Cheng Gong

On‐chip photonic logic operations are emerging as a leading candidate for post‐Moore's computing and the terahertz (THz) band is crucial for next‐generation integrated applications. However, THz on‐chip Boolean logic gates still lack a universal paradigm for multifunctionality and reconfigurability, which is largely limited by the inadequate multiplexing and dynamic modulation capabilities. Here, we demonstrate a reconfigurable liquid crystal‐integrated plasmonic metasurface for THz full‐set logic operations. A three‐level coherent synthesis strategy is first established to customize spatiotemporal‐frequency‐spin multiplexed surface plasmonic vortices. Furthermore, a spatio‐temporal encoding mechanism is incorporated to support flexible surface field manipulations and reconstruct multi‐input‐output mappings for complex logic operations. With dual‐pixel and quad‐level encodings, this device delivers active control of vortex mode superposition and suppression, yielding up to 64 distinct nearfield states with a maximum contrast ratio of 20 dB. Surpassing conventional on‐chip logic devices, this platform executes multi‐bit logic operations up to 7‐bit inputs and 2 ¹²⁸ full‐set schemes, which enable parallel encryption and logic computing across multiple on‐chip nodes. This work paves the way for THz ultra‐compact on‐chip photonic links, advancing high‐density data communication and massive data processing applications.

Metalenses have attracted significant attention due to their advantages in on-chip and multifunctional integration, but are still limited by a restricted number of multiplexing channels, unsatisfactory focusing efficiency, and operation at a single frequency. In this work, we designed and characterized a four polarization channel all-dielectric terahertz metalens using an alternate-row supercell structure. Through this structure, the metasurface decouples two pairs of orthogonal polarizations: x - and y -linearly polarized, and left- and right-circularly polarized. By introducing both focused wavefront and spatial deflection modulations, we further realize off-axis focusing and spatial separation for these four polarization channels, with each channel having excellent polarization characteristics at its focal point. As a proof of concept, we demonstrate that the metalens can perform polarization detection by analyzing the intensity distribution at the focal spots, enabling the determination of the polarization state of arbitrary incident light. Beyond this, within the 0.4–0.48 THz broadband range, the focusing efficiency reaches 39%, and the mode purity exceeds 68%. The proposed multi-channel polarization metalens shows great application potential in polarization sensing detection, polarization multiplexing imaging, and multi-channel communication.

A metasurface technology is proposed, which uses a fine-line-based mesh to form a resonant structure instead of the traditional resonant pattern. Because the filling factor of the fine lines is low, the metasurface has high optical transmittance. Meanwhile, a highly efficient electromagnetic absorption can be achieved through the stacking of the metasurfaces. To demonstrate the effectiveness, we designed an optically transparent microwave absorber with polarization insensitivity and wide-angle incidence characteristics. The absorber is composed of a top mesh metasurface film, a transparent layer, and a bottom mesh film. Next, the sample with an area of 150 × 150 mm ² was fabricated using nano-imprinting technology. Through testing, the top metasurface and the bottom film achieved an average optical transmittance of 91.53% and 92.67%, respectively. Furthermore, by adjusting the stacking gap (transparent layer thickness), the absorption rate could be adjusted from 94.15% to 18.4%. Embedding the metasurface films into transparent windows or materials can achieve both efficient electromagnetic absorption and optical transparency.

Array detection chip is one of the key components of terahertz (THz) systems, with important applications in nondestructive testing, perspective imaging, and high-speed communication. This letter proposes an optical readout THz stacked metamaterial array chip operating at a frequency near the atmospheric window (0.22 THz). It adopts the design of upper and lower chips separation and then bonding to achieve the stacked structure. The upper chip combines with metamaterial cantilever pixels to achieve sensing and execution functions, while the lower chip undertakes auxiliary and support functions. The incident THz radiation can be absorbed and converted to mechanical energy of pixels, then read out in parallel at high speed by the optical system. The stacked mechanism reduces the size and thickness of the sensing/execution structure and improves the radiation–thermal–mechanical sensitivity of the chip. Spectral measurements show that its absorptivity is 97%. Meanwhile, the time measurement results indicate that the chip can quickly respond to THz radiation, with a response time of 1.62 ms.

