoluminescence (PL) intensity around 1.54 μm by about 40 times. The existence of nitrogen in the specimen was proved firmly by means of the math(d,α)math nuclear reaction analysis. Further, the Ne+ irradiation was conducted instead of the N+ irradiation, but no effect was observed in the PL spectra. So, it was concluded that the substitution of N for O could modify the local structure around Er3+, resulting in the surprisingly large enhancement of the PL intensity.
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78.55.Et II-VI semiconductors
61.82.Fk Semiconductors
61.72.uj III-V and II-VI semiconductors
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects

Self-consistent theory of the gain linewidth for quantum-cascade lasers

F. Banit, S.-C. Lee, A. Knorr, and A. Wacker

Appl. Phys. Lett. 86, 041108 (2005); http://dx.doi.org/10.1063/1.1851004 (3 pages) | Cited 33 times

Online Publication Date: 20 January 2005

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The linewidth in intersubband transitions can be significantly reduced below the sum of the lifetime broadening for the involved states, if the scattering environment is similar for both states. This is studied within a nonequilibrium Green function approach here. We find that the effect is of particular relevance for a recent, relatively low doped, Terahertz quantum-cascade laser.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Room-temperature, continuous-wave, single-mode quantum-cascade lasers at λ ≃ 5.4 μm

Stéphane Blaser, Dmitri A. Yarekha, Lubos Hvozdara, Yargo Bonetti, Antoine Muller, Marcella Giovannini, and Jérôme Faist

Appl. Phys. Lett. 86, 041109 (2005); http://dx.doi.org/10.1063/1.1853511 (3 pages) | Cited 54 times

Online Publication Date: 20 January 2005

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We demonstrate room-temperature, single-mode, continuous-wave operation of a λ ≃ 5.4 μm quantum-cascade laser up to the temperature of 30 °C. Processing is done using standard lithography in a ridge waveguide mounted junction-up. The active region is based on a bound-to-continuum transition. The high performances were achieved with a low active region doping and a thick electroplated gold deposition, resulting in a characteristic temperature of T0 = 155 K in continuous-wave with a threshold current density of jth = 2.05 kA/cm2 at 300 K.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Strong exciton-photon coupling in a length tunable optical microcavity with J-aggregate dye heterostructures

C. E. Finlayson, G. Vijaya Prakash, and J. J. Baumberg

Appl. Phys. Lett. 86, 041110 (2005); http://dx.doi.org/10.1063/1.1850189 (3 pages) | Cited 10 times

Online Publication Date: 20 January 2005

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We report the incorporation of thin films of a cyanine dye J aggregate into a versatile, length tunable, optical microcavity. The dense J-aggregate layers give an optical response that can be modified by embedding them at specific positions within heterostructures of dielectric and metal layers. The microcavities are composed of separate gold mirrors, which can be individually nanopositioned, and give sharp resonant modes in the red/near-infrared region of the spectrum. With the dye layer favorably placed, anticrossing behavior is observed as the cavity modes are successively swept through the absorption resonance. Large Rabi splittings of up to 170 meV are achieved at room temperature, agreeing well with predictions from a transfer-matrix model. These strongly coupled microcavities pave the way for microelectromechanical systems-integrated microdevices with tailored nonlinear optical properties.
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78.66.Qn Polymers; organic compounds
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.30.Jw Organic compounds, polymers

Beam divergence measurements of InGaN/GaN micro-array light-emitting diodes using confocal microscopy

C. Griffin, E. Gu, H. W. Choi, C. W. Jeon, J. M. Girkin, M. D. Dawson, and G. McConnell

Appl. Phys. Lett. 86, 041111 (2005); http://dx.doi.org/10.1063/1.1850599 (3 pages) | Cited 11 times

