High-Q microsphere biosensor - analysis for adsorption of rodlike bacteria
H. Ren, F. Vollmer,, S. Arnold and A. Libchaber
Opt. Express 15, 17410 (2007)

Theory is developed for frequency shift and linewidthbroadening
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.