The simultaneous conversion circular dichroism and wavefront shaping play a vital role in light-matter interactions. The conversion circular dichroism achieved either by intrinsic chirality of nano-antennas or by using multilayer structures which have fabrication complexities. We propose a unique single-layered all-dielectric metasurface for circular asymmetric transmission in the visible regime. We introduce the combination of achiral structures as the building block of metasurface for the simultaneous conversion circular dichroism and wavefront modulation by utilizing hydrogenated amorphous silicon (a-Si:H). The proposed material is a low-loss and a CMOS compatible solution for realizing efficient all-dielectric metasurfaces for the visible domain. The demonstrated methodology exhibits highly efficient transmittance under right circularly polarized (RCP) illumination while completely blocking the light for the opposite spin of the incident light. The multifunctionality of the proposed metasurface can provide a promising route for chiral imaging, CD spectroscopy and spin-selective optical systems.
Artificially engineered light-matter interactions provide a unique degree of freedom to tailor wavefront of the incident waves, through pixelated engineering of its phase, amplitude, and polarization. Such dynamic control introduces various intriguing functionalities. Here, we propose a highly efficient metamirror with circular dichroism, which enables selective reflection with preserved handedness and complete absorption of other polarization. The building block of circular dichroism metamirror working on the principle of Jones calculus. For such a phenomenon, it is necessary to break the nfold rotational (n < 2) symmetry and mirror symmetry simultaneously. The proposed highly efficient metamirror with circular dichroism designed in the microwave regime for wavefront engineering. The demonstrated methodology exhibits full reflection for left circularly polarized EM waves without reversing its handedness and completely absorbing the other handedness. Multifunctionality and fabrication simplicity makes the proposed light-matter interaction a promising route for detection and manipulation of circularly polarized light, encryption, and chiral imaging.
Recently emerged metasurfaces, the two-dimensional (2D) counterpart of three dimensional (3D) metamaterials, gained significant attention in optics and photonics due to their less challenging fabrication requirements (compared to 3D metamaterials) and unique capabilities of wavefront manipulation by introducing abrupt phase shift. Realization of multiple functionalities in a single metasurface, is an intriguing perception to achieve further miniaturization and cost effectiveness. In this paper, we propose a polarization insensitive, highly efficient metasurfaces for the visible spectrum. For the design wavelength of 633nm, negligible absorption coefficient (k) and adequately large refractive index (n) of proposed hydrogenated amorphous silicon (a-Si:H) leads to considerably efficient and cost-effective solution towards metasurfaces design. Inherent property of cylindrical pillar to be polarization insensitive is exploited and 400 nm thick cylindrical nano–waveguide is opted as building block to construct the metasurface. A novel design strategy of achieving multiple functionalities from a single metasurface is proposed, where a combined effect of lensing and optical vortices with different topological charges at different focal planes is demonstrated for the proof of concept. Such unique design strategy of integrating multiple phases into a single device provides an innovative way of miniaturizing the optical devices and systems exhibiting versatile functionalities for on–chip applications.