Three-dimensional Woodpile Photonic Crystals Research Articles

The dispersion properties of three-dimensional woodpile magnetized plasma photonic crystals including function dielectric under magneto-optical Faraday effect

In this paper, the dispersion properties of three-dimensional function magnetized plasma photonic crystals (FMPPCs) are theoretically studied by a modified plane wave expansion method, when the magneto-optical Faraday effect is considered, and the directions of the electromagnetic wave vector and the extrinsic magnetic field are always parallel to each other. The arrangement of these FMPPCs is that the function dielectric square columns are embedded into the plasma background, and the inserted dielectric columns are arranged by woodpile lattices with face-centered-tetragonal symmetry. The relative permittivity of function square columns depends on the space coordinates. The relationships between the parameters of FMPPCs and the photonic bandgaps (PBGs) for the right and left circular polarization waves also are investigated. The calculated results demonstrate that those PBGs can be tailored by those parameters, and the right and left circular polarization waves can be split when the extrinsic magnetic field is large enough.In this paper, the dispersion properties of three-dimensional function magnetized plasma photonic crystals (FMPPCs) are theoretically studied by a modified plane wave expansion method, when the magneto-optical Faraday effect is considered, and the directions of the electromagnetic wave vector and the extrinsic magnetic field are always parallel to each other. The arrangement of these FMPPCs is that the function dielectric square columns are embedded into the plasma background, and the inserted dielectric columns are arranged by woodpile lattices with face-centered-tetragonal symmetry. The relative permittivity of function square columns depends on the space coordinates. The relationships between the parameters of FMPPCs and the photonic bandgaps (PBGs) for the right and left circular polarization waves also are investigated. The calculated results demonstrate that those PBGs can be tailored by those parameters, and the right and left circular polarization waves can be split when the extrinsic magnetic fie...

Woodpile结构三维光子晶体中的四端口通道下载滤波器

Woodpile结构三维光子晶体中的四端口通道下载滤波器

Three-dimensional woodpile photonic crystals for visible light applications

Three-dimensional woodpile photonic crystals for the visible light regime were fabricated using a layer-by-layer electron beam lithography process. The materials consisted of silicon nitride for the high index material and the planarization was accomplished using a spin-coated nano-porous silica material which was left in place as the interstitial material. This fabrication procedure presents a simplified route for constructing multilayer structures where planarization is necessary, including three-dimensional photonic crystals (3DPCs) or three-dimensional metamaterials. To demonstrate the robustness of the approach, multiple 3DPCs were fabricated and optically characterized. Multiplane waveguide defects were inserted in the crystals and characterized. The vertical waveguides demonstrate enhanced transmission of light, and work continues to realize waveguiding through the full three-dimensional network of waveguides.

Investigation of defect cavities formed in three-dimensional woodpile photonic crystals

We report the optimisation of optical properties of single defects in three-dimensional (3D) face-centred-cubic (FCC) woodpile photonic crystal (PC) cavities by using plane-wave expansion (PWE) and finite-difference time-domain (FDTD) methods. By optimising the dimensions of a 3D woodpile PC, wide photonic band gaps (PBG) are created. Optical cavities with resonances in the bandgap arise when point defects are introduced in the crystal. Three types of single defects are investigated in high refractive index contrast (Gallium Phosphide-Air) woodpile structures and Q-factors and mode volumes ($V_{eff}$) of the resonant cavity modes are calculated. We show that, by introducing an air buffer around a single defect, smaller mode volumes can be obtained. We demonstrate high Q-factors up to 700000 and cavity volumes down to $V_{eff}<0.2(\lambda/n)^3$. The estimates of $Q$ and $V_{eff}$ are then used to quantify the enhancement of spontaneous emission and the possibility of achieving strong coupling with nitrogen-vacancy (NV) colour centres in diamond.

