UV laser photo-induced refractive index changes in poly-methyl-meth-acrylate and plastic optical fibres for application as sensors and devices

Initial attempts to photo-induce refractive index changes in bulk poly methyl methacrylate (PMMA) and in PMMA based plastic optical fibres (POF) using UV light are described. Optimum changes have been achieved at 216 nm, causing path length changes of 10π, corresponding to possible refractive index modulation of between 5 and 14 % over thicknesses up to 100 μm. The effects of refractive index changes on the far field modal distribution of tapered PMMA plastic optical fibres are described.