Optical waveguides obtained by swift-ion irradiation on silica (a-SiO2)

The preparation of optical waveguides for visible light in silica (a-SiO2) by means of swift heavy-ion irradiation (F at 5 MeV, Cl at 20 MeV) is reported. They originate from the refractive index enhancement (compaction) brought about by the electronic excitation. Their main features are discussed in relation to those prepared by light ion irradiation (H, He) and implantation. In particular, irradiation fluences to achieve waveguiding may be considerably reduced. On the other hand, the measured refractive index profiles have been used to discuss the mechanisms of electronic damage. Moreover, the measurement of the index profiles provides a novel optical method, alternative to IR spectroscopy, to estimate the radius of the irradiation-induced tracks.