The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

Metamaterials — transparent materials containing tiny metallic inclusions of various shapes and arrangements — cause light to propagate in unusual ways. Now a new, theoretical metamaterial architecture is proposed, with the potential to bring light to a complete standstill. In contrast to previous methods of decelerating and storing light, this scheme simultaneously allows both high in-coupling efficiency and broadband, room-temperature operation. At a critical point a light ray is prevented from propagating; each frequency component (or colour) of the wave stops at a slightly different place, leading to the formation of a 'trapped rainbow'. This work bridges the gap between two important contemporary realms of science, metamaterials and slow light, and may lead to applications in optical data processing and storage or the realization of quantum optical memories. Light usually propagates inside transparent materials in well known ways1. However, recent research2,3,4,5,6 has examined the possibility of modifying the way the light travels by taking a normal transparent dielectric and inserting tiny metallic inclusions of various shapes and arrangements. As light passes through these structures, oscillating electric currents are set up that generate electromagnetic field moments; these can lead to dramatic effects on the light propagation, such as negative refraction. Possible applications include lenses that break traditional diffraction limits3,4 and ‘invisibility cloaks’ (refs 5, 6). Significantly less research has focused on the potential of such structures for slowing, trapping and releasing light signals. Here we demonstrate theoretically that an axially varying heterostructure with a metamaterial core of negative refractive index can be used to efficiently and coherently bring light to a complete standstill. In contrast to previous approaches for decelerating and storing light7,8,9,10,11,12,13, the present scheme simultaneously allows for high in-coupling efficiencies and broadband, room-temperature operation. Surprisingly, our analysis reveals a critical point at which the effective thickness of the waveguide is reduced to zero, preventing the light wave from propagating further. At this point, the light ray is permanently trapped, its trajectory forming a double light-cone that we call an ‘optical clepsydra’. Each frequency component of the wave packet is stopped at a different guide thickness, leading to the spatial separation of its spectrum and the formation of a ‘trapped rainbow’. Our results bridge the gap between two important contemporary realms of science—metamaterials and slow light. Combined investigations may lead to applications in optical data processing and storage or the realization of quantum optical memories.

‘Trapped rainbow’ storage of light in metamaterials

Colloidal photonic crystals and materials derived from colloidal crystals can exhibit distinct structural colors that result from incomplete photonic band gaps. Through rational materials design, the colors of such photonic crystals can be tuned reversibly by external physical and chemical stimuli. Such stimuli include solvent and dye infiltration, applied electric or magnetic fields, mechanical deformation, light irradiation, temperature changes, changes in pH, and specific molecular interactions. Reversible color changes result from alterations in lattice spacings, filling fractions, and refractive index of system components. This review article highlights the different systems and mechanisms for achieving tunable color based on opaline materials with close-packed or non-close-packed structural elements and inverse opal photonic crystals. Inorganic and polymeric systems, such as hydrogels, metallopolymers, and elastomers are discussed.

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Tunable Colors in Opals and Inverse Opal Photonic Crystals

Inverse opals or three-dimensionally ordered macroporous (3DOM) materials, prepared by colloidal crystal templating (CCT) methods, possess distinctive structural features that are important for the design of photonic crystals, sensors, power sources, catalysts, and various other applications. In the past decade, vast progress has been made in shaping these materials at various length scales. It is now possible to prepare 3DOM materials in a variety of simple and complex compositions, in which pore sizes, pore shapes, and skeletal geometries can be adjusted statically and sometimes even dynamically to alter the physical properties of the material. Hierarchical pore structures can be achieved by combining CCT with additional templating techniques. Furthermore, shaped porous nanoparticles may be synthesized using CCT methods. This review will highlight recent advances in controlling both the internal structure of inverse opals and their external morphology, enhancing compositional complexity, endowing these ...

