Dielectric Block Research Articles

A Wideband Dual-Polarized Dielectric Magnetoelectric Dipole Antenna

A new wideband ±45° dual-polarized metal loop dielectric resonator magnetoelectric antenna is proposed in this communication. The antenna consists of two orthogonal dielectric bars that support two orthogonal electric dipoles and two cross interlaced metal semi-loops that are equivalent to two orthogonal magnetic dipoles above the ground. With a legitimate combination of the electric and magnetic dipoles, a unidirectional radiation with low backward radiation and equal E-plane and H-plane radiation patterns can be achieved. The antenna can be made of a monolithic dielectric block with simple installation. To validate the new antenna configuration, a prototype is designed, manufactured, and measured. The prototype antenna using ceramic with the electrical size of $0.33\lambda _{o} \times 0.33\lambda _{o} \times 0.21\lambda _{o}$ demonstrates that an impedance bandwidth of 11.4% ( $\vert S_{11}\vert dB) in the 3.5 GHz frequency band can be achieved with the measured forward/backward ratio of better than 22 dB. The proposed antenna is suitable as antenna element for massive-MIMO array antennas, where a large number of antenna elements need to be installed in a compact space.

A Broadband Millimeter-Wave Waveguide Window: A Low-Cost Design for Environmental Protection

In this paper, a full W-band waveguide window for the protection of components from the environment is presented. The window is based on rectangular dielectric block placed inside the rectangular waveguide. Electrical design steps for broadband performance are presented, and a simple cost effective mechanical process flow is employed for the fabrication of windows. Four different dielectric windows are evaluated, and they exhibited less than 0.3-dB insertion loss and better than 20-dB return loss: two windows over full W-band, whereas other two over 3-GHz bandwidth. Temperature testing is carried out for 4 h at −40 °C and +70 °C, and the humidity level is set at 95% at +70 °C. Minimum insertion loss variation of ±0.5 dB over the temperature range is observed. To check the compatibility of the windows with millimeter-wave components, a W-band switch is tested with the windows at its input and output ports. The experimental results show that the windows have low-loss characteristics and are free from ghost modes.

Combined Mie Resonance Metasurface for Wideband Terahertz Absorber

In this paper, we propose a combined metasurface consisting of an aluminum substrate and an array of TiO2 blocks to achieve a wideband terahertz absorber. We incorporated several similar dielectric blocks with different side length into each unit cell. Each dielectric block could cause magnetic-resonance-inducing absorption effect with different peak wavelengths. Thus, our combined metasurface could achieve wider absorption frequency band than the traditional design when these dielectric blocks were properly designed. The absorption bandwidth could be widened nearly 2.5 times and 5 times compared to a single block case when there were four and nine blocks, respectively, andcouldbe further improved by increasing the number of combinations in structures (variable parameters included number, spacing, dimensions etc.). For both TE00 (the electric fields of the light polarized along the y-axis) and TM00 (the electric fields of the light polarized along the x-axis) polarization states, the absorption bandwidth could be widened effectively; even when the incident angle was 45°, the absorption rate could still reach about 75%. This structure is simple and easy to fabricate, and this design concept can also be used in various other application fields.

Printed, 1 V electrolyte-gated transistors based on poly(3-hexylthiophene) operating at >10 kHz on plastic

Electrolyte-gated transistors (EGTs) based on poly(3-hexylthiophene) (P3HT) offer low voltage operation, high transconductance, good operational stability, and low contact resistance. These characteristics derive from the massive electrochemical or double layer capacitance (∼10–100 μF/cm2) of the electrolyte layer that serves as the gate dielectric. However, electric double layer (EDL) formation at the source/electrolyte and drain/electrolyte interfaces results in significant parasitic capacitance in EGTs which degrades dynamic switching performance. Parasitic capacitance in EGTs is reduced by covering the top surfaces of the source/drain electrodes with a low-ĸ dielectric (∼0.6 nF/cm2). The low-ĸ dielectric blocks EDL formation on the electrode surfaces that are in direct contact with the gate electrolyte, reducing the parasitic capacitance by a factor of 104 and providing a route to printed P3HT EGTs on plastic operating at switching frequencies exceeding 10 kHz with 1 V supply voltages.

