We have been studying fluorescence enhancement from labeled oligonucleotides immobilized inside metallic
nanoapertures. Fluorescence enhancement is a direct result of the localized field intensity enhancement within
these nanoapertures from plasmonic excitation. We have also been developing specific surface chemistries
for metallic films to localize capture oligos only inside these nanoapertures. Some of our recent results are
We study light transmission through individual and arrays of sub-wavelength metallic apertures of conical shape as a function of their taper angle. With a fixed aperture size at the substrate, there is a dramatic increase in light throughput with increasing taper angle. Similar behaviors hold when considering the intensity enhancement inside the aperture near the substrate interface, where more than four-fold increase can be obtained. When arranged in regular arrays, apertures can interact via surface waves, creating distinct minima and maxima in light transmission and intensity enhancement. The effect of aperture taper is also to dramatically increase light transmission and intra-aperture intensity, but with a red shift in the maxima and negligible shift in the minima. The use of conical apertures should improve the efficiency of nonlinear optical processes as well as applications of light harvesting, such as biomolecule detection.