Tunable multiband asymmetric transmission based on flexible chiral metamaterial for refractive index sensing

Tunable multiband asymmetric transmission (AT) effect is effectively demonstrated using a polydimethylsiloxane (PDMS)-based flexible chiral metamaterial (FCM) in the mid-infrared region. The unit cell of the FCM comprises J-shaped and F-shaped gold patterns to achieve three-dimensional (3D) chirality, and a multiband AT effect can be realized. Due to the excitation of enantiomerically sensitive plasmons, the FCM can realize a tunable multiband AT effect that is rarely reported, whose peak values can reach 51.89%, 37.72%, and 28.91% at resonance wavelengths of 9.03 µm, 10.25 µm, and 12.77 µm, respectively. The tunability of the FCM demonstrated that the peaks of AT shift to longer wavelengths when stretching along different directions respectively. Compared with reported refractive index sensors based on chiral metamaterial, FCM has tunable multibands and better refractive index sensitivity, which can reach 7875 nm/RIU, 3375 nm/RIU, and 1625 nm/RIU, respectively. Our proposed FCM opens an avenue to develop refractive index sensors.