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Metasurfaces are arrays of subwavelength spaced nanostructures that can manipulate the amplitude, phase, and polarization of light to achieve a variety of optical functions beyond the capabilities of 3D bulk optics. However, they suffer from limited performance and efficiency when multiple functions with large deflection angles are required because the non-local interactions due to optical coupling between nanostructures are not fully considered. Here we introduce a method based on supercell metasurfaces to demonstrate multiple independent optical functions at arbitrary large deflection angles with high efficiency. In one implementation the incident laser is simultaneously diffracted into Gaussian, helical and Bessel beams over a large angular range. We then demonstrate a compact wavelength-tunable external cavity laser with arbitrary beam control capabilities – including beam shaping operations and the generation of freeform holograms. Our approach paves the way to novel methods to engineer the emission of optical sources. The angular dependence is a well-known issue in metasurface engineering. Here the authors introduce a supercell metasurface able to implement multiple independent functions under large deflection angles with high efficiency, leading to a wavelength tunable laser with arbitrary wavefront control.

Bound states in the continuum (BICs) have attracted attention in photonics owing to their interesting properties. For example, BICs can effectively confine light in a counterintuitive way, and the far-field radiation of photonic structures that exhibit BICs has fascinating topological characteristics. Early research into photonic BICs was primarily focused on designing artificial structures to produce BICs. However, since the mid-2010s, exploring the potential applications of BICs has been a growing trend in research. In this Review, we detail the unique properties of BICs, including the ability to achieve enhanced light confinement, sharp Fano resonances and topological characteristics. We explore phenomena derived from BICs, including the generation of circularly polarized states and unidirectional guided resonances, and the impact of BICs on various applications such as lasing, nonlinear frequency conversion, waveguiding, sensing and wavefront control. We also discuss the insights provided by BICs in several emerging research frontiers, such as parity–time symmetric systems, higher-order topology, exciton–photon coupling and moiré superlattices.Photonic systems provide a versatile platform to explore and use bound states in the continuum. This Review discusses the potential of these states for enhancing light–matter interactions in various applications and investigating the physics of emerging photonic systems.

Vertical cavity surface-emitting lasers (VCSELs) have made indispensable contributions to the development of modern optoelectronic technologies. However, arbitrary beam shaping of VCSELs within a compact system has remained inaccessible until now. The emerging ultra-thin flat optical structures, namely metasurfaces, offer a powerful technique to manipulate electromagnetic fields with subwavelength spatial resolution. Here, we show that the monolithic integration of dielectric metasurfaces with VCSELs enables remarkable arbitrary control of the laser beam profiles, including self-collimation, Bessel and Vortex lasers, with high efficiency. Such wafer-level integration of metasurface through VCSEL-compatible technology simplifies the assembling process and preserves the high performance of the VCSELs. We envision that our approach can be implemented in various wide-field applications, such as optical fibre communications, laser printing, smartphones, optical sensing, face recognition, directional displays and ultra-compact light detection and ranging (LiDAR).Non-intrusive integration of metasurfaces with vertical cavity surface-emitting lasers enables fully arbitrary wavefront control for directional laser emission.

Retrieving the pupil phase of a beam path is a central problem for optical systems across scales, from telescopes, where the phase information allows for aberration correction, to the imaging of near-transparent biological samples in phase contrast microscopy. Current phase retrieval schemes rely on complex digital algorithms that process data acquired from precise wavefront sensors, reconstructing the optical phase information at great expense of computational resources. Here, we present a compact optical-electronic module based on multi-layered diffractive neural networks printed on imaging sensors, capable of directly retrieving Zernike-based pupil phase distributions from an incident point spread function. We demonstrate this concept numerically and experimentally, showing the direct pupil phase retrieval of superpositions of the first 14 Zernike polynomials. The integrability of the diffractive elements with CMOS sensors shows the potential for the direct extraction of the pupil phase information from a detector module without additional digital post-processing. Retrieving the pupil phase of a optical beam path is a central problem for imaging systems across scales. The authors use Diffractive Neural Networks to directly extract pupil phase information with a single, compact optoelectronic device.

Adaptive optics (AO) is critical in astronomy, optical communications and remote sensing to deal with the rapid blurring caused by the Earth’s turbulent atmosphere. But current AO systems are limited by their wavefront sensors, which need to be in an optical plane non-common to the science image and are insensitive to certain wavefront-error modes. Here we present a wavefront sensor based on a photonic lantern fibre-mode-converter and deep learning, which can be placed at the same focal plane as the science image, and is optimal for single-mode fibre injection. By measuring the intensities of an array of single-mode outputs, both phase and amplitude information on the incident wavefront can be reconstructed. We demonstrate the concept with simulations and an experimental realisation wherein Zernike wavefront errors are recovered from focal-plane measurements to a precision of 5.1 × 10 −3   π radians root-mean-squared-error. Adaptive optics wavefront sensors need to be in a pupil plane and are insensitive to certain wavefront-error modes. The authors present a wavefront sensor based on a photonic lantern fibre-mode-converter and deep learning, which can be placed at the same focal plane accessing nondegenerate wavefront information and reconstructing the wavefront.

