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7 Jun 2004

Volume 84, Issue 23, pp. 4599-4816

Issue Cover Spotlight Figure

Appl. Phys. Lett. 84, 4650 (2004); http://dx.doi.org/10.1063/1.1759390 (3 pages)

David I. Woodward, Ian M. Reaney, Gaiying Y. Yang, Elizabeth C. Dickey, and Clive A. Randall
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Waveguide networks in three-dimensional layer-by-layer photonic crystals

Curtis Sell, Caleb Christensen, Jason Muehlmeier, Gary Tuttle, Zhi-Yuan Li, and Kai-Ming Ho

Appl. Phys. Lett. 84, 4605 (2004); http://dx.doi.org/10.1063/1.1751212 (3 pages) | Cited 21 times

Online Publication Date: 19 May 2004

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Different types of waveguides and connections between them were fabricated in a three-dimensional (3D) layer-by-layer photonic crystal. The waveguides were formed by removing either a single rod or a series of rod fragments running in three mutually orthogonal directions. This provides the potential of forming a 3D network of waveguide channels with cross sectional dimensions on the order of one lattice constant. The propagation behavior of guided modes in these waveguide networks was probed using a network analyzer. High transmission efficiency (with loss below 0.5 dB) through various waveguide bends and networks with carefully designed geometries has been achieved. © 2004 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers

Ultrafast valence intersubband hole relaxation in InGaN multiple-quantum-well laser diodes

Kian-Giap Gan, Chi-Kuang Sun, Steven P. DenBaars, and John E. Bowers

Appl. Phys. Lett. 84, 4675 (2004); http://dx.doi.org/10.1063/1.1760211 (3 pages) | Cited 7 times

Online Publication Date: 19 May 2004

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The ultrafast carrier dynamics in InGaN multiple-quantum-well (MQW) laser diodes were investigated using a time-resolved bias-lead monitoring technique. From the optical selection rules of TE and TM polarized light, one can selectively excite and probe different valence-subband-to-conduction-subband transitions in the MQW structure with different polarized pump and probe light. The subband structure of the MQW structure of the laser diode was calculated and is verified by electroluminescence measurement. Using this technique, ultrafast valence intersubband hole relaxation processes (τ<0.35 ps) were found to dominate the observed carrier dynamics. © 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.47.-p Spectroscopy of solid state dynamics
78.67.De Quantum wells

Femtosecond optical pulse propagation in subwavelength metallic slits

A. Dechant and A. Y. Elezzabi

Appl. Phys. Lett. 84, 4678 (2004); http://dx.doi.org/10.1063/1.1760215 (3 pages) | Cited 20 times

Online Publication Date: 19 May 2004

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Subwavelength slit arrays embedded in thin silver films demonstrate a marked ability to modify an incident optical pulse’s temporal profile. Ultrashort pulse propagation through these arrays is accompanied by both an increased initial transmission, as well as a subsequent pulse train re-radiation. The role of impulsively excited surface plasmons is investigated as a mechanism for this enhanced transmission and re-radiation. By simply changing the geometrical parameters of the array, pulse reshaping is easily achieved, and in some cases superluminal light flow is observed. © 2004 American Institute of Physics.
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78.66.Bz Metals and metallic alloys
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.40.Kc Metals, semimetals, and alloys
78.30.Er Solid metals and alloys

Observation of resonant energy transfer in Au:CdS nanocomposite

G. H. Ma, J. He, K. Rajiv, S. H. Tang, Y. Yang, and M. Nogami

Appl. Phys. Lett. 84, 4684 (2004); http://dx.doi.org/10.1063/1.1760220 (3 pages) | Cited 15 times

Online Publication Date: 19 May 2004

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Au:CdS nanocomposite film was investigated using femtosecond pump–probe measurement at 800 nm. Time dependence of transmittance shows a two-photon absorption followed by a saturable absorption and recovery process, which clearly demonstrates that resonant energy transfer between CdS and Au nanocomposite systems occur with excitation at 800 nm. In addition, enhancement of the two-photon absorption coefficient in Au:CdS nanocomposite with a factor of more than 6 was observed compared to that of bulk CdS. © 2004 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters

Arbitrary angle waveguiding applications of two-dimensional curvilinear-lattice photonic crystals

Javad Zarbakhsh, Frank Hagmann, Sergei F. Mingaleev, Kurt Busch, and Kurt Hingerl

Appl. Phys. Lett. 84, 4687 (2004); http://dx.doi.org/10.1063/1.1760222 (3 pages) | Cited 24 times

