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20 Aug 2007

Volume 91, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 91, 083504 (2007); http://dx.doi.org/10.1063/1.2772752 (3 pages)

Jeong-M. Choi, Jae Hoon Kim, and Seongil Im
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Fourier plasmonics: Diffractive focusing of in-plane surface plasmon polariton waves

Liang Feng, Kevin A. Tetz, Boris Slutsky, Vitaliy Lomakin, and Yeshaiahu Fainman

Appl. Phys. Lett. 91, 081101 (2007); http://dx.doi.org/10.1063/1.2772756 (3 pages) | Cited 24 times

Online Publication Date: 20 August 2007

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An in-plane Fresnel zone plate (FZP) for focusing surface plasmon polariton (SPP) fields has been designed, fabricated, and tested. The fabricated device consists of 400 nm tall by 5 μm wide amorphous Si-based SPP FZP on an Al film integrated with a pair of two-dimensional nanohole arrays for excitation of the incident and detection of the diffracted SPP fields. Diffracted SPP fields from each Fresnel zone constructively interfere at the expected focal point to produce focusing with threefold intensity enhancement. Temporal and spatial characteristics of the focused SPP fields are studied with time-resolved spatial-heterodyne imaging technique. Good agreement with average power measurements is demonstrated. Diffractive focusing of SPP fields, based on Fourier plasmonics, represents an approach to SPP in-plane microscopy.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Fabrication of organic bulk heterojunction solar cells by a spray deposition method for low-cost power generation

Doojin Vak, Seok-Soon Kim, Jang Jo, Seung-Hwan Oh, Seok-In Na, Juhwan Kim, and Dong-Yu Kim

Appl. Phys. Lett. 91, 081102 (2007); http://dx.doi.org/10.1063/1.2772766 (3 pages) | Cited 74 times

Online Publication Date: 20 August 2007

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The authors report on a spray deposition method as a cost-efficient technique for the fabrication of organic solar cells (OSCs). Active layers of OSCs were fabricated using conventional handheld airbrushes. Although the spray deposited film showed a relatively rougher surface than spin coated ones, pinhole-free and constant thickness films could be obtained. An optimized OSC showed 2.83% of power conversion efficiency and 52% of incident photon to current conversion efficiency even though the device was fabricated in air. The performance of sprayed OSCs was comparable to that of the spin coated devices fabricated in air.
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84.60.Jt Photoelectric conversion

Design of negative-refractive-index materials on the basis of rods with a gradient of the dielectric constant

V. V. Sergentu, V. V. Ursaki, I. M. Tiginyanu, F. Foca, H. Föll, and Robert W. Boyd

Appl. Phys. Lett. 91, 081103 (2007); http://dx.doi.org/10.1063/1.2770964 (3 pages) | Cited 3 times

Online Publication Date: 20 August 2007

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The authors propose an approach to the design of negative-refractive-index materials based on the use of dielectric rods with a gradient of the dielectric constant. A triangular-lattice photonic crystal assembled from multilayer dielectric rods with a refractive index approximating a fish-eye profile is shown to exhibit a negative refractive index in the wavelength range defined by the inequality 0.67<a/λ<0.83, where a is the lattice constant of the photonic crystal. A lens consisting of a plane-parallel slab of such a photonic crystal slab is shown to be able to form an image of a point source in this wavelength range. According to the calculations, particularly high-quality images can be obtained at the wavelength λ = (3/2)a, where the fish-eye dielectric rods scatter the light like a medium with the refractive index equal to −0.85.
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42.25.Gy Edge and boundary effects; reflection and refraction
42.70.Qs Photonic bandgap materials

Enhanced Raman scattering from focused surface plasmons

J. T. Bahns, A. Imre, V. K. Vlasko-Vlasov, J. Pearson, J. M. Hiller, L. H. Chen, and U. Welp

Appl. Phys. Lett. 91, 081104 (2007); http://dx.doi.org/10.1063/1.2759985 (3 pages) | Cited 11 times

Online Publication Date: 20 August 2007

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Surface plasmon polaritons launched at concentric arcs can be focused into a subwavelength wide focal spot of high near-field light intensity. The focused plasmons give rise to enhanced Raman scattering from R6G molecules placed in the focal area. By exploiting the polarization dependence of the focusing the authors establish an enhancement of the Raman signal by a factor of ∼ 6. The results show that focusing of propagating surface plasmons on flat metal surfaces may be an alternative to localized plasmons on metal nanostructures for achieving enhanced Raman scattering. In particular, a flat metal substrate enables better control over the local electric fields and the placement of analyte molecules, and, therefore, ultimately better fidelity of Raman spectra.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.30.-j Infrared and Raman spectra
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures

