Tapered fiber tips for fiber optic biosensors

Tapered fiber tips with different geometries are fabricated for developing a fiber optic biosensor. Fluorescence experiments are performed to compare the coupling efficiency of light for different fiber tip configurations. When light is generated in a ''thick'' layer (>1 mu m) around a fiber core, the continuously tapered tip with the steepest taper collects light more efficiently than the longer combination tapered tip, To demonstrate the applicability of our results, we have successfully detected weak chemiluminescent signal collected by a bundle of fibers with the short continuously tapered tips using a cooled CCD array detector. The chemiluminescence reaction was catalyzed by alkaline phosphatase immobilized on the fiber tips by a set-gel technique.