Coupling of terahertz radiation to metallic wire using end-fire technique

We demonstrate coupling of THz radiation at 625 GHz onto a copper wire. The end-fire technique is used in combination with an axicon to excite the azimuthally polarized surface plasmon polaritons on the wire's front facet. A small lateral offset of the wire relative to the optical axis is used to achieve significant plasmon exication. Coupling efficiencies of about 17% were measured. Here, we discuss the coupling mechanism theoretically using the overlap integral and verify the plasmonic excitation and propagation by measuring the radiated field at the wire end.