Online Publication Date: 19 May 2004

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We introduce a fresh class of photonic band-gap materials, curvilinear-lattice photonic crystals, whose distinctive feature is that their individual scatterers are arranged in a curvilinear lattice. We show that adhering to some restrictions in the acceptable lattice transformations, one can achieve omnidirectional photonic band gaps for an entire subclass of such structures. We demonstrate, designing an efficient arbitrary-angle waveguide bend, that curvilinear-lattice photonic crystals can be employed for creation of original types of nanophotonic devices. © 2004 American Institute of Physics.
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42.70.Qs Photonic bandgap materials
42.79.Gn Optical waveguides and couplers

Time-domain measurement of picosecond light-pulse propagation in a two-dimensional photonic crystal-slab waveguide

Takashi Asano, Kazuaki Kiyota, Daisuke Kumamoto, Bong-Shik Song, and Susumu Noda

Appl. Phys. Lett. 84, 4690 (2004); http://dx.doi.org/10.1063/1.1760224 (3 pages) | Cited 30 times

Online Publication Date: 19 May 2004

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The optical properties of line-defect waveguides in two-dimensional photonic crystal slabs are investigated using picosecond light pulses. Time-domain waveforms of the light pulse propagating through the waveguide are successfully observed using an autocorrelation method. The group velocity of the waveguide is directly determined from the group delay time for light pulses reflected back and forth along the waveguide. A small group velocity of one-twentieth the speed of light in vacuum is observed at a frequency near the edge of the waveguide mode. The frequency dependence of the group velocity is also measured, and the group-velocity dispersion is found to be larger than that of normal single-mode optical fibers by a factor of 104–105. © 2004 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Deep blue widely tunable organic solid-state laser based on a spirobifluorene derivative

D. Schneider, T. Rabe, T. Riedl, T. Dobbertin, O. Werner, M. Kröger, E. Becker, H.-H. Johannes, W. Kowalsky, T. Weimann, J. Wang, P. Hinze, A. Gerhard, P. Stössel, and H. Vestweber

Appl. Phys. Lett. 84, 4693 (2004); http://dx.doi.org/10.1063/1.1760227 (3 pages) | Cited 22 times

Online Publication Date: 19 May 2004

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We report on amplified spontaneous emission and optically pumped deep blue lasing in the organic spirobifluorene derivative 2,7-bis(biphenyl-4-yl)-2′,7′-di-tert-butyl-9,9′-spirobifluorene. Solid-state lasing is observed in thin films of this material deposited on a distributed-feedback (DFB) grating substrate. The laser wavelength can be tuned from 401.5 to 434.2 nm depending on the grating period of the Bragg reflector. The blue edge of this interval at 401.5 nm makes this laser an extremely short wavelength organic DFB laser. When pumping with a pulsed nitrogen laser at 337 nm, we observe a laser threshold energy density of 83 μJ/cm2. These results render this spiro compound an excellent candidate for blue-emitting diode lasers. © 2004 American Institute of Physics.
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42.55.Rz Doped-insulator lasers and other solid state lasers
85.60.Jb Light-emitting devices

Electroluminescence from self-organized “microdomes”

Olaf Karthaus, Chihaya Adachi, Shigeya Kurimura, and Takahito Oyamada

Appl. Phys. Lett. 84, 4696 (2004); http://dx.doi.org/10.1063/1.1760592 (3 pages) | Cited 15 times

Online Publication Date: 19 May 2004

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The preparation of a self-organized, microstructured organic electroluminescent device is reported. A dewetting process is used to form (sub)micrometer-sized dewetted patches (“domes”) of a hole transport material (tolyl-phenyl-diaminobiphenyl, TPD) on an indium-tin-oxide electrode. The domes are regular in size and spacing. Evaporation of an electron transport material (tris-8-hydroxyquinoline aluminum, Alq3) and an Mg/Ag top electrode leads to a device with electroluminescing spots of micrometer dimensions and a spacing of a few micrometers. © 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.55.-a Thin film structure and morphology

Light coupling with multimode photonic crystal waveguides

Zhi-Yuan Li, Lan-Lan Lin, and Kai-Ming Ho

Appl. Phys. Lett. 84, 4699 (2004); http://dx.doi.org/10.1063/1.1760596 (3 pages) | Cited 17 times

Online Publication Date: 19 May 2004

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We use a transfer-matrix method (TMM) to investigate light coupling into and out of single-end multimode photonic crystal waveguides. Without multiple-reflection complexity, this approach allows for unambiguous quantitative determination of the coupling efficiency of external light into each guided mode and transition among various guided modes. The TMM can provide a powerful analytical tool to understand and design complex multimode photonic crystal waveguides. © 2004 American Institute of Physics.
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42.79.Gn Optical waveguides and couplers
42.70.Qs Photonic bandgap materials

