Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session U16: Photonic Crystals II |
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Sponsoring Units: DCMP Chair: J. Albrecht, WP-AFB AFRL/SNDD Room: LACC 404A |
Thursday, March 24, 2005 8:00AM - 8:12AM |
U16.00001: Wave Propagation in High Impedance Surfaces Michael Petras, Ramamurthy Ramprasad High impedance (hi) surfaces are artificially structured surfaces that form A sub-class of 2-d photonic band gap (pbg) materials. An interesting feature Of metallo-dielectric hi surfaces is the presence of a surface Electromagnetic (em) band gap at frequencies where the wavelength is larger Than the lattice dimension---a feature absent in all-dielectric pbg Materials. Due to this ``sub-wavelength'' behavior, effective medium Theories (emt) can be used to describe their dispersion characteristics. A General emt framework has been developed, and a new mechanism to describe The occurrence of band gaps in hi surfaces is presented. It is shown that The eigenmode of a surface em wave at any frequency can be written as a Linear combination of two ``pure'' modes: a backward mode that propagates Below the surface, and a forward mode that resides on the surface. At the Band gap frequencies these two modes cancel, resulting in no propagation. It Is anticipated that this model will be a powerful tool for understanding and Exploring a large class of periodic systems. [Preview Abstract] |
Thursday, March 24, 2005 8:12AM - 8:24AM |
U16.00002: Design and Modeling of Periodically Loaded Transmission Line Metamaterial Structures Sushil Bharatan, Michael Petras, Chandra Ramiah, R. Ramprasad Transmission lines periodically loaded with suitable elements form a class of photonic band gap (PBG) materials that display unusual properties at frequencies where the electromagnetic (EM) wavelength is much smaller than the spacing between periodic loading. So, effective medium theories which use circuit elements as building blocks can be used to describe these systems. A design framework to determine the properties of such meta-material structures has been developed based on circuit models of the unit cells. The models were parameterized using full wave EM field solvers, and the parameterization has been used in subsequent designs of a large class of structures. The predictions of our effective medium model and that of the EM simulations have been validated by measurements. The effective medium model is orders of magnitude faster than full wave EM simulations, reflecting the efficiency of this approach in rapid design. This technique is applied here to 1-D transmission line structures loaded periodically with metal posts. However, it can easily be extended to other types of periodic loading and to 2-D structures as well. [Preview Abstract] |
Thursday, March 24, 2005 8:24AM - 8:36AM |
U16.00003: Control of complete bandgap in two-dimensional photonic crystals with open veins Tzong-Jer Yang, Weng-Long Liu, Ben-Yuan Gu Two-dimensional photonic crystals of a square lattice with square dielectric rods growing thin (6.5{\%} lattice constant) veins on the middle side of each square dielectric rods in air are proposed. Band structures are calculated by the plane-wave expansion method. The complete photonic band gap (PBG) is found in higher frequency band. Then growing thin veins, this PBG is gradually disappeared. At certain length of thin veins, a complete PBG starts to appear in a lower frequency band. But the greatest complete PBG can be gotten while veins are not connected at the boundary of the unit cell of the lattice. The reason of this finding will be given in this report. Our results may provide a new direction for designing PBG of two-dimensional photonic crystals. [Preview Abstract] |
Thursday, March 24, 2005 8:36AM - 8:48AM |
U16.00004: Electrical switching of light using liquid crystal-infilled 2D photonic crystals. Jorge Antonio Reyes Avenda\~no, Peter Halevi Sar, Juan Adrian Reyes Cervantes We have studied two-dimensional photonic crystals of hollow cylinders (made of Si or Ge) that are infilled with the nematic liquid crystal (NLC) 5CB. The dielectric tensor of the NLC cylinders is obtained by minimizing the free energy, which has elastic and electrostatic contributions [1]. Our calculations of the photonic band structure show that an applied electric field can produce switching of the transmitted light; this is realized due to a phase transition from the escaped radial to the axial configuration of the NLC molecules. Specifically, for a square lattice, with propagation in the [110] direction, the light is completely reflected when the field is off; on the other hand, it is partially transmitted when a sufficiently strong electric field is applied parallel to the cylinders. [1] J. A. Reyes-Cervantes, J. A. Reyes-Avenda\~{n}o, P. Halevi. Proc SPIEl \textbf{5511}, 50. [Preview Abstract] |
Thursday, March 24, 2005 8:48AM - 9:00AM |
U16.00005: Electro-Optical Control of Directional Switching Based on Degenerate Defect State Spliting in Photonic Crystal Natalia Malkova, Cun-Zheng Ning We study the splitting of the degenerate defect states inside a two-dimensional photonic crystal. Using the group-theory analysis we find the perturbation potentials that allow for the most efficient splitting of the degenerate states. The results of the theoretical analysis are applied to the particular examples of the two-dimensional square and hexagonal photonic lattices of the dielectric rods in vacuum doped by the defect rod, giving the doubly degenerate E state in the first TM band gap. We show how the choice of the perturbation potential can control both the magnitude and symmetry of the splitting. The perturbation potential can be generated either by piezoelectric effect resulting in lattice distortion or by electro-optical effect resulting in change of the dielectric function. We concentrate on the perturbation potential caused by the electro-optical effect. Application of the effect in fast switch of waveguide devices is presented. We also discuss use of the effect in the design of electrically tunable lasers. [Preview Abstract] |
