All-in-one Cascadable Dynamic Terahertz Logic Gates Enabled by Polarization Encoding and Multiplexing

Abstract

Metasurfaces bring an advanced paradigm for optical computing through extraordinary beam manipulation. A metasurface logic gate needs function multiplexing to process different input signals. Integration of multiple gates in one design further increases the multiplexing channels, which necessitates the diffractive neural networks with challenges of decreased system stability, difficulty for connection, and large insertion loss. Here an optical logic gate is demonstrated by sequentially encoding the input signals into polarization and decoding through a 4-polarization-multiplexed metasurface. By introducing an idler polarization state, a convenient strategy is developed to integrate and dynamically switch 4 or full 7 logic gates in a single module through overall polarization rotation and proper polarization-truth multiplexing relation. The all-in-one logic gate is validated at 140 GHz through the steady-state and dynamic test, with the resulting contrast of 6.5 dB, flexible test ranges of 80 mm, and insertion loss of 2.2 dB. The computing result is represented by both the focusing position and the polarization, with the later as a consistent input and output physical quantity for cascading. Cascaded AND–AND gates and AND-OR gates are demonstrated with 6 dB result contrast, showing great promise for building robust logic systems for future optical signal processing.