A stacked metamaterial MEMS (meta-MEMS) chip is proposed, which can perfectly absorb electromagnetic waves, convert them into mechanical energy, drive movement of the optical micro-reflectors array, and detect millimeter waves. It is equivalent to using visible light to image a millimeter wave. The meta-MEMS adopts the design of upper and lower chip separation and then stacking to achieve the “dielectric-resonant-air-ground” structure, reduce the thickness of the metamaterial and MEMS structures, and improve the performance of millimeter wave imaging. For verification, we designed and prepared a 94 GHz meta-MEMS focal plane array chip, in which the sum of the thickness of the metamaterial and MEMS structures is only 1/2500 wavelength, the pixel size is less than 1/3 wavelength, but the absorption rate is as high as 99.8%. Moreover, a light readout module was constructed to test the millimeter wave imaging performance. The results show that the response speed can reach 144 Hz and the lens-less imaging resolution is 1.5 mm.

A terahertz metamaterial waveguide (meta-waveguide) and a meta-waveguide-based lens-free imaging system are presented. The meta-waveguide not only inherits the low-loss transmission performance of a waveguide but also breaks through the diffraction limit under the action of the metamaterial, achieving subwavelength focusing. The focusing distance is far greater than the Rayleigh length, thus enabling far-field scanning imaging. For verification, a metal ring-based meta-waveguide was fabricated by 3D printing and metal cladding technology. Then, a transmission scanning imaging system working at 0.1 THz was built. High quality terahertz images with a resolution of 1/3 of the wavelength were obtained by placing the imaging targets at the focus and performing two-dimensional scanning. The focusing and transmission of terahertz wave in the meta-waveguide were simulated and analyzed.

Terahertz (THz) scattering-type scanning near-field optical microscopy (s-SNOM) is an important means of studying and revealing material properties at the nanoscale. The nanotip is one of the core components of THz s-SNOM, which has a decisive impact on the resolution of the system. In this paper, we focus on the theory and design of the nanotip and conduct comprehensive research on it through simulation. The theoretical model is based on full-wave numerical simulation and dipole moment analysis, which can describe the overall nanotip electromagnetic response under the incident field. A comprehensive design model of nanotip geometry, sample materials, and incident field is established to significantly improve the near-field coupling efficiency and spatial resolution to achieve optimal performance.

Due to the limitation of Abbe diffraction limit, the traditional terahertz (THz) continuous wave imaging methods based on lenses or mirrors are difficult to achieve super-resolution. Here we present a confocal waveguide scanning method for THz reflective super-resolution imaging. In the method, a low loss THz hollow waveguide is used to replace the traditional terahertz lens or parabolic mirror. Through optimizing the size of the waveguide, we can achieve far field subwavelength focusing at 0.1THz and achieve super-resolution terahertz imaging. In addition, a slider-crank high-speed scanning mechanism is used in the scanning system, and the imaging speed is more than 10 times faster than the traditional step scanning system based on linear guides. In addition, its application in the field of nondestructive testing is introduced.

A terahertz (THz) metamaterial design mechanism based on a stacked chip is proposed. Unlike the traditional sandwich-type metamaterial design mechanism based on the “resonant layer–dielectric layer–ground layer” structure, it adopts a stacked design of upper and lower metamaterial chips to achieve a new structure based on the “dielectric layer–resonant layer–air layer–ground layer” structure. This could break through the thickness limitations and construct an ultra-thin metamaterial upper chip. To verify the effectiveness of this method, we applied it to the field of THz perfect absorbers. We designed, simulated, and prepared a terahertz stacked chip-based perfect absorber with an upper-chip thickness less than 1/800 of the wavelength. Then, a reflective spectroscopy system based on a vector network analyzer is built to test the absorption performance. The measured results show that it has an absorptivity of 98.4% at 0.222 THz, which is in good agreement with simulations.