Dielectric Strip Research Articles

Efficient Optical Coupling between Dielectric Strip Waveguides and a Plasmonic Trench Waveguide

Efficient Optical Coupling between Dielectric Strip Waveguides and a Plasmonic Trench Waveguide

The limit of anisotropic epitaxial lateral overgrowth in heteroepitaxial systems

The separation of Ge and Si by an electrically isolating dielectric layer is essential to yield high efficiency for optical telecommunication applications and electronic applications such as Ge MOSFETs. Ge epitaxial lateral overgrowth (ELOG) is a promising approach to achieve Ge on Si separated by a thin dielectric layer. However, a general understanding of the anisotropic dynamics of ELOG Ge on Si is limited, which prevents its wide adoption. In this paper, we report how the orientation and width of the dielectric layer controls the ELOG. A competitive ELOG from perpendicular directions on a dielectric strip leads to a rapid growth along the long axis of the dielectric layer, or a mixed coalescence from perpendicular directions yielding various Ge confined configurations at the Ge/dielectric-layer interface. Especially, an angle of 7.5° between dielectric-layer and Si [110] axis shows the most pronounced unidirectional ELOG. ELOG disappears as the width of the dielectric mask exceeds 5.0 μm. The results reported here provide a general framework for ELOG of semiconductor materials.

3D Dirac semimetal supported thermal tunable terahertz hybrid plasmonic waveguides.

By depositing the trapezoidal dielectric stripe on top of the 3D Dirac semimetal (DSM) hybrid plasmonic waveguide, the thermal tunable propagation properties have been systematically investigated in the terahertz regime, taking into account the influences of the structure of the dielectric stripe, temperature and frequency. The results manifest that as the upper side width of the trapezoidal stripe increases, the propagation length and figure of merit (FOM) both decrease. The propagation properties of hybrid modes are closely associated with temperature, in that when the temperature changes in the scope of 3-600 K, the modulation depth of propagation length is more than 96%. Additionally, at the balance point of plasmonic and dielectric modes, the propagation length and FOM manifest strong peaks and indicate an obvious blue shift with the increase of temperature. Furthermore, the propagation properties can be improved significantly with a Si-SiO2 hybrid dielectric stripe structure, e.g., on the condition that the Si layer width is 5 µm, the maximum value of the propagation length reaches more than 6.46 × 105 µm, which is tens of times larger than those pure SiO2 (4.67 × 104 µm) and Si (1.15 × 104 µm) stripe. The results are very helpful for the design of novel plasmonic devices, such as cutting-edge modulator, lasers and filters.

A Dual-Band, Dual-Polarized Filtering Antenna Based on Cross-Shaped Dielectric Strip Resonator.

A dual-band, dual-polarized filtering antenna with a cross-shaped dielectric strip resonator is proposed. The dual-band filtering radiation function is achieved by utilizing the odd and even modes of the stub loaded microstrip resonator to excite the TMδ1 and TMδ3 mode in each polarization direction of the cross-shaped dielectric strip resonator. The cross-shaped dielectric strip resonator is synthesized by the E-field distributions and the magnitude comparison along different polarization directions, which can ensure the isolation between two polarizations. Compared with dual-band filtering dielectric antennas, the proposed antenna has the characteristic of dual-polarized radiation, as well as a low profile. A prototype is fabricated and measured, which operates at 3.5 GHz and 4.9 GHz with the fractional bandwidths (FBW) of 5.40% and 2.03%, respectively, and the gains of these two bands are 6.4 dBi and 6.2 dBi, respectively. The two radiation nulls are located at 4.4 GHz and 5.1 GHz. Furthermore, the measured isolation between the two ports in the frequency band can achieve 16 dB.

