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Directional, enhanced fluorescence from molecules near a periodic surface.

We extend the research of Holland and Hall on the use of waveguide modes to enhance the fluorescent signal from a layer of molecules [Opt. Lett. 10,414 (1985)] by incorporating a grating into the basic sample structure. Our measurements show that the combination of the directionality imposed by the grating and the previously reported enhancement mechanism has the effect of increasing the intensity of the signal detected over a narrow angular range from a layer of fluorescing molecules by a factor of ~ 1000 over that from a reference sample. Simultaneously our method allows for both polarization and wavelength discrimination of the emitted radiation because of the characteristic nature of the incorporated grating.