Metasurface-Based Optical Liquid Crystal Cell as an Ultrathin Spatial Phase Modulator for THz Applications

Buchnev, Oleksandr; Podoliak, Nina; Kaltenecker, Korbinian J.; Walther, Markus; Fedotov, V.A.

doi:10.1021/acsphotonics.0c01263

Cited by 60 publications

(34 citation statements)

References 56 publications

(116 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Liquid crystals are attractive for their inherent birefringent properties, which depend on the orientation of liquid crystal molecules and can be effectively controlled by an external electric field or light [102][103][104][105]. Figure 9a shows a THz spatial light modulator based on liquid crystals combined with metamaterial absorbers [102].…”

Section: Liquid Crystalsmentioning

confidence: 99%

“…Moreover, advanced and developed MEMS manufacturing makes it attractive for reconfigurable THz devices The reconfigurable effective refractive index of liquid crystal makes it suitable for both amplitude and phase modulation [103]. Figure 9d shows a spatial phase modulator of a nematic liquid-crystal layer sandwiched between two orthogonally placed metasurfaces [104].…”

Section: Micro-electromechanical-system (Mems)mentioning

confidence: 99%

See 1 more Smart Citation

Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links

2022

View full text Add to dashboard Cite

The forthcoming sixth generation (6G) communication network is envisioned to provide ultra-fast data transmission and ubiquitous wireless connectivity. The terahertz (THz) spectrum, with higher frequency and wider bandwidth, offers great potential for 6G wireless technologies. However, the THz links suffers from high loss and line-of-sight connectivity. To overcome these challenges, a cost-effective method to dynamically optimize the transmission path using reconfigurable intelligent surfaces (RISs) is widely proposed. RIS is constructed by embedding active elements into passive metasurfaces, which is an artificially designed periodic structure. However, the active elements (e.g., PIN diodes) used for 5G RIS are impractical for 6G RIS due to the cutoff frequency limitation and higher loss at THz frequencies. As such, various tuning elements have been explored to fill this THz gap between radio waves and infrared light. The focus of this review is on THz RISs with the potential to assist 6G communication functionalities including pixel-level amplitude modulation and dynamic beam manipulation. By reviewing a wide range of tuning mechanisms, including electronic approaches (complementary metal-oxide-semiconductor (CMOS) transistors, Schottky diodes, high electron mobility transistors (HEMTs), and graphene), optical approaches (photoactive semiconductor materials), phase-change materials (vanadium dioxide, chalcogenides, and liquid crystals), as well as microelectromechanical systems (MEMS), this review summarizes recent developments in THz RISs in support of 6G communication links and discusses future research directions in this field.

show abstract

Section: Liquid Crystalsmentioning

confidence: 99%

Section: Micro-electromechanical-system (Mems)mentioning

confidence: 99%

Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links

2022

View full text Add to dashboard Cite

show abstract

“…The dynamic control of transmission characteristics was achieved using SRRs, in which the capacitance or conductance components at gaps are varied in different ways, e.g., by using optically [34] or electrically [35] controlled carriers, micro-electro-mechanical systems (MEMS) [36,37], liquid crystals [38][39][40], graphene [41,42], vanadium dioxide [43][44][45], or semiconductor-based devices [46][47][48]. One of the attractive behaviors of SRRs is achieved when the lowest-order eigenmode (a normal mode in an oscillating system) is used, allowing for the size of unit cells to be smaller than the wavelength of the incident The dynamic control of transmission characteristics was achieved using SRRs, in which the capacitance or conductance components at gaps are varied in different ways, e.g., by using optically [34] or electrically [35] controlled carriers, micro-electro-mechanical systems (MEMS) [36,37], liquid crystals [38][39][40], graphene [41,42], vanadium dioxide [43][44][45], or semiconductor-based devices [46][47][48]. One of the attractive behaviors of SRRs is achieved when the lowest-order eigenmode (a normal mode in an oscillating system) is used, allowing for the size of unit cells to be smaller than the wavelength of the incident wave.…”

Section: Introductionmentioning

confidence: 99%

Analysis of Asymmetry in Active Split-Ring Resonators to Design Circulating-Current Eigenmode: Demonstration of Beamsteering and Focal-Length Control toward Reconfigurable Intelligent Surface

Kitayama

Pander

Takahashi

2022

Sensors

View full text Add to dashboard Cite

In this work, toward an intelligent radio environment for 5G/6G, design methodologies of active split-ring resonators (SRRs) for more efficient dynamic control of metasurfaces are investigated. The relationship between the excitation of circulating-current eigenmode and the asymmetric structure of SRRs is numerically analyzed, and it is clarified that the excitation of the circulating-current mode is difficult when the level of asymmetry of the current path is decreased by the addition of large capacitance such as from semiconductor-based devices. To avoid change in the asymmetry, we incorporated an additional gap (slit) in the SRRs, which enabled us to excite the circulating-current mode even when a large capacitance was implemented. Prototype devices were fabricated according to this design methodology, and by the control of the intensity/phase distribution, the variable focal-length and beamsteering capabilities of the transmitted waves were demonstrated, indicating the high effectiveness of the design. The presented design methodology can be applied not only to the demonstrated case of discrete varactors, but also to various other active metamaterials, such as semiconductor-integrated types for operating in the millimeter and submillimeter frequency bands as potential candidates for future 6G systems.

show abstract

“…In recent years, increasing attention has been attracted from passive to active controllable devices. Multiple active modulation approaches based on metasurfaces have been proposed and studied with typical tuning mechanisms including electrical, [ 13–18 ] optical, [ 19,20 ] mechanical, [ 21–24 ] thermal, [ 25–27 ] or chemical [ 28,29 ] schemes.…”

Section: Introductionmentioning

confidence: 99%

Actively Switchable Beam‐Steering via Hydrophilic/Hydrophobic‐Selective Design of Water‐Immersed Metasurface

Wan

Dai

et al. 2021

Advanced Optical Materials

View full text Add to dashboard Cite

Liquid immersion on metasurface was earlier demonstrated to realize spectral control. However, it remains a great challenge to achieve tunable phase modulation and versatile beam‐steering performance, which are critical for practical optoelectronic devices. Here, a new liquid‐immersive mechanism with metasurfaces for active beam‐steering is proposed and experimentally realized. Based on the dielectric‐on‐metal nanostructure with selective hydrophilic/hydrophobic properties, the switchable beam‐steering is initiated and successfully presented in the broadband visible regime with a large reflection angle of ≈±30°. Specifically, the beam diffraction direction is tuned between two opposite‐directional channels by water immersion or drying in a repeatable and controllable manner. The proposed straightforward tuning strategy enjoys great convenience in structural patterning and large‐area implementation, instead of requiring any complicated contact patterning or external modulation. This study provides an alternative optical platform for switchable beam‐steering functionality, which is promising for potential applications in tunable display, directional emission, sensing technologies, etc.

show abstract

Metasurface-Based Optical Liquid Crystal Cell as an Ultrathin Spatial Phase Modulator for THz Applications

Cited by 60 publications

References 56 publications

Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links

Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links

Analysis of Asymmetry in Active Split-Ring Resonators to Design Circulating-Current Eigenmode: Demonstration of Beamsteering and Focal-Length Control toward Reconfigurable Intelligent Surface

Actively Switchable Beam‐Steering via Hydrophilic/Hydrophobic‐Selective Design of Water‐Immersed Metasurface

Contact Info

Product

Resources

About