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12 Jan 2009

Volume 94, Issue 2, Articles (02xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 022101 (2009); http://dx.doi.org/10.1063/1.3065067 (3 pages)

Hong Li and Qing Zhang
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Memory effects in photoinduced femtosecond magnetization rotation in ferromagnetic GaMnAs

J. Wang, I. Cotoros, D. S. Chemla, X. Liu, J. K. Furdyna, J. Chovan, and I. E. Perakis

Appl. Phys. Lett. 94, 021101 (2009); http://dx.doi.org/10.1063/1.3058765 (3 pages) | Cited 10 times

Online Publication Date: 12 January 2009

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We report a photoinduced femtosecond change in the magnetization direction in the ferromagnetic semiconductor GaMnAs, which allows for the detection of a four-state magnetic memory on the femtosecond time scale. The temporal profile of the magnetization exhibits a discontinuity that reveals two distinct temporal regimes, marked by the transition from a carrier-mediated nonthermal regime within the first 200 fs to a thermal, lattice-heating picosecond regime.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.30.Kz Magnetic phase boundaries (including classical and quantum magnetic transitions, metamagnetism, etc.)
75.40.Cx Static properties (order parameter, static susceptibility, heat capacities, critical exponents, etc.)
85.70.-w Magnetic devices
75.50.Dd Nonmetallic ferromagnetic materials
75.50.Pp Magnetic semiconductors

Photodiode characteristics and band alignment parameters of epitaxial Al0.5Ga0.5P

An Chen and Jerry M. Woodall

Appl. Phys. Lett. 94, 021102 (2009); http://dx.doi.org/10.1063/1.3069282 (3 pages) | Cited 1 time

Online Publication Date: 12 January 2009

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Wide-bandgap semiconductor AlxGa1−xP is a promising material candidate for low-noise photodiodes in blue/UV spectrum. Photodiodes were fabricated on Al0.5Ga0.5P epitaxial layer grown lattice matched on GaP substrate by molecular beam epitaxy. Although quantum efficiency is low for standard p-i-n photodiode due to inadvertent photon absorption in the top p-layer, it can be significantly improved by opening a recessed window in the top p-layer or by using a Schottky junction photodiode structure. Al0.5Ga0.5P band alignment parameters can be extrapolated from the current-voltage characteristics of Al0.5Ga0.5P Schottky junctions. The bandgap of Al0.5Ga0.5P was measured to be 2.38 eV.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.30.Kk Junction diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Optical modulation of near-infrared photoluminescence from lead sulfide quantum dots in glasses

Chao Liu, Yong Kon Kwon, and Jong Heo

Appl. Phys. Lett. 94, 021103 (2009); http://dx.doi.org/10.1063/1.3070523 (3 pages) | Cited 7 times

Online Publication Date: 12 January 2009

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The authors report the modulation of photoluminescence intensity from lead sulfide quantum dots using two laser beams with different wavelengths. Photoluminescence from lead sulfide quantum dots in glasses was reversibly switched between the “bright” and “dark” states and degree of darkening to 16% of the initial intensity was realized. Changes in the photoluminescence were insensitive to temperature but strongly dependent on the power densities of the modulating laser beam. This efficient optical modulation has potential for optical switching and memory device applications.
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78.66.Hf II-VI semiconductors
78.55.Et II-VI semiconductors
42.60.Fc Modulation, tuning, and mode locking

Photopumped green lasing on BeZnSeTe double heterostructures grown on InP substrates

Ichirou Nomura, Katsumi Kishino, Tomoya Ebisawa, Yutaka Sawafuji, Rieko Ujihara, Kunihiko Tasai, Hitoshi Nakamura, Tsunenori Asatsuma, and Hiroshi Nakajima

Appl. Phys. Lett. 94, 021104 (2009); http://dx.doi.org/10.1063/1.3058761 (3 pages) | Cited 5 times

Online Publication Date: 13 January 2009

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Double heterostructures (DHs) consisting of BeZnSeTe active and MgSe/BeZnTe superlattice cladding layers were fabricated on InP substrates by molecular beam epitaxy. By photoexciting the DHs, green lasing emissions at 548 nm were obtained at room temperature. The threshold excitation power density was 70 kW/cm2, from which we estimated the threshold carrier density and threshold current density assuming a green laser diode (LD) with a BeZnSeTe active layer to be (1.4–4.6)×1018 cm−3 and 0.22–0.73 kA/cm2, respectively. The experiment proved the applicability of BeZnSeTe as an active layer of green LDs.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Frequency and amplitude modulation in terahertz-sideband generation in quantum wells

