Optical waves in photonic crystals and the photonic flame effect

We present the coupled-mode equations for inclined waves in photonic crystals. Among the eigenmodes, we focus on the evanescent modes. We consider the conjugation of the waves at the interface of the crystal and its metallic substrate. We underscore the role of resonant coupling of the fields at this interface and briefly discuss the field structure in the open space.     

All-optical data-latch experiments for photonic access nodes in the photonic highway

A novel approach to direct access at the optical level is proposed. We conducted experiments on all-optical data-latch functions using bistable laser diodes (LDs) for all-optical droplinsert operation in a 50-Mbitls data highway.     

All-optical data-latch experiments for photonic access nodes in the photonic highway

A novel approach to direct access at the optical level is proposed. We conducted experiments on all-optical data-latch functions using bistable laser diodes (LDs) for all-optical droplinsert operation in a 50-Mbitls data highway.     

Localized photonic modes in photonic crystal heterostructures

In this work, interface modes of two-dimensional photonic crystal heterostructures have been investigated by usage of the supercell method. The photonic crystal heterostructure is made of two photonic crystals with square symmetry in which one of them is composed of circular dielectric rods in air background and the other one is constructed by drilled square holes in dielectric. It is shown that using of a proper supercell plays an important role in obtaining the correct interface modes. We have also showed that the guided interface modes and single mode which is different from those reported in some published works are nearly dispersionless.     

光子晶体中的磁控光子开关线路

提出了一个光子晶体中的磁控光子开关线路的理论模型,并利用平面波展开加超原胞方法计算了它的光学性质.这个模型由设置在空气中的介电柱子光子晶体构成,其中一排柱子被具有同样介电常数的铁氧体柱子替换.当外加磁场时,铁氧体柱子产生了不等于一的磁导率,这就会在光子带隙中产生波导模.当撤去外场,整个体系还原为完美光子晶体.由此便可形成磁控光子开关线路.具体选择了正方形柱子设置在正方形格点上,计算结果证明这种设想是可行的,并给出一些有价值的结果. 关键词： 光子晶体 传导模 磁导率     

Analysis of photonic band gap structure for the design of photonic devices

A detailed analysis, based on Kronig–Penney model and finite-difference time-domain (FDTD) method, is used to explain the air-filling factor effect on the optical properties of defect-free photonic crystals. By the use of the Kronig–Penney model, we calculated the photonic band structure for electromagnetic waves in a structure consisting of a periodic square array of dielectric rods of lattice constant a separated by air holes. Gaps in the resulting band structures are found for waves of both polarisations. We analysed the air-filling factor effect on both polarisations in low and high frequency regions. It is shown that the frequency of the lower TE (transverse-electric) band edge is independent of the air-filling factor in the low frequency region. The opposite behaviour holds for the upper band edge, growing rapidly with the air-filling factor. Using the FDTD we simulated the electric field as the pulse propagates through the structure. The results of both approaches are compared, and the operation characteristics of the measuring air-filling factor device are described. We investigate the optical properties of a single and two defects incorporated in the PC, which can be potentially applied to ultra small surface-emitting-type channel drop filter. It is shown that the frequency and polarisation of the dropped light can be controlled by changing the size and/or shape of the defect. The electric field distribution calculations show that the electric field for a given frequency is located only at the defect, which means that each defect can detect only its corresponding wavelength. To cite this article: F. Ouerghi et al., C. R. Physique 5 (2004).     

Design of photonic bands for opal-based photonic crystals

To make a device from an opal—or otherwise—the photonic bands and the optical properties derived from them are needed. Knowing the effects of different parameters defining the opal geometry and different possible modifications of its structure are needed, too. An accurate definition of the device will be required to obtain a good performance. With this aim, the optics of light with a wavevector in the vicinity of the L point in the Brillouin zone and its coupling to bare opals band structure are presented. An important aspect is the transition from finite to infinite crystal and the study of size effects on the bands. It is possible to substantially alter the photonic band structure of an opal-based system, while maintaining the lattice structure, simply by growing layers of other materials with an appropriate refractive index. Here, it is shown how, by the growth of accurately controlled thin layers of silicon and germanium, and further processing, one can induce the opening of two complete photonic band gaps (PBGs) in an opal structure. Finally, the possibility to fabricate a simple device consisting in a planar waveguide will be shown. By means of a very simple and inexpensive procedure, engineered planar defects acting as microcavities have been realized. These can be viewed as a particular case of a much more general class of heterostructures that can be grown by combining opal vertical deposition and chemical vapour deposition of oxides. A further step is made by applying electron beam lithography to provide lateral definition and facilitate three-dimensional structuring.     

Isotropic photonic gaps in a circular photonic crystal

We investigated the optical properties of a circular photonic crystal (CPC) for which the distance between lattices was systematically distributed. The transmission spectra of CPC composed of alumina cylinders were examined in the frequency region from 0 to 20 GHz. We show that photonic gaps are obtained not only in CPCs but also in phase-shifted CPCs. The isotropic photonic gaps are evidenced by changes in the incident angle of a millimeter wave.     

Tunable photonic Bloch oscillations in electrically modulated photonic crystals

We exploit theoretically the occurrence and tunability of photonic Bloch oscillations (PBOs) in one-dimensional photonic crystals (PCs) containing nonlinear composites. Because of the enhanced third-order nonlinearity (Kerr-type nonlinearity) of composites, photons undergo oscillations inside tilted photonic bands, which are achieved by the application of graded external-pump electric fields on such PCs, varying along the direction perpendicular to the surface of layers. The tunability of PBOs (including amplitude and period) is readily achieved by changing the field gradient. With an appropriate graded pump ac or dc electric field, terahertz PBOs can appear and cover a terahertz band in an electromagnetic spectrum.     

