The performance of a logic inverter based on injection locking in laser diodes is presented. The fast commutation rise and fall times (5 and 2 ns, respectively) allow a 150 MHz repetition rate. Due to the gain existing in laser diodes, low optical switching energies (50 fJ) and large fan‐out rates (30) are also obtained, making such an inverter attractive for the purpose of parallel optical computing, particularly if semiconductor laser arrays are used in place of single laser diodes.