Differentiation Between Analyte Adsorption and Homogenous Index Sensing in WGM Biodetection

We propose new parameters to characterize a whispering gallery mode spectrum, which can be regarded as reliable independent biodetection indicators for an instantaneous microsphere's spectrum. With these parameters, since there is no need for spectral comparison to an analyte-free reference, three-dimensional stirring of fluorescent microspheres in fluidic setup is allowed. Through an analysis of fluorescent microspheres in the presence of bacterial spores, we found five insightful quantitative independent parameters for biodetection. Unveiled by this analysis, we demonstrate the possibility to discriminate between analyte presence and homogeneous variation of the solution's refractive index.