Chirality-Assisted Aharonov–Anandan Geometric-Phase Metasurfaces for Spin-Decoupled Phase Modulation

Abstract

In this work, a quasi-nondispersive and spin-decoupled phase modulation strategy was proposed based on the chiral structure. Owing to the spindependent response of the chiral structure, the evolution of the Aharonov− Anandan (AA) geometric phase can be controlled by tuning different structural parameters independently. Additionally, the chiral structure was designed nonresonant or weak-resonant to minimize the influence of strong resonant absorption and large dispersive propagation phase shift, leading to an efficiently quasi-nondispersive phase modulation. To prove the validity of the strategy, a series of umbrella-shaped reflection-type metal−insulator−metal structures were designed as the unit cells and simulated with the finite element method. Moreover, the metasurfaces were designed based on such unit cells to generate broadband orbital angular momentums with different topological charges and spin-switchable holograms, respectively. Simulated and experimental results are in good agreement with the theoretical results. To the best of our knowledge, broadband spindependent phase modulation has been achieved without intentionally merging other types of phases for the first time in this work. We believe that this strategy provides a flexible approach for complex spin-or polarization-related applications in optical communication, integrated optics, optical sensing, and other related fields.

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

“…According to the simulated surface current distributions shown in Figure b, the surface current evolves with the varying radian of the corresponding arm and generates a relevant phase shift. The phase shift only depends on the change of the radian, and the generated phases for orthogonal CP incident waves can return to identical final states after undergoing cyclic evolutions in different paths, which are entirely consistent with the properties of the AA geometric phase originating from the optical Coriolis effect. − In the light of the Coriolis shift, the co-polarized reflection AA phases of the proposed meta-atom under LCP and RCP illumination can be expressed as follows: where α L and α R denote the radians of the left arm and right arm, respectively. The simulation results depicted in Figure a are basically in accordance with eq , and the discrepancies between the simulation results and the theoretical predictions are due to material loss and structural resonance.…”

“…The phase shift only depends on the change of the radian, and the generated phases for orthogonal CP incident waves can return to identical final states after undergoing cyclic evolutions in different paths, which are entirely consistent with the properties of the AA geometric phase originating from the optical Coriolis effect. 47−49 In the light of the Coriolis shift, the co-polarized reflection AA phases of the proposed meta-atom under LCP and RCP illumination can be expressed as follows: 50 l…”

A Single-Celled Metasurface for Multipolarization Generation and Wavefront Manipulation

“…The emergence of metasurfaces has provided a promising and artful approach to solving the above problem. Benefiting from an unprecedented and flexible capability in the manipulation of the intensity, polarization, and phase of light [ 1 , 2 , 3 ], recent years have witnessed the development of various metasurface-based devices, such as metalenses [ 4 , 5 , 6 , 7 ], vortex generators [ 8 , 9 , 10 , 11 , 12 , 13 ], holograms [ 2 , 9 , 14 , 15 , 16 , 17 ], metagratings [ 1 , 18 ], nanoprints [ 19 , 20 , 21 , 22 ], and so on. Among them, in terms of polarization conversion, imposing different phase retardations on orthogonal linear/circular polarizations is the general design strategy [ 10 , 23 , 24 ].…”

“…Very recently, another geometric phase, the nonadiabatic Aharonov–Anandan (AA) phase was introduced in the design of a metasurface [ 9 , 10 , 28 ]. In the scheme of the nonadiabatic AA phase, the structure parameters are changed to rotate the polarization ellipse and therefore introduce geometric phase shift.…”

“…In this way, it provides a promising approach to decouple the angle of rotation of the polarization ellipses respectively corresponding to the RCP and LCP phases. Therefore, as a kind of geometric phase, the AA phase has attracted much attention as it not only possesses the advantage of nondispersive phase control but also has the potential to artfully avoid the intrinsic symmetry of LCP and RCP phases [ 9 , 28 , 29 ]. Benefiting from such merit and the spin-dependent response of the chiral structure, an umbrella-shaped metasurface was proposed as an example to verify the validity of the spin-decoupled AA phase manipulation mechanism.…”