Improved fluorescence signal with tapered polymer optical fibers under side-illumination

The effects of combining the tapering of a polymer optical fiber with a side-illuminated setup are studied for fluorescent sensor applications. The tapered sensor is fabricated removing part of the cladding via solvent immersion and the fluorophore is added afterwards depositing a fluorescent ink on the treated fiber. The sensor has been tested both under non-directed (diffuse) light and a UV-LED. The system provides an increase of the fluorescence signal with respect to some other configurations such as those based on evanescent wave or collection from a fiber tip. Since the fluorescence signal obtained is so high it can be easily distinguished from the excitation signal allowing an optical filter free system. Thus, the basis for new low cost and easy to handle sensors is laid down.