Beam shaping and effective guiding in the bulk of photorefractive crystals through linear beam dynamics

E. DelRe, A. Pierangelo, E. Palange, A. Ciattoni, and A. J. Agranat

Appl. Phys. Lett. 91, 081105 (2007); http://dx.doi.org/10.1063/1.2772177 (3 pages) | Cited 4 times

Online Publication Date: 20 August 2007

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The authors demonstrate a technique to optically imprint through linear beam propagation an index pattern in the bulk of a photorefractive crystal capable of beam reshaping and waveguiding. The procedure is based on the separation into two distinct phases of the photosensitive and refractive response, so that light is in all cases undergoing only linear propagation. When saturation in the response becomes dominant, the scheme is able to achieve both one-dimensional and two-dimensional waveguiding. The result allows the straightforward writing of multiwaveguide circuits, where traditional schemes based on spatial solitons are in practice burdened by nonlinearity.
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42.82.Et Waveguides, couplers, and arrays
42.70.Gi Light-sensitive materials

Narrow ( ≈ 4 meV) inhomogeneous broadening and its correlation with confinement potential of pyramidal quantum dot arrays

K. Leifer, E. Pelucchi, S. Watanabe, F. Michelini, B. Dwir, and E. Kapon

Appl. Phys. Lett. 91, 081106 (2007); http://dx.doi.org/10.1063/1.2772178 (3 pages) | Cited 10 times

Online Publication Date: 20 August 2007

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The inhomogeneous broadening in the luminescence spectra of ordered arrays of pyramidal GaAs/AlGaAs semiconductor quantum dots (QDs) was studied as a function of the dot size. Dot arrays with inhomogeneous broadening as small as 4.1 meV and a corresponding ground state to first excited state transition separation of 28 meV were obtained. By evaluating the QD energy levels using a multiband k∙p model, the authors estimated that the observed inhomogeneous broadening corresponds to dot height fluctuations of about 1–2 ML across the array.
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78.66.Fd III-V semiconductors
78.67.Hc Quantum dots
78.55.Cr III-V semiconductors

InGaAs single photon avalanche detector with ultralow excess noise

Kai Zhao, Arthur Zhang, Yu-hwa Lo, and William Farr

Appl. Phys. Lett. 91, 081107 (2007); http://dx.doi.org/10.1063/1.2772231 (3 pages) | Cited 11 times

Online Publication Date: 20 August 2007

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An InGaAs single photon avalanche detector capable of sub-Geiger mode (Photomultiplier-tube-like) operation is reported. The device achieves a stable gain at around 106. The gain fluctuation is greatly suppressed through a self-quenching effect, thus an equivalent excess noise factor as low as 1.001 is achieved. In the photon counting experiment, the device is operated in the nongated mode under a dc bias. Because of its unique characteristics of self-quenching and self-recovery, no external quenching circuit is needed. The device shows a single photon response of around 30 ns and a self-recovery time of about 300 ns.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
29.40.-n Radiation detectors

Amplified spontaneous emission and lasing properties of bisfluorene-cored dendrimers

J. C. Ribierre, G. Tsiminis, S. Richardson, G. A. Turnbull, I. D. W. Samuel, H. S. Barcena, and P. L. Burn

Appl. Phys. Lett. 91, 081108 (2007); http://dx.doi.org/10.1063/1.2761833 (3 pages) | Cited 19 times

Online Publication Date: 21 August 2007

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A study of the amplified spontaneous emission (ASE) properties of three bisfluorene-cored dendrimers in the solid state is reported. The results show that the dendron type has a strong impact on the photoluminescence quantum yield and affects the ASE threshold, the optical gain, and loss coefficients. Optically pumped distributed feedback lasers operating in the blue spectral region were fabricated by spin coating the dendrimer films on top of a two-dimensional corrugated fused silica substrate. A best lasing threshold of 4.5 μJ/cm2 and a slope efficiency of 8.3% were obtained, which demonstrate the high potential of these materials for laser applications.
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78.45.+h Stimulated emission
78.55.Kz Solid organic materials
42.55.-f Lasers
42.70.-a Optical materials
42.60.By Design of specific laser systems

