Chiral metasurfaces of wavy rectangle resonators with tunable circular dichroism

Chiral metasurfaces operating at the mid-infrared frequencies are of great interest for chiral molecule vibrational sensing and other applications. Here, mid-infrared chiral metasurfaces of wavy rectangle resonators with strong chiroptical response and tunable circular dichroism (CD) are demonstrated. The chiral metasurface exhibits a high CD value of more than 0.57 as the chiral plasmonic resonance wavelength is tuned from 4.96 to 5.82 µm by enlarging the geometric dimensions of the unit cell. Furthermore, CD values can be continuously tuned from positive to zero and negative without altering the chiral plasmonic resonance wavelength, by simply relocating the cutting slot to change the geometric symmetry of the wavy rectangle structure. These results aim to advance the development of many promising applications in mid-infrared frequencies including protein molecule detection, thermal emission control, and infrared-light communication.