Enhancement of second harmonic generation in MnF2/graphene sandwich structure

We propose an efficient method for increasing the second harmonic (SH) generation by embedding the graphene (Gr) in SiO2/MnF2/ZnF2 sandwich structure. The external magnetic field is perpendicular to the surface of MnF2/Gr sandwich. Two cases where the Gr layer is put above or below the MnF2 film are compared. For the MnF2/Gr case, the numerical simulation results show that the SH outputs obviously increase one order magnitude compared with the MnF2 sandwich without the Gr layer. In addition, the position and intensity of the SH outputs can be easily controlled by adjusting the external magnetic field strength and gate voltage. However, for the Gr/MnF2 case, the SH outputs rapidly decrease almost near to zero. The electric field distributions show that, in this case, the light intensity in the MnF2 film is further weakened, which causes that SH generations cannot be effectively excited. Besides, the effect of the magnetic field and the Fermi energy on the SH outputs are also studied.