Generation of 10 GHz, 200 fs Fourier-transform-limited optical pulse train from modelocked semiconductor laser at 1.55 μm by pulse compression using dispersion-flattened fibre with normal group-velocity dispersion

The authors report the generation of 10 GHz, 200 fs Fourier-transform-limited optical pulses at 1.55 μm. The 3 dB spectral width of 1.7 ps optical pulses generated from a modelocked semiconductor laser is broadened from 1.8 to 22 nm, while the pulses travel through a dispersion-flattened fibre with a small normal group-velocity dispersion. Linear up-chirp is induced in the spectral broadening process, and the up-chirped pulses are compressed down to 200 fs by using a proper amount of anomalous dispersion of optical fibres. The compressed pulses are almost Fourier-transform limited, and the compression factor is as high as 8.5