Dong Kwon Kim and D. S. Citrin

Appl. Phys. Lett. 94, 021105 (2009); http://dx.doi.org/10.1063/1.3068494 (3 pages)

Online Publication Date: 13 January 2009

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A narrow-band optical beam incident on a quantum well modulated at terahertz frequencies results in the formation of terahertz sidebands, i.e., optical signals at the input optical frequency plus integer multiples of the modulation frequency. The terahertz sidebands originate in the modulated complex optical susceptibility. In this study, we analyze theoretically terahertz-sideband generation in the context of frequency and amplitude modulations of the incident optical beam. We find that, at the optimum bias field, the frequency and amplitude modulations contribute almost equally to the maximum first-order sideband. The theoretical approach could offer simple yet useful tools for further engineering and optimization of modulator-type sideband-generation or wavelength-conversion devices.
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78.67.De Quantum wells

Wafer-bonded single-crystal silicon slot waveguides and ring resonators

Ryan M. Briggs, Michael Shearn, Axel Scherer, and Harry A. Atwater

Appl. Phys. Lett. 94, 021106 (2009); http://dx.doi.org/10.1063/1.3070541 (3 pages) | Cited 3 times

Online Publication Date: 13 January 2009

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We fabricated horizontal Si slot waveguides with a 25 nm SiO2 slot layer by bonding thin Si-on-insulator wafers. After removing the Si substrate and buried oxide from one side of the bonded structure, grating-coupled waveguides and ring resonators were partially etched into the Si/SiO2/Si device layers. The gratings exhibit efficiencies of up to 23% at 1550 nm and the ring resonators were measured to have loaded quality factors near 42 000 for the lowest-order transverse-electric mode, corresponding to a propagation loss of 15 dB/cm. The leaky lowest-order transverse-magnetic mode was also observed with a propagation loss of 44 dB/cm.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
42.79.Dj Gratings

Pulse generation at 346 GHz using a passively mode locked quantum-dash-based laser at 1.55 μm

K. Merghem, A. Akrout, A. Martinez, G. Aubin, A. Ramdane, F. Lelarge, and G.-H. Duan

Appl. Phys. Lett. 94, 021107 (2009); http://dx.doi.org/10.1063/1.3070544 (3 pages) | Cited 17 times

Online Publication Date: 13 January 2009

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We report on subpicosecond pulse generation at 346 GHz repetition rate based on InAs/InP quantum dash passively mode locked lasers emitting at 1.55 μm. This is achieved owing to the high optical modal gain of the multilayer InAs/InP quantum dash active region.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Optimum quantum well width for III-nitride nonpolar and semipolar laser diodes

Mikhail V. Kisin, Robert G. W. Brown, and Hussein S. El-Ghoroury

Appl. Phys. Lett. 94, 021108 (2009); http://dx.doi.org/10.1063/1.3072345 (3 pages) | Cited 6 times

Online Publication Date: 13 January 2009

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The advantage of using wider quantum wells in III-nitride lasers offered by nonpolar/semipolar technology is limited by narrower valence subband separation, thermal hole redistribution, and resulting optical gain degradation in wider wells. We show that corresponding increase in radiative carrier lifetime in wider quantum wells can lower the laser threshold, thus inferring the existence of an optimum quantum well width for laser design.
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85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
73.20.At Surface states, band structure, electron density of states

Gain recovery in an electric oxygen-iodine laser

J. W. Zimmerman, G. F. Benavides, A. D. Palla, B. S. Woodard, D. L. Carroll, J. T. Verdeyen, and W. C. Solomon

Appl. Phys. Lett. 94, 021109 (2009); http://dx.doi.org/10.1063/1.3064163 (3 pages) | Cited 7 times

