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15 Jul 2009

Volume 106, Issue 2, Articles (02xxxx)

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Photoresistances of semi-insulating GaAs photoconductive switch illuminated by 1.064 μm laser pulse

Minghe Wu, Xiaoming Zheng, Chengli Ruan, Hongchun Yang, Yunqing Sun, Shan Wang, Kedi Zhang, and Hong Liu

J. Appl. Phys. 106, 023101 (2009); http://dx.doi.org/10.1063/1.3172668 (6 pages) | Cited 2 times

Online Publication Date: 17 July 2009

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The Shockley–Read–Hall model (SRHM) and its simplified model (SSRHM) were used to describe the characteristics of a photoconductive semiconductor switch (PCSS) made from a semi-insulating (SI) gallium arsenide (GaAs) chip, biased at low voltage, and illuminated by a 1.064 μm laser pulse. These characteristics include the free carrier densities, dynamic photoresistance, and time evolution of output pulses of the PCSS. The deep donor EL2 centers in SI GaAs play a dominant role in both the SRHM and SSRHM as electrons at EL2 unionized centers are strongly excited by the subband-gap photons at the wavelength of 1.064 μm. Theoretical modeling on the evolution of the experimental measured output pulses led to a two-step micromechanism of electron excitation process within the GaAs chip. The minimum photoresistances predicted by the SSRHM are in good agreement with experimental measurements, which confirms the dominant role of EL2 in the generation of electric pulses from a SI GaAs photoconductivity switch on which the 1064 nm laser pulse is illuminated.
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85.60.Bt Optoelectronic device characterization, design, and modeling
71.20.Nr Semiconductor compounds
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
71.55.Eq III-V semiconductors
72.20.-i Conductivity phenomena in semiconductors and insulators
72.40.+w Photoconduction and photovoltaic effects

Electrically controlled reflection bands in a cholesteric liquid crystals slab

A. Castellanos-Moreno, P. Castro-Garay, S. Gutiérrez-López, R. A. Rosas-Burgos, A. Corella-Madueño, and J. Adrian Reyes

J. Appl. Phys. 106, 023102 (2009); http://dx.doi.org/10.1063/1.3153155 (5 pages) | Cited 1 time

Online Publication Date: 20 July 2009

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We considered a cholesteric slab whose axis is normal to their borders, when a uniform electric field is perpendicularly applied to the helix axis. We found the solution of the boundary value problem for the reflection and transmission of normally incident waves due to the slab. We showed that a left-circularly polarized thin reflection band is immersed in a wider right-circularly polarized band reflection, when the cholesteric is subjected to low amplitude fields. For larger field values, both reflection bands redshift simultaneously as the field increases. A device based on this phenomenon can be used as a electrically tunable universal filter.
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61.30.Dk Continuum models and theories of liquid crystal structure
78.20.Jq Electro-optical effects

Pulse shaping and energy storage capabilities of angularly multiplexed KrF laser fusion drivers

R. H. Lehmberg, J. L. Giuliani, and A. J. Schmitt

J. Appl. Phys. 106, 023103 (2009); http://dx.doi.org/10.1063/1.3174444 (10 pages) | Cited 3 times

Online Publication Date: 23 July 2009

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This paper describes a rep-rated multibeam KrF laser driver design for the 500 kJ Inertial Fusion test Facility (FTF) recently proposed by NRL, then models its optical pulse shaping capabilities using the ORESTES laser kinetics code. It describes a stable and reliable iteration technique for calculating the required precompensated input pulse shape that will achieve the desired output shape, even when the amplifiers are heavily saturated. It also describes how this precompensation technique could be experimentally implemented in real time on a reprated laser system. The simulations show that this multibeam system can achieve a high fidelity pulse shaping capability, even for a high gain shock ignition pulse whose final spike requires output intensities much higher than the ∼ 4 MW/cm2 saturation levels associated with quasi-cw operation; i.e., they show that KrF can act as a storage medium even for pulsewidths of ∼ 1 ns. For the chosen pulse, which gives a predicted fusion energy gain of ∼ 120, the simulations predict the FTF can deliver a total on-target energy of 428 kJ, a peak spike power of 385 TW, and amplified spontaneous emission prepulse contrast ratios IASE/I<3×10−7 in intensity and FASE/F<1.5×10−5 in fluence. Finally, the paper proposes a front-end pulse shaping technique that combines an optical Kerr gate with cw 248 nm light and a 1 μm control beam shaped by advanced fiber optic technology, such as the one used in the National Ignition Facility (NIF) laser.
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28.52.Cx Fueling, heating and ignition
28.52.Lf Components and instrumentation
52.57.Kk Fast ignition of compressed fusion fuels
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.55.Lt Gas lasers including excimer and metal-vapor lasers

