Advancing Plasmonic Computing with Single-Beam Logic Primitives

Plasmonic logic circuits combine ultrafast operation with nanoscale integration, making them a strong candidate for next-generation optical computing. Realizing this potential, however, requires overcoming practical challenges such as bulky interferometric designs and reliance on secondary control signals. This work advances plasmonic logic by introducing a single-global threshold mechanism in plasmonic two-wire transmission lines, empowered with polarization modal selectivity and geometric tuning to enable versatile circuit functionality. The scheme embeds the control signal with a single laser beam, supporting six deterministic polarization states and eliminating the need for auxiliary inputs. With this framework, we experimentally demonstrate advanced logic operations, including a 2-bit comparator, parity checkers, and encoder/decoder circuits. The approach reduces circuit footprint by 67% and power consumption by 50% relative to state-of-the-art systems, while maintaining low latency and high stability. By unifying thresholding, polarization, and geometry into a compact, source-free scheme, this work pushes plasmonic nanocircuitry from device-level novelty toward scalable, energy-efficient architectures for next-generation optical processors.