A polarization-maintaining pedestal-free femtosecond pulse compressor incorporating an ultrafast dispersion-imbalanced nonlinear optical loop mirror

We report a polarization-maintaining and dispersion-flattened pulse compressor based on a dispersion decreasing fiber (DDF) for compression and a dispersion-imbalanced nonlinear optical loop mirror (DI-NOLM) for pedestal removal. A dispersion management scheme was used in the DI-NOLM to reduce dispersive spreading, which allows efficient switching for ultrashort pulses. Input pulses of 3 ps duration at 10 GHz were compressed to as short as 140 fs with a spectral width of 56 nm, time-bandwidth product of 0.96, and average power of 8.5 mW. This pulsewidth was limited by the higher order dispersion in the DI-NOLM. Using a post filter and a post amplifier, we obtained transform-limited 170 fs pulses at an average power of 100 mW with peak-to-pedestal ratios exceeding 35 dB. The compressor was adjustment-free, which is critical for practical use.