Grating writing through fibre coating at 244 and 248 nm

High quality fibre Bragg gratings have been written through the fibre coating using both 244 nm frequency-doubled Ar⁺-ion and 248 nm KrF excimer lasers for the first time. A standard off-the-shelf coating was used, and 92% reflectivity gratings were obtained with an index change of 2.4×10^-4.