Nonreciprocal photonic band structure of low-symmetry magnetic photonic crystals

We propose multicomponent magnetic photonic crystals as a basis component for nonreciprocal optical elements. It is shown that introduction of three or more components may provide violation of mirror reflection symmetry, which is a necessary condition for obtaining nonreciprocity in the dispersion of the structure's eigenmodes. Numerical simulations confirm that nonreciprocity indeed develops in the form of nonreciprocal photonic band structure of three-component low-symmetry photonic crystal. We find that symmetry constraints produce fine structure in the nonreciprocity at high-symmetry points of the Brillouin zone.     

Control of photonic band gaps in one-dimensional photonic crystals

The photonic band gaps in one-dimensional photonic crystals (PCs) are theoretically investigated. A new method to broaden the photonic band gaps is introduced. Based on the similar method, a kind of photonic crystals is constructed to generate photonic band gaps with proportioned central frequencies. This technology can be used for designing nonlinear PCs for harmonic generation.     

Extension of photonic band gaps in one-dimensional photonic crystals

A method is proposed for extending photonic band gaps by constructing periodic structures from two or more consecutively located photonic crystals with different lattice constants or filling factors. The photonic band gaps with a maximum extension are predicted by superposing the photonic band gap maps on one another. It is demonstrated that both the lowest and higher order band gaps can be merged in photonic crystals with a high refractive index contrast.     

Larger complete photonic bandgaps in two-dimensional photonic crystal heterostructure

A two-dimensional photonic crystal heterostructure with a large complete photonic bandgap is presented. It consists of two photonic crystals, whose dielectric configurations are reverse, with triangular lattice of circular columns. The structure retains the ease of fabrication while increasing the maximum quality factor of the gap 2–3 times after optimization. Photonic bandgap properties are calculated using a plane-wave method and the transmission spectra are obtained.     

Modelling of photonic crystals for the design of photonic device based on SOI substrate

In this paper, we report a photonic integrated circuit (PIC), which consisting of a photonic crystal (PC) coupled by a dielectric waveguide to an optical fibre. The PC consists of a sequence of dielectric rods based on a silicon (Si) strip on a silicon dioxide (SiO₂) layer. The finite-difference time-domain (FDTD) method is reviewed and then used to model and predict the optical and the geometrical parameters used to design the fundamental elements of the PIC. The air gap width and the etching depth of the grooves are characterised. The coupling between the PC, and traditional dielectric waveguides is studied and coupling efficiency is evaluated. Diffractive losses are shown to affect strongly the performances of the proposed PIC. In addition, the effect of the air gap width on the diffractive losses and the coupling efficiency between successive neighbouring silicon sections is analysed. The field profile distribution in the structure is calculated and performed. The effects of an incorporated defect are studied, showing a high quality factor.     

Impact of geometry on the TM photonic band gaps of photonic crystals and quasicrystals

Here we demonstrate a novel quantitative procedure to pursue statistical studies on the geometric properties of photonic crystals and photonic quasicrystals (PQCs) which consist of separate dielectric particles. The geometric properties are quantified and correlated to the size of the photonic band gap (PBG) for wide permittivity range using three characteristic parameters: shape anisotropy, size distribution, and feature-feature distribution. Our concept brings statistical analysis to the photonic crystal research and offers the possibility to predict the PBG from a morphological analysis.     

Temperature dependence of the photonic bandgap and the orientational order parameter for a cholesteric photonic crystal

The reflection spectra of a cholesteric photonic crystal have been measured. The experimental spectra are described by a theoretical expression that follows from the analytical solution of the Maxwell equations. The photonic bandgap width Δν has been determined. The photonic bandgap width changes abruptly as the position of the diffraction band changes. The temperature dependence of the relative bandgap width Δν/ν₀ and the order parameter for a photonic crystal are described by Landau’s theory of phase transitions.     

Zitterbewegung in the honeycomb photonic lattice

The propagation of a wave packet in a honeycomb photonic lattice has been studied using the time-dependent wave packet dynamics. It is found that the wave packet, superposed from the positive and negative energy modes at the vicinity of the two inequivalent Dirac points, can transform into a double-ring structure, which is caused by the interference between the two positive and negative energy modes around the Dirac points and is closely related to the Zitterbewegung (ZB). Also, a possible way to detect the ZB effect is proposed in the honeycomb photonic lattice.     

Effective photonic pseudogap of a two-phase composite opaline photonic crystal

We report the observation of suppression of the green photoluminescence from an optically active ZnO-infiltrated composite opal fabricated by electrodeposition templated on a self-assembled polystyrene opal. This is interpreted to be the consequence of an effective photonic pseudogap formed by the composite opaline photonic crystal. The effective pseudogap’s effect on emission of the composite opal, one ‘raw’ and one ‘inverted’, is simply the addition of the effect of each component opal, with no noticeable interaction effect, thus suggesting a simple route for engineering the photonic behavior of heterogeneous photonic crystals. PACS 42.70.Qs; 78.55.-m; 78.66.Hf     

Polaritonic and photonic gap interactions in a two-dimensional photonic crystal

If an ionic material is used in a photonic crystal, the lattice resonance creates a polaritonic gap in the infrared range. The interaction between a polaritonic gap and the structure gap in a 2D square photonic crystal is studied by transfer matrix photonic band structure calculations. The polaritonic gap appears for a surprisingly low volume density of the ionic material. The TM gaps are larger than the TE gaps, as in the dielectric case. By varying the lattice constant, the structure gaps can be shifted across the polaritonic gap, and the effects of merging the two gaps can be studied.