Design of a three-dimensional photonic band gap cavity in a diamondlike inverse woodpile photonic crystal

We theoretically investigate the design of cavities in a three-dimensional (3D) inverse woodpile photonic crystal. This class of cubic diamondlike crystals has a very broad photonic band gap and consists of two perpendicular arrays of pores with a rectangular structure. The point defect that acts as a cavity is centered on the intersection of two intersecting perpendicular pores with a radius that differs from the ones in the bulk of the crystal. We have performed supercell band structure calculations with up to $5\ifmmode\times\else\texttimes\fi{}5\ifmmode\times\else\texttimes\fi{}5$ unit cells. We find that up to five isolated and dispersionless bands appear within the 3D photonic band gap. For each isolated band, the electric-field energy is localized in a volume centered on the point defect, hence the point defect acts as a 3D photonic band gap cavity. The mode volume of the cavities resonances is as small as 0.8 ${\ensuremath{\lambda}}^{3}$ (resonance wavelength cubed), indicating a strong confinement of the light. By varying the radius of the defect pores we found that only donorlike resonances appear for smaller defect radius, whereas no acceptorlike resonances appear for greater defect radius. From a 3D plot of the distribution of the electric-field energy density we conclude that peaks of energy are found in sharp edges situated at the point defect, similar to how electrons collect at such features. This is different from what is observed for cavities in noninverted woodpile structures. Since inverse woodpile crystals can be fabricated from silicon by CMOS-compatible means, we project that single cavities and even cavity arrays can be realized, for wavelength ranges compatible with telecommunication windows in the near infrared.

Flat lensing in the visible frequency range by woodpile photonic crystals

We experimentally demonstrate full two-dimensional focalization of light beams at visible frequencies by a three-dimensional woodpile photonic crystal. The focalization (the flat lensing) with focal distances of the order of 50-70 μm is experimentally demonstrated. Experimental results are compared with numerical calculations and interpreted by harmonic expansion studies.

A three-dimensional silicon photonic crystal nanocavity with enhanced emission from embedded germanium islands

We report the realization of a silicon three-dimensional photonic crystal nanocavity containing self-assembled germanium-island emitters. The three-dimensional woodpile photonic crystal was assembled layer by layer by micromanipulation using silicon plates grown by molecular beam epitaxy. An optical nanocavity was formed in the center of the photonic crystal by introducing a point defect into one of the plates. Measurements of the filtered spontaneous emission from the Ge islands in the active plate through the localized modes of the structure directly reveal information on the evolution of the frequency and Q-factor as upper cladding plates are sequentially added. An exponential increase of the cavity-Q is observed when the number of upper cladding plates is increased up to a maximum of ten. The emission of germanium-islands within the cavity reveals several strongly polarized cavity modes with quality-factors up to ≈13 600. The emission intensity of the cavity modes is enhanced by large factors up to ≈58× as compared with the active plate outside the photonic environment.

Photonic Paint Developed with Metallic Three-Dimensional Photonic Crystals

This work details the design and simulation of an inconspicuous photonic paint that can be applied onto an object for anticounterfeit and tag, track, and locate (TTL) applications. The paint consists of three-dimensional metallic tilted woodpile photonic crystals embedded into a visible and infrared transparent polymer film, which can be applied to almost any surface. The tilted woodpile photonic crystals are designed with a specific pass band detectable at nearly all incident angles of light. When painted onto a surface, these crystals provide a unique reflective infra-red optical signature that can be easily observed and recorded to verify the location or contents of a package.

Optical properties of three-dimensional woodpile photonic crystals composed of circular cylinders with planar defect structures

The optical properties of three-dimensional woodpile photonic crystals (PhCs) composed of circular cylinder rods with a planar defect structure at the central layer are theoretically investigated using the parallel finite-difference time-domain method and plane-wave expansion method. Three types of planar defects are introduced into the PhC by alternating respectively the dielectric constant, cylinder diameter, and misalignment of the rods at the defect layer. The transmission spectrum and band diagram of each planar defect structure are systematically studied. The resonance and transmission properties of the defect structures can be characterized by two distinct resonant modes, the defect mode and the band-edge resonant mode, which have been identified by detailed spectrum analysis, calculated mode profiles and field patterns. It is shown that, by modifying the rod diameter or the dielectric constant of materials at the defect layer, the resonant modes can be varied and controlled. Also, by applying dislocation to a layer of dielectric rods, the photonic band edges can be shifted.

