Metallic Photonic Band Gap Research Articles

Three-dimensionally periodic conductive nanostructures: network versus cermet topologies for metallic PBG

Highly periodic three-dimensional metallic mesh composites with silica have been prepared by micromolding synthetic opals using melts of metals and semimetals. These metallic photonic crystals show photonic and electronic properties, which strongly depend on their geometry. Network topology, created in a form of interconnected spherical cages of 200–400 nm diameter, shows a reflectivity peak in the infrared (IR) spectral range, due to a metallic photonic band gap (MPBG), reminiscent of plasmon edge of bulk metal, which is significantly shifted to longer wavelengths. On the other hand, a discontinuous topology of separated clusters in a matrix (so called cermet topology) obtained by three distinct techniques involved controlling the pressure and temperature of the melt during the infiltration process), do not show any MPBG. In the visible spectral range, bright sharp colors of Bragg scattering are observed from both topologies, which are more intense than in conventional, dielectric gem opals in agreement with computer modeling of light reflection from cermet metallo-dielectric photonic crystals. This metallic PBG structures can be used as novel type IR reflectors, color mirrors and conductive electrodes having properties controlled by the topology of 3-D superstructure.

The influence of the dielectric–air interface on the radiation pattern of an antenna in a metallic photonic bandgap structure in a dielectric host medium

The influence of the dielectric–air interface on the radiation pattern of an antenna in a metallic photonic bandgap structure in a dielectric host medium

Metallic photonic band-gap materials (MPBG) as angular selective reflector or radome: Application to antenna grating lobe reduction

This paper presents numerical and experimental results on metallic photonic band-gap materials (mpbg), composed of metallic wires and used as antenna reflector or radome. Attention is focused on mpbg angular response. In fact, with specified angular characteristics, MPBG materials can be interesting in order to reduce antenna grating lobes. One possible grating lobe reduction solution is based on the use of mpbg as angular filter. The radiation characteristics obtained with this solution are then improved by using a mpbg reflector to enhance the gain. Regarded to a classical metallic reflector, 20 dB and 12 dB gain improvement in the theoretical and in the experimental cases are respectively obtained, when the reflector is composed of more than two layers. The scanning performances are also presented. We show that angular filtering characteristics can be improved either by changing the array interface or by changing the mpbg lattice. In order to select the structure with the best angular behavior, an experimental and numerical characterization method is also presented.

New type of metallic photonic bandgap materialsuitable for microwave applications

A new type of metallic photonic bandgap is proposed which has a wider forbidden frequency band than currently available photonic bandgap materials. Inspired by natural photonic bandgap materials, such as that in butterfly wings, the proposed bandgap material is suitable for microwave and infrared applications.

The influence of the dielectric-air interface on the radiation pattern of an antenna in a metallic photonic bandgap structure in a dielectric host medium

The influence of the dielectric-air interface on the radiation pattern of an antenna in a metallic photonic bandgap structure in a dielectric host medium

Active metallic photonic band-gap materials (MPBG): experimental results on beam shaper

We focus our attention on the possibilities to control the beam radiated by antennas, which are initially omnidirectional using active metallic photonic band-gap materials (AMPBG). In fact, MPBG composed of continuous or discontinuous wires present different and interesting characteristics when they are used as an antenna reflector or a radome. Adding active components on wires allows one to switch from continuous to discontinuous structures. Wires with active elements on can then be placed inside a structure, which shapes the beam radiated by a dipole antenna. Experimental results show that it allows one to switch on/off the beam or to change its shape.

