Signal enhancement of surface plasmon-coupled directional emission by a conical mirror

A simple strategy for increasing the collection efficiency of surface plasmon-coupled emission (SPCE) is demonstrated. SPCE is a near-field phenomenon occurring when excited fluorophores are in close proximity to a subwavelength metal film. The energy of the fluorophores induces surface plasmons that radiate the coupled energy at highly specific angles. In an attempt to maximize the collected emission, a conical mirror was placed around the coupling prism. The result was a nearly 500 fold enhancement over the free space signal as detected from a single point from a poly(vinyl alcohol) layer doped with ruthenium. Coupling this large enhancement with LED excitation could lead to the development of inexpensive, handheld fluorescent devices with high sensitivity.