Electromagnetic study of the quality factor of pillar microcavities in the small diameter limit

Ph. Lalanne, J. P. Hugonin, and J. M. Gérard

Appl. Phys. Lett. 84, 4726 (2004); http://dx.doi.org/10.1063/1.1759375 (3 pages) | Cited 24 times

Online Publication Date: 20 May 2004

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A thorough electromagnetic study of pillar microcavities reveals a surprising behavior for their Q factors in the strong confinement limit. Q displays a fast oscillatory variation as a function of the pillar diameter, and reaches values well in excess of the quality factor of the reference planar cavity. This behavior is explained by the hybrid character of the cavity mode in the small diameter limit, which results mainly from the electromagnetic coupling of the HE11 (i.e., fundamental) and EH11 guided modes of the cavity spacer through the associated Bloch modes in the Bragg mirrors. © 2004 American Institute of Physics.
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42.79.-e Optical elements, devices, and systems

Double focusing of hard x rays using combined multilayer and Bragg–Fresnel optics

M. Yasa, Y. Li, C. B. Mammen, J. Als-Nielsen, J. Hoszowska, C. Mocuta, and A. Freund

Appl. Phys. Lett. 84, 4744 (2004); http://dx.doi.org/10.1063/1.1759779 (3 pages) | Cited 3 times

Online Publication Date: 20 May 2004

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A multilayer Bragg–Fresnel x-ray lens (MBFL) structure that combines diffraction and geometric focusing on a single device is presented. With the MBFL, the linear BFL focuses the x-ray beam vertically while the bent multilayer focuses x rays horizontally. This combination eliminates the need for a second mirror in the conventional Kirkpatrick–Baez-based microprobe, which will be advantageous in x-ray fluorescence microscopy as well as microdiffraction applications. The characterization of the MBFL was carried out at the European Synchrotron Radiation Facility and a 1.6 μm (vertical)×12 μm (horizontal) focus was obtained from a 250 μm (V)×200 μm (H) incident beam. With a binary Fresnel lens efficiency of about 35% this yields a gain of almost three orders of magnitude compared to obtaining the same spot size by a raw aperture. © 2004 American Institute of Physics.
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41.50.+h X-ray beams and x-ray optics

Comprehensive analysis of the internal losses in 2.0μm (AlGaIn)(AsSb) quantum-well diode lasers

M. Rattunde, J. Schmitz, R. Kiefer, and J. Wagner

Appl. Phys. Lett. 84, 4750 (2004); http://dx.doi.org/10.1063/1.1760216 (3 pages) | Cited 11 times

Online Publication Date: 20 May 2004

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We have fabricated and characterized high-power 2.0 μm-wavelength (AlGaIn)(AsSb) quantum-well diode lasers emitting a power of 1.7 W in continuous-wave operation and over 9 W in pulsed operation at 300 K heat sink temperature. For potential further improvement of laser performance, the different contribution to the internal losses αi has been analyzed in detail for the present laser structure. Consistent results have been obtained for a series of samples, for which different design parameters were varied systematically: As expected, the losses in the cladding layers are dominated by free carrier absorption in the p-doped cladding. The cross section for free-hole absorption in Al0.84Ga0.16As0.06Sb0.94 is determined to σP = 4.6×10−17 cm2, which is comparable to values reported in the literature for (AlGaIn)(AsP)-based lasers emitting at 1.5 μm. The losses in the active region were found to increase linearly with increasing number of quantum wells at a rate of 1.5 cm−1 per quantum well, whereas the losses in the separate confinement layers are negligible. © 2004 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
81.65.-b Surface treatments

Er3+-doped BaTiO3 nanocrystals for thermometry: Influence of nanoenvironment on the sensitivity of a fluorescence based temperature sensor

Márcio A. R. C. Alencar, Glauco S. Maciel, Cid B. de Araújo, and Amitava Patra

Appl. Phys. Lett. 84, 4753 (2004); http://dx.doi.org/10.1063/1.1760882 (3 pages) | Cited 59 times