Morphological Control in Colloidal Crystal Templating of Inverse Opals, Hierarchical Structures, and Shaped Particles†

[신간안내] Computational Electrodynamics (the finite difference time - domain method)

A review of the properties of silicon-based two-dimensional (2D) photonic crystals is given, essentially infinite 2D photonic crystals made from macroporous silicon and photonic crystal slabs based on silicon-on-insulator basis. We discuss the bulk photonic crystal properties with particular attention to the light cone and its impact on the band structure. The application for wave guiding is discussed for both material systems, and compared to classical waveguides based on index-guiding. Losses of resonant waveguide modes above the light line are discussed in detail. © 2003 Elsevier B.V. All rights reserved.

/pdf/silicon-based-two-dimensional-photonic-crystal-waveguides-f90t9u6w59.pdf

Silicon-based two-dimensional photonic crystal waveguides

We present a detailed analytical study of surface plasmon polaritons SPPs in generalized asymmetric slab waveguides with a core of negative permittivity and permeability. Profiting from the duality principle, we confine ourselves to the analysis of p-polarized TM SPP eigenmodes, which also occur in thin metallic films. It is shown that the left-handed LH structures considered here support a richer variety of SPPs when compared to their metallic counterparts. Depending on the refractive index distribution, the permittivity of each medium and the thickness of the core, a total of 30 solutions to the involved characteristic equation are identified in a unified manner and classified systematically. In order to identify conclusively all SPPs, we follow an analytical methodology based directly on the solution constraints inherent in the associated transcendental equation. This treatment reveals striking features of the formed SPP eigenmodes, such as the existence of “supermodes” when no SPP is supported at one of the slab interfaces. Moreover, our study reveals the opening of gaps in the SPP dispersion diagrams, occurrence of monomodal propagation for specific choices of the material parameters, presence of SPPs with no cutoff thickness and coexistence of three eigenmodes, with double mode-degeneracy points occurring twice. The eigenmodes with negative energy flux that give rise to negative group velocity are identified via a closed-form expression for the time-averaged power flow P in the guide. For each eigenmode, we examine the variation of P with the reduced slab thickness and discuss key features of the effective index geometric dispersion diagram, most of which are unique to the generalized structures studied herein.

Surface plasmon polaritons in generalized slab heterostructures with negative permittivity and permeability

A finite three-dimensional photonic-crystal structure with a complete photonic bandgap is shown to drastically modify the spontaneous-emission rate of an embedded dipole. Calculations on the basis of the finite-difference time-domain method with perfectly matched layer boundary conditions demonstrate a strong position and polarization dependence of spontaneous emission within the unit cell. Strong enhancement effects are predicted at interfaces between the high-index and the low-index material. The inhibition of spontaneous emission within the bandgap is of the order of two magnitudes, even for relatively small crystallites.

Modified spontaneous-emission rate in an inverted-opal structure with complete photonic bandgap

Photonic crystals with a complete banclgap can stop the propagation of light of a certain frequency in all directions. We introduce double-inverse-opal photonic crystals (DIOPCs) as a new kind of optical switch. In the DIOPC, a movable, weakly scat-tering sphere is embedded within each pore of the inverse-opal photonic crystal lattice. Switching between a diffusive reflector and a photonic crystal environment is experimentally demonstrated. Theory, shows that a complete hanclyap can be realized that can he opened or closed by moving the spheres. This functionality opens up new possibilities for the control of light emission and propagation. The close link and interaction between the chemical synthesis and the computalional design and analysis underlines the interdisciplinary focus of this report.

Double-Inverse-Opal Photonic Crystals: The Route to Photonic Bandgap Switching†

We give an overview of the Finite-Difference Time-Domain (FDTD) method and its application to modeling photonic crystal defect structures. The application of the FDTD method for calculation of band structures and the 3D Bloch eigenmodes of photonic crystal slab structures and photonic crystal fibers is discussed as well as the simulation of the propagation of an ultrashort optical pulse through a photonic cyrstal defect structure.

Christian Hermann

Papers

Silicon-based two-dimensional photonic crystal waveguides

Surface plasmon polaritons in generalized slab heterostructures with negative permittivity and permeability

Modified spontaneous-emission rate in an inverted-opal structure with complete photonic bandgap

Double-Inverse-Opal Photonic Crystals: The Route to Photonic Bandgap Switching†

Finite-Difference Time-Domain simulations of photonic crystal defect structures