Evanescent field devices: a comparison between tapered optical fibres and polished or D-fibres

Abstact This paper examines the operation of tapered optical fibres and polished or D-fibres as evanescent field devices. Both devices operate through the evanescent field outside the fibre interacting with chemicals in the surrounding external medium. The incoming field is absorbed and may be reradiated through fluorescence. The absorption and fluorescence recapture characteristics of both configurations are compared, showing that the tapered fibre device permits a stronger interaction and is therefore more efficient. Furthermore, it is shown that the characteristics of both configurations are sensitive to the refractive index of the external medium.