Plasma Metamaterials Broad-band Perfect Absorber Based On VO₂ Phase Transition

Since Landy first proposed and demonstrated metamaterial perfect absorbers at microwave region,many efforts have been made to achieve near unit absorbance at microwave,terahertz,infrared,and optical frequencies.The unit cell of the highly absorbing metamaterial structure typically consists of a trilayer system with a top structured metallic layer and a bottom continuous metal layer separated by a continuous dielectric layer.The dielectric material placed in between the metal layers,plays an important role in manipulating the resonance conditions for the perfect absorption through the effective capacitance.Vanadium dioxide?VO₂?is a smart material that undergoes a ultrafast Mott insulator to metal transition at 68?,and its conductivity changes dramatically across the transition by three to four orders of magnitude.Due to the reversible change in electrical,magnetic and optical properties in the phase transition,VO₂ has been used for dynamical control of metamaterial absorber.This paper first introduces the classification,characteristics and application of the electromagnetic wave absorber,and then introduces the concept and development of metamaterials,the absorbing mechanism of electromagnetic wave absorber material is also introduced.Finally,elaborates the evolution and research progress of metamaterial perfect absorbers based on VO₂ phase transition at present stage.In order to achieve better absorption characteristics of the Au triangle arrays/VO₂dielectric layer/Pt reflector layer structure,we first prepared VO₂/Pt thin film structure.The morphology,crystal structures and optical properties of VO₂/Pt thin film structure were analyzed and investigated by field emission scanning electron microscope?FESEM?,X-ray diffraction?XRD?,atomic Laser Raman spectrometer?RENISHAW inVia reflex?and double beam ultraviolet-infrared spectrophotometer?PerkinElmer Lambda 950?.Perfect absorption wavelength can be dynamic tuned over a wide wavelength range over 175 nm?from 905 nm to 730 nm in measured spectrum?in visible and near-infrared regime by controlling the temperature.More importantly,its absorption peaks become even stronger during the process of temperature increasing?from the 96.8%at the 905 nm to 98.4%at the 730 nm?.This new structure own high electromagnetic wave absorbing rate with polarization insensitive and wide incident angle?Based on the absorption properties of the VO₂/Pt thin film structure,this paper further studies the optical properties of Au triangular arrays/VO₂/Pt structure,Absorption intensity is tuned from 95%to 33.8%at the wavelength of 2298nm,In order to understand the electric field confinement and absorption mechanism of our absorbers in two phases of VO₂?insulator and metallic?,we calculated the power absorption map at the resonance wavelength of 2298nm for the design.These absorption maps revealed that the absorption mostly takes place in the upper surface VO₂ layer and at the junction between the VO₂ layer and the reflective layer.