Detailed optical characterization of three-dimensional visible-frequency polarization-independent carpet invisibility cloak

Abstract The invention of the three-dimensional woodpile photonic crystal by Costas M. Soukoulis and coworkers in 1994 has stimulated much further research—excellent research stimulates further research. Here, we report on using spatially inhomogeneous polymer woodpile structures in the long-wavelength limit as artificial graded-index structures. After briefly reviewing previous work on carpet invisibility cloaks designed by transformation optics, we present new experiments for various focus planes of the inspecting microscope as well as for different inspection angles in three-dimensional space. Numerical ray-tracing modeling is also provided. These data confirm our previous assessment that three-dimensional cloaking is quite robust for these structures.

Generation of λ/12 Nanowires in Chalcogenide Glasses

Nanowires have been widely studied and have gained a lot of interest in the past decade. Because of their high refractive index and high nonlinearity, chalcogenide glasses (ChGs) are a good candidate for the fabrication of photonic nanowires as such nanowaveguides provide the maximal confinement of light, enabling large enhancement of nonlinear interactions and group-velocity dispersion engineering. Here we report on the generation of λ/12 (∼68 nm) nanowires based on the theoretical and experimental study of the influence of the laser repetition rate on the direct laser fabrication in ChGs (λ = 800 nm). Through a numerical model of cumulative heating, the optimum conditions for high-resolution fabrication in As(2)S(3) are found. Nanowires with dimensions down to ∼λ/12 are for the first time successfully fabricated in ChGs. We show that the generated nanowires can be stacked to form a three-dimensional woodpile photonic crystal with a pronounced stop gap.

Observation of Backscattering-Immune Chiral Electromagnetic Modes Without Time Reversal Breaking

A strategy is proposed to realize robust transport in a time reversal invariant photonic system. Using numerical simulation and a microwave experiment, we demonstrate that a chiral guided mode in the channel of a three-dimensional dielectric layer-by-layer photonic crystal is immune to the scattering of a square patch of metal or dielectric inserted to block the channel. The chirality based robust transport can be realized in nonmagnetic dielectric materials without any external field.

Lifetime distribution of spontaneous emission from emitter(s) in three-dimensional woodpile photonic crystals

Spontaneous emission lifetime distribution in the basic unit cell or on a plane of the excited emitters embedded in woodpile photonics crystals with low refractive index contrast are investigated. It is found that the spontaneous emission lifetime distribution strongly depends on the position and transition frequency of the emitters, and has the same symmetry as that of the unit cell. The lifetimes of emitters near the upper gap edge are longer than that in the center of the pseudo-gap, which is quite a contrast to the conventional concept. Furthermore, it is revealed that the polarization orientation of the emitters has significant influence on the lifetime distribution, and may result in a high anisotropy factor (defined as the difference between the maximum and minimum values of the lifetime) up to 4.2. These results may be supplied in probing the lifetime distribution or orientation-dependent local density of states in future experiments.

Signature of a three-dimensional photonic band gap observed on silicon inverse woodpile photonic crystals

We have studied the reflectivity of CMOS-compatible three-dimensional silicon inverse woodpile photonic crystals at near-infrared frequencies. Polarization-resolved reflectivity spectra were obtained from two orthogonal crystal surfaces using an objective with a high numerical aperture. The spectra reveal broad peaks with maximum reflectivity of $67%$ that are independent of the spatial position on the crystals. The spectrally overlapping reflectivity peaks for all directions and polarizations form the signature of a broad photonic band gap with a relative bandwidth up to $16%$. This signature is supported with stop gaps in plane-wave band-structure calculations and with the frequency region of the expected band gap.