High gain low profile horn array with circular polarization using a 3D printed anisotropic dielectric composite material at 38 GHz

In this work, the design of a fully 3D-printed dielectric polarizer based on anisotropic engineered material operating at 38 GHz is presented. The anisotropy conditions to obtain circular polarization are achieved by using an array of dielectric strips, manufactured using two different commercially available filaments for 3D-printing. To illuminate the polarizer, a low-profile horn linear array fed by transverse slots is designed and manufactured. The results show good agreement between simulations and measurements, with the designed polarizer covering the whole operation band of the antenna by keeping a similar gain when compared to the structure without the polarizer.

Flexible control of multi-focus with geometric phase encoded metalens based on the complex digital addition principle

A transmissive encoding metasurface based on the geometric phase principle is proposed. The encoding unit adopts an anisotropic Si dielectric strip and SiO2 substrate on the upper layer, and realizes the phase modulation of the incident wave in the span of 0–2π on the premise of achieving high polarization conversion efficiency. 1-bit, 2-bit and even multi-bit coding units are constructed by rotating surface units. In order to realize the multi-focus function of imaging space, we propose to introduce the principle of complex code addition into the design of metalens. Compared with traditional scalar encoding, complex encoding reveals the intrinsic connection between different encoded bits, thus closer to the essence of electromagnetism. The multi-angle control of multi-focus in free space is realized by the complex coding of four groups of single-focal metalenses and their addition operations. The multifocal metalens at this time also has the angular characteristics of the previous single focus lens, and multiple angles have no influence on each other. Our proposed complex additive multifocal metalens provides a new idea for future multifocal metalens design, especially the design of polarization-sensitive devices.

Enabling MIMO Antenna Miniaturization and Wide Circular Polarization Coverage by Amalgamation of a Dielectric Strip Between Meandered Traces and Slotted Ground

This letter presents a dual-element multiple-input–multiple-output antenna for applications in the very high frequency band. A compact geometry of microstrip line-fed radiators engaging 0.04 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \times $</tex-math></inline-formula> 0.04 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\boldsymbol{\lambda }}}^2$</tex-math></inline-formula> footprint at 150 MHz was fabricated on an FR-4 substrate and tested in the anechoic chamber. Good circularly polarized radiation patterns were generated by employing two corner-fed meander lines and integrating slots at strategic locations of the ground. A dielectric strip was stacked above the substrate and between the two meandered elements to enable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ -$</tex-math></inline-formula> 10 dB impedance bandwidth of 24%. In the operating frequency band from 133 to 169 MHz, the proposed antenna offered axial ratio of <3 dB, mutual coupling of >-25 dB, gain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim $</tex-math></inline-formula> 3 dBi, efficiency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\boldsymbol{\eta }}$</tex-math></inline-formula> ) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim $</tex-math></inline-formula> 80%, envelope correlation coefficient of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ &lt; $</tex-math></inline-formula> 0.5 and diversity gain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim $</tex-math></inline-formula> 10 dB.

A High-Efficiency Dual-Band Self-Filtering Antenna Based on Three Dense Dielectric Strip Resonators

A high-efficiency dual-band dielectric filtering antenna based on three parallel placed dense dielectric strip resonators (DDSRs) is proposed for the self-filtering property. That means both the filtering responses of the two bands are only determined by the three DDSRs themselves without extra filtering circuits. The even-mode coupling of the TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1δ</sub> mode (TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3δ</sub> mode) between the middle and two-sided DDSRs is used to form the first (second) radiation band, while the odd-mode coupling contributes one radiation null at the upper edge of each radiation band. Therefore, the proposed dual-band dielectric antenna exhibits relatively high total efficiency benefited from the self-filtering characteristic. Additionally, the presented one without extra filtering circuits obtains the features of low profile, enhanced bandwidth, and gain. For test and verify, a prototype was measured at 7.7 and 13.35 GHz with the fractional bandwidths of 11.4% and 4.8%, the peak gains of 7.65 and 10.5 dBi, and the total efficiencies of 89% and 87%, respectively. Radiation nulls are generated at 8.5 and 13.8 GHz, respectively.

