3D-printed terahertz metamaterial for electromagnetically induced reflection analogue

Influence of the Interfacial Transition Zone Properties on Chloride Corrosion in Reinforced Concrete-Characterization of ITZ

We propose a graphene plasmonic structure by applying two graphene layers mingled with a thin gold layer in a silicon grating. By utilizing the finite-difference time-domain (FDTD) method, we investigate the optical response of the system, and observe that the design achieves dual tunable electromagnetically induced transparency (EIT)-like effect at terahertz frequencies. The EIT-like effect arises from the destructive interference between the grapheme-layer bright modes and the gold-layer dark mode. The EIT-like phenomenon can be adjusted by the Fermi level, which is related to the applied voltage. The results show that the group delay of the present structure reaches 0.62 ps in the terahertz band, the group refractive index exceeds 1200, the maximum delay-bandwidth product is 0.972, and the EIT-like peak frequency transmittance is up to 0.89. This indicates that the device has good slow light performance. The proposed structure might enable promising applications in slow-light devices.

Tunable manipulation of electromagnetically induced transparency in resonance amplitude based on metal-graphene complementary metamaterial

Deep beams are structural elements loaded as beams in which a significant amount of the load is transferred to the supports by a compression strut trajectory joining the loads and the reactions. A comparative study is performed to predict the strain contribution of horizontal and vertical web bar located at compression strut trajectory from support points to load points. For investigation in this purpose, three high strength self compacted concrete (HSSCC) rectangular-section deep beams with the length to depth ratio less than three were designed based on American Concrete Institute (ACI) code with variation of tensile bar percentage and casted and loaded in laboratory. The longitudinal, web steel strains and concrete strains were measured for every incremental load. Before of first crack occurrences, the vertical bar strain is more than horizontal bar strain. When first crack happened, strain in vertical and horizontal web bar was same and by load increasing the strain in horizontal increased more than vertical. The strain became more than two times in horizontal bras comparison to strain in vertical bar when tensile bar yielded. At ultimate load the strain contribution of horizontal bar was more than four times in comparison by vertical bars.

The electromagnetically induced transparency (EIT) metamaterials with active or passive modulation have been extensively studied and applied in slow-light devices, light on-off, and light storage. However, the preparation complexity and characterization difficulties of the EIT metamaterials limit their optoelectronic applications. Here, we have employed a structure-based tunable design to fulfill the passive modulation of EIT metamaterial. We propose a simple but effective EIT structural model composed of a cutting wire and two circular split rings. Through theoretical analysis and computational simulation, it is found that the localized surface plasma and the inductive-capacitive resonance mode coincidently contribute to the EIT effect, giving rise to a narrow transparency window. Moreover, the amplitude of the transparency peak gradually decreases at the same resonance frequency with the increment of the lateral distance between the wire and split ring, while it decreases proportionally with the increment of the radius of the split ring. Interestingly, when the radius continues to increase, the asymmetry of the EIT window aggravates and the second EIT broad transparency window appears, indicating the existence of another intriguing coupling mechanism. Our work unveils a simple and practical modulation strategy for EIT-based multifunctional optical devices and shed light on its potential application on the optical devices.

In this paper, a novel terahertz metamaterial structure composed of a pair of sub-wavelength reverse U-shaped split ring resonators (RUSRs) and cut wire (CW) resonator is designed to realize electromagnetically induced transparency (EIT) effect in weak coupling region. Theoretical and simulated results show that by modulating the relative coupling distance between CW and SRR or mutual distance between SRR pair, the EIT-like phenomenon can be tailored. Furthermore, by introducing photosensitive silicon (Si) cell into the units of the dark mode resonator, actively optical control of the EIT-like effect is realized through increasing the dark mode damping rate. The present work provides an alternative method to design ultrasensitive sensors, filters and slow-light devices in the THz regime.

