▎ 摘　　要

A new model is suggested for controlling the optical bistability (OB) and group velocity of transmitted light via coherent and incoherent control of applied fields. Our proposed structure is studied theoretically based on quantum coherence and interference mechanism in a defect dielectric slab with a monolayer of quantized four-level graphene system. Our results show that the manipulation of OB by adjusting the controllable parameters can be possible at one or more points of the bistable spectrum. Moreover, our investigations on the transmitted and reflected pulses show that the subluminal and superluminal light propagation can be possible in a specific situation of parametric conditions.