A high-performance broadband terahertz absorber based on sawtooth-shape doped-silicon

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.

Broadband electrically tunable VO2‑Metamaterial terahertz switch with suppressed reflection

“…The first layer is a periodic metamaterial array of double‐step high‐resistivity silicon cylinders. These cylinders act as a broadband THz metamaterial layer to closely match the impedance of free space to minimize the reflection of incident light, as well as to trap back reflected light within the device . The second layer is a high‐resistivity silicon substrate which supports the device, and out of which the metamaterial layer is etched.…”

“…These cylinders act as a broadband THz metamaterial layer to closely match the impedance of free space to minimize the reflection of incident light, as well as to trap back reflected light within the device. [36][37][38] The second layer is a high-resistivity silicon substrate which supports the device, and out of which the metamaterial layer is etched. Next is a layer of VO 2 , a phase change material that undergoes an IMT slightly above room temperature at ~60 C. Finally, the bottom layer consists of a gold interdigitated electrode, which, with an applied bias, induces the IMT in the underlying VO 2 via Joule heating.…”

A Flexible and Ultra‐Wideband Terahertz Wave Absorber Based on Pyramid‐Shaped Carbon Nanotube Array via Femtosecond‐Laser Microprocessing and Two‐Step Transfer Technique

“…Typically, THz absorbers based on silicon, [27][28][29][30] metallic oxide [31] and polymer [32] in different shapes such as pyramid-based structures have been demonstrated for antireflection purposes. The silicon nanotip arrays were utilized as antireflection layers to achieve a low-loss and spectrally broadband optical-driven THz modulator.…”

An Ultra-Wideband THz/IR Metamaterial Absorber Based on Doped Silicon

“…To tackle this problem, doped silicon substrates have been used to create broadband MPAs. Different unit cells patterns, including circular holes [12], rectangular cubes [13,14,15], cross-cave patches [16] sawtooth structures [17], crosses [18,19] and dumbbell shapes [20], have been demonstrated. The broadband absorptions are mainly due to the excitation of plasmonic waveguide modes or by multi-interference and diffraction effects [21].…”