Coherent terahertz detection with a large-area photoconductive antenna

F. Peter, S. Winnerl, S. Nitsche, A. Dreyhaupt, H. Schneider, and M. Helm

Appl. Phys. Lett. 91, 081109 (2007); http://dx.doi.org/10.1063/1.2772783 (3 pages) | Cited 8 times

Online Publication Date: 21 August 2007

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We present a nonresonant photoconductive terahertz detection antenna suitable for detection of both focused and unfocused terahertz radiations. Our system consists of a scalable terahertz emitter based on an interdigitated electrode structure and a detection antenna with similar electrode geometry. While the emitter is fabricated on semi-insulating GaAs we compare different ion-implanted GaAs-based detection antennas. We studied the dependence of the measured terahertz signal on the power and spot size of the gating laser pulse. In addition we compare the performance of our antenna with that of electro-optical sampling.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
85.25.Pb Superconducting infrared, submillimeter and millimeter wave detectors
85.60.Bt Optoelectronic device characterization, design, and modeling
84.40.Ba Antennas: theory, components and accessories

Photorefractive organic material for optical thresholding

M. Talarico, R. Termine, and A. Golemme

Appl. Phys. Lett. 91, 081110 (2007); http://dx.doi.org/10.1063/1.2771531 (3 pages) | Cited 1 time

Online Publication Date: 22 August 2007

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The authors studied the photorefractive performance of bistable surface stabilized chiral smectic C cells doped with C70. Diffraction efficiency strongly depends on the combination of (a) the application time of the electric field used during the writing process and (b) light intensity. By choosing the conditions of the writing process, gratings with high efficiency can form only for certain levels of light intensity.
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42.70.Gi Light-sensitive materials
42.70.Jk Polymers and organics
42.70.Df Liquid crystals
42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.30.-d Imaging and optical processing
61.30.-v Liquid crystals

Dielectric stripes on gold as surface plasmon waveguides: Bends and directional couplers

B. Steinberger, A. Hohenau, H. Ditlbacher, F. R. Aussenegg, A. Leitner, and J. R. Krenn

Appl. Phys. Lett. 91, 081111 (2007); http://dx.doi.org/10.1063/1.2772774 (3 pages) | Cited 46 times

Online Publication Date: 22 August 2007

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Dielectric thin film stripes on a metal surface can be applied as surface plasmon (SP) waveguides. Here, the authors demonstrate experimentally that such structures can be used to build SP waveguide bends and couplers. On one hand, they show that SP transmission through a waveguide bend can be maximized by assuming the trade-off of propagation and bend induced radiation losses. On the other hand, the authors combine two waveguides to form a directional SP coupler.
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42.79.Gn Optical waveguides and couplers
77.55.-g Dielectric thin films

Effect of facet angle on effective facet reflectivity and operating characteristics of quantum dot edge emitting lasers and superluminescent light-emitting diodes

Z. Y. Zhang, I. J. Luxmoore, C. Y. Jin, H. Y. Liu, Q. Jiang, K. M. Groom, D. T. Childs, M. Hopkinson, A. G. Cullis, and R. A. Hogg

Appl. Phys. Lett. 91, 081112 (2007); http://dx.doi.org/10.1063/1.2772845 (3 pages) | Cited 8 times

Online Publication Date: 22 August 2007

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The authors report the creation of low reflectivity angled facets by focused-ion-beam postfabrication etching. A method to directly measure the effective facet reflectivity of such facets, utilizing gain saturation effects in the quantum dots is described. The reflectivities of the angled facets are shown to decrease by increasing the facet angle from 0° to 15°. With a reflectivity of <1×10−6 obtained for a facet with a 15° angle, allowing quantum dot superluminescent light-emitting diodes to be fabricated. The use of different angled facets to control the emission wavelength of both quantum dot lasers and superluminescent light-emitting diodes is outlined.
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85.60.Jb Light-emitting devices
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Blue electroluminescent properties of poly(N-arylcarbazole-2,7-ylene) homopolymers

Norifumi Kobayashi and Masashi Kijima

Appl. Phys. Lett. 91, 081113 (2007); http://dx.doi.org/10.1063/1.2773740 (3 pages) | Cited 7 times