Online Publication Date: 20 January 2005

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The recent development of high-density, two-dimensional arrays of micrometer-sized InGaN/GaN light-emitting diodes (micro-LEDs) with potential applications from scientific instrumentation to microdisplays has created an urgent need for controlled manipulation of the light output from these devices. With directed light output these devices can be used in situations where collimated beams or light focused onto several thousand matrix points is desired. In order to do this effectively, the emission characteristics of the devices must be fully understood and characterized. Here we utilize confocal microscopy to directly determine the emission characteristics and angular beam divergences from the individual micro-LED elements. The technique is applied to both top (into air) and bottom (through substrate) emission in arrays of green (540 nm), blue (470 nm), and UV (370 nm) micro-LED devices, at distances of up to 50 μm from the emission plane. The results are consistent with simple optical modeling of the expected beam profiles.
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85.60.Jb Light-emitting devices
78.55.Cr III-V semiconductors

Photonic molecule laser composed of GaInAsP microdisks

Atsuo Nakagawa, Satoru Ishii, and Toshihiko Baba

Appl. Phys. Lett. 86, 041112 (2005); http://dx.doi.org/10.1063/1.1855388 (3 pages) | Cited 33 times

Online Publication Date: 20 January 2005

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We fabricated a photonic molecule consisting of GaInAsP microdisks, and obtained the lasing operation by photopumping. We also observed mode splits arising from the optical coupling, which was confirmed by an anticrossing characteristic against the disk diameter detuning and a miniband being dependent on the number of disks, their arrangement and coupling strength. The coupling characteristics were explained by considering bonding and antibonding states of modes, and by finite-difference time-domain calculation. Such a laser is expected to be some functional devices, and the concept of the photonic molecule will be helpful for the understanding of complex coupled modes.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Sa Microcavity and microdisk lasers
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.60.Fc Modulation, tuning, and mode locking

Coupling of Er ions to surface plasmons on Ag

J. Kalkman, L. Kuipers, A. Polman, and H. Gersen

Appl. Phys. Lett. 86, 041113 (2005); http://dx.doi.org/10.1063/1.1856133 (3 pages) | Cited 30 times

Online Publication Date: 21 January 2005

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Er3+ ions located 100 nm beneath the surface of silica glass show an enhanced photoluminescence decay rate when the glass is covered with Ag. Correcting for concentration quenching effects, the decay rate is enhanced by 70%, compared to the case without Ag. The data are in agreement with a model that takes into account variations in local density of states and excitation of surface plasmons and lossy surface waves, resulting in direct evidence for the efficient generation of surface plasmons by excited Er3+ ions. Using the model, optimum conditions for coupling to surface plasmons are derived, which can be used to enhance the emission rate and quantum efficiency of a wide range of Er-doped materials.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
73.20.At Surface states, band structure, electron density of states
71.55.Jv Disordered structures; amorphous and glassy solids
61.72.S- Impurities in crystals
78.55.Hx Other solid inorganic materials
78.68.+m Optical properties of surfaces

Subpicosecond shifting of the photonic band gap in a three-dimensional photonic crystal

Dmitry A. Mazurenko, Robert Kerst, Jaap I. Dijkhuis, Andrey V. Akimov, Valery G. Golubev, Alexander A. Kaplyanskii, Dmitry A. Kurdyukov, and Alexander B. Pevtsov

Appl. Phys. Lett. 86, 041114 (2005); http://dx.doi.org/10.1063/1.1856687 (3 pages) | Cited 20 times

Online Publication Date: 21 January 2005

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We demonstrate spectral shifting of the photonic band gap in a three-dimensional photonic crystal within a time of less than 350 fs. Single 120 fs high-power optical pulses are capable to induce the transition from the semiconductor to the metallic phase of VO2 in the pores of our artificial silica opal. The phase transition produces a substantial decrease of the real part of the effective refractive index of the photonic crystal and shifts the spectral position of the photonic band gap.
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42.70.Qs Photonic bandgap materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.47.-p Spectroscopy of solid state dynamics
72.60.+g Mixed conductivity and conductivity transitions

A polarization insensitive 2×2 optical switch fabricated by liquid crystal–polymer composite

