LOCKING BANDWIDTH OF ACTIVELY MODE-LOCKED SEMICONDUCTOR-LASERS USING FIBER-GRATING EXTERNAL CAVITIES

We demonstrate numerically that actively mode-locked semiconductor las ers employing a linearly-chirped fiber grating in an external cavity c an exhibit multiple drive frequency ranges of stable pulse generation, and thus give a large locking bandwidth, The locking bandwidth define s the range of RF drive frequencies over which the laser will generate pulses with low timing jitter. The stable optical pulses are generate d with leading or trailing subpulses due to optical energy circulating within the fiber grating. The multiple stable ranges merge if loss is introduced into the fiber-grating region. We also show that the locki ng bandwidth can be improved if chirp is introduced into the grating, Suprisingly, however, chirp of either sign improves the locking bandwi dth.