3-D-Printed Wideband Circularly Polarized Dielectric Resonator Antenna With Two Printing Materials

A new 3-D-printed wideband circularly polarized (CP) dielectric resonator antenna (DRA) with two printing materials is investigated. The DRA has a multilayer comb-shaped structure at its top for generating CP fields. Three dielectric strips are embedded inside the DRA body to support multiple transverse-electric (TE) DRA modes to widen the DRA bandwidth. To slightly improve the axial-ratio (AR) performance, the DRA is twisted in the horizontal plane. For demonstration, a prototype operating in C-band was designed and printed with two different materials. The reflection coefficient, AR, radiation pattern, antenna gain, and efficiency of the antenna are measured, and reasonable agreement between the measured and simulated results is observed. The prototype has a measured 10 dB impedance bandwidth of 69.7% (4.80–9.94 GHz) and 3 dB AR bandwidth of 68.6% (4.52–9.24 GHz), achieving a wide overlapping bandwidth of 63.2% (4.80–9.24 GHz). Both the AR and overlapping bandwidths are record-high for a single-fed CP DRA. The prototype has a measured peak antenna gain of 8.3 dBic inside the overlapped passband.

Dynamically controlled nanofocusing metalens based on graphene-loaded aperiodic silica grating arrays.

A new plasmonic nanofocusing metalens based on aperiodic silica grating arrays was designed and investigated. Assisted by the graphene surface plasmon, the infrared polarized light can be focused in a nanospot with a dynamically controlled focal length by varying the dielectric strip width or the graphene Fermi level Ef. For instance, with λ0 = 8 µm and Ef at 0.3, 0.6 and 0.9 eV, focal lengths of 4.5, 3.8 and 3.5 µm with its corresponding FWHM of 64, 232 and 320 nm, respectively, can be realized. The variation of the focusing efficiency with respect to the incident wavelength and the Fermi level were also investigated. The results of theoretical analysis based on light differential equations agree well with the finite element analysis simulation, which further validate the model.

Broadband circularly polarized dielectric resonator antenna with L‐shaped dielectric resonator strips

A broadband circularly polarized dielectric resonator antenna (CP DRA) with L-shaped dielectric resonator strips (DRS) is presented. The antenna is composed of a square DR, four L-shaped DRS and a square ground plane etched with cross-slot. A stepped-microstrip feeding line is used to adjust the impedance bandwidth (IBW). It is noted that not only the interaction of the cross-slot and square DR could excite CP resonant points, but the four L-shaped DRS can also stimulate a CP resonant point in high frequency. Through utilizing these resonant modes, the CP bandwidth of the proposed DRA could be enhanced greatly. The measured results depict the designed DRA has a broad −10-dB IBW of 44.7% (2.55, 1.98-3.12 GHz), and a 3-dB axial-ratio bandwidth of 38.7% (2.53, 2.04-3.02 GHz).

Leaky Wave-Guide Based Dielectric Resonator Antenna for Millimeter-Wave Applications

In this paper, a leaky wave antenna based on the parallel non-radiative dielectric guide (NRD) has been proposed. This novel design uses two parallel dielectric strip waveguides having a dielectric constant of 2.2 are placed over a substrate of the dielectric constant of 2.55 and both are separated by a ground plane. The upper structure is bounded by deflating conducting strip having distance less than λ0/2. The leakage from this antenna is in the form of surface wave concentrated more in the broadside direction rather than usual endfire or off broadside direction. It has been observed the proposed radiating structure has radiation efficiency of 82%, the peak gain of 5.94 dB with narrow impedance bandwidth, and the resonating frequency at 13.59 GHz, 13.43 GHz, and 13.93 GHz. A comparative analysis is made by increasing the height of the dielectric strip to increase the number of modes. This leaky-wave structure based on a non-radiative dielectric (NRD) guide can be a suitable candidate for the device to device (D2D) communication in the millimeter-wave band.

