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Author

Heting Li

Bio: Heting Li is an academic researcher from Capital Normal University. The author has contributed to research in topics: Terahertz radiation & Photonics. The author has an hindex of 3, co-authored 4 publications receiving 102 citations.

Papers
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Journal ArticleDOI
TL;DR: A tri-layer structure is designed and experimentally demonstrated that the structure can serve as a highly efficient transmissive meta-atom to build PB metadevices for manipulating CP THz waves, paving the way to freely manipulate terahertz beams.
Abstract: The unrestricted control of circularly polarized (CP) terahertz (THz) waves is important in science and applications, but conventional THz devices suffer from issues of bulky size and low efficiency. Although Pancharatnam–Berry (PB) metasurfaces have shown strong capabilities to control CP waves, transmission-mode PB devices realized in the THz regime are less efficient, limiting their applications in practice. Here, based on Jones matrix analysis, we design a tri-layer structure (thickness of ~λ/5) and experimentally demonstrate that the structure can serve as a highly efficient transmissive meta-atom (relative efficiency of ~90%) to build PB metadevices for manipulating CP THz waves. Two ultrathin THz metadevices are fabricated and experimentally characterized with a z-scan THz imaging system. The first device can realize a photonic spin Hall effect with an experimentally demonstrated relative efficiency of ~90%, whereas the second device can generate a high-quality background-free CP Bessel beam with measured longitudinal and transverse field patterns that exhibit the nondiffracting characteristics of a Bessel beam. All the experimental results are in excellent agreement with full-wave simulations. Our results pave the way to freely manipulate CP THz beams, laying a solid basis for future applications such as biomolecular control and THz signal transportation. Ultrathin metasurfaces that can efficiently manipulate circularly polarized terahertz waves in transmission rather reflection have been demonstrated by scientists in China. The devices were fabricated by Min Jia and colleagues from Fudan University and Capital Normal University. The tri-layer structures operate at frequencies of around 0.6 THz and suit future on-chip applications for terahertz photonics. Various designs were tested resulting in a circularly polarized terahertz Bessel beam generator and a device exhibiting the photonic spin Hall effect. The metasurfaces consist of a periodic array of meta-atoms, each composed of three thin layers of metal in a U-shape that are separated and surrounded by polyimide. Changing the angular orientation of the meta-atoms allows different phase gradients to be programmed into the metasurfaces bringing the desired functionality.

96 citations

Journal ArticleDOI
TL;DR: In this paper, a tunable terahertz meta-lens whose focal length is able to be electrically tuned by ∼4.45λ was demonstrated experimentally, where the lens consists of a metallic metasurface and a monolayer graphene.
Abstract: Metasurfaces have become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because they can introduce an abrupt phase change by arrays of scatterers. To be applied more widely, active metasurface devices are highly desired. Here, a tunable terahertz meta-lens whose focal length is able to be electrically tuned by ∼4.45λ is demonstrated experimentally. The lens consists of a metallic metasurface and a monolayer graphene. Due to the dependence of the abrupt phase change of the metasurface on the graphene chemical potential, which can be modulated using an applied gate voltage, the focal length is changed from 10.46 to 12.24 mm when the gate voltage increases from 0 to 2.0 V. Experimental results are in good agreement with the theoretical hypothesis. This type of electrically controlled meta-lens could widen the application of terahertz technology.

73 citations

Journal ArticleDOI
TL;DR: This work gives a full view to understand the evolution characteristics of the THz bottle beam and provide a solid experimental foundation for guiding the future applications of this type of THz beam.
Abstract: A terahertz (THz) bottle beam is realized by adopting the combination of a Teflon axicon and a silicon lens By using a THz imaging system with a focal-plane array, the vector characteristics of the THz bottle beam are coherently measured and detailedly analyzed, including the transverse (Ex) and longitudinal (Ez) components The experimental phenomena vividly reveal the distribution characteristics and the formation origin of the THz optical barrier A vectorial diffraction integral algorithm of a focusing optical system are utilized to exactly simulate the measured results Besides, the features of the THz bottle beam are effectively tuned by varying the parameters of the Teflon axicon and the silicon lens This work gives a full view to understand the evolution characteristics of the THz bottle beam and provide a solid experimental foundation for guiding the future applications of this type of THz beam

4 citations

Journal ArticleDOI
TL;DR: In this article, a Bessel-like terahertz (THz) beam in free space and a metallic semicircular slit was generated for surface plasmon light capsule (TSPLC) in simulation and experiment.
Abstract: Surface plasmon waves with unique intensity profiles are important for developing integrated photonic circuits. By organically combining a Bessel-like terahertz (THz) beam in free space and a metallic semicircular slit, we generate a THz surface plasmon light capsule (TSPLC) in simulation and experiment. The TSPLC has a two-dimensional optical barrier on the surface of a metal foil. Furthermore, we propose and theoretically validate the potential use of the TSPLC in refractive index sensing. This work has major implications for manipulating and applying surface plasmon waves.

