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.
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.
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