Theory is developed for frequency shift and linewidth-broadening induced by rodlike bacteria bound to micro-optical resonators. Optical shift of whispering gallery modes (WGMs) is modeled by introducing a form factor that accounts for random horizontal orientation of cylindrical bacteria bound by their high refractive index cell walls. Linewidth-broadening is estimated from scattering losses. Analytic results are confirmed by measurement using E.Coli as model system (~10(2) bacteria/mm(2) sensitivity), establishing the WGM biosensor as sensitive technique for detection and analysis of micro-organisms.
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Ren et al. (2007) studied this question.