Ms. Lan Shi Profile

Lan Shi

Undergraduate at Capital Normal Univ

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Publications (4)

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Proceedings Article | 12 January 2018 Paper

Studies on the resonant properties in the asymmetric dipole-array terahertz metamaterials

Wei Chen, Qingli Zhou, Chenyu Li, Lan Shi, Changxiang Liu, Cunlin Zhang

Proceedings Volume 10623, 106230P (2018) https://doi.org/10.1117/12.2295599

KEYWORDS: Metamaterials, Terahertz metamaterials, Resonators, Optoelectronics

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Artificial metamaterials with appropriate design can exhibit unique electromagnetic phenomena which do not exist in natural materials. Some studies have shown that the method of breaking the geometric symmetry is capable to modify the electromagnetic response, such as the metamaterial induced transparency in the Fano resonators. In this work, by using the finite-difference time-domain method, we firstly simulate the process that terahertz wave interacts with double-bar structures, in which one bar length is fixed at 36 μm and the other bar length is set to be 12, 24, 36, 48, and 56 μm, respectively. The incident terahertz polarization is along the bar direction. Simulated results show when the variable bar length is less than 36 μm, there is only one obvious resonant dip in transmission spectrum. Meanwhile, with the decreased bar length, this dip frequency presents a slight blueshift. Additionally, by tuning the spacing vertical to bar direction between these two bars, it still exhibits one dip. This result indicates the short bar less than 36 μm does not play important role and the coupling between vertical bars is weak. However, when the variable bar length is larger than 36 μm there are two obvious Fano-shaped resonant dips. With the increased bar length, the low-frequency dip shows a remarkable redshift, while the high-frequency one is almost unchanged. By further tuning the bar spacing vertical to the bar direction, two dips always exist. This phenomenon implies that the coupling between horizontal bars is dominated in this process. Moreover, the metamaterial induced transparency window is found between two resonant dips. The appearance of the resonances is attributed to the excitation of trapped mode. Our obtained results indicate that such metamaterials with very simple configuration could also provide the potential application in the field of terahertz slow-light devices, amplitude and phase modulators.

Proceedings Article | 12 January 2018 Paper

Studies on electromagnetic response in arc-shaped structures in terahertz region

Lan Shi, Qingli Zhou, Huijuan Sun, Chenyu Li, Changxiang Liu, Cunlin Zhang

Proceedings Volume 10623, 106230M (2018) https://doi.org/10.1117/12.2295336

KEYWORDS: Resonators, Electromagnetism, Finite-difference time-domain method, Metamaterials, Terahertz radiation, Superposition, Imaging spectroscopy, Optoelectronics, Modulation, Terahertz metamaterials

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In this paper, we use the finite-difference time-domain (FDTD) method to simulate and study the electromagnetic response characteristics of ring and arc-shaped resonators. Firstly, we study the terahertz transmission properties of two single-ring resonators with different radii. Either the single-ring resonator with a large radius or with a small radius only has one resonance in the transmission spectra. Then, we combine those resonators into a double-ring resonator structure. The results conclude that the two resonant frequencies of the double-ring resonator are caused by the simple superposition of the resonances of the large and small radius single-ring resonators, respectively. Additionally, on the basis of a single-ring resonator, we also study the influence of the symmetrical and asymmetric arc-shaped resonators on electromagnetic response characteristics. The ring resonator is split from the middle into two symmetrical arc-shaped resonators. As the width of the middle gap gradually increases, the resonant frequency shows blueshift and the intensity of the surface current distribution gradually weakens. Finally, the direction of the current is reversed. In order to further compare the relationship between the single-ring resonators and the double-ring resonators, we study the double arc-shaped resonators. The main purpose of this paper is to study the frequency response characteristics of the ring resonator in the terahertz band and to control the terahertz spectrum by changing the symmetry of the ring resonator. In the future, we can further study the coupling response between the ring structures and the multi-frequency response modulation of the multi-ring structures.

Proceedings Article | 24 October 2017 Paper

Studies on the trapped-mode resonant properties in asymmetric terahertz metamaterial

Wei Chen, Qingli Zhou, Chenyu Li, Lan Shi, Changxiang Liu, Cunlin Zhang

Proceedings Volume 10459, 104590D (2017) https://doi.org/10.1117/12.2284323

KEYWORDS: Terahertz metamaterials, Metamaterials, Electromagnetism

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Proceedings Article | 24 October 2017 Paper

Influence of asymmetric structures on electromagnetic response characteristics of terahertz metamaterials

Lan Shi, Qingli Zhou, Changxiang Liu, Huijuan Sun, Chenyu Li, Cunlin Zhang

Proceedings Volume 10459, 104590H (2017) https://doi.org/10.1117/12.2284372

KEYWORDS: Electromagnetism, Terahertz metamaterials, Metamaterials

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Asymmetric split-ring resonators (SRRs) exhibit different resonant modes and phenomena that do not have in symmetric structure, such as Fano resonance, electromagnetic induced transparency, and plasma resonance hybridization. The asymmetric SRR was first confirmed to produce narrow linewidth resonance and has a high quality factor. Then it extends to the terahertz and near infrared bands. It has been found that the most common way to modulate the electromagnetic response characteristics is to change the asymmetry of the SRR and the coupling strength between the resonators. Here we use the finite-difference time-domain (FDTD) method to simulate the electromagnetic response characteristics of asymmetric structures. When the polarization direction along the bottom bar of the U-shaped structure, there are two similar resonance dips like those in typical SRR structure. When the incident wave is perpendicular to the bottom bar, there is only one dipole resonance. However, with the broken of the symmetry, the resonant behaviors will change. In horizontal direction, both the resonant frequency and transmittance has changed. In the vertical polarization, there are three resonant dips in transmission spectrum. Meanwhile a sharp window appears in transmission spectrum. In addition, when we turn the bottom bar of the U-shaped structure into the arc shape, we just find very slight change in frequency-shift and modulation depth in both cases, showing the impact of the short arc is nearly equivalent to the linear dipole resonance. Our obtained results indicate that we could tune the electromagnetic resonances in metamaterials and the interaction mechanism with terahertz wave.

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