Online Publication Date: 14 January 2009

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Recent investigations of an electric oxygen-iodine laser system have shown that computational modeling overpredicts the experimentally measured power output for similar gain conditions. This discrepancy is potentially due to an unknown reaction that competes with the forward pumping of I(2P1/2) by O2(a 1Δ). Measurements of gain recovery downstream of an operating laser cavity were performed. Modeling of this experiment shows that reducing the forward pumping rate by an effective factor of approximately 4 to simulate a competing mechanism results in the computational modeling matching the experimental gain recovery measurements, and in improved agreement between the measured and modeled laser power extraction.
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42.55.Ks Chemical lasers
42.60.By Design of specific laser systems

Fabrication of three-dimensional terahertz photonic crystals with diamond structure by particle manipulation assembly

Kenta Takagi and Akira Kawasaki

Appl. Phys. Lett. 94, 021110 (2009); http://dx.doi.org/10.1063/1.3069283 (3 pages) | Cited 15 times

Online Publication Date: 14 January 2009

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We reported the fabrication of terahertz photonic crystals by three-dimensional (3D) particle manipulation assembly. Our method, which is based on pick-and-place manipulation and interparticle laser welding, enabled accurate assembling of an arbitrary 3D structure, regardless of particle polydispersity. By using this method, we fabricated a diamond crystal from ZrO2/polyethylene composite particles (diameter of 400 μm). The obtained crystal exhibited a photonic stop gap in the 〈111〉 direction; this result was in good agreement with the theoretical result, suggesting that the crystal has a full photonic bandgap at around 0.2 THz.
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81.16.Be Chemical synthesis methods
42.62.-b Laser applications
42.70.Qs Photonic bandgap materials

Ultrafast all-optical modulation in GaAs photonic crystal cavities

Chad Husko, Alfredo De Rossi, Sylvain Combrié, Quynh Vy Tran, Fabrice Raineri, and Chee Wei Wong

Appl. Phys. Lett. 94, 021111 (2009); http://dx.doi.org/10.1063/1.3068755 (3 pages) | Cited 36 times

Online Publication Date: 14 January 2009

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We demonstrate all-optical modulation based on ultrafast optical carrier injection in a GaAs photonic crystal cavity using a degenerate pump-probe technique. The observations agree well with a coupled-mode model incorporating all relevant nonlinearities. The low switching energy ( ∼ 120 fJ), small energy absorption ( ∼ 10 fJ), fast on-off response ( ∼ 15 ps), limited only by carrier lifetime, and a minimum 10 dB modulation depth suggest practical all-optical switching applications at high repetition rates.
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42.70.Qs Photonic bandgap materials
42.65.Pc Optical bistability, multistability, and switching, including local field effects
72.30.+q High-frequency effects; plasma effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.79.Hp Optical processors, correlators, and modulators

Spectral and angular distribution of Rayleigh scattering from plasmon-coupled nanohole chains

Yury Alaverdyan, Eva-Maria Hempe, A. Nick Vamivakas, Haibo E, Stefan A. Maier, and Mete Atatüre

Appl. Phys. Lett. 94, 021112 (2009); http://dx.doi.org/10.1063/1.3070520 (3 pages) | Cited 3 times

Online Publication Date: 14 January 2009

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We experimentally investigate the optical properties of nanohole chains in 20 nm gold films by measuring the far-field radiation patterns and scattering spectra using both white light and single-frequency laser excitations. We observe intensity enhancement in the frequency spectrum originating from resonantly coupled nanohole excitations via thin film surface plasmon polaritons. However, the angular distribution of the far-field pattern is identical to that of a chain of coherently radiating point dipoles both on and off the resonance frequency. We highlight a potential of the k-space imaging technique for studying far-field properties of ordered nanoscale structures.
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78.35.+c Brillouin and Rayleigh scattering; other light scattering
61.46.-w Structure of nanoscale materials
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.66.Bz Metals and metallic alloys
42.79.Wc Optical coatings
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Aspheric silicon lenses for terahertz photoconductive antennas

Florian Formanek, Marc-Aurèle Brun, Tomoyuki Umetsu, Shinji Omori, and Akio Yasuda

Appl. Phys. Lett. 94, 021113 (2009); http://dx.doi.org/10.1063/1.3072357 (3 pages) | Cited 2 times