Online Publication Date: 22 August 2007

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To investigate electroluminescence behaviors of a series of poly(N-phenyl-2,7-carbazole)s having 2-ethylhexyloxy (PEHOC), triethylene oxide (PTEOC), or diphenylamino (PDPAC) group at the N-phenyl portion, single-layer devices of organic light-emitting diode using the as-prepared polymer as the emitting layer material were fabricated. All the devices showed brightness above 1000 cd/m2 at 10 V with moderate luminous efficiencies. The PEHOC (m, p-disubstituted) and PTEOC (p-substituted) devices exhibited a trivial but undesirable redshift due to electro-oxidation and aggregation of the polymer under high driving voltages, while the PDPAC (m-substituted) device displayed a blue electroluminescence [λmax = 450 nm and CIE (x,y) = 0.159,0.173] which had no difference compared with the photoluminescence spectrum.
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85.60.Jb Light-emitting devices

Stress-induced birefringence in siloxane polymer waveguides

Shashikant G. Hegde and Suresh K. Sitaraman

Appl. Phys. Lett. 91, 081114 (2007); http://dx.doi.org/10.1063/1.2773753 (3 pages) | Cited 1 time

Online Publication Date: 22 August 2007

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With the increasing use of siloxane polymers as optical waveguide material, there is a need to understand and thus to reduce the stress-induced birefringence in siloxane polymer due to thermal processing and material property mismatch. In this letter, stress-optical coefficients of a siloxane polymer material are experimentally determined by measuring the refractive indices of the uncured and cured siloxane polymer material in two orthogonal directions. Employing such coefficients and temperature- and direction-dependent material properties, a numerical modeling method is presented to determine the stress-induced birefringence in an optical waveguide system. In the case study that is presented in this work, it is seen that the coefficient of thermal expansion of the planarization layer has the maximum effect on the birefringence, and it is possible to reduce the stress-induced birefringence by reducing the property mismatch between the planarization layer and the core layer. The outlined methodology is generic in nature and can be applied to different waveguide geometries, planarization materials, and substrate/board materials to assess how stress-induced birefringence can be minimized for a given polymer core material.
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42.70.Jk Polymers and organics
42.79.Gn Optical waveguides and couplers
42.25.Lc Birefringence
07.20.-n Thermal instruments and apparatus
07.60.Hv Refractometers and reflectometers

Continuous-wave stimulated emission and optical amplification in europium (III)-aluminum nanocluster-doped polymeric waveguide

K. Yamashita, H. Taniguchi, S. Yuyama, K. Oe, J. Sun, and H. Mataki

Appl. Phys. Lett. 91, 081115 (2007); http://dx.doi.org/10.1063/1.2773933 (3 pages) | Cited 4 times

Online Publication Date: 23 August 2007

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The authors have demonstrated stimulated emission from polymer-based planar waveguide doped with Eu–Al nanoclusters under continuous-wave optical pumping. For the waveguide sample with a nanocluster concentration of 5.0 wt %, amplified spontaneous emission was observed in the spectra of the light decoupled from the waveguide edge under a pumping density of 0.16–1.55 W/cm2. The optical gain coefficient was 0.92 mm−1 when pumped at 1.55 W/cm2. The well-suppressed concentration quenching and multiphonon quenching may cause the high-gain and low-threshold optical amplification. These results show that the Eu–Al nanocluster is a promising material for polymer-based solid-state lasers and waveguide-type optical amplifiers.
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42.79.Gn Optical waveguides and couplers
42.82.Et Waveguides, couplers, and arrays
78.45.+h Stimulated emission

Modified triphenylmethane dye for the efficient nonlinear generation of light in nanostructured materials

Xavier Vidal, Jose Raul Herance, Jordi Marquet, Jose Luis Bourdelande, and Jordi Martorell

Appl. Phys. Lett. 91, 081116 (2007); http://dx.doi.org/10.1063/1.2773934 (3 pages) | Cited 3 times

Online Publication Date: 23 August 2007

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Many nonlinear photonic materials exhibit large extinction coefficients as a result of the active molecule absorption band. The authors show that it is possible to redshift the absorption resonance of such material without a significant alteration of the nonlinear response. A drastic reduction in the absorption coefficient at the wavelength of interest is obtained by adding a triple bond unit to these active molecules. In such case, the nonlinear optical response of a photonic material would be much better than the one obtained with the original molecule or by following the conventional procedure of adding a double bond unit instead.
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42.70.Qs Photonic bandgap materials
42.70.Mp Nonlinear optical crystals
42.70.Jk Polymers and organics
42.65.Yj Optical parametric oscillators and amplifiers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Effect of metal organic vapor phase epitaxy growth conditions on emission wavelength stability of 1.55 μm quantum dot lasers

