Abstract-Switchable multifunctional terahertz metasurfaces employing vanadium dioxide

Xike Li, Shiwei Tang, Fei Ding, Shuomin Zhong, Yuanqing Yang, Tao Jiang,  Jun Zhou, 

https://www.nature.com/articles/s41598-019-41915-6?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+srep%2Frss%2Fcurrent+%28Scientific+Reports%29


In this paper, we design a type of switchable metasurfaces by employing vanadium dioxide (VO2), which possess tunable and diversified functionalities in the terahertz (THz) frequencies. The properly designed homogeneous metasurface can be dynamically tuned from a broadband absorber to a reflecting surface due to the insulator-to-metal transition of VO2. When VO2 is in its insulating state, the metasurface can efficiently absorb the normally incident THz wave in the frequency range of 0.535–1.3 THz with the average absorption of ~97.2%. Once the VO2 is heated up and switched to its fully metallic state, the designed metasurface exhibits broadband and efficient reflection (>80%) in the frequency range from 0.5 to 1.3 THz. Capitalizing on such meta-atom design, we further extend the functionalities by introducing phase-gradients when VO2 is in its fully metallic state and consequently achieve polarization-insensitive beam-steering and polarization-splitting, while maintaining broadband absorption when VO2 is in insulating state.

Abstract- Vanadium Dioxide Integrated Metasurfaces with Switchable Functionalities at Terahertz Frequencies

Fei Ding, Shuomin Zhong, Sergey I. Bozhevolnyi,

http://onlinelibrary.wiley.com/doi/10.1002/adom.201701204/full

Integration of switchable and diversified functionalities into a single metasurface has become an emerging research area that requires dealing with formidable challenges, especially for terahertz (THz) frequencies. Here, polarization-insensitive and switchable THz metasurfaces are proposed with diversified functionalities that exploit insulator-to-metal transition in vanadium dioxide (VO2). The simulations demonstrate that the designed metasurface can be switched from a broadband absorber to a reflecting broadband halfwave plate (HWP). At room temperature, the metasurface efficiently absorbs normally incident waves ranging from 0.562 to 1.232 THz with the total absorption exceeding 90%. Once the temperature is high enough and VO2 is in its fully metallic state, the metasurface becomes a broadband HWP reflecting over 60% of the incident power with the linear polarization conversion efficiency exceeding 95% within the bandwidth of 0.49 THz. Moreover, the broadband performance is sustained over a wide range of incident angles. To extend the functionalities, metasurface supercell made of several VO2 antennas is integrated, consequently achieving directional polarization conversion when VO2 is in its fully metallic state while maintaining broadband absorption at insulating state. The proposed switchable metasurfaces are expected to enable advanced research and smart applications related to other tunable and diverse functionalities at THz frequencies.

Abstract-Detection of internal fields in double-metal terahertz resonators

Oleg Mitrofanov1,2,a), Zhanghua Han3,a), Fei Ding4, Sergey I. Bozhevolnyi4, Igal Brener2,5, and John L. Reno

http://aip.scitation.org/doi/10.1063/1.4975802

Terahertz (THz) double-metal plasmonic resonators enable enhanced light-matter coupling by exploiting strong field confinement. The double-metal design however restricts access to the internal fields. We propose and demonstrate a method for spatial mapping and spectroscopic analysis of the internal electromagnetic fields in double-metal plasmonic resonators. We use the concept of image charges and aperture-type scanning near-field THz time-domain microscopy to probe the fields confined within the closed resonator. The experimental method opens doors to studies of light-matter coupling in deeply sub-wavelength volumes at THz frequencies.