We investigate the superluminal effect of transmitted probe field in three‐level quantum dot molecules (QDMs) assisted optomechanical system which consist of mechanical resonator. We show that the superluminal behavior of transmitted probe field can be controlled by changing the tunneling strength and number of QDMs inside the cavity. Furthermore, it is shown that in the absence of tunneling strength, the transmitted probe field shows the fast light effect and by increasing the number of QDMs, the enhancement in superluminal behavior is decreased and converts into slow light. While, in the presence of the tunneling strength, with the increase of the number of QDMs the superluminal behavior of transmitted field is obtained at smaller detuning frequency. The influence of tunneling strength and number of QDMs on superluminal part of the transmitted probe field is quite useful in optical memory, optical buffers, and quantum information processing.

We theoretically examined the slow light effect in a one‐sided optomechanical system with a two‐level atom placed inside it. When the cavity without atoms is driven by the input field, an optomechanically induced transparency (OMIT) window appears in the transmission spectrum due to destructive interference. We observed that due to the existence of atoms, the OMIT window shifted to normal‐mode splitting and steeper Fano shapes. Our results exhibit that coupling strength has a very prominent effect on the transmission part. The Larger the coupling strength, the larger will be the effect on the transmission. This leads to rapid positive phase dispersion in the transmitted field, gives rise to the corresponding slow light effect.