Dual-polarized transmissive metasurfaces for near-unitary-NA analog spatial computing empowered by impedance matching and mismatching.

In recent years, due to the increasing requirement for real-time and massive data processing, optical analog computation has arisen as a promising alternative to digital computation. Optical spatial differentiation plays a fundamentally important role in various emerging technologies, including augmented reality, autonomous driving, and object recognition. However, previous demonstrations encountered several limitations, such as the dependence on polarization states and a typically limited numerical aperture (NA) of about 0.

Spatial Information Lasing Enabled by Full-k-Space Bound States in the Continuum.

Optical amplification and massive information transfer in modern physics depend on stimulated radiation. However, regardless of traditional macroscopic lasers or emerging micro- and nanolasers, the information modulations are generally outside the lasing cavities. On the other hand, bound states in the continuum (BICs) with inherently enormous Q factors are limited to zero-dimensional singularities in momentum space.

Polarization-insensitive high-numerical-aperture metalens for wide-field super-resolution imaging.

The development of super-oscillatory lens (SOL) offers opportunities to realize far-field label-free super-resolution microscopy. Most microscopes based on a high numerical aperture (NA) SOL operate in the point-by-point scanning mode, resulting in a slow imaging speed. Here, we propose a high-NA metalens operating in the single-shot wide-field mode to achieve real-time super-resolution imaging.

Twofold optical display and encryption of binary and grayscale images with a wavelength-multiplexed metasurface.

The remarkable capability in regulating light polarization or amplitude at the nanoscale makes metasurface a leading candidate in high-resolution image display and optical encryption. Diverse binary or grayscale meta-images were previously shown concealed in a single metasurface, yet they are mostly stored at same encryption level and share an identical decryption key, running the risk of exposing all images once the key is disclosed. Here, we propose a twofold optical display and encryption scheme demonstrating that binary and grayscale meta-images can be concurrently embedded in a nonspatially multiplexed silicon metasurface, and their decryptions demand for drastically different keys.

Polarity-Tunable Field Effect Phototransistors.

Field-effect phototransistors feature gate voltage modulation, allowing dynamic performance control and significant signal amplification. A field-effect phototransistor can be designed to be inherently either unipolar or ambipolar in its response. However, conventionally, once a field-effect phototransistor has been fabricated, its polarity cannot be changed.

Design Strategies and Applications of Dimensional Optical Field Manipulation Based on Metasurfaces.

Recent rapid progress in metasurfaces is underpinned by the physics of local and nonlocal resonances and the modes coupling among them, leading to tremendous applications such as optical switching, information transmission, and sensing. In this review paper, an overview of the recent advances in a broad range of dimensional optical field manipulation based on metasurfaces categorized into different classes based on design strategies is provided. This review starts from the near-field optical resonances of artificial nanostructures and discusses the far-field optical wave manipulation based on fundamental mechanisms such as mode generation and mode coupling.

Color-selective three-dimensional polarization structures.

Polarization as an important degree of freedom for light plays a key role in optics. Structured beams with controlled polarization profiles have diverse applications, such as information encoding, display, medical and biological imaging, and manipulation of microparticles. However, conventional polarization optics can only realize two-dimensional polarization structures in a transverse plane.

Realization of maximum optical intrinsic chirality with bilayer polyatomic metasurfaces.

Optical chirality plays a key role in optical biosensing and spin-selective optical field manipulation. However, the maximum optical intrinsic chirality, which is represented by near-unity circular dichroism (CD), is yet to be achieved in a wide bandwidth range based on nanostructures. Here, we utilize dielectric bilayer polyatomic metasurfaces to realize the maximum optical intrinsic chirality over a wide bandwidth range.

Ultrahigh Photogain Short-Wave Infrared Detectors Enabled by Integrating Graphene and Hyperdoped Silicon.

Highly sensitive short-wave infrared (SWIR) detectors, compatible with the silicon-based complementary metal oxide semiconductor (CMOS) process, are regarded as the key enabling components in the miniaturized system for weak signal detection. To date, the high photogain devices are greatly limited by a large bias voltage, low-temperature refrigeration, narrow response band, and complex fabrication processes. Here, we demonstrate high photogain detectors working in the SWIR region at room temperature, which use graphene for charge transport and Te-hyperdoped silicon (Te-Si) for infrared absorption.

