Modelling, fabrication and testing of tapered optical fiber evanescent wave devices

Abstract

Single mode tapered fibers and multimode tapers were fabricated and used to develop a fluorescence based evanescent wave pH sensor. The tapers were initially immersed into solutions premixed with fluorescein. The single mode tapers showed poor performance as pH sensors since the index of the surrounding medium had to be increased close to that of the fiber to cause the mode to spread out sufficiently to obtain enough excitation of the surrounding medium. The multimode tapers, however, gave a measured recaptured fluorescence of at least an order of magnitude higher than the single mode tapers. This is because the excitation of the fluorescein was dominated by radiation modes, which leads to s..