Abstract
Strong (>20 dB) long-period fibre gratings were fabricated by combining F2-laser photosensitivity-locking of hydrogen-soaked telecommunication fibre and KrF-laser grating formation. The 157 nm pretreatment permanently enhances the fibre photosensitivity response to the low-energy 248 nm photons. Thermal annealing at 120°C for 24 h improves the grating stability without diminishing the enhancement.