We attempt to demonstrate optical phase switches in a typical light storage experiment. We computed propagation dynamics of light pulses in sodium-23, rubidium-87, and potassium-39 vapours. These vapours have the same tensorial sets of the density matrix with a nuclear spin I=3/2. The energy scheme is known as the double- Λ system. We considered an excitation mechanism in which one of two Λ systems is excited by two-colour pulses, probe and drive, following the standard electromagnetically induced transparency configuration. The probe channel contains two more pulses at far times. Gain is generated through the drive channel and exposed during propagation. Generated train propagates with a nearly minimum uncertainty product. We further investigated the spatiotemporal phase variations of the pulses and found discrete phase distribution for different vapours. The spatiotemporal evolution of the irreducible tensorial sets defines structural differential equations. Additionally, it is particularly suitable for parallel processing. We hope our study finds an application in comparison to alkali vapour magnetometry.