Online Publication Date: 14 January 2009

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We report on the design and characterization of aspheric focusing silicon lenses for terahertz photoconductive antennas. The lenses are engineered using ray-tracing software and characterized using an optical fiber terahertz time-domain spectroscopy system. We find that using aspheric lenses improves terahertz radiation coupling from the emitter and enables improved collection by the detector. The signal-to-noise ratio and the cutoff frequency of measured terahertz spectra are improved. Minimized aberrations also reduce the focal spot size. Simulations based on Fresnel–Kirchhoff diffraction theory, taking into account the radiation pattern of the emitter and aberrations of the lenses, show good agreement with our measurements.
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42.79.Bh Lenses, prisms and mirrors
42.15.Dp Wave fronts and ray tracing
84.40.Ba Antennas: theory, components and accessories
42.81.Qb Fiber waveguides, couplers, and arrays
42.15.Eq Optical system design
42.15.Fr Aberrations

The power of light: Self-organized formation of macroscopic amounts of silica melts controlled by laser light

J. Günster, C. Oelgardt, J. G. Heinrich, and J. Melcher

Appl. Phys. Lett. 94, 021114 (2009); http://dx.doi.org/10.1063/1.3000637 (3 pages)

Online Publication Date: 15 January 2009

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CO2 laser systems with a power output of up to 12 kW continuous wave have been employed for melting high purity amorphous silica (SiO2) powders. Under the intense light irradiation, the migration of matter on the silica sample has been observed. A net mass transport results in the formation of macroscopic structures in the liquid phase. Protrusions of up to 7 mm height are formed against gravitational force and surface tension. For the first time, this work reports on the self-organized formation of macroscopic structures by viscous flow of a dielectric melt driven by laser light.
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64.75.Yz Self-assembly
64.70.dj Melting of specific substances
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
68.03.Cd Surface tension and related phenomena

Probing quantum efficiency by laser-induced hot-electron cooling

Miriam S. Vitiello, Gaetano Scamarcio, Jerome Faist, Giacomo Scalari, Christophe Walther, Harvey E. Beere, and David A. Ritchie

Appl. Phys. Lett. 94, 021115 (2009); http://dx.doi.org/10.1063/1.3054644 (3 pages) | Cited 9 times

Online Publication Date: 15 January 2009

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Experimental evidence of a physical phenomenon characteristic of semiconductor lasers, i.e., cooling of the electrons above the threshold for stimulated emission, is reported. We show that this effect is directly related with the internal quantum efficiency (ηint), which is one of the central physical quantities in the theory of semiconductor lasers. As a model system we selected the terahertz quantum-cascade laser that is particularly suitable for the investigation of nonequilibrium electronic ensembles. The reported procedure for the assessment of ηint can be easily extended to other model systems, enlightening the relevance of including hot-electron distributions in semiconductor laser modeling.
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42.55.Px Semiconductor lasers; laser diodes
72.20.Ht High-field and nonlinear effects

The impact of nearest neighbor interaction on the resonances in terahertz metamaterials

Ranjan Singh, Carsten Rockstuhl, Falk Lederer, and Weili Zhang

Appl. Phys. Lett. 94, 021116 (2009); http://dx.doi.org/10.1063/1.3063051 (3 pages) | Cited 20 times

Online Publication Date: 15 January 2009

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By using terahertz time-domain spectroscopy and rigorous simulations, we investigate the impact of gap orientation of neighboring split rings on the three lowest order eigenmodes for a metamaterial based on split ring resonators. We distinct scenarios where neighboring split rings have their gap either on the same or on opposite sides. The two lowest order eigenmodes are marginally affected, whereas the higher order eigenmode experiences a significant spectral reshaping. By modifying the period it is shown that due to a coherent interaction a huge resonance sharpening is observed. Hence potential application can be anticipated by using such materials, e.g., in sensing devices.
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84.40.Az Waveguides, transmission lines, striplines

Terahertz wave generation from gas plasma using a phase compensator with attosecond phase-control accuracy

Jianming Dai and X.-C. Zhang

Appl. Phys. Lett. 94, 021117 (2009); http://dx.doi.org/10.1063/1.3068501 (3 pages) | Cited 17 times