D. Franke, M. Moehrle, J. Boettcher, P. Harde, A. Sigmund, and H. Kuenzel

Appl. Phys. Lett. 91, 081117 (2007); http://dx.doi.org/10.1063/1.2773971 (3 pages) | Cited 9 times

Online Publication Date: 23 August 2007

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InAs quantum dots (QDs) on InP were implemented as active layers in laser structures completely grown by metal organic vapor phase epitaxy (MOVPE). In laser structures due to growth of the upper InP cladding layers onto the QDs, a marked blueshift of the emission wavelength and a simultaneous degradation of photoluminescence intensity were observed. This behavior was systematically investigated using thermal treatment to simulate the growth of the upper cladding layer. Using an adequate growth procedure emission behavior was achieved that has proven to be fairly insensitive to over-/regrowth steps. Broad-area 1.55 μm emitting laser devices were fabricated by incorporating seven QD layers in an all-MOVPE grown structure. Transparency current densities per dot layer of 80 A cm−2 were achieved which is close to values of multiple quantum well lasers processed in the same way.
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42.55.Px Semiconductor lasers; laser diodes
85.40.Sz Deposition technology

Surface texturing by solution deposition for omnidirectional antireflection

Meng Tao, Weidong Zhou, Hongjun Yang, and Li Chen

Appl. Phys. Lett. 91, 081118 (2007); http://dx.doi.org/10.1063/1.2775805 (3 pages) | Cited 20 times

Online Publication Date: 24 August 2007

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Surface texturing by solution deposition has been developed for antireflection in solar cells. The surface texture is formed by a monolayer of microscale silica particles partially immersed into a spin-on-glass film with a thickness less than the height of the particles. When the silica particles have a spherical shape, the low reflectance from this coating becomes omnidirectional, a desirable feature in fixed-orientation solar panels. It has been experimentally found that the coating improves the transmittance of a quartz wafer in the spectral range of 400–1100 nm and in the incident-angle range of surface normal to at least 30°. The surface texture can be applied to different types of solar cells as an add-on coating.
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42.79.Wc Optical coatings
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
84.60.Jt Photoelectric conversion

Direct real-time observation of catastrophic optical degradation in operating semiconductor lasers using scanning tunneling microscopy

R. J. Cobley, K. S. Teng, M. R. Brown, S. P. Wilks, and P. Rees

Appl. Phys. Lett. 91, 081119 (2007); http://dx.doi.org/10.1063/1.2775049 (3 pages) | Cited 3 times

Online Publication Date: 24 August 2007

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Cross-sectional scanning tunneling microscopy is performed on operating semiconductor quantum well laser devices to reveal real time changes in device structure. Low and nominally doped capping regions adjacent to the quantum well active region are found to heat under normal operating conditions. The increase in anion-vacancy defect formation and the generation of surface states pins the Fermi level at the surface and begins the process of catastrophic optical degradation which eventually destroys the device. The technique has implications for the study of defect generation and in-operation changes in all nanostructures.
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42.55.Px Semiconductor lasers; laser diodes

Single bump, two-color quantum dot camera

E. Varley, M. Lenz, S. J. Lee, J. S. Brown, D. A. Ramirez, A. Stintz, S. Krishna, Axel Reisinger, and Mani Sundaram

Appl. Phys. Lett. 91, 081120 (2007); http://dx.doi.org/10.1063/1.2775087 (3 pages) | Cited 21 times

Online Publication Date: 24 August 2007

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The authors report a two-color, colocated quantum dot based imaging system used to take multicolor images using a single focal plane array (FPA). The dots-in-a-well (DWELL) detectors consist of an active region composed of InAs quantum dots embedded in In.15Ga.85As quantum wells. DWELL samples were grown using molecular beam epitaxy and fabricated into 320×256 focal plane arrays with indium bumps. The FPA was then hybridized to an Indigo ISC9705 readout circuit and tested. Calibrated blackbody measurements at a device temperature of 77 K yield midwave infrared and long wave infrared noise equivalent difference in temperature of ∼ 55 and 70 mK.
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81.07.Ta Quantum dots
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
07.68.+m Photography, photographic instruments; xerography
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Spatial confinement effects in laser-induced breakdown spectroscopy

X. K. Shen, J. Sun, H. Ling, and Y. F. Lu

Appl. Phys. Lett. 91, 081501 (2007); http://dx.doi.org/10.1063/1.2770772 (3 pages) | Cited 9 times

