Broadband terahertz absorber with tunable frequency and bandwidth by using Dirac semimetal and strontium titanate

Abstract

A bifunctional broadband absorber in the terahertz band based on patterned bulk Dirac semimetal (BDS) and strontium titanate (STO) is proposed. The properties of the absorber are investigated using the finite-difference time-domain (FDTD) method. The results show that the width of absorption can be modulated from 0.59 THz to 0.7 THz when the Fermi energy of the BDS is independently shifted from 40 meV to 50 meV. By tuning the temperature from 250 K to 400K, the center frequency of the broadband absorption spectrum can be changed from 1.311 THz to 1.505 THz, and the absorption bandwidth broadens from 0.66 THz to 0.81 THz. In addition, the simulation results show that the absorber is insensitive to electromagnetic wave polarization, and can still maintain a stable broadband absorption effect when the oblique incidence is within 40° for TE and TM modes. Based on the impedance matching theory, the physical mechanism of the broadband absorption is analyzed theoretically. This work can provide an alternative way to design high-performance multifunctional tunable terahertz devices.

Terahertz Metamaterial Absorbers

“…The first is that the unit cells with the same geometric shape but different size are arranged periodically. For instance, doped graphene disks are placed in a period with a STO [32,65,93,114] Ge [47] InSb [67,98] Liquid crystal [71] Air [85,103] radius of 0.8 and 0.4 µm, respectively (Figure 5a). [36] The LSPR triggered by the graphene disks with two different sizes results in two electric dipole resonances.…”

Switchable Terahertz Absorber from Single Broadband to Dual Broadband Based on Graphene and Vanadium Dioxide

“…Metamaterials, as special electromagnetic response materials, are composed of sub-wavelength microstructures produced by artificial designs [7,8]. Using the combination of metamaterials and THz technology, researchers have designed a variety of high-efficiency optical devices such as filters [9,10], modulators [11], switchers [12], and absorbers [13,14]. Among them, THz absorbers based on metamaterials have shown promising applications in the fields of invisibility cloaks, wireless communications, and thermal emitters [15][16][17].…”

Tunable Dual-Broadband Terahertz Absorber with Vanadium Dioxide Metamaterial

“…Among them, metamaterial perfect absorbers (MPAs) are widely used in the THz range due to their widespread applications in imaging [ 13 , 14 ], stealth technologies [ 15 , 16 ] and so on [ 17 , 18 , 19 ] and play a very important role within. In 2008, Landy et al used a classical three-layer structure as a metamaterial perfect absorber (MPA) so that the incident wave was perfectly absorbed by the metamaterial absorber [ 20 ], and since then, various single-band [ 21 , 22 , 23 , 24 ], double-band [ 25 , 26 , 27 , 28 ] and multi-band absorbers [ 29 , 30 ] have been proposed. However, the absorption bandwidth of these MPAs are relatively narrow, and their electromagnetic responses cannot be adjusted after the structure has been determined, which limits their practical application.…”