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4 Dec 2006

Volume 89, Issue 23, Articles (23xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 89, 233120 (2006); http://dx.doi.org/10.1063/1.2402115 (3 pages)

S. Yeo, Y. Horibe, S. Mori, C. M. Tseng, C. H. Chen, A. G. Khachaturyan, C. L. Zhang, and S.-W. Cheong
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Coherent spin oscillations in bulk GaAs at room temperature

P. E. Hohage, G. Bacher, D. Reuter, and A. D. Wieck

Appl. Phys. Lett. 89, 231101 (2006); http://dx.doi.org/10.1063/1.2398909 (3 pages) | Cited 18 times

Online Publication Date: 4 December 2006

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Time-resolved Kerr rotation in Voigt geometry is used to study the coherent evolution of spin states in moderately doped n-GaAs crystals with picosecond excitation. Due to the small spectral width of the exciting laser pulses, selective excitation of different electronic states is feasible, which allows one to extract both the dependence of the g factor and the spin dephasing time on energy. The authors are able to observe coherent spin oscillations in bulk n-GaAs at room temperature and deduce a g factor of g = −0.316±0.004 at 300 K and a magnetic field dependent room temperature spin dephasing time of, e.g., T2* = 110 ps at B = 1.2 T.
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78.66.Fd III-V semiconductors
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.20.Nr Semiconductor compounds
78.47.-p Spectroscopy of solid state dynamics

Modeling white light-emitting diodes with phosphor layers

Dun-Yen Kang, Enboa Wu, and Da-Ming Wang

Appl. Phys. Lett. 89, 231102 (2006); http://dx.doi.org/10.1063/1.2400111 (3 pages) | Cited 15 times

Online Publication Date: 4 December 2006

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With a blue light-emitting diode and a phosphor layer to downconvert blue light to a second light, such as yellow, white light can be produced. The authors developed a one-dimensional model to describe the light propagating in the phosphor layer in terms of light absorption, conversion, and reflection. The parameters required for the model were determined from the data obtained by using multiple-layer phosphor films. The model predicts that, with a reflector between the diode and the phosphor layer that is blue-light transparent but reflects other visible light, the normalized white light intensity is above 0.9, higher than that of conventional packages (0.6–0.8).
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85.60.Jb Light-emitting devices
85.30.De Semiconductor-device characterization, design, and modeling

Add-drop filters in three-dimensional layer-by-layer photonic crystals using waveguides and resonant cavities

Preeti Kohli, Caleb Christensen, Jason Muehlmeier, Rana Biswas, Gary Tuttle, and Kai-Ming Ho

Appl. Phys. Lett. 89, 231103 (2006); http://dx.doi.org/10.1063/1.2400398 (3 pages) | Cited 14 times

Online Publication Date: 4 December 2006

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A three-dimensional layer-by-layer photonic crystal with a complete photonic band gap is used to experimentally and theoretically demonstrate a sharp tunable bandpass filter. The structure consists of input and output waveguide sections coupled through a nearby cavity. The authors show experimentally and verify with finite difference time domain simulations that this configuration is a bandpass filter where a particular resonant frequency of the cavity is selected from the input guide and transmitted to the output guide leaving out other input frequencies. An excellent coupling efficiency near 100% between the waveguide and the cavity is found for the drop frequencies.
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42.79.Ci Filters, zone plates, and polarizers
42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers

CdSe quantum dot microdisk laser

Johannes Renner, Lukas Worschech, Alfred Forchel, Suddhasatta Mahapatra, and Karl Brunner

Appl. Phys. Lett. 89, 231104 (2006); http://dx.doi.org/10.1063/1.2402263 (3 pages) | Cited 14 times

Online Publication Date: 5 December 2006

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Laser emission from optically pumped CdSe quantum dots embedded in a ZnSe/ZnMgSSe microdisk was observed at low temperatures. Laser thresholds below 20 μW and spontaneous emission coupling β-factors exceeding 0.8 were determined. For different modes of the same microdisk cavity the laser threshold increases with higher mode energy, which the authors associate to a better coupling of larger quantum dots with the optical mode. Also the linewidth and energy shift of lasing modes as a function of pump power were analyzed.
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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
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Time evolution of the second-order nonlinearity layer in thermally poled optical fiber