Enlarging the Purcell Enhancement by Inserting a Dielectric Film in Dielectric‐Loaded Surface‐Plasmon‐Polariton Waveguides

AbstractThe deterministic integration of single‐photon emitters with large Purcell enhancements and waveguides is vital for integrated quantum circuits and quantum chips. Purcell enhancements are not only related to waveguide structures, but are also greatly affected by the position of single‐photon emitters in waveguides. Here, the insertion of a thin dielectric film with a controllable thickness between a dielectric strip and a metal surface to precisely position a single‐photon emitter in a dielectric‐load surface‐plasmon‐polariton (DLSPP) waveguide is proposed, and the Purcell enhancement is greatly enlarged. Simulations show that the vertical position of the single‐photon emitter above the metal surface is more important than its in‐plane position in the DLSPP waveguide for achieving enlarged Purcell enhancements. In the experiment, the vertical position of the single‐photon emitter in the modified DLSPP waveguide is controlled by evaporating a thin MgF2 film, and the in‐plane position is controlled by combining aligned electron beam lithography and photoluminescence imaging. The Purcell factor in the emitter‐waveguide system is measured to be Fp = 22.4, which is greater than those obtained using conventional DLSPP waveguides (Fp ≤ 6.0) in previous studies.

A compact filtering antenna using dielectric strip resonator and parallel microstrip feed line

A filtering antenna using dielectric strip resonator and parallel microstrip feed line is proposed to achieve compact dielectric size and filtering response without gain reduction. The compact dielectric size is contributed by the dielectric strip resonator with high permittivity operated in the TMδ1 cavity mode, whose electric field distribution along the short side is far less than half-wavelength distribution. Therefore, the size of the proposed dielectric strip resonator is smaller than the traditional dielectric patch resonator operated in the TM11 cavity mode. Additionally, the parallel placed microstrip line not only can excite the dielectric strip resonator for filtering response without gain reduction, but also can provide one upper-edge radiation null for frequency selectivity enhancement. Compared with the reported filtering dielectric antennas, the proposed design exhibits the features of compact dielectric size, simple structure and wide stopband. For demonstration, one prototype operating at 4.9 GHz is fabricated, achieves the dielectric size of 0.00078 λ3 0 (λ0 is the wavelength in the free space at the center frequency), the measured peak gain of 7.1 dBi, the 10-dB impedance matching bandwidth of 4%, the stopband (> 16 dB) up to 1.84 f0, and the cross-polarization level of 20 dB within 3-dB beam range.

Detection of metallic andnonmetallicconcealed targets based on millimeter‐wave inverse scattering approach

A millimeter-wave radar based on active invers scattering approach for two dimensional screening of metallic and nonmetallic concealed targets is presented. The perceived challenges of detecting a nonmetallic target exhibiting poor dynamic range for measurement systems are analyzed and discussed by comparing the performance of three different antenna sensors. A short time duration pulse with frequency sweep covering 27 to 33 GHz band is used to feed the antenna sensors. In our experimental test, we buried a concealed target consists of metallic or dielectric strips under a dielectric layer that simulates the human body model. Waveguide and printed antipodal Vivaldi antennas are considered to study the target detectability and the quality of the measured millimeter-wave images. The use of proposed AVA resulted in a better-quality image with lower noise effect for both metallic and nonmetallic cases.

Integrated photonic guided metalens based on a pseudo-graded index distribution

In this article, we report an integrated optical nanolens exhibiting a pseudo-graded index distribution in a guided configuration. This dielectric metalens relies on a permittivity distribution through dielectric strips of the core material, which is compatible with existing silicon photonic technology. We show in this paper that effective medium theory (EMT) inaccurately predicts the focal length of such devices, and we propose an efficient and accurate design approach based on 2D finite element method (FEM) mode calculations that are in good agreement with 3D FDTD simulations. The lens was fabricated on a 200 mm silicon on insulator pilot line, and fibre-to-fibre optical characterizations revealed an excellent transmission of 85% for TM polarization, in line with the simulated performance (90%). The proposed approach can be easily extended to width-variable strips, enabling the realization of all types of graded index devices, especially those derived from transformation optics.

