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The metamaterial perfect absorber (MPA) is a new type of electromagnetic wave absorber first proposed by Landy.  Compared  with  the  traditional  electromagnetic  wave  absorber,  MPA has  many  advantages,  including ultra-high absorption efficiency, ultra-thin, compact structure, easily tunable resonances, etc. so it is gradually applied to ultra-sensitive sensing, imaging, detection and other fields. Nowadays, the MPA research focuses on two areas. One area focuses on the absorption efficiency modulation and absorption wavelength tuning, and the other area is to broaden the absorption bandwidth and achieve high absorptions at different optical frequencies. Previously,  the  MPA  absorption  efficiency  modulation  or  absorption  wavelength  tuning  was  realized  by changing  the  device  structure  or  the  surrounding  medium  material.  But  these  methods  can  increase  the difficulty in processing and increase the device volume. In order to achieve the control of absorption wavelength and absorption efficiency without increasing the difficulty in processing or the device volume. We propose to use vanadium dioxide and graphene as the materials of MPA, which has high absorption efficiency in the infrared band.  It  is  found  that  the  absorption  efficiency  of  MPA  at  9.66  μm  wavelength  can  reach  96%  when  the temperature  of  vanadium  dioxide  is  5 °C by  using  finite  difference  time  domain  (FDTD)  method.  However, when  the  vanadium  dioxide  temperature  rises  to  68 °C,  the  absorption  efficiency  of  MPA suddenly  drops  to 2.8%. The modulation depth of absorption efficiency can reach 97.08%. We propose that the MPA be able to control  not  only  the  absorption  efficiency,  but  also  the  absorption  wavelength.  By  changing  the  voltage  of graphene, the chemical potential Ef of graphene can be controlled and the absorption wavelength of MPA can be tuned. When Ef increases from 0.1 eV to 3 eV, the absorption wavelength of MPA will be blue-shifted from 9.66 μm to 6.46 μm. The magnetic field distribution of MPA at the absorption wavelength shows that the MPA has a high absorption efficiency because of the Fabry-Pérot (FP) cavity resonance is formed in MPA. Therefore, the change of structure parameters of MPA will affect its absorption characteristics. It is found by the FDTD method  that  the  absorption  wavelength  of  MPA  will  be  redshifted,  when  the  radius,  thickness,  period  and thickness  of  the  nanocolumn  array  increase.  This  study  can  provide  theoretical  guidance  for  designing  and preparing the controllable MPA, which has compact structure and low process difficulty merits.

Metamaterial absorber with controllable absorption wavelength and absorption efficiency