Metasurfaces are capable of fully reshaping the wavefronts of incident beams in desired manners. However, the requirement for external light excitation and the resonant nature of their meta-atoms, make challenging their on-chip integration. Here, we introduce the concept and design of a fresh class of metasurfaces, driven by unidirectional guided waves, capable of arbitrary wavefront control based on the unique dispersion properties of unidirectional guided waves rather than resonant meta-atoms. Upon experimentally demonstrating the feasibility of our designs in the microwave regime, we numerically validate the introduced principle through the design of several microwave meta-devices using metal-air-gyromagnetic unidirectional surface magneto-plasmons, agilely converting unidirectional guided modes into the wavefronts of 3D Bessel beams, focused waves, and controllable vortex beams. We, further, numerically demonstrate sub-diffraction focusing, which is beyond the capability of conventional metasurfaces. Our unfamiliar yet practical designs may enable full, broadband manipulation of electromagnetic waves on deep subwavelength scales. Here the authors develop a class of metasurfaces based on robust, unidirectional waves. Such metasurfaces, driven by guided one-way waves, may facilitate their on-chip integration, as well as the precise manipulation of wavefronts on deep-subwavelength scales.

The strong interaction of light with micro- and nanostructures plays a critical role in optical sensing, nonlinear optics, active optical devices, and quantum optics. However, for wavefront shaping, the required local control over light at a subwavelength scale limits this interaction, typically leading to low-quality-factor optical devices. Here, we demonstrate an avenue towards high-quality-factor wavefront shaping in two spatial dimensions based on all-dielectric higher-order Mie-resonant metasurfaces. We design and experimentally realize transmissive band stop filters, beam deflectors and high numerical aperture radial lenses with measured quality factors in the range of 202–1475 at near-infrared wavelengths. The excited optical mode and resulting wavefront control are both local, allowing versatile operation with finite apertures and oblique illumination. Our results represent an improvement in quality factor by nearly two orders of magnitude over previous localized mode designs, and provide a design approach for a new class of compact optical devices. Wavefront manipulation with metasurfaces is typically limited to low quality factors. Here, the authors show how higher-order Mie modes can be leveraged to design high quality factor optical metasurfaces for wavefront manipulation in two dimensions.

The shear wavefront propagates in a single direction, influenced by the phase deviation of the missing orthogonal direction in the interference pattern. Furthermore, the restriction of phase sampling points in the shear direction has a certain impact on attaining high spatial resolution in wavefront reconstruction. To attain high-precision wavefront reconstruction, it is necessary to acquire additional sampled data from various orthogonal shear directions. During our investigation, a wavefront reconstruction method was proposed for multi-directional orthogonal lateral shearing interferometry. This method establishes a relationship model that corresponds to multi-directional differential wavefront and differential Zernike polynomials. Using the principle of wavefront reconstruction with differential Zernike polynomials, it allows for the reconstruction of wavefronts from any orthogonal-direction lateral shearing interference patterns. To validate the efficacy of the proposed method, the wavefront reconstruction accuracy of various sets of arbitrarily oriented shearing interferograms was simulated and analyzed. Additionally, the results were compared to those obtained from the average differential wavefront of multiple orthogonal shearing interferograms. The results show that by choosing multiple orthogonal shear directions to improve phase sampling data, wavefront reconstruction can be successfully accomplished using any number of orthogonal lateral shearing interferograms. This effectively reduces the impact of both random and systematic errors on the spatial resolution of the wavefront during the reconstruction process. Ultimately, the accuracy of the proposed method was confirmed through experimental validation. After comparing the repeatability measurement with the results obtained from the ZYGO interferometer, it was discovered that the precision of the relative measurement error in RMS was superior to 0.01λ.

Metasurfaces have exhibited exceptional proficiency in precisely modulating light properties within narrow wavelength spectra. However, there is a growing demand for multi-resonant metasurfaces capable of wavefront engineering across broad spectral ranges. In this study, we introduce a microcavity-assisted multi-resonant metasurface platform that integrates subwavelength meta-atoms with a specially designed distributed Bragg reflector (DBR) substrate. This platform enables the simultaneous excitation of various resonant modes within the metasurface, resulting in multiple high- Q resonances spanning from the visible to the near-infrared (NIR) regions. The developed metasurface generates up to 15 high- Q resonant peaks across the visible-NIR spectrum, achieving a maximum efficiency of 81% (70.7%) in simulation (experiment) with an average efficiency of 76.6% (54.5%) and a standard deviation of 4.1% (11.1%). Additionally, we demonstrate the versatility of the multi-resonant metasurface in amplitude, phase, and wavefront modulations at peak wavelengths. By integrating structural color printing and vectorial holographic imaging, our proposed metasurface platform shows potential for applications in optical displays and encryption. This work paves the way for the development of next-generation multi-resonant metasurfaces with broad-ranging applications in photonics and beyond. Previous multi-wavelength metasurfaces are restricted to a few wavelengths or lack wavefront control ability. Here, the authors introduce a microcavity-assisted metasurface that achieves multi-resonant wavefront engineering at 15 high-Q peak wavelengths from 480 nm to 1000 nm.

We report on studies and experiments we carried out at the Advanced Photon Source (APS) at Argonne National Laboratory to develop automatic optics alignment and wavefront control systems, supported by artificial intelligence technologies and advanced real-time wavefront sensing techniques. The ultimate goal is to achieve near-perfect wavefront control and support APS beamlines and user to achieve and maintain the beam properties at the sample, while at the same freeing the operator and the user from the burden of lengthy manual alignment and beam optimization. We discuss the prototype systems we developed and successfully tested at a beamline. These systems are engineered to manage the optics of the featured beamlines of the new synchrotron.