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26 Jul 2004

Volume 85, Issue 4, pp. 513-696

Issue Cover Spotlight Figure

Appl. Phys. Lett. 85, 642 (2004); http://dx.doi.org/10.1063/1.1776327 (3 pages)

Zhijun Sun and Hong Koo Kim
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Effects of carbon nanosolids on the electro-optical properties of a twisted nematic liquid-crystal host

Wei Lee, Chun-Yu Wang, and Yu-Cheng Shih

Appl. Phys. Lett. 85, 513 (2004); http://dx.doi.org/10.1063/1.1771799 (3 pages) | Cited 87 times

Online Publication Date: 23 July 2004

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We present results of the electro-optical effect in 90° twisted nematic cells of pristine and doped liquid crystals under an applied dc voltage. The doped cells were fabricated with a minute addition of either buckminsterfullerene C60 or multiwalled carbon nanotubes (CNTs). Investigated were the switching behaviors as well as the hystereses and time evolutions of both the optical transmittance and electrical capacitance of the display samples. It is shown that doping with nanotubes can effectively reduce the dc driving voltage and improve the switching behavior.
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42.70.Df Liquid crystals
61.30.-v Liquid crystals
78.20.Jq Electro-optical effects
42.79.Kr Display devices, liquid-crystal devices

Strong blue photoluminescence from as-fabricated amorphous-Si:H∕SiO2 multilayers

Zhongyuan Ma, Kunji Chen, Xinfan Huang, Jun Xu, Wei Li, Da Zhu, Jiaxin Mei, Feng Qiao, and Duan Feng

Appl. Phys. Lett. 85, 516 (2004); http://dx.doi.org/10.1063/1.1775878 (3 pages) | Cited 5 times

Online Publication Date: 23 July 2004

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Amorphous-Si:H∕SiO2 multilayers were layer-by-layer deposited and in situ plasma oxidized by a plasma-enhanced chemical vapor deposition system. Blue photoluminescence at room temperature was observed from as-fabricated samples without annealing. By controlling the thickness of the amorphous-Si:H sublayer from 4 to 1.5 nm, the photoluminescence peak blueshifts from 466 to 437 nm. Strong and stable photoluminescence could be observed by the naked eye for all the samples. Based on the analysis of microstructure and absorption spectra, the mechanism of the blue photoluminescence was discussed.
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68.65.Ac Multilayers
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Hx Other solid inorganic materials
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.40.Gh Other heat and thermomechanical treatments

Millimeter-wave, terahertz, and mid-infrared transmission through common clothing

J. E. Bjarnason, T. L. J. Chan, A. W. M. Lee, M. A. Celis, and E. R. Brown

Appl. Phys. Lett. 85, 519 (2004); http://dx.doi.org/10.1063/1.1771814 (3 pages) | Cited 37 times

Online Publication Date: 23 July 2004

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This letter reports electromagnetic transmission measurements through cloth samples from eight types of fabrics common in garments and baggage. The transmission at millimeter-wave and terahertz frequencies was measured with a custom ErAs:GaAs tunable photomixing spectrometer. The IR transmission between 3 and 8 μm was measured with a Fourier-transform infrared spectrometer. All samples were usefully transparent at millimeter-wave frequencies (up to 300 GHz) based on a 3 dB criterion, but became progressively opaque at higher frequencies in a highly sample-dependent manner. This is explained by the samples becoming “optically dense” in the THz region, so that the transmission becomes exponentially dependent on sample thickness. The attenuation in the IR region is very high (⩾25 dB) except in two samples (rayon and nylon), whose exceptional transparency (e.g., −12 dB in nylon) is attributed to pores intrinsic to the material.
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41.20.Jb Electromagnetic wave propagation; radiowave propagation
42.25.Bs Wave propagation, transmission and absorption

InP photonic crystal membrane structures: Fabrication accuracy and optical performance

Aimin Xing, Marcelo Darvanco, Daniel J Blumenthal, and Evelyn L Hu

Appl. Phys. Lett. 85, 522 (2004); http://dx.doi.org/10.1063/1.1776336 (3 pages)

Online Publication Date: 23 July 2004

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Two-dimensional photonic crystal membranes with coupled ridge waveguides were fabricated in InP∕InGaAsP by using e-beam lithography and reactive ion etching. The optical transmission characteristics were measured and a photonic band gap with better than 20 dB extinction ratio was observed. The band-gap dependence on radius-to-lattice constant ratio (r∕a) was numerically and experimentally investigated. Predictable, accurate placement of the band edge by varying r∕a is demonstrated.
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81.05.Ea III-V semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
42.70.Qs Photonic bandgap materials

