Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session H28: Photonic Crystals |
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Sponsoring Units: DCMP Chair: Mark Sherwin, University of California, Santa Barbara Room: Morial Convention Center 220 |
Tuesday, March 11, 2008 8:00AM - 8:12AM |
H28.00001: Moving the band gaps and changing the transmission of magnetic photonic crystals Shiyang Liu, Junjie Du, Zhifang Lin, Siu Tat Chui We classify different types of the photonic band gaps (PBGs) of two dimensional magnetic photonic crystals (MPCs) consisting of arrays of magnetic cylinders and study the different tunability (by an external static magnetic field) of these PBGs. One type of the band gaps comes from infinitely degenerate flat bands and is closely related to those in the study of plasmonics. We calcualte the transmission of the PBG's and found excellent agreement with the results of the photonic band structure calculation. Positional disorder of the lattice structure affects the different types of PBGs differently. [Preview Abstract] |
Tuesday, March 11, 2008 8:12AM - 8:24AM |
H28.00002: Probing states with macroscopic circulations in magnetic photonic crystals Siu Tat Chui, Zhifang Lin We predict that when light is reflected off a magnetic photonic crystal (MPC) there is a grazing component that is {\bf parallel} to the surface; the magnitude of this component can be changed by an external field. The direction of this parallel component is reversed (dotted line) as the direction of the magnetization is reversed. This provides a way to probe states with macroscopic circulations inside the MPC. [Preview Abstract] |
Tuesday, March 11, 2008 8:24AM - 8:36AM |
H28.00003: Experimental investigation of photonic gaps in optical Thue-Morse multilayers fabricated using nanostructured thin films Matthew Hawkeye, Michael Brett One-dimensional Thue-Morse (TM) multilayers are realized by stacking together layers of different refractive index according to simple rules. The result is a deterministically generated aperiodic system representing an intermediate stage between a periodic medium and a random one. This work focuses on the formation of photonic band gap regions at multiple frequencies relating to local positional correlations in the TM structure. TM multilayers are realized in the visible and near-IR spectral regions using glancing angle deposition (GLAD), a single-step nanofabrication technique providing control over the internal columnar structure of a deposited thin film. The effective refractive index of the deposited layer is tuned by controlling the columnar structure leading to great flexibility over the choice of refractive index in the experiment. Using GLAD, TM multilayers are fabricated out of titanium dioxide by varying the density of the columnar structures. The resulting photonic gaps are characterized using transmittance and reflectance spectroscopy and compared with the results of transfer matrix simulations. The creation of gaps in different generations of the TM system will also be examined. [Preview Abstract] |
Tuesday, March 11, 2008 8:36AM - 8:48AM |
H28.00004: Effective medium theory of photonic crystals W.T. Lu, S. Zhang, Y.J. Huang, S. Sridhar We develop an effective medium theory for photonic crystals including negative index metamaterials. This theory is based on field summation within the unit cell. The unit cell is determined by the surface termination. The orientation of the surface breaks the field summation symmetry. This theory is self-consistent. The effective permittivity and permeability tensors will give the exact dispersion relation obtained from the band structure calculation. For waves incident into multilayered structures, our theory gives exact transmittance and reflectance for any wavelengths. For interface with periodic surface structures, our theory gives very accurate results for wavelength down to being comparable with the lattice spacing. By properly taking into account the multiple Bloch modes inside the photonic crystal, our theory can be made to give exact Bragg coefficients. [Preview Abstract] |
Tuesday, March 11, 2008 8:48AM - 9:00AM |
H28.00005: Refraction at a photonic crystal surface: exact characterization Prabasaj Paul Refraction at plane air-photonic crystal surfaces in a class of photonic crystals is studied. The class of photonic crystals has particularly simple band-structure and Bloch wave solutions, which make the evaluation of exact reflection and transmission coefficients relatively simple. New analytical results are presented, and the effects of variation in surface location and orientation are explored. A close look is taken at two important issues -- negative refraction, and the validity of the Rayleigh hypothesis. The results obtained are consistent with those in existing literature. [Preview Abstract] |
Tuesday, March 11, 2008 9:00AM - 9:12AM |
