Planar waveguides for fluorescence-based biosensing: optimization and analysis

Optimization of planar waveguides for fluorescence biosensing is presented in this paper. In particular, the authors show that optical (refractive index) and geometrical parameters have a strong influence on the efficiency of excitation and collection of fluorescent signals. Numerical analyses show that a single-mode slab waveguide, operating at its fundamental transverse magnetic mode and near its cutoff point, results in an efficient fluorescence excitation when employed as evanescent wave biosensor. A high-refractive index contrast is demonstrated to be the key parameter for an efficient fluorescence collection. Other geometries that are an alternative to the classical slab waveguide may result in an improvement of the fluorescence excitation and collection efficiencies.