Optimization of photonic crystal enhanced fluorescence by excitation laser angle scanning

Photonic crystal enhanced fluorescence (PCEF) has been demonstrated as an effective technique for amplifying the electromagnetic excitation and emission extraction from surface-bound fluorescent molecules. Although optimal coupling of a fluorophore-exciting light source to the PC occurs with the use of collimated plane waves, PCEF surfaces are also capable of coupling light from focused sources but with a reduction in the obtainable enhancement factor. Using computer simulations and experimental measurements, we describe the interaction between the resonant bandwidth of a PCEF device surface and the optical design of the detection instrumentation that is used to provide fluorescence excitation. We show that highly collimated illumination is required for achieving the greatest PCEF enhancement factors, but at the expense of poor tolerance to non-uniformities in resonant wavelength across the PCEF surface. To overcome this limitation, we demonstrate a fixed wavelength/multiple incident angle scanning detection system that is capable of measuring every pixel in a PCEF fluorescence image under conditions that optimize resonant excitation efficiency.