In this study, the signal processing in three-port and four-port plasmonic coupler devices by coherently controlling the phases and amplitudes of launched surface plasmons is investigated by finite-difference time-domain method (FDTD) simulation. This device is composed of two metal-dielectric-metal waveguides with a strip cavity imbedded in the shared metal layer. Interference between the plasmonic signals of two input ports is caused by the tunneling effect of surface plasmons in the strip cavity. The functions of signal modulation, recovery, filtering, and plasmon-induced transparency (PIT) of the proposed devices are proposed and demonstrated. The all-optical logic gates based on the proposed devices are also designed and verified.
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