Light controlled surface plasmon polaritons switch based on a gradient metal grating

A surface plasmon polaritons (SPPs) switch controlled by a pump light in the terahertz (THz) regime is designed. The switch is based on the surface slow-light technology. A gradient metal grating on a silicon (Si) layer is adopted to slow the SPP waves. By adjusting the grade of grating depths, the location of stopped waves can be tuned. By changing the intensity of pump light shining on the Si layer, the carrier density of Si layer can be modulated and thus the dielectric constant of Si layer. Then the SPPs can switched between two states: going through the structure or being stopped. The bandwidth of the captured surface wave can be effectively broaden by using this kind of depth gradient grating. This approach may provide a new method to design controllable SPPs devices.