Online Publication Date: 15 January 2009

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We report the use of a precise phase compensator for the generation of intense terahertz waves from laser-induced gas plasma excited by a femtosecond pulse (ω) and its second harmonic (2ω) at both close contact and standoff distances. The attosecond accuracy phase-control capability of the device enables further optimization of the terahertz emission from gas plasma and elimination of the temporal walkoff between the ω and 2ω pulses traveling in dispersive media, resulting in intense terahertz generation at a distance of over 100 m by sending the optical beams far away and focusing them locally.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Lead salt microdisk lasers operating in continuous wave mode at 5.3 μm wavelength

M. Eibelhuber, T. Schwarzl, G. Springholz, and W. Heiss

Appl. Phys. Lett. 94, 021118 (2009); http://dx.doi.org/10.1063/1.3072358 (3 pages) | Cited 6 times

Online Publication Date: 15 January 2009

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Lead salt microdisk lasers with midinfrared emission around 5.3 μm are demonstrated. The laser structures were grown by molecular beam epitaxy on BaF2 substrates and consist of Pb0.95Sr0.05Se spacer layers and a ten-period PbSe/Pb0.95Sr0.05Se multi-quantum-well active region. Under optical excitation, single mode continuous-wave lasing is obtained up to temperatures of 135 K from microdisks with a diameter of 45 μm. With increasing temperature the laser emission continuously switches to resonator modes at shorter wavelengths. The lasers exhibit a threshold pump power of only 1.47 mW (75 W/cm2) at 115 K.
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42.55.Sa Microcavity and microdisk lasers
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking

Influence of nitrogen doping on growth rate and texture evolution of chemical vapor deposition diamond films

T. Liu and D. Raabe

Appl. Phys. Lett. 94, 021119 (2009); http://dx.doi.org/10.1063/1.3072601 (3 pages) | Cited 5 times

Online Publication Date: 16 January 2009

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Chemical vapor deposition (CVD) diamond films were prepared using a variation in nitrogen addition into the gas source admixture by a direct current CVD method. The influence of nitrogen addition on the crystallographic texture and grain shape evolution in heteroepitaxial polycrystalline diamond films was investigated using high-resolution electron backscattering diffraction and x-ray diffraction. The analysis reveals that an addition of 1.5% N2 to the CH4 gas flow leads to a strong enhancement in a {110} fiber texture. The phenomenon is discussed in terms of a competitive growth selection mechanism.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.jm Texture
61.72.up Other materials
68.55.ag Semiconductors
81.05.Cy Elemental semiconductors
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Atmospheric plasma jet array in parallel electric and gas flow fields for three-dimensional surface treatment

Z. Cao, J. L. Walsh, and M. G. Kong

Appl. Phys. Lett. 94, 021501 (2009); http://dx.doi.org/10.1063/1.3069276 (3 pages) | Cited 42 times

Online Publication Date: 13 January 2009

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This letter reports on electrical and optical characteristics of a ten-channel atmospheric pressure glow discharge jet array in parallel electric and gas flow fields. Challenged with complex three-dimensional substrates including surgical tissue forceps and sloped plastic plate of up to 15°, the jet array is shown to achieve excellent jet-to-jet uniformity both in time and in space. Its spatial uniformity is four times better than a comparable single jet when both are used to treat a 15° sloped substrate. These benefits are likely from an effective self-adjustment mechanism among individual jets facilitated by individualized ballast and spatial redistribution of surface charges.
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52.77.-j Plasma applications
52.75.-d Plasma devices
52.80.Hc Glow; corona
81.65.-b Surface treatments

Effect of laser-induced double-step ionization of a gas on vacuum electron acceleration

Devki Nandan Gupta, Hyo Jae Jang, and Hyyong Suk

Appl. Phys. Lett. 94, 021502 (2009); http://dx.doi.org/10.1063/1.3070529 (3 pages) | Cited 2 times

Online Publication Date: 13 January 2009

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The effect of laser-induced double ionization of a helium gas on electron acceleration is investigated. The optical field ionization of a gas of sufficient density can significantly change its refractive index, which makes the incident laser pulse diverge. For an enough laser intensity, the helium gas can be found doubly ionized and it strengthens the divergence of the pulse. As a result, electrons feel a very low laser intensity at the trailing part of the laser pulse. Hence, there is not much electron deceleration at the trailing part of the pulse. Therefore, a significant enhancement in electron energy by the laser acceleration may be observed.
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51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
51.70.+f Optical and dielectric properties

