Polymeric microresonators for biosensing applications

Abstract

We report on whispering gallery mode (WGM) resonators consisting of poly(methyl methacrylate) (PMMA) which are promising candidates for labelfree biosensing applications. The optical modes in these resonators experience a wavelength shift when the refractive index of the surrounding medium changes or when molecules attach to the resonator. Different methods can be used for functionalization of the resonator surface to obtain sensors which are sensitive to specific molecules. To obtain higher sensitivities coupled resonators can be produced. If the resonators are close enough the modes of the single cavities couple and supermodes extending over both cavities develop. Analogously to the hydrogen molecule a bonding and an anti-bonding optical mode is observed. The bonding mode shows a field enhancement in the gap which results in a stronger interaction of the mode with the surrounding medium.