Sol–gel coatings for interstitial fiberoptic laser applicators

The suitability of the silica sol–gel based coatings for the construction of sol–gel fiberoptics applicators for interstitial light therapy was analyzed in this study. The various applicators were developed: bare core, tapered and so-called ‘zebra’ type. The sol–gel layers were placed on bare fiber core by dip-coating or painting techniques. Various materials were tested: silica sol–gels produced with molar ratios R=5, 15, 32, 50, where molar ratio denotes the number of solvent moles to the number of precursor moles. In this study tetraethoxysilane as a precursor and ethyl alcohol as a solvent were used. The distribution of light scattered from the applicator was examined. It was proved that the radiation pattern strongly depends on the material characteristic (R ratio), shape of the fiber tip and number of sol–gel coating layers. The most intensive scattering was observed in the case of sol–gel material produced with R=5.