Tailoring Circular Dichroism for Simultaneous Control of Amplitude and Phase via Ohmic Dissipation Metasurface

Circular dichroism, as one of the exotic phenomena, derives from chirality biomolecules in nature, expressing differential absorption of spin angular momentum. The concept of dichroism has been migrated to the field of artificial materials and acquired adequate development. However, there is still a lack of a flexible strategy to tailor circular dichroism for providing another promising level to achieve spin-selective multi-dimensional manipulation of electromagnetic waves. In this work, a paradigm of reflective chiral metasurface is proposed to promote this aspect of exploration. By introducing loss resistors into the chiral meta-atoms, the magnitude of differential absorption effect can be tailored by varying the corresponding resistance, leading to the variation of co-polarization reflection amplitude. Combining with the Pancharatnam–Berry phases of chiral meta-atom, both the reflective amplitude and phase are flexibly controlled in independent manners. Accordingly, the pattern of reflection fields can be theoretically shaped into arbitrary forms through Fourier transform in spatial domain. Here, metasurfaces for achieving rectangular-shaped beam and complex-amplitude hologram are demonstrated as two proofs-of-principle. Encouragingly, this effort provides an alternative approach for simultaneous control of amplitude and phase, which may pave a new route in the fields of beam-forming technology and spin-selective integrated systems.