Gaff, KMariman, ElaineDall (previously Weijers), TessicaLove, JohnBoswell, Roderick2015-12-132015-12-130013-5194http://hdl.handle.net/1885/90261The observation is reported of a strong negative change in the refractive index of tin-doped thin silica films deposited by helicon activated reactive evaporation. Samples with concentrations between 5 and 25 mol% SnO2 were exposed to 2kJ/cm2 of 248 nm UV radiation. Negative refractive index changes as large as -2.7 × 10-3 were observed on irradiation.Keywords: Evaporation; Excimer lasers; Low temperature operations; Optical fibers; Photosensitivity; Refractive index; Semiconductor doping; Silica; Systematic errors; Tin; Ultraviolet radiation; Helicon activated reactive evaporation; Negative index refractive; Ti200010.1049/el:200005742015-12-12