Characterization and compression of femtosecond optical pulses nonlinearly propagated in a tapered fiber

Summary form only given. A tapered-silica fiber has recently been used in producing an ultra-broad band spectrum. By heating and stretching a 10 mm silica fiber with a 125 /spl mu/m outer diameter and a 9 /spl mu/m core diameter, a 70 mm totally long tapered fiber was produced with a 25 mm long waist of 2 /spl mu/m uniform diameter. A typical resultant ultra-broad band spectrum was found to range from 425 to 955 nm. By using our second-harmonic frequency-resolved optical gating (SH-FROG) apparatus, the intensity and phase profiles of the output pulse from the fiber in both temporal and frequency domains were determined. The output pulse was centered at 785 nm and had an averaged power of 26 mW for the input with a 150 fs duration. We performed pulse compression with a liquid crystal spatial light modulator (SLM) on the basis of the spectrum phase information obtained by the SH-FROG measurement. This was the first pulse compression of an output pulse from a tapered fiber using an SLM. That is, chirp compensation of the complicated frequency-dependent phase in comparison with that of the conventional silica-fiber output was carried out successfully by the spatial light modulation technique for the first time.