We show that an asymmetrically chirped, single‐section distributed‐feedback (DFB) laser is capable of sustained self‐pulsations at frequencies in excess of 200 GHz. These pulsations arise from mode beating and are absent in uniform or symmetrically chirped DFB lasers. For sufficiently large coupling constants, the pulsation frequency can approach a terahertz. ©1996 American Institute of Physics.