Multifrequency Coherent Absorption Properties Of Terahertz Metamaterial

Metamaterials could modulate electromagnetic waves by designing the geometry,direction and arrangement of microstructures for obtaining special electromagnetic characteristics,which have broad application prospects in many fields such as sensing,communication,imaging,and other fields.The interaction of terahertz waves with matter will be enhanced by metamaterial,and flexibly designing of terahertz devices could fill the so-called"Terahertz gap."Once the general terahertz metamaterial being designed,the electromagnetic response is fixed,which cannot satisfy the needs of dynamic modulation of electromagnetic wave.The coherent control can realize the dynamic function modulation of terahertz metamaterials,such as absorption and polarization state control,which provides a way for fulfilling tunable terahertz metamaterials.In this paper,a bilayer asymmetrically split ring metamaterial structure is proposed to realize the coherent perfect absorption of multiband terahertz waves.And the dynamic modulation of coherent absorption is realized by integrated phase change material vanadium dioxide（VO₂）,which provides a new scheme for the design and exploration of metamaterial tunable absorbers.The research is as follows:The single-layer asymmetrically split ring structure was designed and studied,and its absorption characteristics and resonant mode corresponding to the absorption peak were analyzed.The bilayer asymmetrically split ring structure with rotation angles of 0°and 180°between the layers was studied,the geometrical dependence of the split ring structure on its absorption characteristics was analyzed,the electromagnetic response of the bilayer metamaterial under single X and Y polarized incident light was analyzed,and the resonant mode of the bilayer metamaterial was analyzed by multipolar decomposition.The coherent perfect absorption characteristics of the bilayer asymmetrically split ring structure were further studied.Whether the rotation angle between the layers is 0°or 180°,the double-layer asymmetrically split ring structure can always exhibit three low-frequency coherent absorption peaks at X-polarized light incidence and two high-frequency coherent absorption peaks at Y-polarized light incidence,and the coherent absorption peak frequency coincides well with that at a single beam incidence,and the coherent absorption range from 0 to 1 could be obtained by changing the phase difference between the two coherent lights at the resonant frequency.A VO₂-integrated bilayer asymmetrically split ring structure metamaterial was designed,and its tunable coherent absorption characteristics were studied.When VO₂phase state changes from the insulating state to the metallic state,the tunable coherent absorption characteristics of terahertz waves at different frequencies are analyzed.When the phase difference of two coherent beams of incident light changes in the range of 0-2π,the modulation depth of coherent absorption of tunable bilayer metamaterials is calculated.The coherent absorption characteristics of structures could also be influenced by different VO₂conductivity,and the tunable coherent absorption function of VO₂-integrated hybrid metamaterial in the terahertz band was realized,which provided a new way for exploring tunable terahertz absorbers.