Optically Tunable Terahertz Metasurface Absorber

Tunable absorbers are promising for reconfigurable metasurface applications. Here a tunable terahertz (THz) perfect absorber is proposed which consists of high resistance silicon (undoped silicon) and can realize the switch between perfect reflection and perfect absorption (optical pumping, 1064 nm continuous wave). The proposed THz absorber exhibits perfect absorption around 0.74 THz and a 90% absorption bandwidth of 0.5 THz. Additionally, the working frequency range of the device can be easily designed by adjusting the side length and height of the square silicon pillars. Effective medium theory, mode analysis, and impedance matching theory are used to design and explain the proposed THz absorber. The experimental results agree well with the simulations. The proposed scheme allows for more flexible design of THz absorbers, and the device is easier to be fabricated. The proposed tunable THz absorber can find applications in THz sensing, modulator, and optic-electro switches.