Metallic Photonic Band Gap Research Articles

Nonlinear Bloch waves in metallic photonic band-gap filaments

We demonstrate the occurrence of nonlinear Bloch waves in metallic photonic crystals (PCs). These periodically structured filaments are characterized by an isolated optical pass band below an effective plasma gap. The pass band occurs in a frequency range where the metallic filament exhibits a negative, frequency-dependent dielectric function and absorption loss. The metallic losses are counterbalanced by gain in two models of inhomogeneously broadened nonlinear oscillators. In the first model, we consider close-packed quantum dots that fill the void regions of a two-dimensional (2D) metallic PC, and whose inhomogeneously broadened emission spectrum spans the original optical pass band of the bare filament. In the second model, we consider thin (10-50 nm) layers of inhomogeneously broadened two-level resonators, with large dipole oscillator strength, that cover the interior surfaces of 2D metallic (silver and tungsten) PCs. These may arise from localized surface plasmon resonances due to small metal particles or an otherwise rough metal surface. For simplicity, we treat electromagnetic modes with electric field perpendicular to the plane of metal periodicity. In both models, a pumping threshold of the resonators is found, above which periodic nonlinear solutions of Maxwell's equations with purely real frequency within the optical pass band emerge. These nonlinearmore » Bloch waves exhibit a laserlike input pumping to output amplitude characteristic. For strong surface resonances, these nonlinear waves may play a role in light emission from a hot tungsten (suitably microstructured) filament.« less

Properties of Metallic Photonic Band Gap Material with Defect at Microwave Frequencies: Calculation and Experimental Verification

In this paper, the properties of a Metallic Photonic Band Gap Prism (MPBGP) with defects are studied. The MPBGP is made of metallic rods disposed in an isosceles right-angled triangle. The commercial software HFSS based on the finite element method is used to study the behavior of Photonic Band Gap structure by means of three-dimensional dispersion diagrams, iso-frequency curves, radiation patterns and the cartography of electric field. Numerical results showed that the metallic photonic band gap without and with defects behaves like a homogeneous and ultrarefractive medium in the first allowed frequency band. The distribution of defects doesn't modify the propagation of electromagnetic waves through the metallic photonic band gap material, it has properties similar to that of a perfect prism. In the forbidden frequency bands, the anomalous transmission has been obtained by means of surface defects in Metallic structure. This anomalous transmission in forbidden band has also been observed in simulations carried out on a dielectric photonic band gap material made of dielectric rods disposed in an isosceles right-angled triangle. Theoretical results presented in this paper have been successfully validated by measurements carried out in the frequency range [7–16 GHz].

Study of 2D metallic photonic band gap structures

In order to study 2D metallic photonic crystal, a new plane-wave expansion method was proposed. Based on traditional plane wave expansion method, the “original problem” to be solved was extended to a “new problem”. First, the relation between them were given, second, the “new problem” was transformed to an integral-differential eigen equation through an auxiliary function. The eigen equation was solved to obtain the band gap structures of the “new problem”. The band gap structures of the “original problem” were deduced according to “new problem”. Finally, numerical computations were done for 2D square-lattice square metallic rods photonic crystal, and excellent results were achieved.

The two-dimensional metal photonic band gap structure consisting of a skew lattice in a nonorthogonal coordinate system

The metal photonic band gap structure has potentialities in the areas of high-energy accelerators,microwave vacuum electron devices, and terahertz radiation sources etc. The real space transfer matrix method in a nonorthogonal coordinate system is used to study the two-dimensional metal photonic band gap structure consisting of a skew lattice. A general formula for calculating the complete band gap structure is derived for transverse-electric and transverse magnetic modes, and the influences of the filling fraction, skew angle and cross section of the metal rod on band gap are analyzed. The results are in good agreement with results of other methods in some special cases.

THz parallel plate photonic waveguides

We have observed narrowband transmission or rejection in the frequency spectra of THz pulses transmitted through air-spaced parallel plate photonic waveguides. These waveguides have one of the metal plates covered by a silicon plate with a metallic photonic band gap (PBG) surface precisely fabricated by lithographic techniques. We use two different PBG surface types: an array of metallic cylindrical pillars, and an array of metallic cylindrical holes. With the inversion of the PBG structures from cylinders to holes, the output spectra changes from narrow bandpass to narrow band-reject filtering. These photonic waveguides show extremely sharp spectral responses in regions as large as 1 THz, with stop bands or transmission bands having contrasts of as much as 90 dB.

