Splitting and unidirectional excitation of surface plasmon polaritons by two uniform metallic nanoslits with a nanocavity antenna

A tunable splitter and source of surface plasmon polaritons (SPPs) is proposed. The structure is composed of two Ag films, with two uniform nanoslits fabricated in the lower Ag film and lying above is a movable Ag film. By changing the horizontal position of the top Ag film, the splitting ratio of the SPPs varies periodically based on SPP interference. The field distribution of the structure is investigated by using the finite-difference time-domain (FDTD) method. The period obtained by the FDTD agrees well with the Fabry–Pérot cavity model. When the SPP splitting ratio is large (or small), our structure acts as a low noise SPP source. Compared with other SPP sources, our model possesses better directionality.     

Tunable beam focusing based on optical bistability with a composite Kretschmann configuration involving a Kerr medium

A beam focuser with a composite Kretschmann configuration involving a Kerr medium is investigated theoretically. The structure employs a silver film with four slits filled with the Kerr medium. Optical bistability and beam focusing are demonstrated, and changes to the incident intensity result in optical bistability characteristics in the reflection, focused intensity, spot size, and depth of focus. The proposed structure has the potential to be applied for optical switching and nano-illumination.