Application of nanoparticle-containing laser plasmas for optical harmonic generation

R. A. Ganeev, L. B. Elouga Bom, and T. Ozaki

J. Appl. Phys. 106, 023104 (2009); http://dx.doi.org/10.1063/1.3176493 (5 pages) | Cited 4 times

Online Publication Date: 23 July 2009

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Nanoparticle-containing media can be used for efficient high-order harmonic generation of laser radiation. We present the results of studies of the harmonics generated in the laser-produced plasmas containing Cr2O3, Ag, Cu, and Au nanoparticles. These results are compared with the harmonics generated in the plasma produced on the surface of bulk targets at different delays between the subnanosecond heating prepulse and femtosecond pulse and different intensities of prepulse on the target surface. We discuss the harmonic enhancement, which was observed in the case of nanoparticle-containing plumes with regard to the monoparticle-containing plasmas. Morphological studies of plasma debris confirmed the presence and integrity of nanoparticles in the plumes.
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61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
52.77.-j Plasma applications
78.47.J- Ultrafast spectroscopy (<1 psec)
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Modeling the temperature characteristics of InAs/GaAs quantum dot lasers

Marco Rossetti, Andrea Fiore, Grzegorz Sęk, Carl Zinoni, and Lianhe Li

J. Appl. Phys. 106, 023105 (2009); http://dx.doi.org/10.1063/1.3176499 (8 pages) | Cited 2 times

Online Publication Date: 23 July 2009

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A systematic investigation of the temperature characteristics of quantum dot lasers emitting at 1.3 μm is reported. The temperature dependence of carrier lifetime, radiative efficiency, threshold current, differential efficiency, and gain is measured, and compared to the theoretical results based on a rate equation model. The model accurately reproduces all experimental laser characteristics above room temperature. The degradation of laser characteristics with increasing temperature is clearly shown to be associated to the thermal escape of holes from the confined energy levels of the dots toward the wetting layer and the nonradiative recombination therein.
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42.60.By Design of specific laser systems
42.55.Px Semiconductor lasers; laser diodes
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.63.Kv Quantum dots

Study of polarization properties of light emitted from a-plane InGaN/GaN quantum well-based light emitting diodes

Hung-Hsun Huang and Yuh-Renn Wu

J. Appl. Phys. 106, 023106 (2009); http://dx.doi.org/10.1063/1.3176964 (6 pages) | Cited 16 times

Online Publication Date: 23 July 2009

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This paper discusses the optical characteristics of a nonpolar a-plane InGaN/GaN quantum well with different indium compositions, quantum well widths, and injection carrier densities. The self-consistent Poisson and 6×6 k⋅p Schrödinger solver has been applied to study the band structures in nonpolar a-plane InGaN-based quantum well light emitting diodes (LEDs). We find that the larger indium composition and smaller well width make the energy separation of |Y〉-like state to |Z〉-like state larger, and as a result enhance the polarization ratio of light. However, the polarization ratio decreases as the carrier injection increases, which might be a drawback for high power applications. We have studied the optimization condition for designing the a-plane InGaN quantum well LED for applications, such as liquid crystal display backlight modules and lasers, which would be useful information for device designs.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

Birefringence and absorption coefficients of alpha barium borate in terahertz range

Jingle Liu and X. C. Zhang

J. Appl. Phys. 106, 023107 (2009); http://dx.doi.org/10.1063/1.3176965 (5 pages) | Cited 3 times

Online Publication Date: 23 July 2009

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In this paper we experimentally investigated the birefringence and absorption coefficients of alpha barium borate (α-BBO) crystal in the range of 0.3–10 THz by using a broadband air photonic terahertz time-domain spectrometer in both transmission and reflection modes. Several phonon modes were observed for o and e beams. The highest phonon mode at 6.8 THz has absorption coefficient of 1000 cm−1. The comparison between the optical properties of the α-BBO and beta barium borate crystals showed that their phonon frequencies are different and α-BBO crystal has smaller refractive index, birefringence, and absorption coefficients in low frequency region. The blueshift behavior of the lowest phonon of the α-BBO crystal over the temperature range of 10–293 K has also been characterized.
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78.20.Fm Birefringence
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.-a Optical materials
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Surface plasmon isolator based on nonreciprocal coupling