Magnetic photonic band-gap material at microwave frequencies based on ferromagnetic nanowires

We present an experimental investigation of a class of microwave photonic band-gap (PBG) materials, in which the magnetic permeability μ varies periodically within the material. This material is fabricated using a periodic arrangement of arrays of magnetic nanowires. As for dielectric or metallic PBG, the band-gap behavior varies with the geometrical parameters fixing the spatial periodicity of the magnetic structure. The magnetic photonic band gap is induced by the presence of a ferromagnetic resonance effect in the vicinity of the band gap.

Experimental observation of photonic-crystal emission near a photonic band edge

A three-dimensional tungsten photonic crystal is realized with a photonic band edge at λ∼4 μm wavelength. Its thermal emission is suppressed in the band gap regime and, at the same time, exhibits sharp peaks near the band edge. It is further observed that energy conversion efficiency from one side of the sample reaches η∼40%. This finding is attributed to a complete metallic photonic band gap in the infrared (λ⩾6 μm) and the enhanced density of photon states near the band edge of our tungsten photonic crystal.

Designer infrared filters using stacked metal lattices

We have designed and fabricated infrared filters for use at wavelengths ≳15 microns. Unlike conventional dielectric filters used at the short wavelengths, ours are made from stacked metal grids, spaced at a very small fraction of the performance wavelengths. The individual lattice layers are gold, the spacers are polyimide, and they are assembled using integrated circuit processing techniques; they resemble some metallic photonic band-gap structures. We simulate the filter performance accurately, including the coupling of the propagating, near-field electromagnetic modes, using computer aided design codes. We find no anomalous absorption. The geometrical parameters of the grids are easily altered in practice, allowing for the production of tuned filters with predictable useful transmission characteristics. Although developed for astronomical instrumentation, the filters are broadly applicable in systems across infrared and terahertz bands.

Asymptotic analysis of dispersion characteristics in two-dimensional metallic photonic band gap structures

We present a self-consistent technique for the asymptotic analysis of dispersion curves in two-dimensional metallic photonic band gap structures representing square and triangular arrays of metal rods. The technique is applicable for the structures with rod radii (a), which are small compared to the distance between the rods (b) and to the wavelength (λ). The induced current and charge distributions on the rods are expressed self-consistently in terms of the electromagnetic wave field. The dispersion characteristics are calculated for the TE and TM modes. The results are in agreement with those obtained previously using the Photonic Band Gap Structure Simulator code.

Photonic band gap studies on periodic metallic structures in the microwave region

AbstractWe present our experimental findings on microstrip‐type metallic photonic band gap (PBG) periodic structures prepared using a commercial aluminum foil. Effect of change in geometry of the periodic dielectric structure, namely, period, rectangular hole length, and defect on PBG, is studied. It is found that as the rectangular‐hole‐cut dimension decreases in terms of length, the lower edge of the band gap decreases toward the lower frequency side of the microwave region. It is also observed that as the defect length increases, the band gap edge again shifts toward the lower frequency side. These findings of band gap with air as substrate confirm the role of wave impedance in purely metallic periodic structures. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 483–486, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10644

Analytical method to compute metallic photonic band‐gap radar cross section

AbstractThe electromagnetic scattering by Metallic Photonic Band‐Gap materials, composed of cylindrical wires, is considered. A fast and accurate analytical method is proposed to compute the radar cross section of such structures with or without defects. Results are given and compared with success to those of numerical methods. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 145–150, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10542

Second harmonic generation in two-dimensional metal photonic band gap materials

With plane-wave expansion and the Green function method, the second harmonic generation in a two-dimensional metal photonic band gap (PBG) material is studied theoretically. By appropriately selecting the structural parameters of the PBG material, the wave vectors of the fundamental and the second harmonics can be set at the edges of the PBG. In this case, the second harmonic can be realized efficiently due to metal surface nonlinearity. The discussion can be generalized to three-dimensional systems.