Honglin An and Simon Fleming

Appl. Phys. Lett. 89, 231105 (2006); http://dx.doi.org/10.1063/1.2402897 (3 pages) | Cited 6 times

Online Publication Date: 5 December 2006

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Time evolution of the second-order nonlinearity induced in a single-hole D-shaped fiber thermally poled at 3.5 kV and 320 °C has been investigated with second-harmonic microscopy. It was found that the nonlinear layer moved towards the cathode with increasing poling time until it finally reached the cathode surface. The magnitude of the nonlinear coefficient first increased, saturated at ∼ 0.32pm/V between 5 and 20 min after poling, and then began to decrease for longer poling time. The nonlinearity remained large even when the nonlinearity layer reached the centerline between the two electrodes. In samples poled long enough (>45 min), apart from the main nonlinearity layer at the cathode, weak second-order nonlinearity was also induced at the core-cladding interface sections that were nearly parallel to the poling direction.
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42.81.Cn Fiber testing and measurement of fiber parameters
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
07.60.Pb Conventional optical microscopes

Nonlinear pulse-shaping phenomena of semiconductor saturable absorber mirror

Jiun-Cheng Wang, Chi-Kuang Sun, and Juen-Kai Wang

Appl. Phys. Lett. 89, 231106 (2006); http://dx.doi.org/10.1063/1.2400396 (3 pages) | Cited 3 times

Online Publication Date: 5 December 2006

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The authors report the experimental investigation of pulse-shaping effects of a semiconductor saturable absorber mirror (SESAM). The induced pulse shortening and phase variation exhibit fluence dependences which follow the saturation behavior of nonlinear reflectivity. The experimental results have been compared with the prediction based on saturable population relaxation model. The study provides an unprecedented opportunity to investigate the role of SESAM in ultrafast mode-locked lasers.
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42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Bh Lenses, prisms and mirrors

Photonuclear fission with quasimonoenergetic electron beams from laser wakefields

S. A. Reed, V. Chvykov, G. Kalintchenko, T. Matsuoka, P. Rousseau, V. Yanovsky, C. R. Vane, J. R. Beene, D. Stracener, D. R. Schultz, and A. Maksimchuk

Appl. Phys. Lett. 89, 231107 (2006); http://dx.doi.org/10.1063/1.2400400 (3 pages) | Cited 9 times

Online Publication Date: 5 December 2006

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Recent advancements in laser wakefield accelerators have resulted in the generation of low divergence, hundred MeV, quasimonoenergetic electron beams. The bremsstrahlung produced by these highly energetic electrons in heavy converters includes a large number of MeV γ rays that have been utilized to induce photofission in natural uranium. Analysis of the measured delayed γ emission demonstrates production of greater than 3×105 fission events per joule of laser energy, which is more than an order of magnitude greater than that previously achieved. Monte Carlo simulations model the generated bremsstrahlung spectrum and compare photofission yields as a function of target depth and incident electron energy.
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25.85.Jg Photofission
25.20.-x Photonuclear reactions
27.90.+b A ≥ 220

UV-modulated one-dimensional photonic-crystal resonator for visible lights

S. Y. Yang, P. H. Yang, C. D. Liao, J. J. Chieh, Y. P. Chen, H. E. Horng, Chin-Yih Hong, and H. C. Yang

Appl. Phys. Lett. 89, 231108 (2006); http://dx.doi.org/10.1063/1.2402876 (3 pages) | Cited 5 times

Online Publication Date: 6 December 2006

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The one-dimensional photonic-crystal (A/SiO2)6/ZnO/(SiO2/A)6 resonators at visible lights are fabricated and characterized, where A may be ZnO or indium tin oxide. Owing to the absorption of ultraviolet (UV) light by the ZnO layers, the refractive index of ZnO layers is changed temporally. This fact led to a temporary shifting of the forbidden band and the resonant mode of the resonator under UV irradiation. Besides, via adjusting the thickness of the ZnO defect layer, the resonant wavelength is manipulated. These experimental data show good consistence with simulated results.
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42.70.Qs Photonic bandgap materials
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Size-dependent strain effects in self-assembled CdSe quantum dots with Zn0.38Cd0.23Mg0.39Se barriers

J. S. Reparaz, A. R. Goñi, M. I. Alonso, M. N. Perez-Paz, and M. C. Tamargo

Appl. Phys. Lett. 89, 231109 (2006); http://dx.doi.org/10.1063/1.2402881 (3 pages) | Cited 2 times

