Resonant waveguide grating (RWG): overcoming the problem of angular sensitivity by conical, broad-band illumination for fluorescence measurements

Abstract

Most biomedical applications are based on the light–matter interaction; the measurement of absorption, scattering or fluorescence at the visible and near visible region of the electromagnetic spectrum. This can be enhanced with nanophotonical devices. Most often, metallic nanoparticles are used for this purpose. However, metallic – as well as non-metallic – nanostructures have their limitations. In this report we introduce an all-dielectric structure, namely resonant waveguide grating (RWG), which can respond to the demands of optical enhancement of measurements. RWG's are, however, notorious for their angular sensitivity, which can be problematic, particularly in terms of enhancing fluorescence. We introduce a solution to this problem, which could enable RWG's to be harnessed for the benefit of cost-efficient and sensitive fluorescence measurements in the field of life sciences. This report represents a 30-fold fluorescence enhancement using RWG within a conventional fluorescence microscope and the theoretical calculations support our idea.