Online Publication Date: 20 August 2007

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The spatial confinement effects in laser-induced breakdown of aluminum (Al) targets in air have been investigated both by optical emission spectroscopy and fast photography. A KrF excimer laser was used to produce plasmas from Al targets in air. Al atomic emission lines show an obvious enhancement in the emission intensity when a pair of Al-plate walls were placed to spatially confine the plasma plumes. Images of the Al plasma plumes showed that the plasma plumes evolved into a torus shape and were compressed in the Al walls. The mechanism for the confinement effects was discussed using shock wave theory.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
82.50.-m Photochemistry
52.38.Mf Laser ablation
52.35.Tc Shock waves and discontinuities

Production of high-current heavy ion jets at the short-wavelength subnanosecond laser-solid interaction

J. Badziak, A. Kasperczuk, P. Parys, T. Pisarczyk, M. Rosiński, L. Ryć, J. Wołowski, S. Jabłoński, R. Suchańska, E. Krousky, L. Láska, K. Mašek, M. Pfeifer, J. Ullschmied, L. J. Dareshwar, et al.

Appl. Phys. Lett. 91, 081502 (2007); http://dx.doi.org/10.1063/1.2771378 (3 pages) | Cited 4 times

Online Publication Date: 20 August 2007

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Generation of ion fluxes at the interaction of 70 J, 0.438 μm subnanosecond laser pulse with a massive planar target has been investigated. It is shown that after proper optimization of high-Z (Cu or Ta) target irradiation, a highly collimated heavy ion jet of the ion current >100 A and the ion current density >1 A/cm2 at 1 m from the target can be produced with an energy conversion efficiency nearly 10%.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Fi Transport properties
52.38.Ph X-ray, γ-ray, and particle generation

Enhanced microwave transmission through quasicrystal hole arrays

N. Papasimakis, V. A. Fedotov, A. S. Schwanecke, N. I. Zheludev, and F. J. García de Abajo

Appl. Phys. Lett. 91, 081503 (2007); http://dx.doi.org/10.1063/1.2773763 (3 pages) | Cited 14 times

Online Publication Date: 23 August 2007

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The authors report on the observation of enhanced microwave transmission through quasiperiodic hole arrays in metal films. The fraction of transmitted light reaches 50% in a self-standing metal film and approaches 90% when the film is sandwiched between thin dielectric slabs, while the holes occupy only 10% of the sample area. The maximum transmission exhibits a Breit-Wigner resonance behavior, accompanied by zero phase change and rendering the film almost invisible over a wide frequency range. The extraordinary transmission phenomenon is interpreted in terms of resonances in the self-consistent interaction between holes, which are represented by effective electric and magnetic dipoles.
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78.66.Bz Metals and metallic alloys
61.44.Br Quasicrystals
68.55.-a Thin film structure and morphology

Impedance matching for an asymmetric dielectric barrier discharge plasma actuator

Kunwar Pal Singh and Subrata Roy

Appl. Phys. Lett. 91, 081504 (2007); http://dx.doi.org/10.1063/1.2773932 (3 pages) | Cited 6 times

Online Publication Date: 23 August 2007

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A typical dielectric barrier discharge plasma actuator requires a power supply capable of delivering power at a frequency range of several kilohertz and a rms voltage up to 20 kV. An impedance mismatch resulting from the absence of a matching network causes a large reflected power from the plasma actuator back to the power supply. This does not contribute to plasma formation and requires an expensive over-rated power supply. The authors suggest an impedance matching network for a realistic asymmetric dielectric barrier discharge plasma actuator with a virtual electrode.
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52.75.-d Plasma devices
52.80.-s Electric discharges

Additional focusing of a high-intensity laser beam in a plasma with a density ramp and a magnetic field

Devki Nandan Gupta, Min Sup Hur, and Hyyong Suk

Appl. Phys. Lett. 91, 081505 (2007); http://dx.doi.org/10.1063/1.2773943 (3 pages) | Cited 6 times

Online Publication Date: 23 August 2007

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Propagation of a high power Gaussian laser beam through a plasma with a density ramp where a magnetic field is present has been investigated. The spot size of the laser beam decreases as the beam penetrates into the plasma due to the role of a plasma density ramp. The studies show that the combined effect of a plasma density ramp and a magnetic field enhances the self-focusing property of the laser beam. Both factors not only reduce the spot size of the laser beam but also maintain it with only a mild ripple over several Rayleight lengths.
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52.38.Hb Self-focussing, channeling, and filamentation in plasmas
52.38.Dx Laser light absorption in plasmas (collisional, parametric, etc.)
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
52.25.Xz Magnetized plasmas
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