In this article, we have investigated the optical properties of intersubband transitions in an asymmetric AlGaAs/GaAs coupled quantum wells system. We solved the Schrödinger equation numerically using homemade finite difference codes to determine the electronic structure. The susceptibilities were calculated in frame of density matrix equations. The effect of relative phase variation between applied fields, on the linear absorption coefficients, relative refractive index changes, and group velocity has been investigated. The results show that the linear optical properties are extremely phase-dependent. By adjusting the phase, it is possible to obtain absorption curves with dispersion-like profile and vice versa. © 2015 Taylor and Francis.