On AC-Field-Induced Nonlinear Electroosmosis next to the Sharp Corner-Field-Singularity of Leaky Dielectric Blocks and Its Application in on-Chip Micro-Mixing.

Induced-charge electroosmosis has attracted lots of attention from the microfluidic community over the past decade. Most previous researches on this subject focused on induced-charge electroosmosis (ICEO) vortex streaming actuated on ideally polarizable surfaces immersed in electrolyte solutions. Starting from this point, we conduct herein a linear asymptotic analysis on nonlinear electroosmotic flow next to leaky dielectric blocks of arbitrary electrical conductivity and dielectric permittivity in harmonic AC electric fields, and theoretically demonstrate that observable ICEO fluid motion can be generated at high field frequencies in the vicinity of nearly insulating semiconductors, a very low electrical conductivity, of which can evidently increase the double-layer relaxation frequency (inversely proportional to the solid permittivity) to be much higher than the typical reciprocal RC time constant for induced double-layer charging on ideally polarizable surfaces. A computational model is developed to study the feasibility of this high-frequency vortex flow field of ICEO for sample mixing in microfluidics, in which the usage of AC voltage signal at high field frequencies may be beneficial to suppress electrochemical reactions to some extent. The influence of various parameters for developing an efficient mixer is investigated, and an integrated arrangement of semiconductor block array is suggested for achieving a reliable mixing performance at relatively high sample fluxes. Our physical demonstration with high-frequency ICEO next to leaky dielectric blocks using a simple channel structure offers valuable insights into the design of high-throughput micromixers for a variety of lab-on-a-chip applications.

RETRACTED ARTICLE: A focus on the features of polyaniline nanofibres prepared via developing the single crystals of their block copolymers with poly(ethylene glycol)

Poly(ethylene glycol) (PEG)–polyaniline (PANI) diblock and triblock copolymers were synthesized via copolymerization of aniline with amine-terminated PEG by interfacial polymerization using sulphuric acid as dopant and ammonium peroxydisulfate (APS) as well as potassium hydrogen diiodate (PHD) as oxidants. The PHD-based synthesized PANI nanorods possessed longer lengths, narrower diameter distribution and higher conductivity. The electroactivity of synthesized copolymers was characterized using ultraviolet–visible (UV–Vis) spectrometry, cyclic voltammetry (CV) and resistivity measurement. Even in the presence of dielectric PEG blocks, the synthesized block copolymers had a conductivity around 3 S $$\hbox {cm}^{-1}$$ . In a further step, the solution-grown single crystals were prepared to investigate the general features of grafted PANI nanorods using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Based on AFM and SAXS analyses, the bimodal gel permeation chromatography (GPC) traces obtained from the block copolymers were originated from the diameter distribution of nanofibres, not from the dispersity of their lengths and molecular weights.

Optimizing power oscillations in an ellipsometric system

Ellipsometry is a powerful and well-established optical technique used in the characterisation of materials. It works by combining the components of elliptically polarized light in order to draw information about the optical system. We propose an ellipsometric experimental set up to study polarization interference in the total internal reflection regime for Gaussian laser beams. The relative phase between orthogonal states can be measured as a power oscillation of the optical beam transmitted through a dielectric block and whose orthogonal components are then mixed by a polarizer. We show under which conditions the plane wave analysis is valid and when the power oscillation can be optimized to reproduce a full pattern of oscillation and to simulate quarter and half wave plates.

