A numerical and theoretical study is presented on the realization of the tunable plasmon-induced transparency (PIT) effect in Dirac semimetal films (DSFs) that are known as “three-dimensional graphene”. The weak hybridization between the two parallel bright modes leads to the novel PIT optical response. The properties of the PIT system can be controlled by adjusting the geometric parameters of the DSF strips. Meanwhile, the resonant frequency of the PIT can be dynamically tuned by varying the Fermi energy of the DSFs instead of refabricating the structures. Correspondingly, by adjusting the Fermi energy of the DSFs, a large group delay of more than 1.86 ps is obtained in the vicinity of the transparency peaks. Such proposed DSFs-based PIT system may open up avenues for tunable terahertz switching, slow-light devices, sensing technology and some other THz devices.

We present a bifunctional polarization converter based on Dirac semimetals (DSMs) and vanadium dioxide (VO₂), which consists of two layers of DSMs on both sides, a metal grating and a VO₂ board. The polarization converter frequency is dynamically tuned by changing the Fermi energy level of the DSMs. The result suggests that when VO₂ is in an insulated state, the device behaves as a transmissive polarization converter. The dual-band transmissive polarization conversion and asymmetric transmission (AT) function of circularly polarized (CP) waves are realized at 1.99 THz and 3.46 THz, with the polarization converter ratio (PCR) reached 97.6% and 95.8%, respectively. In addition, when VO₂ is in the metal state, the designed polarization converter is a reflective device, which can maintain the chirality of the reflected CP wave to the incident wave in a wide band. The polarization-maintaining ratio (PMR) in the range of 2 THz to 3.55 THz is higher than 88%. When the angle of incidence is less than 60°, the frequency band of the PMR is narrowed and the amplitude reaches more than 90%.

We propose a dynamically tunable broadband linear-to-circular cross polarization converter based on Dirac semimetals. The proposed converter unit cell consists of a center-cut cross-shaped metallic patterned structure with a sandwiched Dirac semimetal ribbon on a polyimide substrate bottomed with gold. The proposed system converts linear waves to right-hand circular polarized waves in the frequency ranges of 1.5–2.8 THz or to left-hand circular polarized waves in two narrow frequency ranges of 1.20–1.25 and 3.04–3.07 THz. The polarization conversion is dynamically tunable by varying the Fermi energy without re-optimizing the microstructures, which may further tunable polarizers and polarization switchers developments.

We present a dynamic metamaterial based on Dirac semimetals and capable of realizing broadband and tunable asymmetric transmission in the terahertz region. The Dirac semimetal resonators have a chiral structure patterned with double-T resonators that results in partial polarization conversion of waves incident upon the material, leading to asymmetric transmission across a wide frequency range. We show how the gradual shift of the semimetal Fermi energy permits a method of control over the asymmetric total transmission.

We propose a dual-controlled switchable broadband metamaterial sandwich-structured absorber composed of black phosphorus (BP) and vanadium dioxide (VO ₂ ), suitable for operation in the terahertz range. The proposed absorber consists of multi-layered sinusoidally patterned BP, sandwiched between dielectric layers, and a VO ₂ bottom layer. Numerical results reveal that the broadband absorption can be dynamically tuned over a wide range by adjusting the electron doping of BP and conductivity of VO ₂ . Owing to the fully metallic state of VO ₂ , the proposed absorber realizes a more than 98% absorptance with the bandwidth of 2.9 THz under TE polarization and more than 90% absorptance with the bandwidth of 3.25 THz under TM polarization when the armchair direction of BP is along the y -axis and x -axis, respectively. Most importantly, by utilizing the dual independent controls in tandem, the state of proposed absorber can be switched from absorption (>98%) to reflection (>63.5%) while maintaining the broad bandwidth. Our research that utilizes the advantages of BP and VO ₂ presents a new perspective on the design of tunable broadband THz absorbers promising for potential applications such as switching, modulation, and sensing.