Stretchable Chiral Metamaterial for Flexible Control of Broadband Asymmetric Transmission

Flexible control of broadband asymmetric transmission (AT) is demonstrated by using a polydimethylsiloxane (PDMS)-based stretchable chiral metamaterial (SCM) in the mid-infrared. The unit cell of the SCM consists of two identical Ω-shaped Au patterns with 180° rotation relative to each other to achieve three-dimensional (3D) chirality, and broad AT band with a flat top can be realized in the wavelength region of 12.26–13.71 µm. The AT value of the SCM is enhanced due to the excitation of the hybrid magnetic-electric dipole mode, and broadband AT responses can be realized through the antireflection (AR) design of the PDMS. By stretching the SCM along the orthogonal directions, the flat AT band can be tailored over a wide wavelength region. In addition, the proposed SCM exhibits large fabrication tolerance, and the broadband AT responses are robust to the variations of the structural parameters. This work offers a further step in developing tunable and broadband polarization converters for photodetection and other polarization-sensitive electromagnetic devices.