scholarly journals Optical properties of GaAs 2D Archimedean photonic lattice tiling with the p4g symmetry

2008 ◽  
Vol 40 (2) ◽  
pp. 167-173 ◽  
Author(s):  
Dj. Jovanovic ◽  
R. Gajic ◽  
K. Hingerl
Keyword(s):  
Optical Properties ◽  
Photonic Crystal ◽  
Photonic Crystals ◽  
Negative Refraction ◽  
Group Symmetry ◽  
Electromagnetic Propagation ◽  
Space Group Symmetry ◽  
Space Group ◽  
Left Handedness ◽  
Archimedean Lattice

In this paper we present our investigation of 2D Archimedean lattice photonic crystals with p4g space group symmetry. The structures are made of GaAs both as air holes and dielectric rods in air. In order to analyze the photonic crystal optical properties we performed calculations of the band structures, equi-frequency contours and electromagnetic propagation through the basic structures and waveguides. In addition, we investigated negative refraction and left-handedness in the p4g photonic crystal.

Negative Refraction and Left-Handedness in 2D Archimedean Lattice Photonic Crystals

2007 ◽  
Vol 555 ◽  
pp. 83-88 ◽  
Author(s):  
Rados Gajić ◽  
R. Meisels ◽  
F. Kuchar ◽  
Dj. Jovanović ◽  
K. Hingerl
Keyword(s):  
Photonic Crystals ◽  
Band Gap ◽  
Experimental Verification ◽  
Negative Refraction ◽  
Electromagnetic Propagation ◽  
Band Structures ◽  
Left Handedness ◽  
Fdtd Simulations ◽  
Archimedean Lattice

Study of the refraction and rightness effects in 2D Archimedean lattice photonic crystals is presented. A special emphasis is placed on possibilities of negative refraction and left-handedness in these structures. Besides the familiar Archimedean lattices like square, triangular, honeycomb and Kagome ones, we consider also, the less known 32,4,3,4 (ladybug) and 3,4,6,4 (honeycombring) structures. This involves the calculations of band structures, band-gap maps, equifrequency contours, FDTD simulations of electromagnetic propagation through the structures, as well as an experimental verification of negative refraction at microwaves.

scholarly journals Far-Field Focus and Dispersionless Anticrossing Bands in Two-Dimensional Photonic Crystals

2007 ◽  
Vol 2007 ◽  
pp. 1-8
Author(s):  
Xiaoshuang Chen ◽  
Renlong Zhou ◽  
Yong Zeng ◽  
Hongbo Chen ◽  
Wei Lu
Keyword(s):  
Photonic Crystal ◽  
Photonic Crystals ◽  
Negative Refraction ◽  
Far Field ◽  
Two Dimensional ◽  
Surface Polaritons ◽  
Concave Lens ◽  
Bloch Mode ◽  
Two Dimensional Photonic Crystal ◽  
Photonic Band

We review the simulation work for the far-field focus and dispersionless anticrossing bands in two-dimensional (2D) photonic crystals. In a two-dimensional photonic-crystal-based concave lens, the far-field focus of a plane wave is given by the distance between the focusing point and the lens. Strong and good-quality far-field focusing of a transmitted wave, explicitly following the well-known wave-beam negative refraction law, can be achieved. The spatial frequency information of the Bloch mode in multiple Brillouin zones (BZs) is investigated in order to indicate the wave propagation in two different regions. When considering the photonic transmission in a 2D photonic crystal composed of a negative phase-velocity medium (NPVM), it is shown that the dispersionless anticrossing bands are generated by the couplings among the localized surface polaritons of the NPVM rods. The photonic band structures of the NPVM photonic crystals are characterized by a topographical continuous dispersion relationship accompanied by many anticrossing bands.

scholarly journals NEGATIVE REFRACTION AND SUBWAVELENGTH FOCUSING USING PHOTONIC CRYSTALS

2004 ◽  
Vol 18 (25) ◽  
pp. 1275-1291 ◽  
Author(s):  
EKMEL OZBAY ◽  
KAAN GUVEN ◽  
ERTUGRUL CUBUKCU ◽  
KORAY AYDIN ◽  
B. KAMIL ALICI
Keyword(s):  
Optical Properties ◽  
Photonic Crystals ◽  
Negative Refraction ◽  
Numerical Study ◽  
Effective Index ◽  
Index Of Refraction ◽  
Far Field ◽  
Two Dimensional ◽  
Flat Lens ◽  
Effective Index Of Refraction

