Fibre-optic 100 fs pulse amplification and transmission system in the telecom range

We have fabricated and investigated an efficient all-fibre source of ultrashort pulses of 100 fs duration with an energy of up to 5 nJ in the telecom range (near λ = 1.56 mm). Pulses from an erbium-doped fibre master oscillator with a minimum duration of 127 fs and repetition rate of 38.1 MHz were amplified in an erbiumdoped active fibre to a maximum average power of 194.3 mW with a 30% efficiency under pumping by 640-mW single-mode laser diodes at a wavelength λ_pump = 976 nm and then compressed to an ~100 fs duration in a silica fibre with reduced nonlinearity (LMA fibre). The compressed pulses were launched with an efficiency over 80% into a hollow-core microstructured revolver fibre (HCRF) with a cladding formed by noncontacting cylindrical silica glass capillary tubes and a 61-μm-diameter hollow core. The measured loss for the fundamental mode of this fibre was under 30 dB km^-1 at λ = 1.56 μm. Owing to the weak nonlinearity and low dispersion of the HCRF, output pulses were similar in characteristics (duration and spectrum) to input pulses even at HCRF lengths above 10 m.