Controlling the optical bistability via quantum interference in a four-level N-type atomic system

► We modulate the optical bistability (OB) in a four-level N-type atomic system. The effect of spontaneously generated coherence on OB is discussed. ► Spontaneously generated coherence makes the medium phase dependent. ► The frequency of coupling field can reduce OB threshold. ► We discuss the effect of an incoherent pumping field on reduction of OB threshold.