In this letter generation of up to 130 GHz high frequency self‐pulsation in ultrafast gain‐switched InGaAs/InGaAsP dynamical single‐mode lasers with monolithically integrated external cavities is reported. With various active cavity lengths and external cavity lengths, the dependence of the pulsation frequency on the length of the respective cavity is shown and analyzed in detail for a pulsation frequency range from 50 to 130 GHz. Theoretically, by treating the external cavity as a gain‐switched laser amplifier and taking into account the coherent time‐dependent amplification, shortening and reflection of an incident picosecond optical pulse in the gain‐switched amplifier, we can well understand and simulate the observed high frequency self‐pulsations. ©1995 American Institute of Physics.