H28.00006: Quantum interference near a photonic band edge beyond the weak field approximation Paul M. Alsing, David A. Cardimona, Danhong H. Huang We investigate spontaneous emission and quantum interference effects involving a three level atom in the vicinity of a photonic band edge, beyond the weak driving field approximation. We consider two different three-level atoms, each subject to a probe field from the ground state, and each embedded within a different photonic crystal (PhC). The first atom has the two excited states separated by a dipole transition in the optical frequency range, with this frequency being close to the surrounding PhC's band edge. The probe field couples the ground state and the highest excited state, and is well outside the PhC bandgap. If a coupling field is applied between the two upper levels, Electromagnetically Induced Transparency (EIT) may occur, depending on the position of the band edge. The second atom has the two upper levels each dipole-coupled to the ground state, and close enough that the emissions from each can coherently interfere. This atom is embedded within a PhC whose band edge lies near the lower of the two excited states, and a probe field is applied that lies just beyond this band edge. This atom exhibits a quantum interference phenomenon related to EIT called Field-Induced Transparency (FIT), again depending on the position of the band edge relative to the lower excited state. [Preview Abstract] |
Tuesday, March 11, 2008 9:12AM - 9:24AM |
H28.00007: Microwave transmission measurements through wire array photonic crystals Graeme Dewar, Nathan Souther, Michael Johnson We have measured the microwave transmission between 12.4 and 18.0 GHz through wire arrays formed into two dimensional square lattices. One array made of copper wire 0.16 mm in radius consisted of five rows by 21 columns having a lattice constant of 5.15 mm. This array exhibited a pass band above 15 GHz, in good agreement with the calculated plasma frequency found from an expression for the permittivity$^{1}$ derived in the long wavelength limit. A second array was made with wire of radius 18 microns and lattice constant 0.8 mm. This array was filled with dielectric loaded with powdered magnetite. A sample of this metamaterial 5.8 mm thick and with no externally applied magnetic field exhibited a pass band above 16 GHz. Implications for creating metamaterials with a negative index of refraction from wire arrays embedded in a magnetic host will be discussed. \newline $^{1}$G. Dewar, in \textit{Complex Mediums III: Beyond Linear Isotropic} \textit{Dielectrics}, Akhlesh Lakhtakai, Graeme Dewar, Martin W. McCall, Editors, Proceedings of SPIE Vol. 4806, 156-166 (2002). [Preview Abstract] |
Tuesday, March 11, 2008 9:24AM - 9:36AM |
H28.00008: Tailoring Self-Assembled Metallic Photonic Crystals for Modified Thermal Emission Sang Eon Han, Andreas Stein, David Norris Photonic crystals are solids that are periodically structured on an optical length scale. Previous work has shown that specific photonic crystal structures can lead to changes in the thermal emission spectra of a material. This may allow elimination of unwanted heat from emission sources, such as tungsten filaments in conventional light bulbs, or lead to new materials for thermophotovoltaics. Here, we study the possibility that metallic photonic crystals obtained via self-assembly can modify thermal emission. These structures, known as inverse opals, are easy to fabricate. However, experiments on tungsten inverse opals suggest that they also have strong optical absorption. In this case, the light does not interact sufficiently with the periodicity of the crystal and modification of thermal emission does not occur. We consider the origin of this effect and show theoretically how to tailor both absorption and surface coupling in experimentally realizable metallic inverse opals. Calculations for tailored inverse opals made from tungsten, molybdenum, and tantalum show that their optical properties can be similar to or even better than the tungsten woodpile structure, which has previously shown modified thermal emission. [Preview Abstract] |
Tuesday, March 11, 2008 9:36AM - 9:48AM |
H28.00009: Integrated lenses for enhanced coupling into terahertz photonic crystal slab waveguides Cristo Yee, Stephen Parham, Mark Sherwin The fundamental property of a photonic crystal (PC), its optical band gap, can be exploited by the introduction of defects that allow the existence of spatially localized states within the optical band gap. A PC waveguide consist of a line of defects in which the localized states will coalesce to form bands that allow the transmission of light otherwise prohibited. Coupling light directly from a source into the waveguide is restricted by the impedance mismatch of the PC waveguide and the surrounding media. In this work we use integrated lenses to enhance coupling of light into PC waveguides. PC slabs with lattices constants ranging from 56 to 64 microns were fabricated with Reactive Ion Etching on a high-resistivity Si wafer. An narrow band tunable source was employed to measure the transmission trough the waveguides. The results are compared with a full 3D FDTD calculations. This work was supported by NSF under grant CCF0507295 and CONACYT-UCMEXUS. [Preview Abstract] |
Tuesday, March 11, 2008 9:48AM - 10:00AM |
