Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session J35: Focus Session: Emerging Materials and Devices II |
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Sponsoring Units: FIAP DMP Chair: Leonid Tsybeskov, New Jersey Institute of Technology Room: Morial Convention Center 227 |
Tuesday, March 11, 2008 11:15AM - 11:51AM |
J35.00001: Silicon Photonics: An Affordable Solution for Communications at Terabit Data Rates Invited Speaker: Over the past 20 years, laser sources, filters, modulators and detectors have followed the example of lithographic miniaturization provided by the silicon microelectronics industry. Optical devices with sizes smaller than the wavelength of light have evolved, and can be integrated into compact photonic systems. More recently, with the introduction of silicon on insulator (SOI) wafers and with the capability to pattern silicon with 100nm resolution, it has become possible to build high quality optical devices within silicon fabrication lines. Using the very same procedures as silicon electronics inexpensive optical and electronic components can thereby be constructed side by side on 8 inch wafers. This capability enables tuning and switching of complex optical systems with on-chip electronics, as well as data communications at Terabit/second bit-rates, all available at the less than 10 dollars per square centimeter cost traditional in the silicon fabrication industry. By integration of nonlinear optical materials with silicon and the fabrication of high index contrast structures that concentrate light to approximately 1 GW per square centimeter fields, it is also possible to fabricate very fast optical modulators and switches that can operate at THz frequencies. In this presentation, we review the present capabilities of ``silicon photonics'' and examine the prospect for inexpensive silicon photonic devices to switch, generate and detect THz frequencies. [Preview Abstract] |
Tuesday, March 11, 2008 11:51AM - 12:03PM |
J35.00002: Coherence and polarization properties of individual antenna-like metal nanowires Levente Klein, Hendrik Hamann, Yat-Yin Au, Snorri Ingvarsson We investigate the coherence and polarization properties of thermal radiation from resistively heated individual metal nanowires. The high aspect ratio nanowires are fabricated by e-beam lithography with widths from 60 nm up to 2 um, dimensions well below the wavelength of the emitted thermal radiation. The thermal radiation from the metal nanowires has a spatial orientation perpendicular to the substrate with a radiation patterns similar to an electric dipole radiation. Furthermore, the emitted thermal radiation becomes highly polarized as the width of the nanowires decreases. For very narrow nanowires the polarization is oriented along the long axis of the nanowires while its orientation becomes perpendicular to the long axis for widths above 1 um. While in the far field the thermal radiation is incoherent, in the near field the emitted thermal radiation becomes coherent and interference fringes are observed as a mirror approaches the nanowire at gaps smaller than 20 um. The interference fringes are generated by the thermal radiation from the nanowire and its image in the mirror with an increased fringe visibility for narrower nanowires. A lower bound for the coherence length for thermal radiation is 30 um for very narrow metal nanowires. [Preview Abstract] |
Tuesday, March 11, 2008 12:03PM - 12:15PM |
J35.00003: Fullerene microcrystals under pressure Murilo L. Tiago, Fernando A. Reboredo Solid buckminsterfullerene (C$_{60}$) is known to be very soft, with a large number of crystalline phases that can be accessed by temperature or pressure. External pressure reduces the intermolecular distance, which affects the electronic structure in three ways: by increasing the overlap between molecular orbitals on neighbor molecules, by inducing additional chemical bonds between molecules, and by deforming the molecular structure. Having an exciton gap that is sensitive to pressure suggests that C$_{60}$ can be used as active element in an optical pressure gauge: a device that can detect pressure dynamically on the material from the red-shift of its optical spectrum. Using first-principles many-body theories, we calculate the optical gap of solid C$_{60}$ and its pressure dependence. We also analyze the dependence of optical gap with deformations in the molecule. Our calculations are based on solving the Bethe-Salpeter for electron-hole excitations. The electron self-energy is calculated within the GW approximation. We use pseudopotential density-functional theory to determine the electronic structure of C$_{60}$ in its ground state. [Preview Abstract] |
Tuesday, March 11, 2008 12:15PM - 12:27PM |
J35.00004: Nanowire waveguide made of extremely anisotropic metamaterials Y.J. Huang, W.T. Lu, S. Sridhar We consider wave propagation along a cylindrical fiber with anisotropic optical property. Exact solutions are obtained for all the modes. For extremely anisotropic cylinder where the transverse permittivity is negative while the longitudinal permittivity is positive, only transverse magnetic and hybrid modes will propagate on the waveguide. At a given frequency the waveguide support infinite number of eigenmodes. For the TM modes, there exists at most one forward wave. The rest of them are backward waves. These waveguides can be used as filter and phase shifter in integrated optical circuits. [Preview Abstract] |
