Photonic Spin‐Hall Logic Devices Based on Programmable Spoof Plasmonic Metamaterial

Integrated power dividers (PDs) are essential in terahertz (THz) communication and radar systems, but miniaturization often leads to performance degradation due to fabrication inaccuracies and sharp bends. Topological photonics offers a solution to these issues, yet creating THz power dividers with arbitrary splitting ratios remains challenging. We present a design methodology for on-chip topological THz power dividers with customizable splitting ratios using valley-locked photonic crystals. These crystals feature a tri-layered structure with two distinct valley Chern number layers and an intermediate semimetal layer. Utilizing the Jackiw–Rebbi model, we show that the characteristic impedance of the valley-locked photonic crystals, and thus the power division ratio, can be tuned by adjusting the semimetal layer width. Our approach is validated through simulations and experiments for both equal (1:1) and unequal (4:9) power ratios. This method enables efficient navigation around sharp bends and robust THz on-chip connectivity.

Integrated terahertz topological valley-locked power divider with arbitrary power ratios

Wang,

Ren,

et al. 2024

Dual-channel intrinsic and nonlinear chirality for an all-optical logic operation

Zong,

Cai,

Liu

et al. 2024

Chiral metasurfaces hold excellent performance in enhancing spin-dependent light–matter interaction, showing broad application prospects in areas such as chiral imaging, chiral light sources, and chiral sensing. However, utilizing resonant metasurfaces to achieve all-optical logic gates has not been reported yet. In this work, dual-channel intrinsic and nonlinear chiroptical responses are achieved on lithium niobate metasurfaces. The combination of bound states in the continuum (BICs) resonant modes with chiral metasurfaces has revealed its linear and nonlinear chirality. The metasurface achieves linear circular dichroism above 0.9 and nonlinear circular dichroism close to 0.9 on the dual-band. Based on the second-order nonlinear chiroptical response, multiple all-optical logic gates (including NOT, OR, NAND, AND, and NOR) can be realized on the chiral metasurfaces. Our results confirm the operability of resonant metasurfaces in realizing all-optical logic gates, offering a potentially promising approach for the development of new, to the best of our knowledge, all-optical logic devices.

Reexamining the anomalous spin–orbit interactions of light around Fresnel coefficient singularities

Wang,

Tan,

Chen

et al. 2024

Using a full-wave theory to analyze the light beam scattering at sharp interfaces, we reexamine the anomalous spin–orbit interaction (SOI) around the Fresnel coefficient (FC) singularities. We evaluate the spin-dependent beam shifts near the singularity for three typical optical interfaces, comparing our results with existing ones. Existing theories neglect the contribution of the wave vector component k y i near the FC singularities, potentially leading to erroneous results. In contrast, our approach comprehensively considers k x i and k y i contributions in the FC without any approximation. Our analysis reveals significant deformations in scattered light intensity patterns near the FC singularities, causing both out-of-plane and in-plane spin-Hall shifts, uncaptured by prior theories. These findings offer a comprehensive understanding on the spin–orbit interactions at generic optical interfaces.