Shuqi Chen

Dynamically tunable plasmonically induced transparency in periodically patterned graphene nanostrips

We present a dynamically wavelength tunable plasmonically induced transparency (PIT) planar device composed of periodically patterned graphene nanostrips for the mid-infrared region. The PIT effect can be achieved by a single layer of graphene nanostrips for a fixed Fermi energy. The PIT resonant wavelength can be dynamically tuned while maintaining PIT modulation strength, transmission peaks, and spectral line width by varying the Fermi energy of graphene without re-optimizing and re-fabricating the nanostructures. A three-level plasmonic system is demonstrated to well explain the formation mechanism of the wavelength tunable PIT in the graphene nanostrips. This work may offer a further step in the development of a compact tunable PIT device.

Polarization insensitive and omnidirectional broadband near perfect planar metamaterial absorber in the near infrared regime

We present the design, characterization, and experimental demonstration of a polarization insensitive and omnidirectional broadband near perfect planar metamaterial absorber (MA) in the near infrared regime, which does not need to stack multilayer composite structures. Experimental result shows that greater than 80% absorption is obtained across a wavelength range of 0.41 μm, which is in reasonable agreement with the simulation. The electromagnetic response of the MA is theoretically investigated. The broadband planar MA is polarization insensitive and the absorption remains high even at large incident angles.

Dynamically tunable broadband mid-infrared cross polarization converter based on graphene metamaterial

We present a mid-IR highly wavelength-tunable broadband cross polarization conversion composed of a single patterned top layer with L-shaped graphene nanostructures, a dielectric spacer, and a gold plane layer. It can convert linearly polarized light to its cross polarization in the reflection mode. The polarization conversion can be dynamically tuned and realize a broadband effect by varying the Fermi energy without reoptimizing and refabricating the nanostructures. This offers a further step in developing the tunable polarizers and the polarization switchers.

Realization of broadband cross-polarization conversion in transmission mode in the terahertz region using a single-layer metasurface

We present the design specifications and in-depth analysis of a terahertz (THz) broadband cross-polarization converter composed of a single-layer metasurface. This device can convert linearly polarized light into its cross-polarization in transmission mode. Different from other polarization conversion devices, this effect results from the suppression and enhancement for different electric components. The broadband characteristic is also achieved by specific partial symmetries designed in the structure. The proposed polarization converter can aid in the development of novel plasmonic polarization devices, and can help to overcome certain limitations of the customary designs that have been proposed thus far.

Mid-infrared tunable optical polarization converter composed of asymmetric graphene nanocrosses

We present a mid-IR highly tunable optical polarization converter composed of asymmetric graphene nanocrosses. It can convert linearly polarized light to circularly and elliptically polarized light or exhibit a giant optical activity at different wavelengths. The transmitted wavelength and polarization states can also be dynamically tuned by varying the Fermi energy of graphene, without reoptimizing and refabricating the nanostructures. This offers a further step in developing a controllable polarization converter.

Realizing Broadband and Invertible Linear-to-circular Polarization Converter with Ultrathin Single-layer Metasurface

The arbitrary control of the polarization states of light has attracted the interest of the scientific community because of the wide range of modern optical applications that such control can afford. However, conventional polarization control setups are bulky and very often operate only within a narrow wavelength range, thereby resisting optical system miniaturization and integration. Here, we present the basic theory, simulated demonstration, and in-depth analysis of a high-performance broadband and invertible linear-to-circular (LTC) polarization converter composed of a single-layer gold nanorod array with a total thickness of ~λ/70 for the near-infrared regime. This setup can transform a circularly polarized wave into a linearly polarized one or a linearly polarized wave with a wavelength-dependent electric field polarization angle into a circularly polarized one in the transmission mode. The broadband and invertible LTC polarization conversion can be attributed to the tailoring of the light interference at the subwavelength scale via the induction of the anisotropic optical resonance mode. This ultrathin single-layer metasurface relaxes the high-precision requirements of the structure parameters in general metasurfaces while retaining the polarization conversion performance. Our findings open up intriguing possibilities towards the realization of novel integrated metasurface-based photonics devices for polarization manipulation, modulation, and phase retardation.

Polarization-insensitive and wide-angle plasmonically induced transparency by planar metamaterials

We present the design, characterization, and experimental demonstration of a polarization-insensitive wide-angle plasmonically induced transparency (PIT) planar metamaterial (MM) in the near-infrared regime. A four-level plasmonic system is proposed to explain and analyze the forming mechanisms of the PIT planar MM, whose results agree closely with the simulated and experimental results. This shows that the local asymmetrical nanostructure leading to the plasmon-assisted interaction is the key to producing PIT, but it does not mean that PIT cannot be achieved by the whole symmetrical nanostructure. This work offers a further step in developing optical modulation.

A polarization insensitive and wide-angle dual-band nearly perfect absorber in the infrared regime

We report the design, characterization, and experimental demonstration of an infrared dual-band metamaterial absorber composed of simple periodically patterned structures. Experimental results show that two distinct absorption peaks of 74% and 96% are obtained, which are in reasonable agreement with the simulations. We demonstrate two absorption resonances that are derived from the mixture of magnetic and electric plasmon resonances. The dual-band absorber is polarization insensitive and the absorption peaks remain high with large angles of incidence for both transverse electric and transverse magnetic polarizations, which provide more efficient absorptions for nonpolarized or oblique incident beams.

Emergent Functionality and Controllability in Few‐Layer Metasurfaces

Recent progress in metamaterial research has successfully exceeded the limitations imposed by conventional materials and optical devices, enabling the manipulation of electromagnetic waves as desired. The distinct characteristics and controlling abilities of metamaterials make them ideal candidates for novel photonics devices not only in traditional optics but also for biological detection, medical science, and metrology. However, the controllability and functionality of both single-layer metasurfaces and bulk metamaterials are not sufficient to meet the requirements of emerging technologies; hence, new solutions must be found. As such technologies advance, new functionalities will emerge as different or identical single-layer metasurfaces are combined. Thus, innovation in few-layer metasurfaces will become an increasingly important line of research. Here, these metasurfaces are classified according to their functionalities and the few-layer metasurfaces that have been proposed up to now are presented in a clear sequence. It is expected that, with further development in this area, few-layer metasurfaces will play an important role in the family of optical materials.

Dynamically tunable plasmonically induced transparency by planar hybrid metamaterial.

We design and numerically analyze a dynamically tunable, plasmonically induced transparency (PIT) planar hybrid metamaterial (MM) in a near-infrared regime, which combines the near-field coupling effect into dynamic MM. The embedded position of tunable material in dynamic MM is optimized. Thermal-tunable VO(2) stripes are filled in the cut-out slots as components of a plasmonic system, which dramatically improve the dynamic modulation depth of the PIT. We also present a four-level plasmonic system to quantitatively analyze the dynamically tunable PIT device. This work may offer a further step in the design of the tunable PIT effect.