Thursday, March 24, 2005 9:00AM - 9:12AM |
U16.00006: Nonlinear Photonic Crystals as a Source of Entangled Photons William Irvine, Michiel de Dood, Dirk Bouwmeester Nonlinear photonic crystals can be used to provide phase matching for frequency conversion in optically isotropic materials. The phase-matching mechanism proposed here is a combination of form birefringence and phase velocity dispersion in a periodic structure. Since the phase matching relies on the geometry of the photonic crystal, it becomes possible to use highly nonlinear materials. This is illustrated considering implementable one-dimensional periodic structures for the generation of light at wavelengths between 700nm and 1500nm. We show that phase-matching conditions used in schemes to create entangled photon pairs can be achieved in photonic crystals. [Preview Abstract] |
Thursday, March 24, 2005 9:12AM - 9:24AM |
U16.00007: Polymer-Based Hypersonic Phononic Crystals Taras Gorishnyy, Chaitanya Ullal, Martin Maldovan, Ji Hyun Jang, George Fytas, Edwin Thomas The ability to influence high frequency phonons has great importance for both fundamental science and practical applications. A number of important physical processes, such as thermal energy flow, charge carrier mobility and lifetime, and the superconductivity transition, can be altered by modifying the phononic dispersion relation of a medium. Applications range from thermal management and thermoelectricity, to enhanced microelectronic and opto-electronic devices. In this talk we will discuss the use hypersonic phononic crystals to achieve control over the emission and propagation of high frequency phonons. We fabricate high quality, 2D single crystalline hypersonic crystals using interference lithography and perform direct measurement of their phononic band structure with Brillouin light scattering. Numerical calculations are employed to explain the nature of the observed propagation modes. This work lays the foundation for experimental studies of hypersonic crystals and, more generally, phonon-dependent processes in periodic nanostructures. [Preview Abstract] |
Thursday, March 24, 2005 9:24AM - 9:36AM |
U16.00008: X-ray Microscopy on Thin Metallic Photonic Crystals Vasilica Crecea, Christoph Rau, Xindi Yu, Paul Braun, Ian Robinson We present a high-resolution microscopy experiment that uses hard X-rays supplied by Sector 34-ID C from the Advanced Photon Source. The sample of interest is a two-layered inverted nickel photonic crystal with spherical voids of 1900nm diameter and an expected feature size of c. 200nm. Although existing soft X-ray microscopy techniques can reach a sub-hundred nanometer resolution, nickel does not transmit light with energies in the range of the beams used in these cases (c. 1keV), thus rendering them inappropriate for the imaging of such samples. However, with hard X-rays nickel absorbs very little (c. 2-4 percent) light whose energy lies about its absorption edge, which is at 8.4keV. In this new experiment we were able to obtain a magnified image of the Ni photonic crystal with a resolution of 100nm, a result that is unprecedented in this type of system. The experimental set-up uses advanced hard X-ray optical components, such as Kirkpatrick-Baez mirrors, Fresnel zone plates, and a scintillator screen. [Preview Abstract] |
Thursday, March 24, 2005 9:36AM - 9:48AM |
U16.00009: Enhancement of Magneto-Chiral Effect in Photonic Crystals Kei Sawada, Naoto Nagaosa We theoretically study a magneto-chiral effect magnified in photonic crystals. A magneto-chiral effect is a directional birefringence even for unpolarized light. This effect occurs in a material such as GaFeO$_3$ in which both time-reversal and inversion symmetries are broken. Unfortunately the wave vector dependence of a dielectric function is typically the order of $10^{-4}$, which is too small to observe. We consider one-dimensional photonic crystals composed of the magneto-chiral medium and air, and calculate the reflectivity. We found that the difference in the reflectivities with respect to different magnetization configurations is thousands of times enhanced compared with that in a bulk material. [Preview Abstract] |
Thursday, March 24, 2005 9:48AM - 10:00AM |
U16.00010: A new picture for gap solitons in nonlinear photonic crystals Xunya Jiang, J.D. Joannopoulos We construct a new local-Bloch theory for the interplay between the nonlinearity and the periodicity. Based on this first order theory, we can get gap soliton solutions composed of local Bloch waves over the entire gap. Some important unique properties of the gap solitons are revealed, such as the periodicity-amplified nonlinearity, the periodicity-generated high order nonlinearity, the touching-local-gap-edge property and the intrinsic-ultrashort-pulse property. Besides these properties, the envelope equations of both stationary and time-dependent cases are obtained. The stationary envelope equation is a cubic-quintic nonlinear Schrodinger equation which can be solved exactly. From this simple equation, we can give a clear explanation of earlier theoretical results. The time-dependent envelope equation includes new important high order time-derivative terms, so that it is much more complex than common nonlinear Schrodinger equations. One of those terms is the self-steepening term which leads to a new dynamical instability of the gap solitons. [Preview Abstract] |
