Semiconductor mode-locked lasers with integrated dispersion control

Semiconductor mode-locked lasers (MLL) often make use of distributed Bragg reflectors (DBRs) as one of the cavity reflectors, allowing both high peak reflectivity, and the central wavelength selection necessary for many applications. However, although the passive filter bandwidth of these reflectors can be up to a few nanometres, the typical mode-locked 3dB bandwidth is significantly smaller. This bandwidth truncation leads directly to pulses with larger temporal widths than those generated in Fabry-Perot (FP) type devices where the bandwidth can be an order of magnitude larger. Furthermore, the generated pulse width from DBR MLLs is highly dependent on the injection current conditions, unlike their FP counterparts.