Analysis of plasmonic subwavelength waveguide-coupled nanostub and its application in optical switching

Numerical analysis of subwavelength metal-di-electric-metal waveguide perpendicularly coupled to a single nanostub, which is also a dielectric cavity embedded in a metallic medium, is demonstrated using the concept of transmission line theory. The transmission of the optical field is explained in terms of impedance matching and phase response in wavelength regime. Asymmetric nature of the spectral line shape has also been explained by complex plane investigation. Detailed study related to the influence of structural parameters on the resonant line shape has been carried out in order to facilitate proper choice of device parameters for different nanoplasmonic applications. Application of the device as an optical switch is also demonstrated. Incorporation of an active material within the stub and excitation by an optical pump provides the on-off switching mechanism. Certain physical parameters have been defined for performance evaluation of this switch, and switching efficiency has been evaluated in terms of these parameters considering operation at different infrared wavelengths.