Examination of light distribution from fibers coated with sol-gel films doped with porphyrine

The modification of optical fibers by exploiting various coatings may be important for construction of fiberoptics, sensors or applicators for interstitial laser therapy. We report here on sol-gel films placed on fiber cores, replacing the original fiber coatings. The silica sol-gel coatings where prepared form silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid catalyzed hydrolysis. The matrices were produced with various ratios R=5, 15, 20, 32, 40, 50, whereas R denotes the number of solvent moles (here ethanol) to the number of TEOS moles. Two types of coatings were produced: pure sol-gel matrices and sol-gel doped with Protophyrin IX in two various concentrations. The angular light intensity distribution was examined in order to find out the influence of R factor on the light intensity distribution near the fiber tip. Then, the light pattern was captured by means of CCD camera and the three dimensional luminances were calculated. The same experiments were repeated for silica sol-gel coatings doped with natural porphyrine Protoporphyrine IX and different patterns were observed.