Long-period fibre grating fabrication with femtosecond pulse radiation at different wavelengths

The fabrication of long-period fibre gratings (LPFGs) in optical fibres by femtosecond pulses at different wavelengths is reported. Several types of fibres were used and it was found that LPFGs with strong attenuation peaks (more than 20 dB) can be induced in hydrogen-loaded germanosilicate fibres using the second harmonic of a femtosecond Ti:sapphire laser without the use of an amplifier (400 nm, 70 fs and 2.5 nJ) and amplified, frequency-quadrupled pulses from a Nd:glass laser (264 nm, 220 fs and 0.4 mJ). Low 'out-of-band' losses and results of isochronal annealing for the fabricated gratings suggest that the photoinduced refractive index change is not accompanied by damage to irradiated fibres. (C) 2003 Elsevier B.V. All rights reserved.