Monolithic mode-locked laser diodes based on QD active regions are regarded as potentially suitable for a large range of
photonic applications due to their compactness, mechanical stability and robustness, high potential repetition rates and
low potential jitter. Their inherent properties, such as high differential gain, low chirp and fast saturable absorption have
led to demonstration of improved performance over their QW equivalents. Low background loss and the relatively long
lengths of quantum dot laser devices also have encouraged studies of mode-locking at repetition rates previously not
explored in monolithic devices. Applications include biomedicine, high-speed data transmission, clock signal generation
and electro-optic sampling. This paper reviews some of the work at Cambridge on the realization of such devices.