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

Coupling of THz radiation at 625 GHz onto a copper wire is demonstrated. The end-fire technique is used in combination with an axicon to excite the azimuthally polarised 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 excitation. Coupling efficiencies of about 17% were measured. The coupling mechanism is discussed theoretically using the overlap integral and verify plasmonic excitation and propagation by measuring the radiated field at the wire end.