Detection of surface-plasmon evanescent fields using a metallic probe tip covered with fluorescence

A new experimental system has been constructed to detect evanescent fields of metal surface plasmons (SPs) using a metallic probe tip covered with fluorescence cadmium sulfide (CdS). The evanescent fields of the SPs sensitive to the metal interfaces were observed as fluorescent light from CdS on the tip. No additional lock-in detection technique with a vibrating probe tip is necessary in the system, in spite of the scattered light enhanced by SP due to the surface roughness. The fluorescent light measured for the Al film sample shows exponential decay with distance from the sample surface, indicating that the SP evanescent fields are detected with our apparatus.