Polarization Reconfigurable Broadband Dielectric Resonator Antenna With a Lattice Structure

In this paper, a novel technique to design a broadband circularly polarized dielectric resonator antenna (DRA) with a lattice structure is proposed for the first time. Two resonant modes of TE111 and TE211 can be simultaneously excited through a cross-slot to constitute a wide operating bandwidth. On this basis, its reconfigurable version, which can operate in left-handed circular polarization (CP), right-handed CP, and linear polarization (LP) states, has been further presented. The latter possesses a simple design procedure to implement the reconfigurability since all the reconfigurable feeding circuits are isolated from the radiating DRA by the ground plane and only five p-i-n diodes are needed. Besides, a Teflon-based template is adopted to solve the problem of dielectric blocks' critical placement and alignment tolerances. A backed cavity based on substrate integrated waveguide technology is introduced to reduce the unwanted radiation from the surface wave. Measured results indicate that the reconfigurable prototype can achieve a 3-dB axial ratio bandwidth of 20.7% for CP states, an impedance bandwidth of 29.6% for LP state with a cross-polarization level of better than -20 dB, and a peak gain over 7.3 dBi for all states. The proposed antenna can be used for polarization diversity applications of the modern wireless system.

Tunable Surface-Plasmon-Polariton Filter Constructed By Corrugated Metallic Line and High Permittivity Material

This paper presents the development of a novel surface plasmon polariton band-stop filter with tunable operating frequency. The tuning is done by embedding a high permittivity BST dielectric block into the gap of SPP transmission line (T-line). An obvious transmission dip at the certain frequency is observed due to Fabry-Perot interference. The notch frequency is sensitive to the variation of the dielectric constant of the BST ceramic. Specifically, a transmission dip up to −11.5 dB is observed at the notch frequency of 8.12 GHz when the dielectric constant of BST is 425; the notch frequency shifts from 8.7 to 7.6 GHz when the dielectric constant of BST increases from 375 to 475. To further verify the functions of the proposed SPP filter, a prototype is fabricated on the Rogers-4003 dielectric substrate. The measured and the simulated results show good agreements. The proposed structure has outstanding features of a very compact area, simple fabrication, and tunable operating frequency, which have great potential for the applications in tunable frequency selection metamaterials devices.

Conductive poly(3-hexylthiophene) nanofibers and single crystals covered by coily dielectric oligomers and distinctions between their structures developed by self-seeding and isothermal approaches

Fuzzy nanofibers and single crystals developed using poly(3-hexylthiophene) (P3HT)-block-coily oligomers were compared. Based on grazing wide angle X-ray scattering and selected area electron diffraction patterns, grown crystalline structures were mainly edge-on. P3HT fuzzy nanofibers and single crystals were covered by the dielectric coily blocks of polystyrene, poly(methyl methacrylate), and poly(ethylene glycol), leading to brush-like regions on surface of crystals in longitude of P3HT backbones. The atomic force microscopy demonstrated that the single crystals grown by self-seeding method were significantly longer (26–181 µm) and thicker (59 nm–1.4 µm) than the corresponding nanofibers (0.8–21 µm in length and 1.5–23 nm in thickness). P3HT backbones were also more intimately stacked in single crystals in both hexyl side chains and π–π stacking directions, particularly in toluene (13.42–14.63 and 3.30–3.47 Ǻ) than in nanofibers (15.03–16.17 and 3.51–3.67 Ǻ). End coily blocks resulted in slightly higher layer spacings in both nanofibers and single crystals. Shorter P3HT chains were laminated on each other in single crystals; however, they were mostly extended in the nanofibers. Poorer solvents, lower crystallization temperatures, and shorter P3HT chains increased the backbone lamination in single crystals.

Improved image quality and reduced power deposition in the spine at 3 T using extremely high permittivity materials.