Juan Montoya, Krishnan Parameswaran, Joel Hensley, Mark Allen, and Rajeev Ram

J. Appl. Phys. 106, 023108 (2009); http://dx.doi.org/10.1063/1.3177341 (6 pages) | Cited 4 times

Online Publication Date: 23 July 2009

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Integrated photonics require optical isolators that achieve low insertion loss and large optical isolation. Here we describe a surface plasmon enhanced optical isolator based on nonreciprocal coupling from a dielectric waveguide coupled to a surface plasmon waveguide. The surface plasmon core consists of a magnetic metal which results in a large nonreciprocity, allowing for device lengths on the order of 50 μm. The analysis and modeling presented here indicate that greater than 30 dB isolation and less than 3 dB insertion loss are possible.
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42.79.-e Optical elements, devices, and systems
84.40.Az Waveguides, transmission lines, striplines
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
42.82.-m Integrated optics

Hybrid polymer-porous silicon photonic crystals for optical sensing

L. De Stefano, L. Rotiroti, E. De Tommasi, I. Rea, I. Rendina, M. Canciello, G. Maglio, and R. Palumbo

J. Appl. Phys. 106, 023109 (2009); http://dx.doi.org/10.1063/1.3177344 (5 pages) | Cited 4 times

Online Publication Date: 23 July 2009

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Porous silicon based one-dimensional photonic crystals, such as Bragg mirror and optical microcavity, has been modified by infiltration of a new biocompatible polymer, an amino functionalized poly(ε-caprolactone) (PCL-NH2), and characterized as optical biochemical sensors. The entrapped polymer adds strong chemical stability to the nanocrystalline matrix on exposure to alkaline solutions preserving the device sensing abilities in monitoring volatile substances and chemical compounds. On the basis of these results, these hybrid structures can be proposed as a high performance platform for biochemical applications.
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42.70.Qs Photonic bandgap materials
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
87.15.R- Reactions and kinetics
87.85.J- Biomaterials

Diffractive imaging using a polychromatic high-harmonic generation soft-x-ray source

Ruben A. Dilanian, Bo Chen, Garth J. Williams, Harry M. Quiney, Keith A. Nugent, Sven Teichmann, Peter Hannaford, Lap V. Dao, and Andrew G. Peele

J. Appl. Phys. 106, 023110 (2009); http://dx.doi.org/10.1063/1.3176976 (5 pages) | Cited 6 times

Online Publication Date: 27 July 2009

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A new approach to diffractive imaging using polychromatic diffraction data is described. The method is tested using simulated and experimental data and is shown to yield high-quality reconstructions. Diffraction data produced using a high-harmonic generation source are considered explicitly here. The formalism can be readily adapted, however, to any short-wavelength source producing a discrete spectrum and possessing sufficient spatial coherence.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
61.05.cp X-ray diffraction

Spectral properties and luminescence lifetime of blue light of solid state cathodoluminescence based on poly[(2-methoxy-5-(2′-ethyl-hexyloxy)phenylene vinylene]

Chong Qu, Zheng Xu, Xiaoguang Ma, and Xurong Xu

J. Appl. Phys. 106, 023111 (2009); http://dx.doi.org/10.1063/1.3176980 (4 pages) | Cited 1 time

Online Publication Date: 27 July 2009

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The heterojunction of poly[(2-methoxy-5-(2′-ethyl-hexyloxy)phenylene vinylene] (MEH-PPV)/SiO2 was prepared based on a layered optimization scheme. In three different voltage ranges, the emission spectra of the device changed. The red light was obtained at low applied voltages. With increasing the applied voltages, a blue light was observed. In the medium of the voltage range, one can see both of these two emissions. These two types of the emission resulted from the bombardment of the luminescent material of the MEH-PPV by the hot electron that accelerated in the layer SiO2, which was named solid state cathodoluminescence. In this paper we investigated the spectral properties, frequency response, and luminescence lifetime of blue light in solid state cathodoluminescence.
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78.60.Hk Cathodoluminescence, ionoluminescence
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Removing the discontinuous shifts in emission wavelength of a chiral nematic liquid crystal laser