3 citations

Journal ArticleDOI
TL;DR: In this paper , the authors combine theoretical analysis and numerical simulation to study the waveguide effect in the far-infrared oscillator for different waveguide sizes, and the results show that, with a waveguide of 30 mm × 10 mm initially used, a spectral gap will be found at 89 μ m and the FEL power at the wavelength longer than 100 μ m will be rather low.
Abstract: The FELiChEM infrared free-electron laser consists of two oscillators : the mid-infrared oscillator and the far-infrared oscillator, covering the spectral range of 2– 40 μ m and 20– 200 μ m , respectively. The mid-infrared oscillator finished the commissioning in 2020 and a deep spectral gap around the wavelength of 21 μ m existed. In this paper, combining theoretical analysis and numerical simulation, the research on this waveguide effect has been carried out and the simulation results highly agree with the measurement. Through using the same method, we study the waveguide effect in the far-infrared oscillator for different waveguide sizes. The results show that, with the waveguide of 30 mm × 10 mm initially used, a spectral gap will be found at 89 μ m and the FEL power at the wavelength longer than 100 μ m will be rather low. Based on these studies, a reasonable waveguide size of 30 mm × 16 mm has been reselected to make the tunable range of the far-infrared oscillator covering 20– 200 μ m . The recent measurement carried out in 2021 also agree with the prediction of the simulation results.

3 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a transformation media slab is derived as a meta-surface, producing anomalous reflection and refraction for all polarizations of incident light, based on transformation optics.
Abstract: Based on transformation optics, we introduce another set of generalized laws of reflection and refraction (differs from that of [Science 334, 333 (2011)]), through which a transformation media slab is derived as a meta-surface, producing anomalous reflection and refraction for all polarizations of incident light.

230 citations

Journal ArticleDOI
TL;DR: This work proposes a multiplexed anti-counterfeiting metasurface consisting of single-sized nanostructures, which provides a new degree of freedom to increase the information capacity of anti- counterfeiting without burdening the nanostructure design and fabrication.
Abstract: Metasurfaces have recently been used for multichannel image displays with pixel-size lower than a wavelength, which indicates the potential application in ultracompact anticounterfeiting with high-...

118 citations

Journal ArticleDOI
Pei Ding1, Yan Li1, Li Shao1, Ximin Tian1, Junqiao Wang1, Chunzhen Fan1 
TL;DR: It is shown that the graphene apertures' spatially varying length distribution is the key factor for determining the modulation level, rather than the focal length's modulation range, thereby offering great application potential in lightweight and integrated terahertz devices.
Abstract: We theoretically study a tunable reflective focusing lens, based on graphene metasurface, which consists of rectangle aperture array. Dynamic control of either the focal intensity or focal length for terahertz circular polarized waves can be achieved by uniformly tuning the graphene Fermi energy. We demonstrate the graphene apertures with the same geometry; however, spatially varying orientations can only control the focal intensity. To change the focal length, the spatially varying aperture lengths are also required. A comparative study between the metalenses, which generate only geometric or both gradient and geometric phase changes, has shown that the apertures' spatially varying length distribution is the key factor for determining the modulation level, rather than the focal length's modulation range. This kind of metalens provides tunable, high-efficiency, broadband, and wide-angle off-axis focusing, thereby offering great application potential in lightweight and integrated terahertz devices.

73 citations

Journal ArticleDOI
TL;DR: In this article, an overview of dielectric materials employed as spacers, and fabrication methods employed to realize these devices at the terahertz frequency range are also presented; material selection guidelines, material-specific and application-specific fabrication quality metrics are outlined, and new techniques are proposed.
Abstract: Manipulation of terahertz radiation opens new opportunities that underpin application areas in communication, security, material sensing, and characterization. Metasurfaces employed for terahertz manipulation of phase, amplitude, or polarization of terahertz waves have limitations in radiation efficiency which is attributed to losses in the materials constituting the devices. Metallic resonators‐based terahertz devices suffer from high ohmic losses, while dielectric substrates and spacers with high relative permittivity and loss tangent also reduce bandwidth and efficiency. To overcome these issues, a proper choice of low loss and low relative permittivity dielectric layers and substrates can improve field confinement and reduce dissipation. Alternatively, replacing metallic resonators with a moderate relative permittivity dielectric material that supports cavity mode resonances also reduces dissipation due to the absence of conduction current. Herein, an overview of dielectric materials employed as spacers and dielectric resonators is provided, and the fabrication methods employed to realize these devices at the terahertz frequency range are also presented. Material selection guidelines, material‐specific and application‐specific fabrication quality metrics are outlined, and new techniques are proposed.

69 citations