Excitation of multi-order guided mode resonance for multiple color fluorescence enhancement

Higher-order Guided Mode Resonance (GMR) in a symmetric two-dimensional embedded grating-waveguide structure is theoretically demonstrated in this paper through a phase matching mechanism of leaky modes along second-order diffraction planes. In addition to the fundamental-order, multiple resonances are introduced at normal incidence and they are polarization independent. A strong localization of the resonance modes exists in both orders. The device is proposed for multiple color surface enhanced fluorescence that is compatible to a conventional fluorescence reader. The enhancement scheme is by increasing light absorption via the excitation of a strong evanescent wave as an extension of a resonance mode. GMR device is designed to have resonances overlapping fluorophores' absorption spectra. The concept is verified using numerical calculations, Rigorous Coupled Wave Analysis and Homogeneous Waveguide Approach. The device is fabricated and experimentally performed for fluorescence enhancement using a microarray of Cyanine 3-labeled goat antibody and Cyanine 5-labeled goat antibody. The fluorescence signal is characterized using a low-cost CMOS array. This implementation can be very useful in a multiplex detection, where the cost of the reader can be minimized.