An explicit and efficient method for obtaining the radiation characteristics of wire antennas in metallic photonic bandgap structures

An explicit and efficient method for obtaining the radiation characteristics of wire antennas in metallic photonic bandgap structures

Waveguides in three-dimensional metallic photonic band-gap materials

We theoretically investigate waveguide structures in three-dimensional metallic photonic band-gap (MPBG) materials. The MPBG materials used in this study consist of a three-dimensional mesh of metallic wires embedded in a dielectric. An {ital L}-shaped waveguide is created by removing part of the metallic wires. Using finite difference time domain simulations, we found that an 85{percent} transmission efficiency can be achieved through the 90{degree} bend with just three unit cell thickness MPBG structures. thinsp {copyright} {ital 1999} {ital The American Physical Society}

Experimental radiation pattern of dipole inside metallic photonic bandgap material

This paper presents experimental results on a dipole antenna placed inside metallic photonic bandgap materials. Different structures are proposed with single or mixed MPBG configurations. These results demonstrate that a radiated beam can be shaped by appropriately selecting the MPBG. They also show that the antenna bandwidth can be improved by changing the periodicity of the MPBG. These changes must be progressive in order not to disturb the antenna input impedance in the band where it was already working. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 10–16, 1999.

Laser-machined layer-by-layer metallic photonic band-gap structures

Metallic photonic band-gap crystals operating in the microwave frequency range were fabricated by laser precision machining. They consist of stainless steel plates with a tetragonal lattice of holes and a lattice constant of 15 mm. Transmission measurements show that periodic crystals exhibit a cutoff frequency in the 8–18 GHz range, below which no propagation is allowed. The cutoff frequency can be easily tuned by varying the interlayer distance or the filling fraction of the metal. Combinations of plates with different hole diameters create defect modes with relatively sharp peaks, which are tunable. The experimental measurements are in good agreement with theoretical calculations.

Finite-difference time-domain modeling of dispersive-material photonic bandgap structures

Photonic bandgap (PBG) structures constructed from lossy, dispersive dielectric and metallic materials are characterized in terms of their reflection and transmission properties. Particular emphasis is given to PBG structures with defects. These PBG structures are modeled analytically with an ABCD matrix method for their single-frequency response. They also are modeled numerically with a finite-difference time-domain approach to determine their operating characteristics over a wide set of frequencies in a single simulation. It is shown that material dispersion can significantly alter the characteristics of a PBG structure’s frequency response. Metallic PBG structures at optical frequencies thus exhibit bandgap characteristics significantly different from those of their nondispersive dielectric counterparts. It is shown that microcavities whose mirrors are constructed from dispersive-material PBG structures can be designed to outperform similar nondispersive-mirror microcavities.

Transmission and absorption properties of two-dimensional metallic photonic-band-gap materials

Using the multiple-scattering method, we study systematically the transmission and absorption properties of two-dimensional (2D) metallic photonic-band-gap (PBG) materials for a wide range of frequency and structure scales by adopting a realistic dielectric constant for metal cylinders. For both S and P waves, analytic expressions for the absorption power of a single metal cylinder under an arbitrary external field have been derived to explain the absorption behaviors of metallic PBG materials in a coherent way. The discussions and conclusions presented here can be generalized to 3D systems as well.

Optimizing the Q value in three-dimensional metallic photonic band gap crystals

A metallic photonic band gap crystal with different defect structures is fabricated. The structure is designed and built to operate in the 8–26 GHz frequency range. Defects with sharp peaks in the transmission are created by removing portions of the metallic rods in a single defect layer. A high quality factor (Q) for the defect state is obtained by larger filling ratios and spatial separations between the unit cells. An optimized value of Q⩾300 is found for three unit cell metallic photonic band gap structure. The experimental observations agree very well with theoretical calculations using the transfer matrix method.

Influence of metallic photonic bandgap (MPBG) materials interface on dipole radiation characteristics

The MPBG interface influence on half-wavelength dipole radiation characteristics—radiation pattern and input impedance—is analyzed. This study concerns frequency operation within or without an MPBG bandgap. A first analysis has been performed by replacing a wire of a 2-D square lattice MPBG by a dipole. Then, the study of dipole–MPBG distance is presented for different MPBG structures, and is compared to simple and gridded corner reflector characteristics. This demonstrates that the input impedance value can be controlled, and depends on the MPBG structure dimensions and on the dipole position within this structure. It shows that some improvement of angular filter specifications can be obtained when the MPBG interface is no longer a plane. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 407–410, 1998.