The authors used an optical bench to investigate calibration and errors from improper positioning of prism bars manufactured by R.O. Gulden and Luneau. They urged Gulden to redesign its prism bars to be used back-to-back in front of one eye. The horizontal bar is held with its flat face posteriorly within a channel on the flat face of the vertical bar; the interface is positioned perpendicular to the direction of the fixation object, which demands that the horizontal prism bar be calibrated in the frontal plane position and the vertical bar in the Prentice position. Analysis of calibration demonstrated that Gulden's new combination horizontal/vertical prism bar can be used without significant error (within + 0.5δ of labelled values). Gulden's old vertical prism bar is also calibrated in the Prentice position. Luneau's horizontal and vertical prism bars are calibrated close to the frontal plane position (within +1.0δ and +0.4δ respectively). Improper positioning demonstrated an increasing error with larger prisms. Luneau's 25δ segment measured 27.8δ in the Prentice position, the 40δ segment 67.5δ. The 25δ segment of Gulden's new and old vertical prism bars measured 23.25δ in the frontal plane position. Gulden's vertical prism bars should always be held with the flat surface toward the examiner. Luneau's horizontal and vertical prism bars should be held one in front of each eye when used simultaneously; thus, neither eye is looking directly at the fixation object and defining primary and secondary deviations is not possible. The combination horizontal/vertical prism bar is manufactured by Gulden Ophthalmics, 225 Cadwalader Avenue, Elkins Park, PA 19117-2097. The Luneau prism bars are manufactured by Luneau Ophtalmologie, B.P. 252, 28005 Chartres Cedex, France. The authors have no proprietary or financial interest in these products or in the companies involved.

Metamaterial based electromagnetically induced transparency (EIT) analogue have attracted as an alternative way to realize exotic EIT applications such as slow light devices and biosensors. Researches on metamaterial EIT analogues have recently focused on the realization of active system to control the EIT-like spectral properties via various external stimuli, including optical, mechanical, and thermal methods. Graphene based EIT metamaterials have been also reported through the numerical analysis as an electrically controlled active system, but there are no experimental reports in terahertz regime due to insufficient electrical mobility and conductance variation range of practical graphene sheets to realize active EIT analogues. In our previous study, we had reported a new concept of metamaterial analogue to achieve EIT-like phenomena, in which cut-wire (CW) pair and pseudo complementary cut-wire (CCW) were orthogonally combined with each other, generating EIT-like properties by funneling terahertz waves through the pseudo-CCW hole in broad reflection resonance of CW pair. Since this extraordinary transmission could be easily suppressed with resistive conductors along the pseudo-CCW structure, we designed the ion-gel gated graphene lines on the center of meta-atom structures to control the funneling of terahertz waves. Controlling the electromagnetic funneling provided switchable EIT-like spectral properties of the proposed metamaterials and we numerically confirmed that the graphene lines successfully acted as switching materials, even if the lines were formed with practically achievable graphene films. Finally, we verified that the fabricated EIT metamaterials experimentally showed 54.9% of modulation depth and 1ps of group delay change at the transmission peak in terahertz range.

In this paper, a novel EIT analogue consisting of metal-based resonator integrated with graphene is proposed, which can achieve tunable EIT-like effects in terahertz frequencies. For practical applications, a thin Si layer is grown on the resonator to provide a flat surface to transfer monolayer graphene using a wet transfer method. Numerical and theoretical investigations on the tunable EIT-like effect are carried out. The simulations reveal that EIT-like phenomenon is induced by coupling of bright-dark mode of metal-based resonator. Further investigations reveal that the amplitude of EIT window could be modulated by changing the Fermi level of graphene meanwhile the resonant frequencies exhibits slight shift. The physical mechanism underling the modulation phenomenon is mainly attributed to the damping rate of the dark mode and bright mode resonators, which is verified by theoretical analysis of classical two-particle model and absorption of proposed EIT-like analogue. The retrieved effective permittivity and permeability of the proposed metamaterial cell clearly exhibit dispersion in dependence of Fermi level of graphene. This work will offer a new perspective application in terahertz modulation and slow light devices.

