Spectral hole burning in semiconductor lasers manifests as a nonlinear suppression of the mode gain by a few percent. In the presence of a probe wave, the same mechanism can lead to highly nondegenerate four‐wave mixing (NDFWM) by creating the dynamic gain and index gratings at the beat frequency of the pump and probe waves. Since the grating efficiency is governed by the intraband relaxation time (typically <1 ps), significant NDFWM can occur even for a pump‐probe detuning ∼100 GHz. We present the results for the conjugate reflectivity and the probe transmittivity when an InGaAsP laser is used as a traveling‐wave amplifier.