Operating characteristics of an optical filter in metallic photonic bandgap materials

AbstractIn this Letter a new analysis of an optical filter using a metallic photonic bandgap material on the microscopic scale is reported. The proposed filter is capable of working over a wide range of the electromagnetic spectrum and the idea is based on the famous Kronig–Penny model in the solid state. The periodic structure consisting of different conducting materials and dielectrics (air) are considered. The structure is also able to pass the light emitted by a He–Ne laser source by choosing the appropriate values of the controlling parameters, and thus this may act as an efficient monochromator. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 68–71, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10518

Metallic Photonic Bandgap Resonant Antennas with HighDirectivity and High Radiation Resistance

A metallic photonic bandgap (MPBG) resonant antenna is introduced, which hasnovel characteristics (such as high directivity and high radiationresistance for a certain range of frequencies) as compared to conventionalMPBG antennas. The linear MPBG resonant antenna is formed by infinitely longmetallic rods in vacuum. The numerical results for the radiation pattern and theradiation resistance are presented. By adjusting the structure of the MPBGresonant antenna and its working frequency, an optimal structure isachieved. The physical reasons for the novel characteristics of the MPBGresonant antenna are also explained.

Two-dimensional metallic photonic band-gap crystals fabricated by LIGA

Two-dimensional metallic photonic band-gap crystals, consisting of square and triangular lattices of nickel pillars, were fabricated by the LIGA process. In particular, PMMA slabs with a thickness of up to 800 μm were irradiated with synchrotron radiation and the holes produced were then filled with nickel via electroforming. The lattice constant, i.e., the center-to-center distance between the pillars, is either 60 μm or 40 μm for the square and triangular structures respectively. The metal filling ratio is 10% for the square and 20% for the triangular structures. Transmission and reflection measurements demonstrate that the metallic photonic band-gap crystals show a cutoff frequency in the far infrared regime between 2 and 5 THz. It is concluded that LIGA is a promising method for the fabrication of 2-D metallic photonic band-gap structures, which could be potentially used as passive filters in THz devices.

Antennas based on modified metallic photonic bandgap structures consisting of capacitively loaded wires

AbstractAntenna systems based on some improved metallic photonic bandgap (MPBG) structures are introduced. A useful modification is introduced by replacing each wire in a two‐dimensional MPBG structure by a chain of many identical conducting elements of a certain shape. Each such chain forms an effective wire of capacitive impedance. The optimal design for maximal radiation efficiency and directivity is obtained by choosing an appropriate value of the impedance per unit length for the effective wire and the geometry of the modified MPBG structure. The optimal impedance is realized by using elements of various shapes, including broken wire elements and planar H‐shaped elements. Numerical results have shown that the modification can increase the efficiency of the MPGB antenna by a factor of 1000, as well as reduce the thickness of the MPGB structure to about λ/3 in the presence of a metal background plane. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 214–221, 2001.

Explicit formulas for obtaining the radiation characteristics of an antenna based on a three‐dimensional metallic photonic bandgap structure

AbstractAn antenna based on a three‐dimensional metallic photonic bandgap (MPBG) structure consisting of many parallel metallic short wires is considered. An explicit method is introduced to calculate the radiation pattern for such an antenna system. The explicit method is verified numerically by comparing the results obtained by the finite‐difference time‐domain method. The present method improves the computation speed significantly. A genetic algorithm is used to make an optimal design for such a 3‐D MPBG structure‐based antenna. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 376–381, 2001.

Surface modes in two-dimensional dielectric and metallic photonic band gap structures: a FDTD study

In the present Letter, surface modes in two-dimensional dielectric and metallic photonic crystals are studied by a finite-difference time-domain method. The existence of surface modes in metallic photonic crystals is examined. The influence of surface waves on dielectric photonic crystal antennas is also studied.

Metallic photonic bandgap propagation mode characterization

For antennas located inside photonic bandgap (PBG) materials, the coupling between the propagation modes inside the structure and the free-space modes is an important parameter in order to obtain good overall efficiency. In order to optimize the design of PBG, tools must be developed. These tools must also enable the study of defect modes as they offer the possibility to shape the beam radiated by the antenna. A numerical method based on the finite-difference time-domain (FDTD) method and the Fourier transform has been previously used with success by others authors to visualize propagation modes in the reciprocal space for dielectric PBG materials. In this paper, we apply this method to metallic photonic bandgap (MPBG) materials to characterize modes. We show that the MPBG minimizes the radiated field in undesired directions. Different structures are considered either with or without defects. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 28: 434–440, 2001.

Metallic photonic bandgap propagation mode characterization

Metallic photonic bandgap propagation mode characterization