Online Publication Date: 6 December 2006

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From resonant Raman scattering measurements under hydrostatic pressure the authors were able to identify both the strain-shifted longitudinal optical phonon of CdSe quantum dots with different average size embedded in a quaternary ZnCdMgSe material and a Mg-local dot mode due to interdiffusion from the barrier. They show that the large tunability of the light emission, which covers most of the visible spectrum, is not only due to a different degree of confinement but also to a size-dependent built-in strain. The frequency of the Mg mode allowed them also to roughly estimate the amount of Mg interdiffusion into the quantum dots.
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63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
78.67.Hc Quantum dots
78.30.Fs III-V and II-VI semiconductors
78.55.Et II-VI semiconductors
66.30.Ny Chemical interdiffusion; diffusion barriers
81.40.Vw Pressure treatment

Enhanced stability of the second order optical properties of high-Tg fluorinated electro-optic copolymer

A. Belardini, L. Dominici, M. C. Larciprete, F. Michelotti, A. Rousseau, and A. Ratsimihety

Appl. Phys. Lett. 89, 231110 (2006); http://dx.doi.org/10.1063/1.2402886 (3 pages) | Cited 2 times

Online Publication Date: 6 December 2006

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In this work the authors investigated the second order nonlinear optical properties of a group of Disperse Red 1 based electro-optic fluorinated copolymers, synthesized with two fluorinated monomers: the α-fluoroacrylate monomer bearing an adamantane side group and the α-fluoroacrylate monomer bearing the Disperse Red 1 chromophore. By means of nonlinear ellipsometry at λ = 1550 nm, the poling induced electro-optic tensor main component r33 was determined. The polymer’s thermostability was investigated by means of the temperature scanning and isothermal relaxation techniques, leading to the determination of the depolarization temperature Tdep = 136 °C, corresponding to an activation energy for the relaxation of the orientational distribution of the active chromophores EA = 105 kcal/mol. The increased thermostability of the copolymer, given by the adamantane side group, is then compared with that of other two groups of fluorinated copolymers.
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82.35.Ej Nonlinear optics with polymers
82.35.Jk Copolymers, phase transitions, structure
78.20.Jq Electro-optical effects
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
64.70.P- Glass transitions of specific systems
64.70.Q- Theory and modeling of the glass transition
42.70.Jk Polymers and organics
42.65.-k Nonlinear optics

Investigation of whispering gallery mode dependence on cavity geometry of quasiperiodic photonic crystal microcavity lasers

Po-Tsung Lee, Tsan-Wen Lu, Feng-Mao Tsai, and Tien-Chang Lu

Appl. Phys. Lett. 89, 231111 (2006); http://dx.doi.org/10.1063/1.2402894 (3 pages) | Cited 4 times

Online Publication Date: 6 December 2006

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Dodecagonal (12-fold) quasiperiodic photonic crystal (DQPC) microcavity lasers sustaining whispering gallery mode (WGM) are fabricated. Lasing characteristics of DQPC D2 microcavity lasers are obtained and compared with triangular lattice D2 photonic crystal (PC) lasers, and ultralow threshold is obtained. The strong WGM mode dependence on 12 nearest airholes of DQPC D2 microcavity and its fabrication tolerance is investigated and discussed by randomly varying the lattice of two separate regions. This mode dependence also indicates that one can enhance a WGM in different PC microcavities by modifying the cavity boundary to be circular.
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42.55.Tv Photonic crystal lasers and coherent effects
42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Low threshold amplified spontaneous emission based on coumarin 151 encapsulated in mesoporous SBA-15

Dingke Zhang, Sumei Zhang, Dongge Ma, Gulimina, and Xiaotian Li

Appl. Phys. Lett. 89, 231112 (2006); http://dx.doi.org/10.1063/1.2402908 (3 pages) | Cited 7 times

Online Publication Date: 6 December 2006

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Amplified spontaneous emission (ASE) characteristics of a blue dye coumarin 151 encapsulated in a highly ordered mesoporous SBA-15 were studied. The spectra narrowing was observed and found that the threshold and loss were greatly reduced, and the gain is significantly increased compared with spin-coated coumarin 151 doped poly(4-vinylphenol) film. The ASE threshold, gain, and loss, respectively, reached 0.55 mJ pulse−1 cm−2, 44.78 cm−1, and 8.9 cm−1 for the coumarin 151 encapsulated in mesoporous SBA-15 film. The optimized lasing action owes much to the effects of the better spatial confinement of the molecules in the ordered mesoporous structure of the host SBA-15.
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42.55.Mv Dye lasers
42.60.By Design of specific laser systems

