Magnification of photonic crystal fluorescence enhancement via TM resonance excitation and TE resonance extraction on a dielectric nanorod surface

Using a one-dimensional grating surface photonic crystal (PC), we experimentally demonstrate that the detection of fluorescent molecules on a PC surface can be substantially magnified through the combined effects of resonance-enhanced excitation of the fluorescent dye, resonance-enhanced extraction of the fluorescence emission and a dielectric nanorod surface coating increasing the surface area available for fluorophore-PC interaction. Enhanced excitation is obtained by engineering a high-Q TM resonant mode to efficiently couple with an incident TM-polarized λ = 633nm laser for exciting Cyanine-5 (Cy5). Enhanced extraction results from a low-Q TE resonance designed to spectrally overlap the Cy5 emission spectrum for channeling TE-polarized emission towards the detection instrument. The entire PC surface is coated with a porous film of TiO₂ nanorods that allows more fluorophores to penetrate into the region of enhanced near-electric fields. Experimental results reveal a 588-fold enhancement in fluorescence intensity relative to an unpatterned glass surface.