High-Q hybrid 3D-2D slab-3D photonic crystal microcavity

The radiation loss in the escaping light cone with a two-dimensional (2D) photonic crystal slab microcavity can be suppressed by means of cladding the low-Q slab microcavity by three-dimensional woodpile photonic crystals with the complete bandgap when the resonance frequency is located inside the complete bandgap. It is confirmed that the hybrid microcavity based on a low-Q, single-defect photonic crystal slab microcavity shows improvement of the Q factor without affecting the mode volume and modal frequency. Whereas 2D slab microcavities exhibit Q saturation with an increase in the number of layers, for the analyzed hybrid microcavities with a small gap between the slab and woodpiles, the Q factor does not saturate.

Rectangular-cavity resonances enhanced absorption in metallic-nanoshelled 2D rod arrays and 3D photonic crystals

A metallic-nanoshelled rectangular dielectric rod is proposed to flexibly enhance and tune the structural absorption. Due to the ultra-small thickness of the metallic-nanoshells, electromagnetic (EM) waves can penetrate into the rods and rectangular cavity resonances can be formed. At the cavity resonances, the strong EM wave–matter interaction results in an enhancement in the structural absorption by more than one order of magnitude. By stacking the nanoshelled rods, a three-dimensional (3D) woodpile photonic crystal with both the rectangular cavity resonance and the photonic band gap effect is realized. As a result, the structural absorption of the nanoshelled 3D photonic crystal is significantly enhanced to ∼99.99% at the resonant wavelength.

Woodpile photonic crystal fabricated in GaAs by two-directional etching method

Three-dimensional woodpile photonic crystals for 1.55 μm telecommunication wavelength are fabricated in a GaAs wafer by the two-directional etching technique for the first time. Chlorine-based chemically assisted ion beam etching is used for deep anisotropic GaAs etching. High-precision woodpile photonic crystals with 150×150×2.25 unit cells are fabricated in a two-patterning process, which is applicable to the introduction of intentional photonic crystal disorders in epitaxially grown, active materials without wafer bonding process.

High-temperature metal coating for modification of photonic band edge position

Atomic-layer-deposited iridium is coated onto three-dimensional tungsten woodpile photonic crystals to modify the optical properties of the structure. As the lattice constant of a metallic photonic bandgap structure decreases to the scale of the near-IR wavelengths, the band edge becomes pinned and cannot be pushed to shorter wavelengths because of limitations inherent in the material. With a thin coating of iridium, the band edge of a pinned tungsten lattice is pushed from ~1.6 μm to below 1 μm. This shift in the reflectance band edge will be accompanied by a reduction in the absorptance of the structure in the 1-2 μm range.

Effects of defect permittivity on resonant frequency and mode shape in the three-dimensional woodpile photonic crystal

Tuning the resonant frequency of a 1uc defect across the bandgap of a three-dimensional woodpile photonic crystal (PC) was achieved by altering the defect’s permittivity. Experiments were performed at microwave frequencies and calculations were made using the transfer-scattering matrix method. Defect permittivity was varied by using solid materials of different permittivities or by constructing structures smaller than a lattice constant from the the PC lattice materials. These small structures, which will be referred to as “sublattice defects,” produce an effective permittivity between their two materials’ permittivities. Changes in mode shape with resonant frequency and permittivity were also examined.

Numerical investigation of emission in finite-sized, three-dimensional photonic crystals with structural fluctuations

We investigate the inhibited emission of light-emitters embedded in finite, three-dimensional woodpile (or stacked-striped) photonic crystals (PCs) that exhibit structural fluctuations. Finite-difference time-domain calculations reveal that the influence of the positional fluctuations of stacked rods of dielectric material depends on the total number of structural periods. For PCs with up to nine stacked layers, the inhibition of emission is principally determined by intruding free-space modes resulting from the finite nature of the structure, with little influence from fluctuations. In PCs with more periods, the modes resulting from fluctuations dominate the emission properties. The influence of these fluctuations is strongly suppressed when the positional shifts are less than +/-20%.