Simultaneous determination of nonlinear optical and thermo-optic parameters of liquid samples

A. Santhi, Vinu V. Namboodiri, P. Radhakrishnan, and V. P. N. Nampoori

Appl. Phys. Lett. 89, 231113 (2006); http://dx.doi.org/10.1063/1.2403185 (3 pages) | Cited 2 times

Online Publication Date: 6 December 2006

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The authors apply the theory of photothermal lens formation and also that of pure optical nonlinearity to account for the phase modulation in a beam as it traverses a nonlinear medium. It is used to simultaneously determine the nonlinear optical refraction and the thermo-optic coefficient. They demonstrate this technique using some metal phthalocyanines dissolved in dimethyl sulfoxide, irradiated by a Q-switched Nd:YAG laser with 10 Hz repetition rate and a pulse width of 8 ns. The mechanism for reverse saturable absorption in these materials is also discussed.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.47.-p Spectroscopy of solid state dynamics

High power GaAs/AlGaAs lasers (λ ∼ 850 nm) with ultranarrow vertical beam divergence

L. Ya. Karachinsky, I. I. Novikov, Yu. M. Shernyakov, S. M. Kuznetsov, N. Yu. Gordeev, M. V. Maximov, P. S. Kop’ev, U. Ben-Ami, D. B. Arbiv, A. Sharon, T. Kettler, K. Posilovic, O. Schulz, V. A. Shchukin, U. W. Pohl, et al.

Appl. Phys. Lett. 89, 231114 (2006); http://dx.doi.org/10.1063/1.2403906 (3 pages) | Cited 4 times

Online Publication Date: 6 December 2006

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The authors study 850 nm GaAs/AlGaAs longitudinal photonic band crystal lasers with a vertical far field divergence of 9° (full width at half maximum). Differential quantum efficiency of 95% is achieved at a cavity length of 500 μm. A total optical output power from broad area multimode devices was up to 6.3 W and a maximum continuous wave single mode power from narrow stripe devices was 270 mW.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.55.Tv Photonic crystal lasers and coherent effects
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Passive mode locking by carbon nanotubes in a femtosecond laser written waveguide laser

Giuseppe Della Valle, Roberto Osellame, Gianluca Galzerano, Nicola Chiodo, Giulio Cerullo, Paolo Laporta, Orazio Svelto, Uwe Morgner, A. G. Rozhin, V. Scardaci, and A. C. Ferrari

Appl. Phys. Lett. 89, 231115 (2006); http://dx.doi.org/10.1063/1.2403912 (3 pages) | Cited 40 times

Online Publication Date: 7 December 2006

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The authors report on the first demonstration of mode locking in an active waveguide laser manufactured by femtosecond laser writing. The active waveguide is fabricated in an Er–Yb-doped phosphate glass, and the mode locker is a fiber-pigtailed saturable absorber device based on single-wall carbon nanotubes specially designed to efficiently operate at 1.5 μm. Transform-limited 1.6 ps pulses were observed in a ring laser cavity configuration.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
85.35.Kt Nanotube devices

Electroluminescence from ZnO nanoparticles/organic nanocomposites

Chun-Yu Lee, Yau-Te Haung, Wei-Fang Su, and Ching-Fuh Lin

Appl. Phys. Lett. 89, 231116 (2006); http://dx.doi.org/10.1063/1.2404614 (3 pages) | Cited 28 times

Online Publication Date: 7 December 2006

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The authors report ultraviolet electroluminescence from ZnO nanoparticle-based devices prepared by the phase-segregation technique. The conditions for phase segregation are investigated using confocal microscopy. With proper parameters for phase segregation, the ZnO nanoparticles and N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine: poly(methyl methacrylate) can be separated into two layers upon spin-coating process. The method allows electrons and holes to recombine in the ZnO nanoparticles. The I-V curve shows stable and excellent rectification. For the device with 90 nm ZnO nanoparticles, it exhibits a very narrow spectrum with a peak at 392 nm and no defect-related emission. The emission peak well corresponds to the ZnO band-gap energy.
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78.60.Fi Electroluminescence
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.40.Ei Rectification
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.22.-f Electronic structure of nanoscale materials and related systems

