Metallic Photonic Crystal Structures Research Articles

Phase-resolved pulse propagation through metallic photonic crystal slabs: plasmonic slow light.

We characterized the electromagnetic field of ultra-short laser pulses after propagation through metallic photonic crystal structures featuring photonic and plasmonic resonances. The complete pulse information, i.e. the envelope and phase of the electromagnetic field, was measured using the technique of cross-correlation frequency resolved optical gating. In good agreement, measurements and scattering matrix simulations show a dispersive behaviour of the spectral phase at the position of the resonances. Asymmetric Fano-type resonances go along with asymmetric phase characteristics. Furthermore, the spectral phase is used to calculate the dispersion of the sample and possible applications in dispersion compensation are investigated. Group refractive indices of 700 and 70 and group delay dispersion values of 90 000 fs2 and 5000 fs2 are achieved in transverse electric and transverse magnetic polarization, respectively. The behaviour of extinction and spectral phase can be understood from an intuitive model using the complex transmission amplitude. An associated depiction in the complex plane is a useful approach in this context. This method promises to be valuable also in photonic crystal and filter design, for example, with regards to the symmetrization of the resonances.This article is part of the themed issue 'New horizons for nanophotonics'.

Design and Experimental Demonstration of Cherenkov Radiation Source Based on Metallic Photonic Crystal Slow Wave Structure

This paper presents a kind of Cherenkov radiation source based on metallic photonic crystal (MPC) slow-wave structure (SWS) cavity. The Cherenkov source designed by linear theory works at 34.7 GHz when the cathode voltage is 550 kV. The three-dimensional particle-in-cell (PIC) simulation of the SWS shows the operating frequency of 35.56 GHz with a single TM01 mode is basically consistent with the theoretically one under the same parameters. An experiment was implemented to testify the results of theory and PIC simulation. The experimental system includes a cathode emitting unit, the SWS, a magnetic system, an output antenna, and detectors. Experimental results show that the operating frequency through detecting the retarded time of wave propagation in waveguides is around 35.5 GHz with a single TM01 mode and an output power reaching 54 MW. It indicates that the MPC structure can reduce mode competition. The purpose of the paper is to show in theory and in preliminary experiment that a SWS with PBG can produce microwaves in TM01 mode. But it still provides a good experimental and theoretical foundation for designing high-power microwave devices.

Femtosecond laser direct writing of large-area two-dimensional metallic photonic crystal structures on tungsten surfaces.

Metallic photonic crystals (MPCs) and metamaterials operating in the visible spectrum are required for high-temperature nanophotonics, but they are often difficult to construct. This study demonstrates a new approach to directly write two-dimensional (2D) MPCs on tungsten surfaces through the cylindrical focusing of two collinear femtosecond laser beams with certain temporal delays and orthogonal linear polarizations. Results are physically attributed to the laser-induced transient crossed temperature grating patterns and tempo-spatial thermal correlations. Optical properties of the fabricated MPCs are characterized. Such a simple and efficient technique can be used to fabricate large-area, 2D microstructures on metal surfaces for potential applications.

Finite element method analysis of band gap and transmission of two-dimensional metallic photonic crystals at terahertz frequencies

Photonic band gap and transmission characteristics of 2D metallic photonic crystals at THz frequencies have been investigated using finite element method (FEM). Photonic crystals composed of metallic rods in air, in square and triangular lattice arrangements, are considered for transverse electric and transverse magnetic polarizations. The modes and band gap characteristics of metallic photonic crystal structure are investigated by solving the eigenvalue problem over a unit cell of the lattice using periodic boundary conditions. A photonic band gap diagram of dielectric photonic crystal in square lattice array is also considered and compared with well-known plane wave expansion results verifying our FEM approach. The photonic band gap designs for both dielectric and metallic photonic crystals are consistent with previous studies obtained by different methods. Perfect match is obtained between photonic band gap diagrams and transmission spectra of corresponding lattice structure.

Experimental realization of plasmonic filters for multispectral and dual-polarization optical detection

We report the design and implementation of a new class of plasmonic filters that are both wavelength and polarization selective. The plasmonic filter consists of a five-layer metallic photonic crystal structure and operates inside the photonic bandgap regime. We show that by manipulating the middle layer geometry alone, it is possible to tune the Fabry-Perot resonance over a broad spectral range (lambda=1.25to1.63 microm) and in a monolithic fashion. Furthermore, we show that the resonance has a definite polarization character that is determined by the orientation of the first layer grating. The plasmonic filter may be integrated with an array of photodetectors for high-throughput spectral and polarimetric imaging applications.

