Switchable metamaterials for broadband absorption and generation of vector beams

Abstract

Metamaterial (MMs) based on double-split resonator and vanadium dioxide (VO2) in terahertz (THz) region is proposed in this paper, which integrates broadband absorption (ABS) and generation of vector beams (GVB). By tuning the VO2 into metallic phase, the absorption of proposed MMs achieves over 90% in 1.35-2.18 THz. The physical mechanism of broadband absorption is clarified by introducing the impedance matching theory and distributions of electric field. Moreover, absorption characteristics of the designed MMs at different polarization angles and incident angles are also studied, respectively. While VO2 is in insulated state, the radial polarized beam and the angular polarized beam can be generated when the incident wave is x-polarization and y-polarization, respectively. The polarization conversion rate over 90% is realized between 1.37 THz and 2.20 THz within the incident angle of 10°. The bi-functional MMs proposed in this paper has promising applications in modulators, imaging and sensors.

Deep neural network-enabled Multifunctional switchable terahertz metamaterial devices

“…Where Z0 = 377Ω and Z1 represent the effective impedance of the device and the impedance of free space, respectively, and Zr = Z / Z0 represents the relative impedance between the absorber and free space. This is primarily related to the values of the effective dielectric constant (εeff) and magnetic permeability (μeff), which can be expressed as follows 43 .…”

Vanadium dioxide-assisted multifunctional terahertz devices platform: modulator, polarization converter, and biosensor

“…The absorption rate of the incident electromagnetic wave is expressed as A ¼ 1 − jS 11 j 2 − jS 21 j 2 , where S 11 and S 21 are the reflection and transmission coefficients of the incident wave, respectively. 24 Because the thickness of the underlying metal is greater than the skin depth of the THz wave, S 21 is approximately zero, and the absorption rate can be simplified for A ¼ 1 − jS 11 j 2 .…”

“…In the numerical simulation, a periodic unit cell was used in the x–y plane, and an open boundary condition was selected in the z direction. The absorption rate of the incident electromagnetic wave is expressed as A=1−|S11false|2−|S21false|2, where S11 and S21 are the reflection and transmission coefficients of the incident wave, respectively 24 . Because the thickness of the underlying metal is greater than the skin depth of the THz wave, S21 is approximately zero, and the absorption rate can be simplified for A=1−|S11false|2.…”