Influence of the sensitivity of an optical resonator with a surface layer by its properties

ABSTRACT In the last years, optical resonators have emerged as a promising tool for highly sensitive measurements. Espe-cially for label-free measurements of biological substances, the resonators have to be functionalized by additionalsurface layers. Since the properties of the resonator, like the refractive index of the core and the layer as well asthe layer thickness or the core radius can deeply inuence the sensitivity. For this reason, a geometrical opticsbased theory is used to investigate the dependence of the resonance wavelength on the resonator properties. 1. INTRODUCTION It is well known that highly transparent micro spheres exhibit sharp resonances in the range of optical radiation.These resonances depend sensitively on the properties of the medium in contact with the surface of the resonator,beside others. Due to this sensitivity micro resonators came into the focus of the development of extremelysensitive optical biosensors. In most cases spherical microresonators are used.