Enhanced fluorescence biosensing using an array of metallic nanoapertures

We present experimental results confirming that both periodic and randomly placed metallic nanoapertures can be used to enhance the output of a fluorescing molecular monolayer. The metallic nanoapertures were fabricated by e-beam lithography using both positive and negative e-beam resists. Measurements show that the peak fluorescence from the periodic apertures occurs under the conditions of the maximum transmission of excitation light through the structures. There is also an enhancement of fluorescence from randomly placed apertures even though there is no enhancement of the transmission light, which is caused by the incident light evanescently coupling directly through the apertures.