Plasmonic switch based on composite interference in metallic strip waveguides

The optical switch is a key component in photonic integrations that plays an important role in routing the optical signal within a photonic circuit. In this work, compact switches were proposed and demonstrated based on the interference of surface plasmons polaritons (SPP) on free metal surfaces and in waveguides. Thanks to the constructive and destructive interferences implemented in strip waveguides, 2 x 2 ports switch devices with a small footprint were achieved with a maximum modulation depth of about 80%. Moreover, an interesting composite interference was observed and analyzed in the waveguide device, which is considered to arise from a transmission/reflection interference and field superposition interference. The samples of Bragg gratings and slits with different parameters were investigated in detail, which provided convincing evidence supporting the composite interference model. This revealed that the mechanism would possibly inspire new designs and instructions in nanophotonic integrations.