PurposeTo explore the effect of using extremely high permittivity (εr∼1,000) materials on image quality and power requirements of spine imaging at 3 T.Theory and MethodsA linear array of high permittivity dielectric blocks made of lead zirconate titanate (PZT) was designed and characterized by electromagnetic simulations and experiments. Their effect on the transmit efficiency, receive sensitivity, power deposition, and diagnostic image quality was analyzed in vivo in 10 healthy volunteers.ResultsSimulation results showed that for quadrature mode excitation, the PZT blocks improve the transmit efficiency by 75% while reducing the maximum 10g average specific absorption rate (SAR10) by 20%. In vivo experiments in 10 healthy volunteers showed statistically significant improvements for the transmit efficiency, and image quality. Compared to active radiofrequency shimming, image quality was similar, but the required system input power was significantly lower for quadrature excitation using the PZT blocks.ConclusionFor single‐channel transmit systems, using high permittivity PZT blocks offer a way to improve transmit efficiency and image quality in the spine. Results show that the effect, and therefore optimal design, is body mass index and sex specific. Magn Reson Med 79:1192–1199, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Oscillatory behavior of light in the composite Goos-Hänchen shift

For incidence in the critical region, the propagation of gaussian lasers through triangular dielectric blocks is characterized by the joint action of angular deviations and lateral displacements. This mixed effect, known as composite Goos-Haenchen shift, produces a lateral displacement dependent on the axial coordinate, recently confirmed by a weak measurement experiment. We discuss under which conditions this axial lateral displacement, which only exists for the composite Goos-Haenchen shift, presents an oscillatory behavior. This oscillation phenomenon shows a peculiar behavior of light for critical incidence and, if experimentally tested, could stimulate further theoretical studies and lead to interesting optical applications.

High‐Quality Nano/Micro Hairy Single Crystals Developed from Poly(3‐hexylthiophene)‐Based Conductive–Dielectric Block Copolymers Having Flat‐on and Edge‐on Orientations

Highly uniform and conductive single crystals of poly(3‐hexylthiophene) (P3HT)‐based homo and block copolymers with the end coily blocks of polystyrene, poly(methyl methacrylate), and poly(ethylene glycol) are developed using self‐seeding method from varied quality solvents. Edge‐on and flat‐on orientations are detected depending on the thickness and width of single crystals. Coily blocks are excluded from the P3HT crystalline structures, leading to brush‐like or hairy regions on surface of grown single crystals in the longitude of P3HT chains. The larger single crystals possessing flat‐on orientation are obtained from weaker solvents at higher seeding temperatures. The longer P3HT chains are folded, however, the shorter backbones are laminated on each other. The highest backbone lamination occurs for homo‐P3HT7150 (Mn of P3HT = 7150 g mol−1) single crystals grown at 20 °C from anisole, the weakest employed solvent. In contract, highly ordered and folded hairy single crystals are acquired from better solvents and high molecular weight P3HTs. In these conditions, the crystallographic features of the hairy block copolymer single crystals are similar to those of nonhairy homo‐P3HT ones. The coily brush‐covered P3HT48 800 single crystals have more foldings compared to the homo‐P3HT48 800 ones, whereas only two laminated backbones in shorter P3HT blocks are detected. image

Annealing-free multi-thermal techniques comprising aging, cycling and seeding to enhance performance of thick P3HT:PCBM photovoltaic cells via developing hairy crystals

Distinct multi-thermal treatments comprising cycling, aging, and seeding were introduced to prepare very thick bulk heterojunction (BHJ) active layers (ca. 800nm) of poly(3-hexylthiophene) (P3HT):phenyl-C71-butyric acid methyl ester (PC71BM) photovoltaic cells. To this end, various P3HT48800-based rod-coil block copolymers having the coily blocks of polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(ethylene glycol) (PEG) were synthesized. The grazing incidence X-ray scattering, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) analyses proved that the dielectric coily blocks, which were excluded from the P3HT crystalline structure, accumulated on the crystals surface without decreasing the crystal quality and formed hairy crystals. The multi-thermal techniques facilitated stacking of the growth planes in π-π direction for the P3HT crystals, thereby, this dimension was improved from 5 to 27nm for conventionally prepared BHJs to 53–265nm for multi-thermally developed ones. The hydrophobic coily blocks were capable of neutralizing the influence of the PCBM molecules presence in the growth environment, which resulted in the larger P3HT crystals in a similar condition. By switching the conventional spin coating approach to the cycling, aging, and seeding methods, the P3HT crystals and the PCBM clusters were gradually coarsened and the respective d-spacings decreased. This trend enhanced the hole mobility (=8.8×10−5cm2/Vs), electron mobility (=2.5×10−3cm2/Vs), short circuit current density (Jsc=12.02mA/cm2), fill factor (FF=69%), and power conversion efficiency (PCE=4.39%) up to the maximum values for seeding approach. Moreover, the higher percentages of face-on orientation were detected in the BHJs with lower d-spacings in the hexyl side chain direction. Hairy P3HT48800-b-PS crystals developed by seeding method possessed the highest face-on orientation (~5.5%).

