A high-frequency pulse and a short pulse were generated using a quantum dot (QD) mode-locked laser diode (MLLD). We adopted a highly stacked QD structure using a strain-compensation technique within the active region of the QD-MLLD to fabricate a short-cavity MDDL. A two-section MLLD structure was fabricated with a cavity length of 500 μm. This laser exhibited lasing with a threshold current of approximately 34 mA with zero bias within the saturable absorber region. The spectrum of this laser has a well-defined, wide-range longitudinal mode. A short pulse of 464 fs in width and a high repetition rate of 81 GHz was observed through an interference measurement using a Michelson interferometer.