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Widely tunable SPP bandgap in a nonlinear metal-insulator-metal waveguide.

In this article, we propose a novel kind of widely tunable surface plasmon polaritons (SPP) bandgap in a Kerr nonlinear metal-insulator-metal waveguide. By two identical gratings, the pump beam is coupled to two opposing SPP waves, which interfere with each other and results in SPP standing wave in the region between the two gratings. The refractive index of the Kerr nonlinear material is then periodically modulated by the SPP standing wave, and a SPP bandgap is formed. The position of the SPP bandgap can be tuned from 1.4 μm to 1.75 μm by adjusting the pump wavelength, and the relationship between the transmittance contrast of the bandgap and the pump power is also studied. Comparing with existing methods that directly modulate the refractive index (RI) or the width of the waveguide, in our work, the periodic modulation of the RI comes from the interference of the pump light, which can greatly simplify the fabrication. This work may find applications in the design of novel nonlinear devices for future all-optical integrated circuits.