Hybrid Plasmonic Waveguides with Tunable ENZ Phenomenon Supported by 3D Dirac Semimetals.

By depositing a dielectric fiber on top of 3D Dirac semi‐metal (DSM) and Au layers, the tunable propagation properties of hybrid modes are systematically investigated in the mid‐infrared regime, including the effects of the temperatures, the Fermi levels, and rotation angles. Interestingly, due to the importance of inter‐band transition in the mid‐infrared spectral regime, a strong temperature related epsilon‐near‐zero (ENZ) phenomenon has manifested near the transition frequency. Namely, below room temperature, the real part of the effective refractive index (propagation length) shows a peak (valley). Particularly, at 77 K, the according abruption ratio (ratio of maximum to minimum in ENZ region) is 9.71 (204.1). Additionally, the propagation properties are also closely associated with the Fermi level. When the Fermi level varies in the range of 0.08–0.15 eV, the peak position of the real part of the effective refractive index shifts blue from 21.3 to 38.2 THz, and the according abruption ratio of the propagation length can be modulated in the range of 3.81–45.3. These results are very useful for designing tunable plasmonic devices, such as cutting‐edge modulator, filter, and resonators. [ABSTRACT FROM AUTHOR]