Tuesday, March 11, 2008 12:27PM - 12:39PM |
J35.00005: Doping Poly(p-phenylene vinylene) with Phosphomolybdate through Layer-by-Layer Fabrication for Optoelectronic Applications Chris Nelson, Bin Wang Poly(p-phenylene vinylene) (PPV) mulilayers have been prepared from its cationic precursor via the layer-by-layer deposition. The photoluminescence (PL) and film thickness of the multilayers have been examined via fluorimetry and atomic force microscopy. The PL of the multilayers has been observed that is consistent with the literature results. When phosphomolybdate PMo12 is incorporated into the multilayer structure, PL quenching is detected that is proportional to the amount of PMo12 used. The quenching is interpreted as exciton diffusion through the polymer multilayers, followed by exciton dissociation at the polymer/PMo12 interface. We show that the modeling used for calculating the PL intensities derived from inorganic semiconductors is also applicable to conjugated polymers. According to the model, an exciton diffusion length is found to be 11.5$\pm$0.4 nm. [Preview Abstract] |
Tuesday, March 11, 2008 12:39PM - 12:51PM |
J35.00006: Scattering studies of stacked polymer/liquid crystal composites Sameet Shriyan, Kashma Rai, Adam Fontecchio In this work we investigate light scattering from stacked polymer/liquid crystal composite films on several different substrates. Effect of different substrates such as glass, PET and PMMA coated with conductive layers such as Indium-Tin-Oxide (ITO) and PEDOT:PSS conducting polymer are analyzed using scattering and wavefront measurements. Scattering of light in both transmission and reflection mode is measured as a function of angle and its effect using different substrate layers coated with different conducting layers is analyzed. Shack Hartmann wavefront sensor is used to characterize the effect of various substrate and conducting layers on the transmitted wavefront quality in both transmission and reflection mode. Optimal stack length at which the scattering and wavefront degradations are at acceptable levels is derived form the scattering and wavefront measurements. Spectrometry results show notch formations at different wavelength and the effect on transmitted baseline reduction due to scattering using different substrates. SEM imaging shows the effect of different substrates and conducting layers on the formation and quality of gratings along with the LC droplet size which contributes to scattering. Optical path and stack length reduction of up to 45{\%} for a stack of 10 layers is confirmed. [Preview Abstract] |
Tuesday, March 11, 2008 12:51PM - 1:03PM |
J35.00007: Broadband Wavelength Spanning Holographic Polymer Dispersed Liquid Crystals Kashma Rai, Sameet Shriyan, Adam Fontecchio Broadened interaction wavelength of holographic polymer dispersed liquid crystals (HPDLCs) have extensive applications in beam steering for instrument clusters, hyperspectral imaging, wavelength filtering and construction of lightweight optics. A novel simultaneous time and spatial multiplexing formation configuration is proposed here, to increase narrow wavelength reflecting notch to broad range wavelength spanning device. HPDLC films have electro-optic controllability by applying field. No moving parts, light weight, small footprint compared to prisms and lenses, high color purity make the broadband wavelength HPDLCs desirable for the above applications. Varying the incident laser beam exposure angles using motorized rotating stage, during formation is the key step here for their formation in a single medium. The fabricated broadband wavelength sensitive HPDLCs are characterized for the uniformity of the reflected peak and electro optic response. Their output wavefront is analyzed using wavefront analysis technique. [Preview Abstract] |
Tuesday, March 11, 2008 1:03PM - 1:15PM |
J35.00008: 1.54 $\mu$m emitters based on monolithic integration of Er doped GaN with nitride emitters Rajendra Dahal, Cris Ugolini, Ashok Sedhain, Jingyu Lin, Hongxing Jiang, John Zavada Er doped III-nitride semiconductors have emerged as very promising materials for applications in photonic devices due to their novel optical and physical properties. Optoelectronic and photonic devices based on Er doped GaN are expected to meet the demand for next generation telecommunication devices due to efficient and temperature stable 1.54 $\mu $m emission from Er doped GaN. We report here on the successful fabrication of a chip size current injected 1.54 $\mu $m emitters by monolithic integration of Er doped GaN epilayers with 365 nm nitride light-emitting diodes (LEDs). Er doped GaN and In$_{0.06}$Ga$_{0.94}$N epilayers were grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD). The photoluminescence excitation (PLE) and absorption spectra of these epilayrs were investigated to understand the 1.54 $\mu $m emission mechanism. A strong correlation between PLE and absorption spectra near the energy bandgap of host nitride epilayers suggest that band to band absorption and subsequent energy transfer to Er ion for 1.54 $\mu $m emission is a much more effective excitation mechanism compared to the direct absorption by Er ion. The success opens the possibility for next generation IR integrated photonic devices such as emitters, detectors, and optical amplifiers. [Preview Abstract] |
Tuesday, March 11, 2008 1:15PM - 1:27PM |
