Approaches of optimization of coupled quantum wells with pronounced quantum-confined Stark effect in order to reach a high refractive index change are described. A numerical simulation was used to determine the optimal design parameters (quantum well width, barrier thickness and composition) based on GaAs/AlGaAs materials with two symmetric quantum wells, which provides the maximum modulation of the refractive index at a small absorption coefficient. It is demonstrated that, with the electric field strength varied within the range 0-20 kV cm −1 at an optical loss for interband absorption not exceeding 10 cm −1 , the refractive index can be changed by up to 0.0362.