Nanomechanical Plasmonic Switch Based on Multimode Interference

We propose and investigate a 2 × 2 optical switch based on multimode interference in Au-Air-Au gap plasmonic waveguide. The propagation of surface plasmon wave in gap plasmonic waveguide could be tuned by changing the size of air gap through a nanomechanical actuator. By tailoring the dispersion of the gap plasmonic waveguide, the multimode region only supports two lowest order modes with the opposite field symmetry. Switching between two states of gap size in the multimode region, the phase difference of two modes at output port could be tuned from 0 to π leading to switching plasmonic wave energy between two output ports. The proposed structure is simple in design and compact in size, which may find promising applications in active plasmonic devices.