A nonlinear switch formed by the integration of an overmoded multi‐quantum‐well (MQW) section with disordered input and output branching waveguides is presented. The area‐selective disordering of GaAs/AlGaAs MQWs is achieved by diffusion of group III vacancies generated by etching of the surface oxide. The absorption edge of the disordered MQW regions was shifted by 71 nm and the disordered ridge waveguides had a loss figure of 8 dB/cm. Time‐resolved optical pump‐probe measurements were performed on an integrated switch that had more than a 5:1 power split between the two output ports. The measured signal recovery of the switch had a time constant of 110 ps. ©1995 American Institute of Physics.