Y. J. Liu, X. W. Sun, J. H. Liu, H. T. Dai, and K. S. Xu

Appl. Phys. Lett. 86, 041115 (2005); http://dx.doi.org/10.1063/1.1857092 (3 pages) | Cited 22 times

Online Publication Date: 21 January 2005

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A polarization insensitive 2×2 optical switch was fabricated with liquid crystal–polymer composite by means of holography. The highest diffraction efficiency achieved was 85.7%. The rise time and the decay time measured were 36 and 160 μs, respectively, at an applied electric field of 18.2 V/μm. The polarization-dependent loss was 0.03 dB measured for s- and p-polarized light at the wavelength of 632.8 nm.
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42.70.Df Liquid crystals
42.70.Jk Polymers and organics
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.86.+b Optical workshop techniques
42.40.Eq Holographic optical elements; holographic gratings
42.40.Lx Diffraction efficiency, resolution, and other hologram characteristics
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Thermal oxidation of porous silicon: Study on structure

A. E. Pap, K. Kordás, G. Tóth, J. Levoska, A. Uusimäki, J. Vähäkangas, S. Leppävuori, and T. F. George

Appl. Phys. Lett. 86, 041501 (2005); http://dx.doi.org/10.1063/1.1853519 (3 pages) | Cited 20 times

Online Publication Date: 18 January 2005

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The structural changes of porous silicon (PS) samples during oxidation are investigated and analyzed using various microscopy techniques and x-ray diffraction. It is found that the surface roughness of oxidized PS layers increases with the oxidation at 200–400 °C and decreased at 600–800 °C. At 800 °C a partially fused surface is observed. The oxide formed on the wall of porous silicon skeleton is amorphous. The shifts of Si(400) peaks are observed in the x-ray diffraction patterns, which are correlated to the lattice deformation induced by thermal expansion coefficient mismatch between the grown SiO2 and the residual Si, and to the intrinsic stress caused by the Si–O bonds at the Si–SiO2 interface. These explanations are supported by thermomechanical modeling using three-dimensional finite element method.
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81.05.Cy Elemental semiconductors
81.05.Rm Porous materials; granular materials
81.65.Mq Oxidation
61.43.Gt Powders, porous materials
68.35.B- Structure of clean surfaces (and surface reconstruction)
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Effect of the electrostatic plasma lens on the emittance of a high-current heavy ion beam

Yu. Chekh, A. Goncharov, I. Protsenko, and I. G. Brown

Appl. Phys. Lett. 86, 041502 (2005); http://dx.doi.org/10.1063/1.1855428 (3 pages) | Cited 5 times

Online Publication Date: 20 January 2005

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We describe measurements we have made of the emittance of a high-current, moderate-energy ion beam after transport through a permanent-magnet electrostatic plasma lens. The results indicate the absence of emittance growth due to the lens, when the lens is adjusted for optimal beam focusing. The measured normalized emittance for a 32 keV Cu2+ ion beam formed by a vacuum arc ion source was 0.6 π mm mrad at a beam current of 50 mA rising more-or-less linearly to 2.2 π mm mrad at 250 mA, and was conserved in beam transport through the lens. These results have significance for the application of high-current ion sources and the electrostatic plasma lens to particle accelerator injection.
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41.85.Ne Electrostatic lenses, septa
52.75.-d Plasma devices
52.59.Wd Emittance-dominated beams
41.85.Lc Particle beam focusing and bending magnets, wiggler magnets, and quadrupoles
29.27.Eg Beam handling; beam transport
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Physical properties of liquid and undercooled tungsten by levitation techniques

Paul-François Paradis, Takehiko Ishikawa, Ryuichi Fujii, and Shinichi Yoda

Appl. Phys. Lett. 86, 041901 (2005); http://dx.doi.org/10.1063/1.1853513 (3 pages) | Cited 12 times