2-D Terahertz Metallic Photonic Crystals in Parallel-Plate Waveguides

2-D metallic photonic crystals without defects, with point defects, and with a Fabry-Perot (F-P) defect are characterized by terahertz time-domain spectroscopy. The metal parallel-plate waveguide (PPWG) with single TEM-mode propagation is used as a tool to simulate 2-D photonic crystals in free space. The 2-D metallic photonic-crystal structures were fabricated by coating Au on an SU-8 polymer cylinder array. Wide terahertz bandgaps were observed in the photonic crystals within the PPWG. The experimental measurements have excellent agreement to 2-D photonic-crystal theory without defects. Defect modes are observed in the samples with defects and show the F-P defect has a strong localization effect

Visible three-dimensional metallic photonic crystal with non-localized propagating modes beyond waveguide cutoff

We report experimental realization of a 5-layer three-dimensional (3D) metallic photonic crystal structure that exhibits characteristics of a 3D complete bandgap extending from near-infrared down to visible wavelength at around 650 nm. The structure also exhibits a new kind of non-localized passband mode in the infrared far beyond its metallic waveguide cutoff. This new passband mode is drastically different from the well-known defect mode due to point or line defects. Three-dimensional finite-difference-time-domain simulations were carried out and the results suggest that the passband modes are due to intra-structure resonances.

A Polarization Beam Splitter for Optical Telecommunications Based on Two-Dimensional Metallic Photonic Crystal Structures

We proposed a novel method of constructing a chip polarization beam splitter (PBS) based on two-dimensional metallic photonic crystal (2D-MPC) structures that can be realized using the industrial-based semiconductor IC Cu-interconnect technology. The performance of such a PBS at wavelengths for optical telecommunications is evaluated by the finite-difference-time-domain (FDTD) simulation method. This 2D-MPC PBS device uses three rows of one-dimensional (1D) arrays (3×N-MPC-2D-MPC) as a basic building block to construct the PBS. Using this architecture, the incoming transverse magnetic (TM) and transverse electric (TE) waves can be splitted with very high splitting efficiency (polarization ratio over 1000 for both the TM and TE modes). The implication of our scheme is that the fabrication of such a 2D-MPC PBS is totally compatible with current commercial complementary metal oxide semiconductor (CMOS) fabrication technology. This makes it a ready-to-use technology for the fabrication of a chip-base 2D-MPC PBS.

Three-color photonic crystal demultiplexer based on ultralow-refractive-index metamaterial technology

We numerically demonstrate the operation of a novel class of wavelength-division demultiplexing circuit based on photonic crystal waveguides that are entirely synthesized by ultralow-refractive-index metallic nanopillars. The operational principle of the newly proposed device is based on the phenomenon of total external reflections in ultralow-refractive-index metallic photonic crystal structures (metamaterials). In addition we provide detailed design guidelines for optimum device performance. The low propagation losses and compact size, as well as temperature-insensitive operation over a wide temperature range, are only a few of the advantages of the proposed technology, making this new type of demultiplexer an excellent candidate for applications in the visible spectrum.

Optical properties of planar metallic photonic crystal structures: Experiment and theory

We report on results of transmission measurements of metallic nanowire arrays deposited on top of different dielectric substrates. The appearance of grating anomalies, which critically depend on the substrate thickness, provides evidence that the optical response of these planar metallic photonic crystal structures can be strongly modified. While only Rayleigh-type anomalies are observed for thin dielectric substrates, thicker waveguiding substrates can induce strong coupling phenomena. This strong coupling results in the formation of waveguide-plasmon polaritons with a large Rabi splitting up to $250\phantom{\rule{0.3em}{0ex}}\mathrm{meV}$. We show that the coupling phenomena vary with the nanowire grating period, the angle of incidence, and also the waveguide layer thickness. A scattering-matrix-based numerical method is used to calculate the transmission properties and the near-field spatial distributions of such metallic photonic crystal structures. All experimental results are well confirmed by our theoretical calculations.

Optical studies of metal-infiltrated opal photonic crystals

We have studied the optical properties of metal infiltrated opal photonic crystals and metallic replicas made of Sb, Hg, Bi and Pb. We observed dramatic differences in the reflectivity spectra of two kinds of metallic structures, namely those with either network or cermet topologies. We found that all metallic photonic crystals have Bragg stop bands in the visible spectral range. Highly interconnected metallic photonic crystal structures, however, showed about one order of magnitude decrease in the effective plasma frequency compared to that of the bulk metals. Coherent backscattering measurements showed a much larger optical mean free path for the metal-infiltrated opals compared to the skin depth of the metals, in agreement with the reduction in the plasma frequency. We also found an extra band in the reflectivity spectra of network-type samples that is related to surface plasmons. A theoretical model that considers the metallic mesh inside the opal as a cubic wire network agrees well with the experimental results.