Thursday, March 24, 2005 10:00AM - 10:12AM |
U16.00011: Quantum Hall effect analogs in photonic crystals: ``chiral'' (unidirectional) edge modes as ``one-way waveguides'' S. Raghu, F.D.M. Haldane ``Photonic crystals'' constructed from non-reciprocal (Faraday) media with broken time-reversal symmetry can have topologically non-trivial photonic bands with non-zero ``Chern invariants''. In electronic systems, filling such bands produces an (integer) quantum Hall effect (QHE). While photonic (bosonic) bands cannot be ``filled,'' other features of the QHE - ``chiral edge states'' - persist. We present an explicit example of a periodic array of dielectric rods parallel to the Faraday axis of their surrounding medium, with a band gap for photon propagation normal to the rods, and topologically-non-trivial 2D bands. We then examine a ``domain wall'' across which the Faraday axis reverses. As the inevitable consequence of topology, there are modes in the gap which are localized at this interface, and allow flow of electromagnetic energy {\bf in one direction only}, making a ``one-way waveguide'' without counterprogating modes, so it is robust against elastic backscattering at bends (though not against absorbtion, unlike charge flow in the electronic analog). The ``Berry curvature'' introduced by Faraday materials leads to a new class of novel possibilities for ``photonic band-structure engineering,'' with possible technological applications. [Preview Abstract] |
Thursday, March 24, 2005 10:12AM - 10:24AM |
U16.00012: Tuning of the spontaneous emission in a one--dimensional photonic crystal Elizabeth Galindo, Adan S. Sanchez, Peter Halevi The optical properties of a photonic crystal (PC) can be tuned if one of its constituents is a semiconductor [1]. Changing the free carrier concentration (electrons or holes) in the semiconductor, it is possible to modify its dielectric constant, and, consequently, the band structure or the density of optical states of the PC. On the other hand, the rate of spontaneous emission of an atom or a molecule depends on the density of states of its environment. Thus, the rate of emission of an atom immersed in a PC is different from the rate of emission in vacuum. In this work, we compute the rate of spontaneous emission of an Er ion in a one-dimensional, tunable PC made of alternating layers of Si and air. The rate of spontaneous emission can be changed about 30 % around its value in the homogeneous medium. [1] P. Halevi and F. Ramos-Mendieta, Phys Rev Lett. 85, 1875 (2000); A. S. Sánchez and P. Halevi, J. Appl. Phys. 94, 792 (2003). [Preview Abstract] |
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U16.00013: Polariton-assisted coherent thermal emission by heterogeneous structures C.J. Fu, Z.M. Zhang, D.B. Tanner The control of thermal radiation has important applications in thermophotovoltaic devices, solar cells, and space thermal management. Excitation of surface polaritons allows the thermal emission spectra to be modified using nanostructured materials. The coupling of the excited surface polaritons to thermal radiation \textit{via} diffraction by gratings can result in coherent thermal emission. Here, we describe a novel concept of a gratingless coherent thermal source that uses paired single-negative layers: one with a negative permittivity ($\varepsilon )$ and the other with a negative permeability ($\mu )$. We show that coherent thermal emission is feasible for both $s$- and $p$-polarizations, owing to surface polariton excitation at the interface of the negative-$\varepsilon $ and negative-$\mu $ media. Moreover, the emission frequency and emission angle can be controlled by adjusting the film thicknesses. Future development in nanooptical materials with negative-$\mu $ at near-infrared frequencies is critically needed to realize the proposed coherent thermal source. [Preview Abstract] |
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U16.00014: The Role of the Absorption in the Stop Band Tuning of Opals and Inverse Opals Through Coating of Semiconductor Materials Jesus Manzanares-Martinez, Diego Soto-Puebla In this work we report on the modeling of the optical properties of semiconductor in-filled opals and inverse opals for the visible and near infrared spectral region. The crucial influence of the absorption is theoretically investigated by using the three dimensional Transfer Matrix Method (TMM). Fine-tuning of the stop band positioning is achieved with increasing semiconductor infiltration. The red shift of the stop band can be explained by Bragg's law. However, the optical properties depend strongly on the value of the absorption that is directly related to the imaginary part of the Dielectric Constant (DC). We use a realistic model of the DC for a specific semiconductor (InSb) that takes into account the phononic contributions, intrinsic electron and hole densities. By positioning the stop band in the region of the smaller value of the imaginary part of the DC we optimize the value of the lattice constant in order to optimize tuning of the stop band with fewer losses. We also study the influence of absorption in the Fabry-Perot oscillations and in the higher energy stop bands. This work is motivated by new experimental results that show that absorption in 3D structures can be the limiting factor to obtain a useful structure for tuning. [Preview Abstract] |
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