We study the change in coupling between two GaAs lambda‐microcavities embedded in a one‐dimensional photonic crystal composed of GaAs‐AlGaAs Bragg mirrors when the refractive index of the region between the cavities is externally modulated in several diferent ways. We show that the coupling of the cavities can be significantly changed when the refractive index in the intercavity region is modulated with a Gaussian profile, such as could be obtained by illuminating the intercavity region with a strong laser pulse. This opens the way for the implementation of a full optical switch device. For this system we find that it is possible to delocalize an excited cavity mode whilst the fundamental mode remains confined.