Label-Free Fiber Optic Biosensors with Enhanced Sensitivity

A sensitivity-enhanced long-period grating in-fiber Michelson interferometer with diameter-reduced cladding was proposed for the first time, and was also demonstrated as a label-free biosensor based on refractive index measurement. The cladding structure dependence of the sensitivity for antibody–antigen immuno-sensing was studied experimentally. The proposed biosensor has shown an 8.5-fold sensitivity enhancement as compared to sensors without cladding reduction.