A high-performance dielectric block copolymer with a self-assembled superhelical nanotube morphology

A block copolymer consisting of functional polynorbornene and polyacetylene segments was self-assembled into a superhelical nanotube, and displayed good dielectric properties.

Mesa-top quantum dot single photon emitter arrays: Growth, optical characteristics, and the simulated optical response of integrated dielectric nanoantenna-waveguide systems

Nanophotonic quantum information processing systems require spatially ordered, spectrally uniform single photon sources (SPSs) integrated on-chip with co-designed light manipulating elements providing emission rate enhancement, emitted photon guidance, and lossless propagation. Towards this goal, we consider systems comprising an SPS array with each SPS coupled to a dielectric building block (DBB) based multifunctional light manipulation unit (LMU). For the SPS array, we report triggered single photon emission from GaAs(001)/InGaAs single quantum dots grown selectively on top of nanomesas using the approach of substrate-encoded size-reducing epitaxy (SESRE). Systematic temperature and power dependent photoluminescence (PL), PL excitation, time-resolved PL, and emission statistics studies reveal high spectral uniformity and single photon emission at 8 K with g(2)(0) of 0.19 ± 0.03. The SESRE based SPS arrays, following growth of a planarizing overlayer, are readily integrable with LMUs fabricated subsequently using either the 2D photonic crystal approach or, as theoretically examined here, DBB based LMUs. We report the simulated optical response of SPS embedded in DBB based nanoantenna-waveguide structures as the multifunctional LMU. The multiple functions of emission rate enhancement, guiding, and lossless propagation are derived from the behavior of the same collective Mie resonance (dominantly magnetic) of the interacting DBB based LMU tuned to the SPS targeted emission wavelength of 980 nm. The simulation utilizes an analytical approach that provides physical insight into the obtained numerical results. Together, the combined experimental and modelling demonstrations open a rich approach to implementing co-designed on-chip integrated SPS-LMUs that, in turn, serve as basic elements of integrated nanophotonic information processing systems.

Multifunctional all-dielectric nano-optical systems using collective multipole Mie resonances: toward on-chip integrated nanophotonics

We present an analysis of the optical response of a class of on-chip integrated nano-photonic systems comprising all-dielectric building block based multifunctional light manipulating units (LMU) integrated with quantum dot (QD) light sources. The multiple functions (such as focusing excitation light, QD emission rate enhancement, photon guidance, and lossless propagation) are simultaneously realized using the collective Mie resonances of dipole and higher order multipole modes of the dielectric building blocks (DBBs) constituting a single structural unit, the LMU. Using analytical formulation based on Mie theory we demonstrate enhancement of the excitation light simultaneously with the guiding and propagation of the emitted light from a QD emitter integrated with the DBB based LMU. The QD-DBB integrated structures can serve as the basic element for building nano-optical active circuits for optical information processing in both classical and quantum realms.

