Silicon-assisted multifunctional metasurface for broadband absorption, polarization conversion and wavefront manipulation in the terahertz region

• Published in: Materials science in semiconductor processing Vol. 184; p. 108783
• Main Authors: Zhang, Ying, Zhou, Xingtong, Li, You, He, Xunjun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2024
• Subjects: Broadband absorption; Polarization conversion; Silicon; Vanadium dioxide; Wavefront manipulation; Wavefront manipulation; Silicon; Broadband absorption; Polarization conversion; Vanadium dioxide
• ISSN: 1369-8001
• DOI: 10.1016/j.mssp.2024.108783

A silicon-assisted metasurface for broadband absorption, polarization conversion, and wavefront manipulation based on vanadium dioxide (VO2) is proposed in this paper. While VO2 is in the metallic state, the metasurface operates in broadband absorption mode. The perfect absorption bandwidth is 1.38 THz, corresponding to a relative bandwidth of 95 %. By joint modulation of the conductivities of VO2 and photosensitive silicon, absorption performances tunning is realized. In particular, the bandwidth modulation is obtained with central frequency unchanged. In addition, an equivalent circuit model is explored to explain the absorption mechanism. While VO2 is in the insulating state, the metasurface works in polarization conversion mode. The bandwidth of over 90 % cross-polarization reflectivity is 1.13 THz, and PCR approaches 1 in the whole working range. By adjusting photosensitive silicon conductivity, dynamic tuning of PCR is achieved. Through precise phase arrangement, the function integration of deflector and spiral phase plate is realized. Deflected vortex beams are generated in a broad operating frequency from 1.0 THz to 2.0 THz. We also develop a 1D focusing metalens with different presupposed focal lengths, which exhibits remarkable subwavelength focusing capabilities. The functional metasurface has the potential application in optical stealth, communication, imaging, and so on.