We propose an electrostatically actuated spiral structure as a metamaterial for circularly polarized light in the terahertz (THz) frequency range. An array of planar spiral structures was fabricated with micro electro mechanical system technology, and the geometry of the structures can be changed by electrostatic actuation. The actuation transforms the planar spirals into three-dimensional helices, resulting in optical activity in which the differential polarization response of the material depends on whether the incident light is left- or right-circularly polarized. THz spectroscopy confirmed that the optical activity can be tuned with the proposed structures.

References :
Tetsuo Kan, Akihiro Isozaki, Natsuki Kanda, Natsuki Nemoto, Kuniaki Konishi, Makoto Kuwata-Gonokami, Kiyoshi Matsumoto, and Isao Shimoyama, “Spiral metamaterial for active tuning of optical activity,” Applied Physics Letters, vol. 102, no. 22, article no. 221906, 2013. [Paper]

Tetsuo Kan, Akihiro Isozaki, Hidetoshi Takahashi, Kiyoshi Matsumoto, and Isao Shimoyama, “Long stroke out-of-plane actuator using combination of electrostatic and pneumatic forces,” The 27th IEEE International Conference on Micro Electro Mechanical Systems (MEMS2014), San Francisco, USA, pp. 913-916, 26-30 January, 2014. [Proceedings]

Tetsuo Kan, Akihiro Isozaki, Natsuki Kanda, Natsuki Nemoto, Kuniaki Konishi, Makoto Kuwata-Gonokami, Kiyoshi Matsumoto, and Isao Shimoyama, “Spiral Metamaterial For Tunable Circular Dichroism,” The 26th IEEE International Conference on Micro Electro Mechanical Systems (MEMS '13), pp. 701-704, Taipei, Taiwan, 20-24 January, 2013. [Proceedings]

Tetsuo Kan, Akihiro Isozaki, Natsuki Kanda, Natsuki Nemoto, Kuniaki Konishi, Makoto Kuwata-Gonokami, Kiyoshi Matsumoto and Isao Shimoyama, “Fabrication and experimental evaluation of MEMS spiral metamaterial for tunable THz optical activity,” The 7th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials’2013), Bordeaux, France, September 16-21, 2013. [Proceedings]