Ultra-broadband terahertz absorption by exciting the orthogonal diffraction in dumbbell-shaped gratings

Abstract

Metamaterials, artificial electromagnetic media consisting of periodical subwavelength metal-based micro-structures, were widely suggested for the absorption of terahertz (THz) waves. However, they have been suffered from the absorption of THz waves just in the single-frequency owing to its resonance features. Here, in this paper, we propose a simple periodical structure, composed of two 90 degree crossed dumbbell-shaped doped-silicon grating arrays, to demonstrate broadband THz wave absorption. Our theoretical and experimental results illustrate that THz waves can be efficiently absorbed more than 95% ranging from 0.92 THz to 2.4 THz. Such an ultra-wideband polarization-independent THz absorber is realized mainly based on the mechanisms of the anti-reflection effect together with the [±1, 0]-order and [0, ±1]-order grating diffractions. The application of our investigation can be extend to THz couplers, filters, imaging, and so on.

Design and analysis of nanostructured subwavelength metamaterial absorber operating in the UV and visible spectral range

“…[11,[16][17][18] However, more in the recent time, the research in this context has been shifted to the terahertz and the visible regions of the electromagnetic spectrum [19][20][21][22][23][24][25] as well.…”

High-performance terahertz wave absorbers made of silicon-based metamaterials

“…The first absorption peak shifts to the lower frequency when the silicon patches become thicker, which is consistent with the above analysis on the k/4 waveguide resonance nature. 23,26 But the position of the second absorption peak is almost independent on the thickness of silicon patch t 2 . It means that the second order cavity mode is not the main reason for this peak and the bandwidth of the absorber can be enlarged.…”

“…The overall absorption performance of our design is much better than the previous THz results based on the texture of doped silicons. [21][22][23][24][25] Our absorber sample, as schematically shown in Fig. 1(a), is made of a square array of micro-sized silicon patches (cyan) that are capped by a thin layer of SU-8 photoresist (green).…”

“…[20][21][22][23][24][25] Doped silicon with low resistivity can be regarded as a highly lossy material in the THz regime and can be easily processed using standard lithography technologies to produce complex patterns with desired EM properties. Pu et al initially exploited the doped silicon to realize broadband terahertz absorption.…”

Achromatic THz absorption of conductive nanofilms

“…[9][10][11][12][13][14] Various designs of ultrathin THz absorbers have been proposed to achieve the high performance, [15][16][17][18][19][20][21][22][23][24][25][26][27] including ultrabroadband absorption. [28][29][30] Nearly all designs demand complicated micro/nano-fabrication, because the metallic film must be structured with subwavelength patterns that typically feature a micrometer scale. In addition, the nature of resonance in both metamaterials and metasurfaces leads to the disadvantage of single frequency and narrow band operation.…”