Chiroptical effect induced by achiral structures for full-dimensional manipulation of optical waves

Abstract

The chiroptical effects are omnipresent throughout the universe and play a vital role in the sorting and detecting enantiomers in numerous applications like life sciences, pharmaceuticals, agrochemicals, food industry, etc. These chiroptical effects, along with polarization retention and full phase modulation, can have a significant potential for applications such as chiral imaging, anti-counterfeiting, and security. For strong chiroptical effects, all-dielectric metadevices offer a compact and efficient substitute to three-dimensional (3D) chiral metamaterials and flat plasmonic metadevices, which are prone to complex fabrication and ohmic losses, respectively. Here, we propose a unique metasurface based on the combination of achiral structures to achieve chiroptical effect with polarization retention and wavefront shaping. The proposed structure reflects the left hand circularly polarized (LHCP) light while preserving its handedness with complete absorption of the right hand circularly polarized (RHCP) and vice versa. Meanwhile, the structure provides full 2π phase modulation designed by hydrogenated amorphous silicon (a-Si:H), which is a low-loss, CMOS (complementary metal-oxide-semiconductor) compatible material with fabrication ease. The spin-selective reflection with circular dichroism and full phase modulation of designed structure find application in integrated optics, quantum optics, detection, and chiral imaging.