Figure 4.

(a) Scheme of the experimental setup used for the characterization of single-fiber waveguiding. (b) Images of a fiber excited by a focused laser beam, positioned at a variable distance from the fiber tip. The top panel is a bright field image of the investigated nanofiber. (c) Spatial decay of the light intensity (red circles) guided along a single electrospun fiber, deposited on a quartz substrate, as a function of distance, d, from the photoexcitation spot. The continuous line is the best fit of the experimental data by an exponential function, I = I₀ exp(−αd). Bottom-left inset: micrograph showing light guided in a bent active polymer fiber. The horizontal arrow highlights the fiber tip, whereas the bright spot corresponds to the emission directly excited by the focused laser beam. Right-top inset: plot of the fraction of guided power in the fundamental mode as a function of the fiber diameter, calculated by using eq 1. Points labeled as A, B, and C correspond to the average diameter of fibers fabricated by using a THF:DMSO mixture of solvents (A) and by the addition of TBAI (B) and TBAB (C), respectively. The morphology of these fibers shown in Figure 1.