Abstract
In microwave and terahertz frequency band, a textured metal surface can support spoof surface plasmon polaritons (SSPPs). In this paper, we explore a SSPPs waveguide composed of a metal block with pyramidal grooves. Under the deep subwavelength condition, theoretical formulas for calculation of dispersion relations are derived based on the modal expansion method (MEM). Using the obtained formulas, a general analysis is given about the properties of the SSPPs in the waveguides with upright and downward pyramidal grooves. It is demonstrated that the SSPPs waveguides with upright pyramidal grooves give better field-confinement. Numerical simulations are used to check the theoretical analysis and show good agreement with the analytical results. In addition, the group velocity of the SSPPs propagating along the waveguide is explored and two structures are designed to show how to trap the SSPPs on the metal surface. The calculation methodology provided in this paper can also be used to deal with the SSPPs waveguides with irregular grooves.
Highlights
In optical frequency band, a smooth dielectric-metal interface can sustain surface plasmon polaritons (SPPs), which can propagate along the surface with high field-confinement
Under the deep subwavelength condition λ0 ≫d >a (λ0 is the wavelength in free space, a is the groove width), the dispersion relation of the spoof surface plasmon polaritons (SSPPs) is expressed as β2
We have studied the waveguides corrugated with pyramidal grooves and provided a general method to calculate the dispersion relations for the waveguides with various types of grooves
Summary
A smooth dielectric-metal interface can sustain surface plasmon polaritons (SPPs), which can propagate along the surface with high field-confinement. Like its analogues in optical frequency range, the properties of SSPPs in microwave or terahertz band are sensitive to the geometric shape of the metal surface[3,4,5,6,7,8], which makes it possible to realize novel functional devices by modulating the structure geometry. Rectangular groove is just one special case Based on this model, the propagation constant and the field-confinement properties can be deduced readily. The propagation constant and the field-confinement properties can be deduced readily Such method can be extended to SSPPs waveguides with irregular grooves
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