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

Fluorescence excitation on tapered polymer optical fibers through microfiber evanescent field

“…In figure 2b, the evolution of the spectra maxima are also plotted as a distance function. As can be seen, this figure confirms the expected exponential decay behavior of the evanescent field of the guided modes by the microfiber, together with the increase in fluorescence signal as the excitation source becomes more intense as predicted by Stern-Volmer equation [2]. Nevertheless, a remarkably high relative distance between MNF and POF still renders a signal intense enough at a distance of around 2.5 mm, which opens the way to include any media inside the gap between the fibers.…”

“…Among the different available optical fiber sensors, those based on polymer optical fibers (POF) have recently attracted particular attention [1,2]. These fibers present the same advantages of conventional ones, together with larger diameter; easy handling including cut and polishing procedures; durability, flexibility and relative low cost [3].…”

“…Fluorescence-based POF sensors can be easily found in literature [6,7] although their efficiency can be compromised, depending upon the light coupling procedure. In this sense, the use of side-illumination technique provides a promising light coupling method to improve efficiency while keeping a relatively simple setup [2,8]. Besides, it is possible to get strong evanescent fields with recently developed devices based on optical fiber tapering; the so called micro/nano fibers (MNF), where a uniform waist region has a size comparable to the wavelength of the propagating light [9].…”

Highly Sensitive Extrinsic X-Ray Polymer Optical Fiber Sensors Based on Fiber Tip Modification

“…Then in the first sample, labeled as LM-1 in table 1, the outer jacket is simply stripped off in an approximately 2 cm length and the fiber tip polished. The second sample, labeled as LM-2 in table 1, keeps approximately the same length of exposed fiber, but the fiber diameter is homogeneously reduced by chemical etching with pure acetone to a diameter of 880 µm [16][17][18]. With this procedure, cladding and part of the core of the fiber distal end is removed.…”

Microfiber as light source for exciting fluorescence in a polymer optical fiber

“…There are some fluorescence-based POF sensors in literature [9,10], but its efficiency depends on the method used for light coupling. In this sense, side-lighting technique improves coupling efficiency with a relatively simple configuration [11][12][13].…”