Inscription of Bragg reflectors in polypropylene no-core optical fibers using 248nm laser radiation

Inscription and characterization of Bragg reflectors in polypropylene (PP) no-core optical fibers using 248-nm KrF excimer laser radiation are presented for the first time. A new photo-sensitization approach is adopted by means of pre-loading the PP no-core fibers using toluene in-diffusion, for increasing Bragg reflector recording yield. The Bragg reflector inscription process was monitored online, for both pristine and toluene loaded PP no-core fibers under identical exposure conditions, revealing that toluene loaded samples leaded to threefold stronger reflectors and average refractive index changes of the order of 1.1x10-3. The Bragg reflectors were characterized for their response to strain (1.62 pm/με), and temperature (-145 pm/℃), while negligible sensitivity to water diffusion was recorded. The photosensitivity mechanism of the toluene in-diffused PP no-core optical fibers using 248-nm KrF excimer laser radiation is also discussed.