Broad-area laser diode with 0.02 nm bandwidth and diffraction limited output due to double external cavity feedback

Jun Chen, Xiaodong Wu, Jianhong Ge, Andreas Hermerschmidt, and Hans Joachim Eichler

Appl. Phys. Lett. 85, 525 (2004); http://dx.doi.org/10.1063/1.1774248 (3 pages) | Cited 5 times

Online Publication Date: 23 July 2004

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External cavity feedback for a broad-area laser diode (BAL) with antireflection coating on the front facet is investigated experimentally. The feedback is created by a high-reflection mirror and a blazed grating, which reflect two parts of the laser emission back to the BAL, thereby forming an external resonator. When a Fabry–Perot etalon was inserted into the resonator an output beam with a bandwidth of 0.02 nm and power of 150 mW was obtained. The beam diffraction limited factor amounted to M2=1.16.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.79.Dj Gratings
42.79.Wc Optical coatings
42.79.Bh Lenses, prisms and mirrors

Fullerenes surface gratings for liquid crystal alignment

Mara Talarico, Giovanni Carbone, Riccardo Barberi, and Attilio Golemme

Appl. Phys. Lett. 85, 528 (2004); http://dx.doi.org/10.1063/1.1774249 (3 pages) | Cited 9 times

Online Publication Date: 23 July 2004

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We report on the formation of surface structures by photopolymerization of C60 and C70 in isotropic solutions. The structures show the same periodicity of the interference patterns used for photopolymerization and behave as diffraction gratings. Mass spectrometry confirmed that the deposited material contains polymerized fullerenes, while the structure of the deposit was investigated by atomic force microscopy. We have also shown that these periodic structures are useful for inducing mesophase orientation.
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61.48.-c Structure of fullerenes and related hollow and planar molecular structures
42.79.Dj Gratings
68.35.B- Structure of clean surfaces (and surface reconstruction)
82.50.-m Photochemistry

AlGaN-based 280 nm light-emitting diodes with continuous wave powers in excess of 1.5 mW

W. H. Sun, J. P. Zhang, V. Adivarahan, A Chitnis, M. Shatalov, S. Wu, V. Mandavilli, J. W. Yang, and M. A. Khan

Appl. Phys. Lett. 85, 531 (2004); http://dx.doi.org/10.1063/1.1772864 (3 pages) | Cited 28 times

Online Publication Date: 23 July 2004

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We report on AlGaN-based light-emitting diodes over sapphire with peak emission at 280 nm. A modified active layer structure consisting of four multiple quantum wells, addition of an electron blocking magnesium doped p-AlGaN layer, improved contacts along with flip-chip packaging resulted in a cw power of 0.7 mW at 230 mA for a single 200 μm×200 μm device. Flip-chipping four 100 μm×100 μm devices in a parallel configuration improved the dc saturation current and enabled us to obtain a cw power of 1.53 mW (at 450 mA) and a pulse power as high as 24 mW (at 1.5 A). These powers translate to values of 0.36% and 0.12% for the external quantum efficiency and the wall plug efficiency.
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85.60.Jb Light-emitting devices
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)

High-performance photorefractive polymers sensitized by cadmium selenide nanoparticles

Canek Fuentes-Hernandez, Duck Jong Suh, Bernard Kippelen, and Seth R. Marder

Appl. Phys. Lett. 85, 534 (2004); http://dx.doi.org/10.1063/1.1771451 (3 pages) | Cited 27 times

Online Publication Date: 23 July 2004

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We report on efficient and fast hybrid photorefractive polymer sensitized with cadmium selenide (CdSe) quantum dots. The surface of the quantum dots was treated with 4-methylbenzenethiol. This surfactant is responsible for efficient photoinduced charge generation in the composite, leading to fast grating build-up times of 100 ms and below. Overmodulation of the diffraction efficiency was observed at an applied field of 60 V∕μm.
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42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
42.79.Dj Gratings

Interband type-II miniband-to-bound state diode lasers for the midinfrared

C. Mermelstein, J. Schmitz, R. Kiefer, M. Walther, and J. Wagner

Appl. Phys. Lett. 85, 537 (2004); http://dx.doi.org/10.1063/1.1775287 (3 pages) | Cited 5 times

