In-Fiber Michelson Interferometer with Polymeric/Nanoparticle Thin-Film Overlay as a Platform for Biosensing

A polymeric–nanoparticle composite film is used, for the first time, to increase cladding mode evanescent field and, therefore, the sensitivity of an all-in-fiber Michelson interferometer for refractive index (RI) sensing. Utilization of the layer-by-layer polyelectrolyte deposition and metal nanoparticle synthesis within the polymeric composite film allows us to form precisely a very high RI thin overlay required for cladding mode reorganization. As a result, the developed refractomer demonstrates significant sensitivity enhancement over ambient RI change. Potential applications of the refractometer as a biosensor are outlined and discussed.