Dual band terahertz waveguiding on a planar metal surface patterned with annular holes

We report studies of the guiding of terahertz radiation on a copper surface textured with an array of blind annular holes. The structure supports two tightly bound surface plasmon-polaritonlike electromagnetic waves associated with TE11 and TEM coaxial waveguide modes. The TE11-like surface mode has a cutoff determined by the array period while the TEM mode can be arranged to have a lower frequency cut-off by adjusting the hole depth. The ability to guide two modes in independently variable bands could be useful in quantitative chemical sensing.