Broadside coupling to long-range surface plasmons using an angle-cleaved optical fiber

A technique for evanescent broadside coupling to surface plasmons is described and demonstrated. The technique makes use of a polarization maintaining optical fiber cleaved at a steep angle and positioned near the structure to be excited such that the slow mode of the fiber couples evanescently to the surface plasmon propagating thereon. The technique is applied to excite long-range surface plasmons on a metal stripe supported by a freestanding dielectric membrane. The technique should be useful for coupling to other plasmonic or dielectric waveguides, and for optical wafer probing.