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

Abstract

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.

Single-Layer Achiral Metasurface with Independent Amplitude–Phase Control for Both Left-Handed and Right-Handed Circular Polarizations

“…Holography has become one of the most important technologies to achieve three-dimensional imaging since it was invented in 1948 . In addition, based on the amplitude and phase controlled metasurface, the novel meta-hologram has shown promising applications in recent years because of its high imaging fidelity. ,, Nevertheless, most meta-holograms are hard to reconstruct the images with the amplitude and phase modulation in multiple channels at the same frequency point. In accordance with the previous design and analysis of our proposed meta-atom, an amplitude and phase controlled dual-channel meta-hologram is established to reconstruct diverse images with high fidelity and verify the feasibility of our methodology.…”

“…Metasurfaces, the artificial planar arrangements of various subwavelength resonators, possess exceptional capability of tailoring the amplitude, phase, and polarization of electromagnetic waves. − Given the merits of low loss, small size, and simple fabrication, metasurfaces have drawn great attention and shown versatile applications, such as vortex beam generators, , focusing lenses, , meta-holograms, − surface plasmon polariton couplers, , etc. − Notably, some efforts are devoted to construction of chiral metasurfaces to acquire desired chiral effects. − For instance, numerous transmission-reflection-selective chiral structures are designed to block one state of the CP waves and transmit orthogonal CP waves. − Some ingenious metasurfaces can achieve circular dichroism by devising the chiral structures or introducing loss resistors into meta-atoms. − Furthermore, a range of schemes are proposed to independently control the wavefronts of LCP waves and RCP waves based on the integrated design of scaling-induced propagation phases and rotation-induced geometric phases. − More strikingly, certain multilayer multifunctional metasurfaces are established to tailor the amplitude and phase of orthogonal CP waves utilizing chiral structures with unequal dimensions working at distinct frequencies. , Nevertheless, most of the existing paradigms increase the complexity of the structures to obtain the intrinsic chirality or combine multilayer achiral structures to get the external chirality, and it is difficult for chiral metasurfaces to manipulate the amplitude and phase of orthogonal CP incident waves independently at the same frequency based on the present design mechanisms. In contrast, there are few studies on chiral phenomena generated by single-layer achiral structures, which means that the immense potential of chiral effects lies in simple achiral structures.…”

All‐Dielectric Trifunctional Metasurface Capable of Independent Amplitude and Phase Modulation

“…[27] A reflective chiral metasurface was proposed, which can simultaneously control the amplitude and phase via ohmic dissipation. [28] In addition, with the development of subwavelength optics and the demand for multifunctional photonic devices, there is an urgent need to integrate more functions into a single device. [29] All-silicon terahertz metasurfaces were proposed for polarization-dependent wave front manipulation.…”

Stereo Meta‐Atom Enabled Phase–Amplitude Gradient Metasurface for Circularly Polarized Waves

“…[14][15][16] It paves the way to a series of interesting applications, [17,18] and various extension structures are proposed to realize full complex-amplitude modulation. [19][20][21][22][23][24] Though most of the studies about the amplitude and phase regulation of metasurfaces are of linearly polarized waves, some recent studies work on decoupling the A-P for circular polarization (CP) waves, such as by dual geometric phases, [25] dual-phase hybrid, [26] and lossy components [27] in microwaves, and tuning the angle of X-shaped meta-atom [28] and adjusting the thickness of meta-atom [29] in the optical regime. However, the approaches are hindered in the microwave regime because of low efficiency or the limited design freedom.…”