Differential Dual-Band Filter Using Ground Bar-Loaded Dielectric Strip Resonators

In this letter, a new differential dielectric strip resonator (DSR) filter with dual passbands is proposed. By loading a pair of ground bars underneath the traditional half- wavelength ( $\lambda /2$ ) DSR with high permittivity (supported by a low-permittivity substrate with the bottom ground plane), the TM10 and TM30 modes can be controlled to be in a close spacing. Meanwhile, both of them can be differentially excited for the design of the differential dual-band bandpass filter (BPF). The external quality factors and coupling coefficients for both bands can be independently controlled through proper layout; meanwhile, the common-mode (CM) suppression in the two differential-mode (DM) passbands is more than 25 dB. Finally, a differential DSR BPF with dual-band response operating at 8.13 and 11.13 GHz is given to verify the proposed idea.

Efficient Analysis of Inhomogeneous Dielectric Waveguides With Dielectric Strips and Microstrips Using Discrete Mode Matching Method

In this article, the discrete mode matching (DMM) method is extended to characterize multilayered transmission line structures with inhomogeneous anisotropic dielectric layers using only 1-D discretization. We have thoroughly discussed the procedure to analyze hybrid dielectric waveguides with dielectric strips and/or microstrips, i.e., metallization at the interfaces. The analysis of the structures is based on the full-wave equivalent circuit approach, which gives the generalized relation of the field components of the multilayered structure and the corresponding system equation. Accurate results are obtained with very less computational effort. The dispersion curves and the electric field intensity distributions are presented for various dielectric waveguides and validated with the commercial software.

IMPROVEMENT OF DEVICES FOR PRELIMINARY ELECTRIC HEATING OF CONCRETE MIXTURE

Purpose: The aim of this work is to create low-power and low-operational technology of electric heat treatment of concrete mixture and concrete. One of the most important tasks is the development of new approaches to the improvement of the concrete casting technology with the concrete mix heating during concrete placement. This requires elimination of the local overheating of the mixture and the rapid concreting of phase electrodes due to the development of the so-called edge effect. It occurs at the edges of electrodes, regardless of their shape. To realize the low-cost elimination of local overheating of the mixture and concreting of phase electrodes, it is necessary to study the behavior of the electric heat fields in the overheating zone.Outcomes: Based on this research, the improved device for the electric heat treatment of concrete mixture is proposed and patented. The device is based on the electrical field grading in the concrete mixture using narrow plates on phase electrodes.Research findings: The edge effect is based on the fundamental principle of the absence of the tangential component of charges on the electrode surface, that is, charges are in a mutually balanced state. This condition is provided by their accumulation on the edges of electrodes. The resulting non-uniformity of the electric field strength and current density lead to negative consequences. But this non-uniformity is manifested in the local area at the end of electrode and can be stopped at the electrode end by a narrow dielectric strip.

Oblique evanescent excitation of a dielectric strip: A model resonator with an open optical cavity of unlimited Q.

A rectangular dielectric strip at some distance above an optical slab waveguide is being considered, for evanescent excitation of the strip through the semi-guided waves supported by the slab, at specific oblique angles. The 2.5-D configuration shows resonant transmission properties with respect to variations of the angle of incidence, or of the excitation frequency, respectively. The strength of the interaction can be controlled by the gap between strip and slab. For increasing distance, our simulations predict resonant states with unit extremal reflectance of an angular or spectral width that tends to zero, i.e. resonances with a Q-factor that tends to infinity, while the resonance position approaches the level of the guided mode of the strip. This exceptionally simple system realizes what might be termed a "bound state coupled to the continuum".