Plasmonic metamaterials enable manipulation of light at subwavelength scales and exhibit unique optical functionalities. However, the realization of high-performance, large-range, and dynamically tunable optical absorbers based on plasmonic metamaterials remains challenging. Here, we propose and demonstrate a continuously tunable absorbers consisting of a zigzag array of bulk Dirac semimetals (BDS) meta-atoms and a metal reflector spaced by insulator layers. This structure exhibits a collective resonance formed by the electric dipole modes polarized along the long axis of each individual meta-atom, which allows us to precisely control this resonance frequency by fine-tuning the unit cell geometry and the Fermi energy levels of the BDS. In addition, the related physical mechanism behind this complete absorption can explained by employing coupled-mode theory (CMT) and mode-expansion theory (MET). Our results may arouse the investigations of the tunable metamaterials device based on the BDS.
Coherent perfect absorption (CPA) is realized in metasurfaces composed of crossed vertical bulk Dirac semimetal (BDS) stripes and
S
i
O
2
. Under the illumination of two counter-propagating coherent beams, the coherent absorption is continuously controlled from almost 0 (approximately
6.2
×
10
−
5
) to 99.97% by changing the beams’ relative phase, which gives a modulation depth of about
1.6
×
10
4
. Furthermore, the coherent absorption can be controlled substantially by varying the relative intensity, the Fermi energy of BDS, and the structural parameters of the metasurfaces. Further research shows that the metasurface has broadband angular selectivity: CPA frequency splits into TE and TM polarization bands under oblique incidence. Our results provide an effective way to manipulate the interaction of light and BDS, and there may be potential applications in coherent detectors and optical modulators.
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