Restructuring and modification of metallic nanorod arrays using femtosecond laser direct writing

C. Reinhardt, S. Passinger, B. N. Chichkov, W. Dickson, G. A. Wurtz, P. Evans, R. Pollard, and A. V. Zayats

Appl. Phys. Lett. 89, 231117 (2006); http://dx.doi.org/10.1063/1.2398904 (3 pages) | Cited 11 times

Online Publication Date: 8 December 2006

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Local restructuring of metallic nanorod arrays and the fabrication of metallodielectric microstructures using direct femtosecond laser writing technologies have been studied. Femtosecond laser ablation has demonstrated the possibility to create sharp boundaries (down to a single nanorod) on the nanorod array. Polymer structures on the nanorods can be used to control the resonance wavelengths and thus the effective refractive index of surface plasmons supported by the array. The structured nanorods and their polymer composites are important for applications in light guiding and the development of nonlinear optical nanodevices.
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42.62.-b Laser applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.82.Gw Other integrated-optical elements and systems
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Observation of magnetization waves in negative-index photonic metamaterials

G. Dolling, M. Wegener, A. Schädle, S. Burger, and S. Linden

Appl. Phys. Lett. 89, 231118 (2006); http://dx.doi.org/10.1063/1.2403905 (3 pages) | Cited 38 times

Online Publication Date: 8 December 2006

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By measuring and calculating oblique-incidence transmittance spectra of a negative-index photonic metamaterial layer, the authors infer the in-plane dispersion relation of the magnetization wave. From the geometry and the dispersion shape, the authors conclude that coupling is predominantly via magnetic dipoles for wave propagation along the magnetic-dipole direction. These magnetization waves are the classical analog of magnon excitations of quantum-mechanical spins.
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42.70.-a Optical materials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Cr Saturation moments and magnetic susceptibilities

Polaritonic emission via surface plasmon cross coupling

C. Bonnand, J. Bellessa, C. Symonds, and J. C. Plenet

Appl. Phys. Lett. 89, 231119 (2006); http://dx.doi.org/10.1063/1.2403911 (3 pages) | Cited 14 times

Online Publication Date: 8 December 2006

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In this letter the authors demonstrate that the emission of plasmon/exciton polaritons in an organic semiconductor can be extracted using surface plasmon cross coupling. A J-aggregated cyanine dye layer is deposited on a silver film and then the whole structure is periodically corrugated. As a result of this corrugation, the dispersion lines of the surface modes on both sides of the silver layer may cross. At this crossing point, an increase in the polaritonic emission is observed. The contributions of unpolarized incoherent states and of the TM polarized polaritons emission are separated.
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71.38.-k Polarons and electron-phonon interactions
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.35.Lk Collective effects (Bose effects, phase space filling, and excitonic phase transitions)
71.20.Rv Polymers and organic compounds

Amplitude compensation of a diode laser array phase locked with a Talbot cavity

Qiang Li, Pengfei Zhao, and Weirong Guo

Appl. Phys. Lett. 89, 231120 (2006); http://dx.doi.org/10.1063/1.2403924 (3 pages) | Cited 5 times

Online Publication Date: 8 December 2006

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Phase locking of the output beam and in-phase mode selection with the amplitude compensator at a high injection current were achieved experimentally by a quarter-Talbot cavity. The linear array used in the experiment consisted of 49 wide-aperture diodes with a diode width of a = 100 μm and a spacing period of d = 200 μm. Increasing output beam intensity in the far-field central lobe was demonstrated, and 1.46 W of output power distributed on the multilobes was concentrated on the single lobe and changed to 0.92 W by the amplitude compensator. The far-field divergence of the phase-locked beam was 1.69 mrad, and the spectral full width at half maximum of the output beam was suppressed from 1.7 to 0.13 nm.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Low frequency terahertz quantum cascade laser operating from 1.6 to 1.8 THz

Christoph Walther, Giacomo Scalari, Jérôme Faist, Harvey Beere, and David Ritchie

Appl. Phys. Lett. 89, 231121 (2006); http://dx.doi.org/10.1063/1.2404598 (3 pages) | Cited 50 times