Online Publication Date: 18 January 2005

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Maintaining deep undercooling melts represents a formidable challenge when dealing with tungsten due to its high vapor pressure, its melting temperature (Tm = 3695 K), and the risk of contamination. Using electrostatic levitation, properties of liquid tungsten were measured above the melting temperature as well as in the undercooled phase. Over the 3125–3710 K interval, the density was measured as ρ(T) = 1.67×104−1.08(T−Tm) kg m−3. Similarly, the surface tension was measured as σ(T) = 2.478×103−0.31(T−Tm) over the 3360–3700 K range. At Tm, the data agree well with the literature values. The excellent processing conditions also offer opportunities to achieve reproducible and controlled formation of metastable phases.
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64.70.D- Solid-liquid transitions
81.30.Fb Solidification
68.03.Cd Surface tension and related phenomena

Study of band structure InxGa1−xN/GaN multiple quantum wells by high-resolution electron microscopy and electron holography

W. Lü, C. R. Li, and Z. Zhang

Appl. Phys. Lett. 86, 041902 (2005); http://dx.doi.org/10.1063/1.1856138 (3 pages)

Online Publication Date: 18 January 2005

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Two InxGaN1−x/GaN (x = 0.15 and 0.18) multiple-quantum-well samples with strained-layer thickness larger∕less than the critical thickness, respectively, were investigated by high-resolution electron microscopy, electron holography, and photoluminescence (PL). The PL intensity of the sample with strained-layer thickness larger than the critical thickness was weaker than that of the sample with strained-layer thickness less than the critical thickness by five times. Electron holography revealed that the profiles of the inner potential V0 across the quantum wells GaN/InxGaN1−x/GaN of the samples were not too different. The well feature of the sample with strained-layer thickness larger than the critical thickness was very blurry, especially near the top GaN/InGaN interface. It is suggested that the interface sharpness is most critical for optical property of quantum well devices.
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81.07.St Quantum wells
73.21.Fg Quantum wells
78.67.De Quantum wells
68.35.Gy Mechanical properties; surface strains
68.65.Fg Quantum wells
78.55.Cr III-V semiconductors
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Differential scanning calorimetry analysis of the linear parabolic growth of nanometric Ni silicide thin films on a Si substrate

F. Nemouchi, D. Mangelinck, C. Bergman, P. Gas, and Ulf Smith

Appl. Phys. Lett. 86, 041903 (2005); http://dx.doi.org/10.1063/1.1852727 (3 pages) | Cited 15 times

Online Publication Date: 18 January 2005

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The formation of nanometric Ni silicide films on a Si wafer is analyzed using differential scanning calorimetry (DSC) and isothermal x-ray diffraction measurements. The sensitivity of DSC is remarkable even in this experimental configuration constituted of a Ni∕Si bilayer deposited on a Si substrate. Both methods confirm the sequential growth of Ni2Si and NiSi (for T<700 °C). However the kinetics of growth of the first silicide formed (Ni2Si) cannot be fitted, for the two sets of measurements, by a simple parabolic law. Better agreement is obtained using a linear-parabolic growth law and a smaller activation energy for the linear term (0.8 eV) than for the parabolic one (1.5 eV).
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68.37.-d Microscopy of surfaces, interfaces, and thin films

Giant optical anisotropy in a single InAs quantum dot in a very dilute quantum-dot ensemble

I. Favero, G. Cassabois, A. Jankovic, R. Ferreira, D. Darson, C. Voisin, C. Delalande, Ph. Roussignol, A. Badolato, P. M. Petroff, and J. M. Gérard

Appl. Phys. Lett. 86, 041904 (2005); http://dx.doi.org/10.1063/1.1854733 (3 pages) | Cited 21 times

Online Publication Date: 18 January 2005

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We present experimental evidence of giant optical anisotropy in single InAs quantum dots. Polarization-resolved photoluminescence spectroscopy reveals a linear polarization ratio with huge fluctuations, from one quantum dot to another, in sign and in magnitude with absolute values up to 82%. Systematic measurements on hundreds of quantum dots coming from two different laboratories demonstrate that the giant optical anisotropy is an intrinsic feature of dilute quantum-dot arrays.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors

Magneto-controlled nonlinear optical materials

J. P. Huang and K. W. Yu

Appl. Phys. Lett. 86, 041905 (2005); http://dx.doi.org/10.1063/1.1854719 (3 pages) | Cited 14 times

Online Publication Date: 18 January 2005

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We exploit theoretically a magneto-controlled nonlinear optical material which contains ferromagnetic nanoparticles with a nonmagnetic metallic nonlinear shell in a host fluid. Such an optical material can have anisotropic linear and nonlinear optical properties and a giant enhancement of nonlinearity, as well as an attractive figure of merit.
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42.70.Mp Nonlinear optical crystals
75.50.Tt Fine-particle systems; nanocrystalline materials
42.65.An Optical susceptibility, hyperpolarizability
78.20.Ls Magneto-optical effects
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

In situ x-ray diffraction and calorimetric studies of devitrification process in Cu-based bulk glassy alloys

Dmitri V. Louzguine, Alain Reza Yavari, and Akihisa Inoue

Appl. Phys. Lett. 86, 041906 (2005); http://dx.doi.org/10.1063/1.1850589 (3 pages) | Cited 5 times

Online Publication Date: 18 January 2005

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The present work is devoted to an investigation of the formation of the nanoscale icosahedral phase in Cu55Zr30Ti10Pd5 and Cu50Zr30Ti10Pd10 bulk glassy alloys by synchrotron x-ray radiation. Calculations based on the x-ray and selected-area electron diffraction patterns indicate that this phase has a high degree of icosahedral order. Kinetics of the devitrification of Cu55Zr30Ti10Pd5 is also studied in detail.
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64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
61.43.Fs Glasses
61.44.Br Quasicrystals
61.46.-w Structure of nanoscale materials

Influence of an in-plane electric field on exciton fine structure in InAs-GaAs self-assembled quantum dots

K. Kowalik, O. Krebs, A. Lemaître, S. Laurent, P. Senellart, P. Voisin, and J. A. Gaj

Appl. Phys. Lett. 86, 041907 (2005); http://dx.doi.org/10.1063/1.1855409 (3 pages) | Cited 63 times

Online Publication Date: 19 January 2005

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The influence of an in-plane electric field on the optical properties of single quantum dots is investigated. On a sample containing a plane of InAs/GaAs dots, micrometer-size electro-optical structures were produced in order to apply an external electric field in the dot plane. A large decrease of the anisotropic exchange splitting, correlated with the in-plane Stark shift, is observed.
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73.21.La Quantum dots
78.67.Hc Quantum dots
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Cr III-V semiconductors
71.35.Ee Electron-hole drops and electron-hole plasma
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect

Continuous evolution of Ga adlayer coverages during plasma-assisted molecular-beam epitaxy of (0001) GaN

G. Koblmüller, J. Brown, R. Averbeck, H. Riechert, P. Pongratz, and J. S. Speck

Appl. Phys. Lett. 86, 041908 (2005); http://dx.doi.org/10.1063/1.1853530 (3 pages) | Cited 19 times

Online Publication Date: 20 January 2005

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We present a study of the evolution of the Ga adlayer during plasma-assisted molecular-beam epitaxy of (0001) GaN as a function of both Ga flux and growth temperature. In situ quadrupole mass spectrometry was used to quantitatively determine the adsorbed Ga coverage by monitoring its subsequent desorption after GaN growth. Independent of the growth time, the Ga adlayer was found to form steady-state coverages that increase continuously from 0 to 2.5 monolayers when raising the Ga flux from N-rich to moderate Ga-rich growth conditions. At higher Ga fluxes or lower growth temperatures, macroscopic Ga droplets form on top of the Ga adlayer (Ga droplet regime). Based on the temperature dependency for the transition between the Ga adlayer and Ga droplet regime, we determined an apparent activation energy of 3.4 eV, which is discussed with respect to previously reported values.
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81.05.Ea III-V semiconductors
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.43.Mn Adsorption kinetics
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