Full Stokes polarimetry based on an inverse-designed multi-foci metalens.

In the realm of metasurface-based polarimetry, well-known for its remarkable compactness and integration capabilities, previous attempts have been hindered by limitations such as the restricted choices of target polarization states and the inefficient focusing of light. To address these problems, this study introduces and harnesses a novel, to our knowledge, forward-solving model, grounded in the equivalence principle and dyadic Green's function, to inversely optimize the vectorial focusing patterns of metalenses. Leveraging this methodology, we develop and experimentally validate a single multi-foci metalens-based polarimeter, capable of simultaneously separating and concentrating four distinct elliptical polarization states at a wavelength of 10.6 µm. Rigorous experimental evaluations, involving the assessment of 18 scalar polarized beams, reveal an average error of 5.92% and a high contrast ratio of 0.92, which demonstrates the efficacy of the polarimeter. The results underscore the potential of our system in diverse sectors, including military defense, healthcare, and autonomous vehicle technology.

Design of a centimeter-scale achromatic hybrid metalens with polarization insensitivity in the visible.

Achromatic metalenses formed using previous design methods face a compromise between diameter, numerical aperture, and working wave band. To address this problem, the authors coat the refractive lens with a dispersive metasurface and numerically demonstrate a centimeter-scale hybrid metalens for the visible band of 440-700 nm. By revisiting the generalized Snell law, a universal design of a chromatic aberration correction metasurface is proposed for a plano-convex lens with arbitrary surface curvatures. A highly precise semi-vector method is also presented for large-scale metasurface simulation. Benefiting from this, the reported hybrid metalens is carefully evaluated and exhibits 81% chromatic aberration suppression, polarization insensitivity, and broadband imaging capacity.

Silicon metasurface embedded Fabry-Perot cavity enables the high-quality transmission structural color.

While nanoscale color generations have been studied for years, the high-performance transmission structural color, simultaneously equipped with large gamut, high resolution, and optical multiplexing abilities, still remains as a hanging issue. Here, a silicon metasurface embedded Fabry-Perot cavity is demonstrated to address this problem. By changing the planar geometries of meta-atoms, the cavities provide transmission colors with 194% sRGB gamut coverage and 141,111 DPI resolution, along with more than 300% enhanced angular tolerance. Such high density allows two-dimensional color mixing at the diffraction limit scale. Benefitting from the polarization manipulation capacity of the metasurface, arbitrary color arrangements between cyan and red for two orthogonal linear polarizations are also realized. Our proposed cavities can be used in filters, printings, optical storage, and many other applications in need of high quality and density colors.

Design of an achromatic zoom metalens doublet in the visible.

Zoom metalens doublets, featuring ultra-compactness, strong zoom capability, and CMOS compatibility, exhibit unprecedented advantages over the traditional refractive zoom lens. However, the huge chromatic aberration narrows the working bandwidth, which limits their potential applications in broadband systems. Here, by globally optimizing the phase profiles in the visible, we designed and numerically demonstrated a moiré lens based zoom metalens doublet that can achromatically work in the band of 440-640 nm. Such a doublet can achieve a continuous zoom range from 1× to 10×, while also maintaining a high focusing efficiency up to 86.5% and polarization insensitivity.

Broadband achromatic metalens design based on deep neural networks.

For the design of achromatic metalenses, one key challenge is to accurately realize the wavelength dependent phase profile. Because of the demand of tremendous simulations, traditional methods are laborious and time consuming. Here, a novel deep neural network (DNN) is proposed and applied to the achromatic metalens design, which turns complex design processes into regression tasks through fitting the target phase curves. During training, x-y projection pairs are put forward to solve the phase jump problem, and some additional phase curves are manually generated to optimize the DNN performance. To demonstrate the validity of our DNN, two achromatic metalenses in the near-infrared region are designed and simulated. Their average focal length shifts are 2.6% and 1.7%, while their average relative focusing efficiencies reach 59.18% and 77.88%.

Guiding charged particles in vacuum via Lagrange points.

We propose a method for guiding charged particles such as electrons and protons, in vacuum, by employing the exotic properties of Lagrange points. This leap is made possible by the dynamics unfolding around these equilibrium points, which stably capture such particles, akin to the way Trojan asteroids are held in Jupiter's orbit. Unlike traditional methodologies that allow for either focusing or three-dimensional storage of charged particles, the proposed scheme can guide both non-relativistic and relativistic electrons and protons in small cross-sectional areas in an invariant fashion over long distances without any appreciable loss in energy - in a manner analogous to photon transport in optical fibers. Here, particle guiding is achieved by employing twisted electrostatic potentials that in turn induce stable Lagrange points in vacuum. In principle, guidance can be realized within the fundamental mode of the resulting waveguide, thereby presenting a prospect for manipulating these particles in the quantum domain. Our findings may be useful in a wide range of applications in both scientific and technological pursuits. These applications could encompass electron microscopies and lithographies, particle accelerators, quantum and classical communication/sensing systems, as well as methods for shuttling entangled qubits between nodes within a quantum network.

Complex skin modes in non-Hermitian coupled laser arrays.

From biological ecosystems to spin glasses, connectivity plays a crucial role in determining the function, dynamics, and resiliency of a network. In the realm of non-Hermitian physics, the possibility of complex and asymmetric exchange interactions ([Formula: see text]) between a network of oscillators has been theoretically shown to lead to novel behaviors like delocalization, skin effect, and bulk-boundary correspondence. An archetypical lattice exhibiting the aforementioned properties is that proposed by Hatano and Nelson in a series of papers in late 1990s. While the ramifications of these theoretical works in optics have been recently pursued in synthetic dimensions, the Hatano-Nelson model has yet to be realized in real space. What makes the implementation of these lattices challenging is the difficulty in establishing the required asymmetric exchange interactions in optical platforms. In this work, by using active optical oscillators featuring non-Hermiticity and nonlinearity, we introduce an anisotropic exchange between the resonant elements in a lattice, an aspect that enables us to observe the non-Hermitian skin effect, phase locking, and near-field beam steering in a Hatano-Nelson laser array. Our work opens up new regimes of phase-locking in lasers while shedding light on the fundamental physics of non-Hermitian systems.