Online Publication Date: 8 December 2006

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The authors report a GaAs/Al0.1Ga0.9As quantum cascade laser based on a bound-to-continuum transition optimized for low frequency operation. High tunability of the gain curve is achieved by the Stark effect and laser emission is measured between 1.6 and 1.8 THz. Pulsed mode operation up to 95 K and continuous wave operation up to 80 K are reported. The dynamical range in current is as high as 43%.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
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I-P relationship and effective capacitance in external electrode fluorescent lamp

Tae Il Lee, Hyeon Seok Hwang, Ki Wan Park, and Hong Koo Baik

Appl. Phys. Lett. 89, 231501 (2006); http://dx.doi.org/10.1063/1.2400073 (3 pages) | Cited 1 time

Online Publication Date: 5 December 2006

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The authors derived an analytical relationship between rms tube current and input power for various capacitances of the external electrode part and measured their effective capacitances in an external electrode fluorescent lamp. From the fitting derived relation in the measured data, the reliability of the authors’ derivation was certain and effective capacitances were measured. Consequently, it is confirmed that the derived relationship is very useful in estimating the effective capacitance of the external electrode part for any shape of glass tube and electrodes during the lamp operation.
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42.72.Bj Visible and ultraviolet sources

Electron heating mode transitions in dual frequency capacitive discharges

M. M. Turner and P. Chabert

Appl. Phys. Lett. 89, 231502 (2006); http://dx.doi.org/10.1063/1.2402226 (3 pages) | Cited 9 times

Online Publication Date: 6 December 2006

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The authors consider electron heating in the sheath regions of capacitive discharges excited by a combination of two frequencies, one much higher than the other. There is a common supposition that in such discharges the higher frequency is the dominant source of electron heating. In this letter, the authors discuss closed analytic expressions quantifying the Ohmic and collisionless electron heating in a dual frequency discharge. In both cases, the authors show that the lower frequency parameters strongly influence the heating effect. Moreover, this influence is parametrically different, so that the dominant heating mechanism may be changed by varying the low frequency current density.
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52.50.Nr Plasma heating by DC fields; ohmic heating, arcs
52.80.Pi High-frequency and RF discharges
52.40.Kh Plasma sheaths
52.25.Fi Transport properties

Sharp bursts of high-flux reactive species in submicrosecond atmospheric pressure glow discharges

J. L. Walsh and M. G. Kong

Appl. Phys. Lett. 89, 231503 (2006); http://dx.doi.org/10.1063/1.2397570 (3 pages) | Cited 12 times

Online Publication Date: 8 December 2006

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In this letter, the authors present an experimental study of the temporal characteristics of submicrosecond pulsed atmospheric glow discharges. Using electrical measurements and nanosecond-resolved optical emission spectroscopy, they show that a long initial period of each voltage pulse is spent building up space charges and is then followed by a large current pulse in the voltage-falling phase. Reactive plasma species such as oxygen atoms and OH radicals are produced in a train of sharp and independent pulses of 50–100 ns wide. Finally, their production is shown to increase significantly as the voltage pulse width reduces or the repetition frequency increases.
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52.80.Hc Glow; corona
52.50.Dg Plasma sources
52.70.Ds Electric and magnetic measurements
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
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Cathodoluminescence investigations of GaInNAs on GaAs(111)B

J. Miguel-Sánchez, U. Jahn, A. Guzmán, and E. Muñoz

Appl. Phys. Lett. 89, 231901 (2006); http://dx.doi.org/10.1063/1.2398919 (3 pages)

Online Publication Date: 4 December 2006

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In this work, we present a detailed cathodoluminescence characterization of GaInNAs quantum wells grown on GaAs(111)B. As-grown and annealed InGaAs and GaInNAs quantum wells were maeasured and compared by spatially resolved cathodoluminescence at different photon energies. In the case of GaInNAs quantum wells, an increase of the luminescence intensity, a blueshift, and an increment of the modulation depth of intensity profiles were found after rapid thermal annealing cycles. The latter is caused by the presence of nonradiative areas above the GaInNAs quantum well due to stacking faults formed during the growth.
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81.05.Ea III-V semiconductors
81.07.St Quantum wells
78.67.De Quantum wells
78.60.Hk Cathodoluminescence, ionoluminescence
61.72.Cc Kinetics of defect formation and annealing
61.72.Nn Stacking faults and other planar or extended defects
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