High efficient and stabilized photovoltaics via morphology manipulating in active layer by rod-coil block copolymers comprising different hydrophilic to hydrophobic dielectric blocks

The poly(3-hexylthiophene) (P3HT)-based block copolymers were synthesized with hydrophilic and hydrophobic dielectric blocks including poly(ethylene glycol) (PEG), poly(methyl methacrylate) (PMMA), and poly(styrene) (PS), and employed as morphology modifiers (10–80wt%) in P3HT: phenyl-C71-butyric acid methyl ester (PC71BM) bulk heterojunction (BHJ) solar cells. The advantages and drawbacks of the coily blocks were also outlined from perspective of photovoltaic characteristics. A novel matrix-bridged disperses model was proposed to map out well-connected BHJ networks, which was consistent with the scattering data. Rod-coil block copolymers simultaneously controlled some main properties, i.e., crystallinity, d-spacing, domain sizes, and stability. Hydrophobic-based block copolymers (P3HT-b-PS and P3HT-b-PMMA) increased crystallinity, P3HT crystallite size, and PC71BM cluster size and decreased d-spacings. This reflected larger and denser P3HT crystallites and coarser and more packed PC71BM clusters. P3HT crystallites grew up to ∼60 and 30nm in (100) and (020) directions, respectively. In 30wt% of P3HT7150-b-PS, PC71BM clusters were also the largest (=38.87nm). A fully interdigitated hexyl chains (10.05Å) was acquired in 80wt% of P3HT7150-b-PS. Impressing trends of the P3HT-b-PMMA copolymers resembled that of P3HT-b-PS ones, but with a smoother slope. In contrast, hydrophilic-based block copolymers (P3HT-b-PEG and P3HT-b-PEG-b-P3HT) resulted in finer and looser P3HT crystallites and PC71BM clusters. The largest d-spacings in the directions of the hexyl side chains (=19.97Å) and π-π stacking (=4.95Å) were detected in 80wt% of P3HT7150-b-PEG750. The lowest (=3.51Å) and highest (=5.63Å) d-spacings for PC71BM clusters appeared in 80wt% of P3HT7150-b-PS and P3HT7150-b-PEG750, respectively. Unlike PEG-based block copolymers, in P3HT-b-PS and P3HT-b-PMMA ones, lower P3HT molecular weights conduced to higher power conversion efficiencies (PCE=4.43%). The short current density (Jsc=11.68mA/cm2), open circuit voltage (Voc=0.63V), and fill factor (FF=63%) were maximized in well-modified photovoltaic devices.

Experimental confirmation of the transversal symmetry breaking in laser profiles

The Snell phase effects on the propagation of optical beams through dielectric blocks have been matter of recent theoretical studies. The effects of this phase on the laser profiles have been tested in our experiment. The data show an excellent agreement with the theoretical predictions confirming the axial spreading modification and the transversal symmetry breaking. The possibility to set, by rotating the dielectric blocks, different configurations allows to recover the transversal symmetry. Based on this experimental evidence, dielectric blocks can be used as alternative optical tools to control the beam profile.

Mode jumping of split-ring resonator metamaterials controlled by high-permittivity BST and incident electric fields.

We investigate the resonant modes of split-ring resonator (SRR) metamaterials that contain high-permittivity BST block numerically and experimentally. We observe interesting mode-jumping phenomena from the BST-included SRR absorber structure as the excitation wave is incident perpendicularly to the SRR plane. Specifically, when the electric field is parallel to the SRR gap, the BST block in the gap will induce a mode jumping from the LC resonance to plasmonic resonance (horizontal electric-dipole mode), because the displacement current excited by the Mie resonance in the dielectric block acts as a current channel in the gap. When the electric field is perpendicular to the gap side, the plasmonic resonance mode (vertical electric-dipole mode) in SRR changes to two joint modes contributed simultaneously by the back layer, SRR and BST block, as a result of connected back layer and SRR layer by the displacement current in the BST dielectric block. Based on the mode jumping effect as well as temperature and electric-field dependent dielectric constant, the BST-included SRR metamaterials may have great potentials for the applications in electromagnetic switches and widely tunable metamaterial devices.