Controlling the plasmon-induced transparency system based on Dirac semimetal at mid-infrared band

Abstract

A bright–bright coupling mode Plasmon-induced transparency (PIT) system composedof two Dirac semimetal blocks (DSBs) with different sizes is proposed in this paper. The electromagnetic mechanism of this PIT system and its modulation property at mid-infrared band is analyzed by finite-difference time-domain (FDTD) method. Numerical results show that the transparent window, transparent peak and quality factor can be precisely controlled by the geometric parameters of the PIT system, the Fermi energy (EF) of the DSB and refractive index (RI) of the superstrate. The advantage of DSBs grating structure is that its permitivity functions can be adjusted handily by EF through doping or bias voltage. Compared to the PIT system based on bulk Dirac semimetals, our proposed PIT system has much smaller structure size and wider tunability. The resonant frequency of the transparent peak can shift from 17.59 THz to 34.79 THz when EF changing from 40 meV to 80 meV. The second-order nonlinearity of this DSBs system is also investigated by introducing the second-order nonlinear source. This developed Dirac semimetal PIT structure may pave the way to the development of novel THz active devices for light modulation devices, switches, biosensors and other mid-infrared devices.