H28.00010: Modeling Conformal Growth in Photonic Crystals and Comparing to Experiment Andrew Brzezinski, Ying-Chieh Chen, Pierre Wiltzius, Paul Braun Conformal growth, e.g. atomic layer deposition (ALD), of materials such as silicon and TiO$_{2}$ on three dimensional (3D) templates is important for making photonic crystals. However, reliable calculations of optical properties as a function of the conformal growth, such as the optical band structure, are hampered by difficultly in accurately assessing a deposited material's spatial distribution. A widely used approximation ignores ``pinch off'' of precursor gas and assumes complete template infilling. Another approximation results in non-uniform growth velocity by employing iso-intensity surfaces of the 3D interference pattern used to create the template. We have developed an accurate model of conformal growth in arbitrary 3D periodic structures, allowing for arbitrary surface orientation. Results are compared with the above approximations and with experimentally fabricated photonic crystals. We use an SU8 polymer template created by 4-beam interference lithography, onto which various amounts of TiO$_{2}$ are grown by ALD. Characterization is performed by analysis of cross-sectional scanning electron micrographs and by solid angle resolved optical spectroscopy. [Preview Abstract] |
Tuesday, March 11, 2008 10:00AM - 10:12AM |
H28.00011: The couple between modes of planar wave guides and the evanescent fields produced in the total internal reflection. Raul Garcia-Llamas, Jorge Gaspar-Armenta, Ramon Munguia-Arvayo The coupling between the modes of planar wave guides and the evanescent fields produced in the total internal reflection (TIR) system is studied theoretically. The planar guides are assumed as a semi-infinite inhomogeneous periodic medium (IM) with modulation only in the $y$-direction and period $a$, which is perpendicular to the propagation ($z$-axis) of the modes. This medium is separated by a vacuum (VA) gap, of uniform thickness $d_{2}$, from a semi-infinite homogeneous dielectric medium (HM). Then, two interfaces are found, one at z = 0 between HM/VA and other at $z=d_{2}$ between VA/IM. A transverse magnetic electromagnetic plane wave with wavelength \textit{$\lambda $}$_{0}$, is impinging the VA/IM interface and its wave vector, in the $z-y$ plane, is doing an angle \textit{$\theta $}$_{i}$ with the $z$-axes. The solution of the electromagnetic diffracted field in the IM is a multimodal expansion as proposed by Burckhardt [J. Opt. Soc. Am. \textbf{56 }(1966) pp. 1502]. Following the approach used by Glass and Maradudin [Phys. Rev. B \textbf{29} (1984) pp. 321] a matrix equation for the amplitudes of the diffracted field is found. Numerical results of the near field intensity are presented. [Preview Abstract] |
Tuesday, March 11, 2008 10:12AM - 10:24AM |
H28.00012: Negative bi-refraction of acoustic waves in sonic crystals Yan-Feng Chen Optical birefringence and dichroism are classical and important effects originating from two independent polarizations of optical waves in anisotropic crystals. However, it is impossible for acoustic waves in the fluid to show such a birefringence because only the longitudinal mode exists. The emergence of an artificial sonic crystal (SC) has significantly broadened the range of acoustic materials in nature that can give rise to acoustic bandgaps and be used to control the propagation of acoustic waves. Recently, negative refraction has attracted a lot of attention and has been demonstrated in both left-handed materials and photonic crystals. Similar to left-handed materials and photonic crystals, negative refractions have also been found in SCs. Here we report the acoustic negative-birefraction phenomenon in a two-dimensional SC, even with the same frequency and the same `polarization' state. By means of this feature, double focusing images of a point source have been realized. This birefraction concept may be extended to other periodic systems corresponding to other forms of waves, for example, electron for semiconductors, photon for photonic crystals, and plasmon for plasmonic crystals, showing great impacts on both fundamental physics and device applications. [Preview Abstract] |
Tuesday, March 11, 2008 10:24AM - 10:36AM |
H28.00013: Random high-Q cavities in disordered photonic crystal waveguides Frank Vollmer, Juraj Topolancik We demonstrate experimentally that structural perturbations imposed on highly dispersive photonic crystal-based waveguides give rise to spectral features that bear signatures of Anderson localization. Sharp resonances with effective Q's of over 30 000 are found in scattering spectra of disordered waveguides. The resonances are observed in a $\sim $20-nm bandwidth centered at the cutoff of slowly guided Bloch modes. The origin of the spectral features can be explained by the interference of coherently scattered electromagnetic waves which results in the formation of a narrow impurity (or localization) band populated with spectrally distinct quasistates. http://webmac.rowland.org/rjf/vollmer/index.php [Preview Abstract] |
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