Abstract-Tunable terahertz metamaterial absorber based on electricity and light modulation modes

Jinfeng Wang, Tingting Lang, Zhi Hong, Tingting Shen, and Gangqi Wang

(a) Schematic view of the proposed tunable THz absorber. (b) Unit cell of the structure with geometrical parameters, the parameters of the absorber are set as p = 80 μm, t = 2 μm, h = 50 μm, b = 0.2 μm, a = 40 μm. The permittivity dispersion (real part: dotted line and imaginary part: solid line) of doped Si in the different layer under the pump fluence of 200 μJ/cm2 is shown on the middle.

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-10-9-2262

In this paper, a metamaterial absorber that achieved absorption tuning by electricity and light control has been proposed in the terahertz (THz) regime. The THz absorber exhibits an absorbance of 97.5% at a resonant frequency of 0.245 THz. First, we simulated the absorption spectra under different structural parameters. Then the absorption characteristics are analyzed under different Fermi energies and pump fluences. When the Fermi energy changes from 0 to 1 eV, the peak absorbance decreases from 97.5% to 56.2%. As the fluence of the pump beam increases from 0 to 100 µJ/cm2, the peak absorbance decreases from 97.5% to 42.8%. The amplitude modulation depth T of our designed absorber is approximately 0.55. Electric and magnetic resonances are proposed in this article, which allows for nearly perfect absorption. Finally, the absorption for both transverse electric and transverse magnetic modes were investigated under different incident angles, from 0° to 75° with a step-width of 15°. The absorber can be potentially applied to THz detection, imaging, and sensing.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Bessel-like beam generated by an axicon based on parallel-plate waveguides

Tingting Shen, Tingting Lang, Mengru Wu, and Zhanghua Han

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-21-6174

The axicon is the simplest and most effective optical element for generating the zero-order Bessel-like beam. The zero-order Bessel-like beam, which has the characteristics of small spot size, high brightness, good direction, and large collimation distance, can be applied to optical micromanipulation and power transmission. In this paper, we proposed and designed a structure for phase manipulation based on parallel-plate waveguides that can be used to realize the functionality of the axicon in the terahertz (THz) region. Meanwhile, we characterized the influence of the cone angle of the axicon and the waist radius of the incident Gaussian beam on the generated zero-order Bessel-like beam by simulation. The planar structure, consisting of a parallel stack of thin copper plates, can be easily fabricated to fulfill the phase requirement to realize the zero-order Bessel-like beam and also can be utilized in THz imaging systems, THz sensing systems, THz communication systems, etc.

© 2018 Optical Society of America