Electron energy distribution functions in low-pressure oxygen plasma columns sustained by propagating surface waves

L. Stafford, R. Khare, V. M. Donnelly, J. Margot, and M. Moisan

Appl. Phys. Lett. 94, 021503 (2009); http://dx.doi.org/10.1063/1.3072364 (3 pages) | Cited 6 times

Online Publication Date: 14 January 2009

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Electron energy distribution functions (EEDFs) were measured in a 50 mTorr oxygen plasma column sustained by propagating surface waves. Trace-rare-gas-optical-emission spectroscopy was used to derive EEDFs by selecting lines to extract “electron temperature” (Te) corresponding to either lower energy electrons that excite high-lying levels through stepwise excitation via metastable states or higher energy electrons that excite emission directly from the ground state. Lower energy Te’s decreased from 8 to 5.5 eV with distance from the wave launcher, while Te ≈ 6 eV for higher energy electrons and Te>20 eV for a high-energy tail. Mechanisms for such EEDFs are discussed.
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52.40.Db Electromagnetic (nonlaser) radiation interactions with plasma
52.25.Os Emission, absorption, and scattering of electromagnetic radiation

Probing radical kinetics in the afterglow of pulsed discharges by absorption spectroscopy with light emitting diodes: Application to BCl radical

D. Vempaire and G. Cunge

Appl. Phys. Lett. 94, 021504 (2009); http://dx.doi.org/10.1063/1.3067996 (3 pages) | Cited 10 times

Online Publication Date: 15 January 2009

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Measuring decay rates of radical densities in the afterglow of pulsed plasmas is a powerful approach to determine their gas phase and surface loss kinetics. We show that this measurement can be achieved by absorption spectroscopy with low cost and simple apparatus by using light emitting diodes as a light source. The feasibility is demonstrated by monitoring BCl radicals in pulsed low pressure high-density BCl3 plasmas. It is shown that BCl is lost both in the gas phase by reacting with Cl2 with a cross section of 9 Å2 and in the chamber walls with a sticking coefficient of about 0.3.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.80.Hc Glow; corona
52.25.-b Plasma properties
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Annealing effects on faceting of InAs/GaAs(001) quantum dots

E. Placidi, A. Della Pia, and F. Arciprete

Appl. Phys. Lett. 94, 021901 (2009); http://dx.doi.org/10.1063/1.3056654 (3 pages) | Cited 12 times

Online Publication Date: 12 January 2009

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The aspect ratio and faceting evolution of quantum dots grown at 500 °C were studied as a function of postgrowth annealing temperature. We show that faceting and aspect ratio strictly depend on growth conditions. The evolution toward {136} and {137} facets is kinetically limited and occurs under different experimental conditions. Furthermore long annealing procedures lead to the occurrence of low aspect ratio domes different from those forming at higher growth temperatures.
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68.65.Hb Quantum dots (patterned in quantum wells)
61.72.Cc Kinetics of defect formation and annealing
81.05.Ea III-V semiconductors
81.40.Gh Other heat and thermomechanical treatments

Nonlinear optical properties of graphene oxide in nanosecond and picosecond regimes

Zhibo Liu, Yan Wang, Xiaoliang Zhang, Yanfei Xu, Yongsheng Chen, and Jianguo Tian

Appl. Phys. Lett. 94, 021902 (2009); http://dx.doi.org/10.1063/1.3068498 (3 pages) | Cited 36 times

Online Publication Date: 12 January 2009

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The nonlinear optical properties of graphene oxide (GO) were investigated at 532 nm in nanosecond and picosecond regimes. Results show that two-photon absorption dominates nonlinear absorption process of GO in the case of picosecond pulses, while excited state nonlinearities play an important role in the case of nanosecond pulses. Additionally, we compared nonlinear optical properties of three different dimensional carbon-based materials (two-dimensional graphene, one-dimensional carbon nanotube, and zero-dimensional fullerene) in nanosecond and picosecond regimes, respectively. The nonlinear mechanism of GO is distinctly different from nonlinear scattering of carbon nanotube and excited state nonlinearity of fullerene.
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42.65.-k Nonlinear optics
81.05.ub Fullerenes and related materials
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