In this article, we present an experimental and numerical study of novel optical properties of two-dimensional dielectric photonic crystals (PCs) which exhibit negative refraction. We investigate two mechanisms which utilize the band structure of the PC to generate a negative effective index of refraction (n eff <0) and demonstrate the negative refraction experimentally. To the isotropic extend of n eff , different PC slab structures are employed to focus the radiation of a point source. It is shown experimentally that the PC can generate an image of the source with subwavelength resolution in the vicinity of the PC interface. Using a different PC, one can also obtain a far field focusing. In the latter case, we explicitly show the flat lens behavior of the structure. These examples indicate that PC-based lenses can surpass limitations of conventional lenses and lead to novel optics applications.

scholarly journals Symmetrical Analysis Phonon Modes of Crystal -Ag8SnSe6

2015 ◽  
Vol 16 (2) ◽  
pp. 257-260
Author(s):  
І.V. Semkiv ◽  
А.І. Kashuba ◽  
H.A. Ilchuk ◽  
M.V. Chekaylo
Keyword(s):  
Raman Spectra ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Group Symmetry ◽  
Phonon Modes ◽  
Orthorhombic System ◽  
Space Group Symmetry ◽  
Space Group ◽  
Phonon Spectra

Symmetrical analysis of the phonon spectra of  lowtemperature b¢-phase of crystal Ag8SnSe6 carried out. At the room temperature argyrodite Ag8SnSe6 belong to orthorhombic system with space group symmetry Pmn21. Classification of the main phonon modes of crystal carried out. Clarified selection rules for Raman spectra and infrared spectra.

Electron Diffraction Study of α-AlMnSi Crystals Along Non-Crystallographic Zone Axes

1998 ◽  
Vol 12 (22) ◽  
pp. 2279-2303 ◽  
Author(s):  
G. L. Song ◽  
L. A. Bursill
Keyword(s):  
Electron Diffraction ◽  
Significant Proportion ◽  
Group Symmetry ◽  
Structural Basis ◽  
Quasicrystalline Phase ◽  
Thickness Variation ◽  
Crystal Thickness ◽  
Space Group Symmetry ◽  
Space Group ◽  
Diffraction Patterns

The structure of crystalline α-AlMnSi is examined by electron diffraction. Six distinct zone axes are examined, including both normal crystallographic and non-crystallographic zone axes, allowing the space group symmetry of α-AlMnSi to be studied. A method for indexing the non-crystallographic zone axis diffraction patterns, which involve reflections from several nearby crystallographic zone axes, is described and applied to electron diffraction patterns of the quasi-5-fold, 3-fold and 2-fold axes of the icosahedral building units of cubic α-AlMnSi. These are compared with electron diffraction patterns from the corresponding 5-fold, 3-fold and 2-fold axes of the quasicrystalline phase i-AlMnSi, from which we may make some conclusions concerning the occupancies of the icosahedral units in i-AlMnSi. Electron diffraction patterns characteristic of [Formula: see text] were obtained for thicker specimens. However, for thin specimens, as used for HRTEM imaging, the electron diffraction patterns were characteristic of [Formula: see text] space group symmetry. This unusual behaviour arises because the structural basis for the [Formula: see text] to [Formula: see text] phase transition is a weak effect, involving changes in occupancy of the icosahedral structural elements located at the corners (double-MacKay icosahedra) and body-centers (MacKay icosahedra) of the cubic unit cell. The effects of changing the occupancies of the outer shells of the MI and DMI structural units on the diffraction intensities of the weak reflections were examined. Thus, calculation of the dynamical diffraction amplitudes shows that in fact the weak reflections characteristic of [Formula: see text] only develop sufficient intensity if two conditions are satisfied: namely (1) the crystal thickness exceeds approx. 50 nm and (2) if a significant proportion of [Formula: see text] occupancies are included in the structural model. By fitting the observed thickness variation of the diffraction intensities we propose a new set of occupancies for α-AlMnSi, which is consistent with the electron, X-ray and neutron diffraction data.

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