We report spatially nondegenerate four‐wave mixing in a broad‐area laser diode that acts as a fast phase conjugate mirror with nanosecond response times and high efficiencies. Phase conjugate reflectivities were found to depend strongly on the bias current of the broad‐area laser diode. Operating the laser diode in an injection‐locked regime above the lasing threshold gave phase conjugate reflectivities as high as 165%. ©1996 American Institute of Physics.