Dr. Cong Chen Profile

Dr. Cong Chen

at China Univ of Mining and Technology

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Publications (3)

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Proceedings Article | 10 April 2023 Paper

Anomalous reflection and directional excitation of SPPs based on element additive metasurface

Cong Chen, Hai Liu

Proceedings Volume 12614, 126141K (2023) https://doi.org/10.1117/12.2672851

KEYWORDS: Reflection, Spiral phase plates, Silver, Electric fields, Polarization, Incident light, Polarized light, Dielectric polarization, Design and modelling, Light wave propagation

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The efficient combination of multiple functions through a single, planar and compact metastructure has become an emerging research area, offering the possibility to design and realize highly integrated and miniaturized multifunctional devices in photonics, but Huge challenges still need to be solved, especially in the visible wavelengths. Here, we design the metasurface structure by means of unit structure addition, allowing the linear polarization to be effectively separated into x-polarized and y-polarized components at normal incidence, and achieve anomalous reflection of light waves and unidirectional excitation of Surface Plasmon Polaritons (SPPs). The structure can locally propagate the energy of SPPs more efficiently, or reflect more energy out through the phase gradient. When linearly polarized light of 1200 nm is incident vertically, two different linear phase gradients are generated along the same direction, resulting in the realization of the same metasurface distinctly different functions. Among them, by analyzing the local electric field distribution caused by the interaction between the incident light and the structure, it can be clearly found that the x-polarized light effectively excites surface plasmons (SPPs), and most of the energy propagates to the right along the surface of the structure. The y-polarized light achieves an abnormal reflection of 30°, and it is verified that the large-angle deflection characteristic of 20°-60° can be achieved in the wavelength range of 1000nm-1500nm. The bifunctional metasurface developed in this study can provide ideas and methods for the study of photonic integrated devices in the optical band.

Proceedings Article | 21 January 2022 Paper

Design of tunable dual-gas sensor based on phase transition of VO2 in metasurface

Cong Chen, Hai Liu

Proceedings Volume 12154, 1215418 (2022) https://doi.org/10.1117/12.2626425

KEYWORDS: Sensors, Absorption, Hydrogen, Metals, Methane, Gold, Dielectrics, Transition metals, Structural design, Vanadium

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A tunable dual-gas sensor based on VO₂ is proposed, and the metasurface is composed of a multi-layer metal-dielectricmetal (MDM) structure. The first to six layers of the structure are VO₂ cylinder, methane sensitive film, VO₂ film, gold square ring, hydrogen sensitive film, and gold film. The conductance coupling between the metal structures can be manipulated by the metal-insulator phase transition of VO₂ to change the LSPR resonance mode. The transformation realizes active tunable dual-gas detecting of the methane and hydrogen, and the effects of structural parameters and polarization mode on the frequency response characteristics of the structure are investigated respectively. Subsequently, a theoretical study of the active adjustable dual gas sensor was carried out. When the temperature exceeds the phase transition temperature of VO₂ (T<68℃), VO₂ exhibits metallic properties and excites resonant coupling at 1647.4nm. At this time, methane-gas detection is realized and the absorption rate of the sensor reaches 92%, which is not only because of the VO2 cylindrical surface resonance but more electric energy is localized in the methane-sensitive film. The sensor realizes hydrogen detection when VO₂ is in an insulated state (T≤68℃), the incident light penetrates the upper three-layer structure and matches the plasma frequency of the lower three-layer MDM structure to excite resonance at 2191.4nm. However, the energy of the incident light is lost through the upper three-layer structure, which causes the absorption rate of the sensor to be only 83%. In addition, the influence of the external dielectric constant and structural parameters on the sensing characteristics are analyzed to obtain the optimal sensing performance, where the sensitivity of methane is 7.46nm/% and the sensitivity of hydrogen is 1.6nm/%. This conclusion is conducive to the design of active adjustable sensors and has many potential applications in the field of detection.

Proceedings Article | 9 September 2021 Paper

Design of tunable dual-band absorber based on phase transition of VO2 in terahertz metasurface

Cong Chen, Hai Liu

Proceedings Volume 11909, 119090O (2021) https://doi.org/10.1117/12.2605450

KEYWORDS: Absorption, Metals, Gold, Dielectrics, Terahertz radiation, Magnetism, Electromagnetism, Vanadium

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A VO₂ -based Terahertz metasurface is proposed, and the cell structure consists of two parts. One part is composed of VO₂ blocks connected by metal rings with different radius, and the other part is a VO₂ square ring. The conductance coupling between the metal structures can be manipulated by the metal-insulator phase transition of VO₂ to change the LSPR resonance mode. The transformation realizes active tunable dual-band absorption of the terahertz wave, and the effects of incident wave angle and polarization mode on the frequency response characteristics of the structure are investigated respectively. Subsequently, the theoretical study on the Terahertz metamaterial absorber is carried out, and the results indicate that the two absorption peaks are generated by the autonomous resonance of gold rings with different radius when the temperature is 25°C The absorption rate of the absorber can reach 98% and 92% at f THz = 4.16 and f THz = 5.75 , respectively. When the temperature exceeds the VO₂ phase transition temperature (68°C), the VO₂ block is combined with metal rings of different radius to form a current closed-loop which would cause unified resonance and coupling with the VO₂ square ring. Meanwhile, the absorption rate of the absorber can reach 90% at f THz = 5.27 and f THz = 8.5 . In addition, the influence of the external dielectric constant and structural parameters on the absorption characteristics is analyzed, and the applications of the absorber in sensing and thickness detection are explored to obtain the responding sensing detection performance. The conclusions are beneficial for the design of actively tunable Terahertz metasurface absorbers and have many potential applications in the detection field.

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