Spin-encoded subwavelength all-optical logic gates based on single-element optical slot nanoantennas.

Optical logic gates are important elements in optical computing and optical circuits. However, the footprints of the present optical logic gates are still on the micrometer scale. Further miniaturization of the logic gates to nanometer scale remains challenging. Here we propose, and demonstrate experimentally, subwavelength all-optical logic gates based on single-element optical slot nanoantennas. By employing a spin-encoded scheme, we achieve OR, AND, NOT, NAND and NOR logic gates via an L-shaped optical slot nanoantenna with a footprint of 300 nm by 300 nm, and a XNOR logic gate via a rectangle optical slot nanoantenna with a footprint of 220 nm by 60 nm. The SPP launching and logic operation via mode coupling instead of path interference are integrated together at a single-element nanoantenna, which considerably shrinks the dimensions of the device. The experimental results show the potential of the single optical slot nanoantenna in subwavelength all-optical logic computing and nanophotonic information processing.