S. M. Morris, A. D. Ford, and H. J. Coles

J. Appl. Phys. 106, 023112 (2009); http://dx.doi.org/10.1063/1.3177251 (4 pages) | Cited 4 times

Online Publication Date: 27 July 2009

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The laser wavelength of a band-edge liquid crystal laser is known to vary in a stepwise fashion with temperature. This report describes a method for removing the discontinuous shifts in the laser wavelength by doping a nematic sample with two different chiral dopants which exhibit opposing dependences of the natural pitch on temperature. On cooling from the isotropic phase to room temperature the total shift of the laser wavelength is 15 nm with no discontinuities. This is in contrast to that observed for samples consisting of only one chiral dopant whereby the wavelength shift was as large as 75 nm for the same temperature range.
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42.55.-f Lasers
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.79.Kr Display devices, liquid-crystal devices

Optical and electro-optic properties of micrometric thick lead zirconate titanate films on (Pb0.86,La0.14)TiO3/glass

M. M. Zhu, Z. H. Du, and J. Ma

J. Appl. Phys. 106, 023113 (2009); http://dx.doi.org/10.1063/1.3176897 (4 pages) | Cited 3 times

Online Publication Date: 28 July 2009

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Highly (100)-oriented Pb(Zr0.52,Ti0.48)O3 (PZT) films of up to ∼ 2.4 μm are deposited on the (Pb0.86,La0.14)TiO3 (PLT)-coated amorphous substrate by one cycle of sputtering and annealing. The films possess fibrous columnar nanostructures and vertically grow on the PLT/glass substrate. Microstructure analysis and property characterization indicate that the films possess very promising optical, waveguiding, and electro-optic (EO) properties, as well as low propagation loss. The transparency of >80% in the range of λ = 400–1200 nm and the linear EO coefficient of 341.4 pm/V have been measured in the films. Due to the large EO coefficient and the micrometric thickness, a giant phase retardation of 2.93 rad has been measured under an electric field of 50 kV/mm.
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78.66.Nk Insulators
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.20.Jq Electro-optical effects
77.55.-g Dielectric thin films
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.15.Cd Deposition by sputtering

Photoelectric effects of ultraviolet fast response and high sensitivity in LiNbO3 single crystal

Er-Jia Guo, Jie Xing, Kui-Juan Jin, Hui-Bin Lu, Juan Wen, and Guo-Zhen Yang

J. Appl. Phys. 106, 023114 (2009); http://dx.doi.org/10.1063/1.3183957 (4 pages) | Cited 5 times

Online Publication Date: 29 July 2009

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The photoelectric effects in LiNbO3 (LNO) single crystal have been systematically studied with the two kinds of LNO wafers of tilt of 10° and untilted at the ambient temperature. The ultrafast response photoelectric effect of 120 ps rise time was observed in 10° tilted LNO single crystal with a 266 nm laser pulse of 25 ps duration. The photocurrent responsivity of untilted LNO with an interdigitated electrode of 10 μm finger width and 10 μm interspacing is 17.1 mA/W under the irradiation of 300 nm wavelength UV light at 10 V bias. The noise current under sunlight is only 73 pA at 10 V bias. The experimental results suggest that the LNO single crystal is one of the promising materials for photodetectors working in UV region.
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72.40.+w Photoconduction and photovoltaic effects
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Contribution of positive and negative ions to the electrohydrodynamic force in a dielectric barrier discharge plasma actuator operating in air

J. P. Boeuf, Y. Lagmich, and L. C. Pitchford

J. Appl. Phys. 106, 023115 (2009); http://dx.doi.org/10.1063/1.3183960 (9 pages) | Cited 16 times

Online Publication Date: 29 July 2009

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We present a parametric study of the electrohydrodynamic force generated by surface dielectric barrier discharge plasma actuators in air for sinusoidal voltage waveforms. The simulation results confirm that momentum is transferred from the charged particles to the neutral species in the same direction during both positive and negative parts of the cycle. The momentum transfer is due to positive ions during the positive part of the cycle (electrode above the dielectric layer is the anode), and to negative ions during the negative part of the cycle. The relative contribution of the positive and negative parts of the cycle depends on the voltage amplitude and frequency. The model predicts that the contribution of negative ions tends to be dominant at low voltage frequencies and high voltage amplitudes.
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52.65.-y Plasma simulation
52.80.Tn Other gas discharges
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