Abstract
Perfect absorbers with broadband absorption of terahertz (THz) radiation are promising for applications in imaging and detection to enhance the contrast and sensitivity, as well as to provide concealment. Different from previous two-dimensional structures, here we put forward a new type of THz absorber based on sawtooth-shape doped-silicon with near-unit absorption across a broad spectral range. Absorbance over 99% is observed numerically from 1.2 to 3 THz by optimizing the geometric parameters of the sawtooth structure. Our absorbers can operate over a wide range of incident angle and are polarization insensitive. The underlying mechanisms due to the combination of an air-cavity mode and mode-matching resonance on the air-sawtooth interface are analyzed in terms of the field patterns and electromagnetic power loss features.
Highlights
Terahertz (THz) wave, with the typical wavelength ranging from 3 mm to 30μm, has attracted lots of research interests in last two decades, due to its significant applications in various fields, such as time-domain spectroscopy (TDS), non-invasive sensing, biomedicine, high-speed wireless communications and so on.[1,2,3] Under some circumstance, blocking the influence of THz or shielding some objects from THz radiation is in demand
Perfect absorbers with broadband absorption of terahertz (THz) radiation are promising for applications in imaging and detection to enhance the contrast and sensitivity, as well as to provide concealment
Our absorbers can operate over a wide range of incident angle and are polarization insensitive
Summary
Terahertz (THz) wave, with the typical wavelength ranging from 3 mm to 30μm, has attracted lots of research interests in last two decades, due to its significant applications in various fields, such as time-domain spectroscopy (TDS), non-invasive sensing, biomedicine, high-speed wireless communications and so on.[1,2,3] Under some circumstance, blocking the influence of THz or shielding some objects from THz radiation is in demand. In order to get high-efficient polarization-insensitive and wide-angle operant THz absorbers, Cheng et al realized two-dimensional cross-shaped THz absorber[24] and Yin et al proposed a THz absorber using a square array of plastic-caped silicon.[25] the fabrication processes of these two-dimensional THz absorbers are complicated. According to effective medium theory,[28] the permittivity of the top layer of our sawtooth-shape absorber is close to that of air. It is easier for the incident wave to couple into the sawtooth-shape absorber, leading to a better absorption performance. Considering fabrication simplicity, cost and allowance for possible integration into silicon-based systems, our single-layered absorbers are more attractive than its two-dimensional competitors
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