Theoretical study of grating lobes reduction using metallic photonic bandgap materials (MPBG)

A linear array of three half-wavelength dipoles above a metallic reflector is analyzed. The results are then compared with those of the same array above a different kind of metallic photonic bandgap materials. The aim is to find a structure which allows the greatest reduction of the grating lobes (GL). This reduction can be obtained either by a destructive interference in the direction of the grating lobes or by using propagation inside the MPBG, propagation of normal incidence only (main lobe), or in the GL directions only. Then, an MPBG is selected and is completely analyzed (plane wave response, the radiation pattern with just one dipole and with the array in different configurations). As one solution is based on the propagation of particular modes inside the MPBG, this solution can be enhanced by the use of an MPBG reflector on the other side. But this solution is not perfect since there are grating lobes in the E-plane due to the way the waves are guided in the MPBG. One last structure is presented in order to suppress this grating. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 32–41, 1998.

Theoretical study of grating lobes reduction using metallic photonic bandgap materials (MPBG)

Theoretical study of grating lobes reduction using metallic photonic bandgap materials (MPBG)

High-Q radio-frequency structures using one-dimensionally periodic metallic films

High-Q structures are very interesting theoretically, and very important practically, for a variety of engineering applications in communication systems. We address the issue of designing a thin-film metal structure of reflectivity higher than the intrinsic reflectivity of the bulk metal itself. We study a finite array of planar conducting layers of arbitrary thickness periodically placed an arbitrary distance apart, and we arrive at an exact analytical formula for the reflection and transmission coefficients. These structures are equivalent to a one-dimensional metallic photonic bandgap (PBG) system. We apply our formulas to the microwave regime and fully explore the system's three-dimensional parameter space, consisting of the number of layers, their thickness, and their spacing. We find very significant enhancements of the radio frequency-Q, relative to the bulk metal, in narrow regions of the parameter space.

Infrared filters using metallic photonic band gap structures on flexible substrates

Metallic photonic band gap (MPBG) filter structures operating at far infrared wavelengths have been designed, fabricated, and characterized. The MPBGs are multilayer metallic meshes imbedded in a flexible polyimide dielectric. Depending on the periodic pattern of the metal grids, the filters have either simple high-pass or more complex transmission characteristics. The critical frequencies of the filters depend on the spatial periodicity of the metal grids and the interlayer separation. Optical transmission measurements on a high-pass structure show cutoff frequency of 3 THz and attenuation of more than 35 dB in the cutoff region, in good agreement with predicted results. Band-reject filters show similarly good attenuation and large fractional bandwidths. The filters maintain their optical characteristics after repeated bending, demonstrating mechanical robustness of the MPBG structure.

Theoretical study of interactions between antennas and metallic photonic bandgap materials

Theoretical study of interactions between antennas and metallic photonic bandgap materials

Band-reject infrared metallic photonic band gap filters on flexible polyimide substrate

AbstractMetallic photonic band gap (MPBG) structures are multi-layer metallic meshes imbedded in a dielectric medium. We report the successful design, fabrication, and characterization of infrared band-reject filters using MPBG structures in a flexible polyimide substrate. The metal layers of the MPBG have square grid patterns with short perpendicular cross-arm defects added halfway between each intersection. The transmission characteristics of these filters show a higher order band-reject region in addition to a lower order band gap that extends from zero to particular cut off frequency. The critical frequencies of the filters depend on the spatial periodicity of the metal grids and length of the cross-arm defects. Optical transmission measurements of the bandreject filters show lower edge cutoff frequency of about 2 THz and the higher order bandgap region centered around 4.5THz with attenuation of more than 35 dB in the bandgap region. This is in good agreement with the theoretical calculations. The filters maintain their optical characteristics after repeated bending, demonstrating mechanical robustness of the MPBG structure and have minimal dependence on angle of incidence.