Online Publication Date: 20 May 2004

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Frequency upconverted emissions centered at 526 and 547 nm from two thermodynamically coupled excited states of Er3+ doped in BaTiO3 nanocrystals were recorded in the temperature range from 322 to 466 K using a diode laser emitting at 980 nm as the excitation source. The ensemble measurements of the fluorescence intensity ratio (FIR) of the signals at 526 and 547 nm as a function of the temperature showed that the sensitivity (the rate in which the FIR changes with the temperature) of such sensor depends on the size of the nanocrystal. This is explained taking into consideration modifications of nonraditive relaxation mechanisms with the size of the nanocrystals. © 2004 American Institute of Physics.
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78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Hx Other solid inorganic materials
73.22.Lp Collective excitations
07.20.Dt Thermometers

High-efficiency 269 nm emission deep ultraviolet light-emitting diodes

V. Adivarahan, S. Wu, J. P. Zhang, A. Chitnis, M. Shatalov, V. Mandavilli, R. Gaska, and M. Asif Khan

Appl. Phys. Lett. 84, 4762 (2004); http://dx.doi.org/10.1063/1.1756202 (3 pages) | Cited 48 times

Online Publication Date: 21 May 2004

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We report on 269 nm emission deep ultraviolet light-emitting diodes (LEDs) over sapphire. The material quality, device design, and contact processing sequence yielded devices with external quantum efficiencies as high as 0.4% for a pumped pulse current of 200 mA and 0.32% for a dc pump current of 10 mA. For a module of two LEDs connected in series, a record continuous-wave power of 0.85 mW (at 40 mA) and a wall plug efficiency of 0.16% (at 10 mA dc) were measured. © 2004 American Institute of Physics.
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85.60.Jb Light-emitting devices

Diffraction gratings and diffusion coefficient determination of acrylamide and polyacrylamide in sol-gel glass

S. Blaya, A. Murciano, P. Acebal, L. Carretero, M. Ulibarrena, and A. Fimia

Appl. Phys. Lett. 84, 4765 (2004); http://dx.doi.org/10.1063/1.1757024 (3 pages) | Cited 8 times

Online Publication Date: 21 May 2004

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We describe the recording of holographic gratings in a photopolymerizable sol-gel glass based on acrylamide as monomer, triethanolamine as coinitiator, and yellowish eosin as photoinitiator. Although acrylic monomers have been introduced in silica glass by Cheben and Calvo [Appl. Phys. Lett. 78, 1490 (2001)], the well-known acrylamide based composition has not yet been produced by this method. Diffraction efficiencies close to 55% were obtained with an exposure of 8 mJ/cm2. The holographic gratings were not stable and we made use of this instability to determine the diffusion coefficients of acrylamide and polyacrylamide inside this glass. © 2004 American Institute of Physics.
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42.70.Jk Polymers and organics
42.70.Ce Glasses, quartz
42.40.Eq Holographic optical elements; holographic gratings
66.30.J- Diffusion of impurities

Surface plasmon resonant interference nanolithography technique

Xiangang Luo and Teruya Ishihara

Appl. Phys. Lett. 84, 4780 (2004); http://dx.doi.org/10.1063/1.1760221 (3 pages) | Cited 149 times

Online Publication Date: 21 May 2004

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We demonstrate a promising nanofabrication method, used to fabricate fine patterns beyond the diffraction limit, by employing surface plasmon polariton (SPP) resonance. Sub-100 nm lines were patterned photolithographically using surface plasmon polaritonic interference in the optical near field excited by a wavelength of 436 nm. The unperforated metallic mask approach which has corrugated surfaces on both sides is proposed for arbitrary patterning. The corrugated surface of the metallic mask on the illuminated side collects light through SPP coupling, and SPP on the exit side of metallic mask redistributes the light into nanoscale spatial distribution, which can be used to fabricate nanostructures. Preliminary numerical simulations support the experimental results. © 2004 American Institute of Physics.
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81.16.Nd Micro- and nanolithography
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
42.25.Hz Interference

Tunable-focus flat liquid crystal spherical lens

Hongwen Ren, Yun-Hsing Fan, Sebastian Gauza, and Shin-Tson Wu

Appl. Phys. Lett. 84, 4789 (2004); http://dx.doi.org/10.1063/1.1760226 (3 pages) | Cited 57 times

Online Publication Date: 21 May 2004

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A tunable-focus spherical lens using two flat substrates and inhomogeneous electric field over a homogeneous liquid crystal (LC) layer is demonstrated. The top flat substrate has an imbedded spherical indium–tin–oxide (ITO) electrode and the bottom has a planar ITO electrode on its inner surface. The inhomogeneous electric field generates a centrosymmetric gradient refractive index profile within the LC layer which causes the focusing behavior. The focal length of the LC lens can be tuned continuously from infinity to 0.6 m by the applied voltage. © 2004 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
42.70.Df Liquid crystals
61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
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