A unique vertical bar among horizontal bars is salient and pops out perceptually. Physiological data have suggested that mechanisms in the primary visual cortex (V1) contribute to the high saliency of such a unique basic feature, but indicated little regarding whether V1 plays an essential or peripheral role in input-driven or bottom-up saliency. Meanwhile, a biologically based V1 model has suggested that V1 mechanisms can also explain bottom-up saliencies beyond the pop-out of basic features, such as the low saliency of a unique conjunction feature such as a red vertical bar among red horizontal and green vertical bars, under the hypothesis that the bottom-up saliency at any location is signaled by the activity of the most active cell responding to it regardless of the cell's preferred features such as color and orientation. The model can account for phenomena such as the difficulties in conjunction feature search, asymmetries in visual search, and how background irregularities affect ease of search. In this paper, we report nontrivial predictions from the V1 saliency hypothesis, and their psychophysical tests and confirmations. The prediction that most clearly distinguishes the V1 saliency hypothesis from other models is that task-irrelevant features could interfere in visual search or segmentation tasks which rely significantly on bottom-up saliency. For instance, irrelevant colors can interfere in an orientation-based task, and the presence of horizontal and vertical bars can impair performance in a task based on oblique bars. Furthermore, properties of the intracortical interactions and neural selectivities in V1 predict specific emergent phenomena associated with visual grouping. Our findings support the idea that a bottom-up saliency map can be at a lower visual area than traditionally expected, with implications for top-down selection mechanisms.

We propose a hybrid graphene/metamaterials device based on terahertz frequency. By placing the radiative and dark modes in the vertical and horizontal Si bars, we further demonstrate electromagnetically induced transparency (EIT), analogous to the atomic EIT. We theoretically investigate the strong interaction between graphene and EIT of the metamaterials. By varying the Fermi energy of graphene, the simulations show that graphene can actively modulate the transmission amplitude of EIT. Our results suggest that the demonstrated EIT in hybrid graphene metamaterials may offer new possibilities for applications in terahertz modulators and ultra-sensitive sensors.

We show that by treating the weak probe field as a perturbation to the strong coupling fields in the atomic system and using the perturbative method in a master equation, the features of linear response of phenomena of electromagnetically induced transparency (EIT) can be uniformly demonstrated, regardless of the details of atomic energy level configuration. We compare our estimation with both typical and atypical EIT-observed configurations and find that our model indeed provides a description of the sharp transmission window in central area of typical EIT curve. It can also be inferred hereby that for various systems other than atomic gas, as long as the description of the system’s dynamics comes down to the simplified form of master equation, the corresponding EIT analogs and EIT-like phenomena can also be explained in this way.

Electromagnetically induced transparency (EIT) is widely studied in atomic systems and metamaterials. However, there are few studies of EIT on topological insulator (TI). In this paper, the EIT effect is studied in TI which is placed on the dielectric substrate by finite difference time domain (FDTD) method. We discussed the effective permittivity of TI layer on different temperature at terahertz (THz) range. The EIT-like phenomenon can be obtained at transverse electromagnetic (TE) and transverse magnetic (TM) mode. The parameters of dielectric substrate and TI layer are investigated to tune the EIT phenomenon. Moreover, incident angle of electromagnetic (EM) wave is also studied to influence the transmission of the structure. The result was shown the large incident angle and polarization insensitive EIT effect can be realized. The results can provide some potential applications such as terahertz switches, filters and terahertz communications.

A metamaterial with a polarization-independent and angle-insensitive electromagnetically induced transparency (EIT)-like effect is theoretically investigated in the terahertz regime. The proposed metamaterial is composed of square rings and split isosceles triangle rings, which behave as bright elements and quasi-dark elements, respectively. An EIT-like phenomenon, which is caused by the destructive interference between different scattering paths via the bright and quasi-dark elements, is observed with a transparent window. This EIT mechanism is revealed with simulated field distributions as well as the analysis based on coupled-mode theory. Full wave simulations show that EIT-like phenomenon in the proposed metamaterial is independent of polarization and is robust to the angle of the incident light. This structure may have potential applications in terahertz detectors, sensors, and modulators.

The effect of sample duration and cue on a double temporal discrimination