J35.00009: Synthesis of Metal Silicides by Low Energy Ion Implantation Prakash Poudel, Lee Mitchell, Jianyou Li, Brian Gorman, Arup Neogi, Bibhudutta Rout, Jerome Duggan, Floyd McDaniel A 55KeV Osmium beam was used to implant (5x10$^{16}$ atoms/cm$^{2 })$ into p-type-Si (100).The implantation was performed with the ion source of a National Electrostatic Corp. 3 MV Tandem accelerator. The implanted sample was annealed at 650 \r{ }C in a gas mixture that was 4{\%} H$_{2}$ + 96{\%} Ar. Measurements showed that the samples contained a mixture of continuous polycrystalline osmium disilicide and a silicide layer. Rutherford Backscattering Analysis with 1.5 MeV Alpha particles was used to monitor the precipitate formation. Photoluminescence measurements were also performed to study possible applications of silicides in light emission. [Preview Abstract] |
Tuesday, March 11, 2008 1:27PM - 1:39PM |
J35.00010: Sb-doped p-type ZnO and its application on light emitting devices Sheng Chu, Leelaprasanna J. Leela, Zheng Yang, Jae Hong Lim, Lin Li, Jianlin Liu Reliable Sb-doped p-type ZnO on silicon substrate was grown by molecular beam epitaxy. The hole concentrations up to 10$^{19}$/cm$^{3}$ were achieved by tuning the Sb cell temperature. The results from XPS and photoluminescence spectrum confirmed the theoretical prediction that the Sb doping mechanism in ZnO is the formation of complex shallow acceptor Sb$_{Zn}$+2V$_{Zn}$, with a low ionization energy of about 150meV. Then ZnO p-n homojunction light emitting diodes (LED) were fabricated based on the p-type Sb-doped layer, and the Ga-doped n-type ZnO layer. Low specific resistivity Au/NiO and Au/Ti contacts were deposited on top of the p-type and n-type layers, respectively, and the contacts were annealed to obtain ohmic conduction. Electroluminescence measurements were performed on the devices under different temperatures and injection currents. Strong near-band edge emissions were clearly observed at room and low temperatures. The device exhibited dominant UV peak at 3.31eV over the deep level emissions at 9K, which is the result from the large build in potential in the junction and the good film quality. [Preview Abstract] |
Tuesday, March 11, 2008 1:39PM - 1:51PM |
J35.00011: 2.4 $\mu$m GaInAsSb Mesa Photodiode Detectors: Leakage Currents and Ultimate Performance John Prineas, Jeff Yager, Jon Olesberg, Shahram Seydmohamadi Short-wave infrared photodiodes play an important role in areas such as molecular sensing, thermophotovoltaics, and astronomical study of galaxy, star, and planetary formation. Here we present results and analysis of uncoated, unpassivated, GaInAsSb mesa photodiodes. We have currently achieved room temperature peak specific detectivity D*=6x10$^{10}$ Jones, dynamic resistance of 25 $\Omega $-cm$^{2}$, and quantum efficiency of 50{\%}. Devices are limited primarily by sidewall leakage currents, initially due to generation-recombination, and over time due to Ohmic leakage from buildup of sidewall oxides. Based on material parameters obtained in this as well as other studies, ultimate diode performance is predicted, and compared to extended-wave InGaAs/InP and HgCdTe detectors. [Preview Abstract] |
Tuesday, March 11, 2008 1:51PM - 2:03PM |
J35.00012: Optically Active Erbium with Co-dopants in Silicon S. Abedrabbo, A. Haddad, K. Albath, Q. Younis, A.T. Fiory, N.M. Ravindra Erbium impurity centers in silicon with strong optical emission properties in the near-Infrared are being sought for efficient silicon-based light sources because of the inherent advantages of integrating silicon photonics with VLSI technology. This work reports investigations of adding proper co-dopants to erbium in silicon through a cost-effective combination of techniques, comprising physical vapor co-deposition, implantation doping, ion beam mixing, and thermal annealing. Processed samples are characterized optically by photoluminescence and structurally by Rutherford backscattering. [Preview Abstract] |
Tuesday, March 11, 2008 2:03PM - 2:15PM |
J35.00013: Characteristics of a Cr$^{4+}$-doped glass-ceramic; a new material for photonic devices L.L. Isaacs, A.B. Bykov, V. Petricevic, I. Popov, M. Yu. Sharonov, J. Steiner The compound 1.0(Cr-doped Ca$_{2}$GeO$_{4})$-1.0(Li$_{2}$O)-0.2(A$l_{2}$O$_{3})$-0.5(B$_{2}$O$_{3})$, on quenching from the melt and subsequent heat treatment, yields a transparent glass-ceramic. The nanocrystallites formed by the ceramming procedure are distributed homogeneously in the bulk. Differential scanning calorimetry was used to determine the glass to crystal transformation temperature, T$_{g}$, and its dependence on heating rate. The activation energy for the glass to crystallite nucleation is 62kJ/mol. The calculated Avrami exponent is 1, in agreement with scanning electron microscopy observations. X-ray diffraction data indicates that the structure of the nanocrystallites is that of distorted Cunyite (Ca$_{2}$GeO$_{4})$. Electron microscopy indicates that the crystallite sizes are less than 1$\mu $m. The growth mode of the crystallites is ``needle'' like. The material exhibits broadband emission between 1050 to 1600 nm, with a maximum at $\sim$1260 nm. The spectroscopic and optical properties indicate, that this material is a promising candidate for use in microelectronics, micro lasers and as fiber optic transmission lines. [Preview Abstract] |
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