Effects of Nanoscale Morphology on Optical Properties of Photoluminescent Polymer Optical Fibers

Bicomponent photoluminescent polymer optical fibers (PL-POFs) have been melt-spun and in-situ drawn to different extents. The results suggest that scattering in the sheath can effectively increase the photoluminescent dye excitation probability in the fiber core. The core/sheath PL-POFs are made of a semi-crystalline fluoropolymer sheath of low refractive index (RI) and an amorphous cycloolefin polymeric core of high RI, which is doped with a luminescent dye. The axial light emission, as well as the guiding attenuation coefficients of the core/sheath PL-POFs, have been measured using a side-illumination set-up. The incident blue laser is down-converted to red light, which is re-emitted and partially guided by the core. The axial light emission is measured at the fiber tip as a function of the distance from the illumination position to the integrating sphere. It is demonstrated that the presence of a semi-crystalline sheath significantly enhances the axial light emission and that it also lowers the attenuation coefficient, compared to the emission and guiding properties of PL core-only fibers. Additionally, the attenuation coefficient has been found to be lower in more strongly drawn PL-POFs. Wide-angle X-ray diffraction and small-angle X-ray scattering experiments reveal structural differences in differently drawn PL-POFs that can be linked to the observed differences in the optical properties.

Automated summary

The study demonstrates that scattering in the sheath of bicomponent photoluminescent polymer optical fibers (PL-POFs) can effectively increase the excitation probability of the luminescent dye in the fiber core. The presence of a semi-crystalline sheath significantly enhances axial light emission and lowers the attenuation coefficient compared to PL core-only fibers. Additionally, a higher degree of drawing leads to a lower attenuation coefficient in PL-POFs.