The present disclosure relates to structures, systems, and methods for characterizing one or more fluorescent particles. At least one embodiment relates to an integrated waveguide structure. The integrated waveguide structure includes a substrate. The integrated waveguide structure also includes a waveguide layer arranged on top of the substrate. The waveguide layer includes one or more excitation waveguides, one or more emission waveguides, and a particle radiation coupler, which includes a resonator element. In addition, the integrated waveguide structure includes one or more sensing sites configured with respect to the one or more excitation waveguides and the one or more emission waveguides such that a fluorescent particle at one of the sensing sites is activated by an excitation radiation transmitted via the one or more excitation waveguides and radiation emitted by the fluorescent particle is coupled into at least one of the emission waveguides by the particle radiation coupler.