Online Publication Date: 23 July 2004

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A design for midinfrared diode lasers based on interband type-II miniband-to-bound state transitions is proposed and has been demonstrated experimentally. Type-II miniband-to-bound state laser structures emitting at 3.25 μm with active regions consisting of 5 and 10 W periods were grown by solid-source molecular-beam epitaxy and processed into ridge waveguide lasers. Substrate-side down mounted devices with a 10 period active region and uncoated facets could be operated in continuous-wave (cw) mode up to 185 K and as high as 260 K in pulsed mode. A high characteristic temperature of 100 K has been achieved for heat-sink temperatures below 140 K, decreasing to 33 K for the 140 to 185 K interval. At 110 K, a 5 period laser structure exhibited a threshold current density of 177 A∕cm2 and a slope efficiency of 61 mW∕A. Single-ended output powers of 144 mW in cw mode and exceeding 330 mW in pulsed operation were obtained for a substrate-side down mounted 5 period diode laser with high-reflection∕antireflection coated mirror facets, operated at 110 K.
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42.55.Px Semiconductor lasers; laser diodes
81.05.Ea III-V semiconductors
42.79.Wc Optical coatings
68.65.Cd Superlattices
68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Ultrafast all-optical switching at 1.55 μm using an organic multilayer device

Satoshi Tatsuura, Takashi Matsubara, Minquan Tian, Hiroyuki Mitsu, Izumi Iwasa, Yasuhiro Sato, and Makoto Furuki

Appl. Phys. Lett. 85, 540 (2004); http://dx.doi.org/10.1063/1.1775290 (3 pages) | Cited 9 times

Online Publication Date: 23 July 2004

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We report ultrafast all-optical switching at optical communication wavelength using a device with a layered structure containing organic films. Spin-coated layers of di(benzofuranonyl)methanolate (BM) derivative are formed alternately with vacuum evaporated layers of germanium (II) oxide. An optical Kerr shutter is constructed using this BM multilayer with 1.55 μm signal and 1.63 μm gate pulses of 100 fs time durations. As a result, optical switching with signal-to-noise ratio over 20 dB is attained at gate-pulse intensity above 30 pJ∕μm2 and a response time comparable to pulse width is observed. The BM multilayer could be an efficient optical communication device for parallel data processing.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Wc Optical coatings
42.25.Gy Edge and boundary effects; reflection and refraction

Negative effective permeability in polaritonic photonic crystals

Kerwyn Casey Huang, M. L. Povinelli, and John D. Joannopoulos

Appl. Phys. Lett. 85, 543 (2004); http://dx.doi.org/10.1063/1.1775291 (3 pages) | Cited 52 times

Online Publication Date: 23 July 2004

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We find that a two-dimensional photonic crystal composed of polaritonic materials behaves as an effective medium with negative permeability in the micron wavelength range. The resonance in μeff is due to the large values of ϵ(ω) attained near the transverse phonon frequency ωT. The minimal wavelength for achieving an effective permeability less than −1 in a LiTaO3 crystal, obtained by optimizing the rod size and the lattice constant, is around 12 μm, a range previously inaccessible using dielectric metamaterials. For certain dissipation levels, we find that other polaritonic media also exhibit a resonant effect with μeff<−1 for wavelengths ranging from 2 to ∼100 μm.
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71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
63.20.-e Phonons in crystal lattices
77.22.Ch Permittivity (dielectric function)
42.70.Qs Photonic bandgap materials

Multiplex nonresonant pump four-wave mixing

Eun Seong Lee, Dae Sik Choi, Jae Yong Lee, and Jae Won Hahn

Appl. Phys. Lett. 85, 546 (2004); http://dx.doi.org/10.1063/1.1775293 (3 pages) | Cited 4 times

Online Publication Date: 23 July 2004

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We propose a scheme of multiplex nonresonant pump four-wave mixing (NRP-FWM) process which is highly immune to saturation problems. The process is accomplished with two high-intensity pump beams detuned far from the resonance of the sample under investigation and a resonant probe beam as weak as possible not to give rise to nonlinear absorption. Only a single-broadband probe beam is used for the multiplex experiment to detect the electronic swan band spectrum of C2 molecules in a premixed acetylene–oxygen flame. Comparing the signal of the degenerate four-wave mixing (DFWM) experiment on the same sample, we found that the signal level at which the NRP-FWM starts to show saturation is about 250 times higher than in the case of the DFWM.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
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