Bragg gratings in ternary SiO 2 :SnO 2 :Na 2 O optical glass fibers

Bragg gratings have been written in an optical fiber with a core made from ternary SiO2:SnO2:Na2O glass and a SiO2 cladding. The presence of Na2O allows for higher concentrations of SnO2, which are believed to be responsible for the photorefractive response of this composition. In these preliminary experiments significant refractive-index modulations, up to 6.2×10-4, have been achieved with a 248-nm excimer laser and a phase mask to write gratings for reflectivity at ∼1.5 µm. The induced refractive-index changes show enhanced temperature stability, and there is no sign of any erasure up to temperatures exceeding 600 °C.