Low threshold optical bistability based on coupled graphene Tamm states

•A bistable structure based on an asymmetric dielectric Bragg reflector–graphene–dielectric Bragg reflector is proposed.•The threshold of optical bistability can be significantly reduced for the coupling between the Tamm states.•Lower threshold of optical bistability can be obtained by decreasing the Fermi energy of graphene. The optical bistability based on an asymmetric dielectric Bragg reflector (DBR)–graphene–DBR (ADGD) structure is investigated numerically in terahertz frequencies. The threshold of optical bistability can be significantly reduced due to the strong enhancement of localized light field for the coupling between the Tamm states on the two sides of graphene. The threshold value of ADGD is nearly an order of magnitude lower than that in a structure based on graphene–DBR, and can be further reduced by decreasing the Fermi energy of graphene. The results will be helpful for the application of bistable devices in THz range.