The Effect of Ethanol on Abnormal Grain Growth in Copper Foils.

Single-crystal Cu not only has high electrical and thermal conductivity, but can also be used as a promising platform for the epitaxial growth of two-dimensional materials. Preparing large-area single-crystal Cu foils from polycrystalline foils has emerged as the most promising technique in terms of its simplicity and effectiveness. However, the studies on transforming polycrystalline foil into large-area single-crystal foil mainly focus on the influence of annealing temperature and strain energy on the recrystallization process of copper foil, while studies on the effect of annealing atmosphere on abnormal grain growth behavior are relatively rare.

Tunable dual-band and high-quality-factor perfect absorption based on VO-assisted metasurfaces.

Perfect absorbers with high quality factors (Q-factors) are of great practical significance for optical filtering and sensing. Moreover, tunable multiwavelength absorbers provide a multitude of possibilities for realizing multispectral light intensity manipulation and optical switches. In this study, we demonstrate the use of vanadium dioxide (VO)-assisted metasurfaces for tunable dual-band and high-quality-factor perfect absorption in the mid-infrared region.

Multi-band on-chip photonic spin Hall effect and selective excitation of whispering gallery modes with metasurface-integrated microcavity.

We propose an approach to realize a multi-band on-chip photonic spin Hall effect and selective excitation of whispering gallery modes (WGMs) by integrating metasurfaces with microcavities. Free-space circularly polarized light with opposite spin angular momentum can effectively excite WGMs with opposite propagation directions at fixed wavelengths. Moreover, the different WGMs with different propagation directions and polarizations can be selectively excited by manipulating the number of antennas.

Dielectric Resonance-Based Optical Metasurfaces: From Fundamentals to Applications.

Optical metasurface as a booming research field has put forward profound progress in optics and photonics. Compared with metallic-based components, which suffer from significant thermal loss and low efficiency, high-index all-dielectric nanostructures can readily combine electric and magnetic Mie resonances together, leading to efficient manipulation of optical properties such as amplitude, phase, polarization, chirality, and anisotropy. These advances have enabled tremendous developments in practical photonic devices that can confine and guide light at the nanoscale.

Batch production of uniform graphene films via controlling gas-phase dynamics in confined space.

Batch production of continuous and uniform graphene films is critical for the application of graphene. Chemical vapor deposition (CVD) has shown great promise for mass producing high-quality graphene films. However, the critical factors affected the uniformity of graphene films during the batch production need to be further studied.

Vortical Reflection and Spiraling Fermi Arcs with Weyl Metamaterials.

Scatterings and transport in Weyl semimetals have caught growing attention in condensed matter physics, with observables including chiral zero modes and the associated magnetoresistance and chiral magnetic effects. Measurement of electrical conductance is usually performed in these studies, which, however, cannot resolve the momentum of electrons, preventing direct observation of the phase singularities in scattering matrix associated with Weyl point. Here we experimentally demonstrate a helical phase distribution in the angle (momentum) resolved scattering matrix of electromagnetic waves in a photonic Weyl metamaterial.

Spin-Selective Full-Dimensional Manipulation of Optical Waves with Chiral Mirror.

Realizing arbitrary manipulation of optical waves, which still remains a challenge, plays a key role in the implementation of optical devices with on-demand functionalities. However, it is hard to independently manipulate multiple dimensions of optical waves because the optical dimensions are basically associated with each other when adjusting the optical response of the devices. Here, the concise design principle of a chiral mirror is utilized to realize the full-dimensional independent manipulation of circular-polarized waves.

Metasurface-Empowered Optical Multiplexing and Multifunction.

Metasurfaces are planar photonic elements composed of subwavelength nanostructures, which can deeply interact with light and exploit new degrees of freedom (DOF) to manipulate optical fields. In the past decade, metasurfaces have drawn great interest from the scientific community due to their profound potential to arbitrarily control light. Here, recent developments of multiplexing and multifunctional metasurfaces, which enable concurrent tasks through a dramatic compact design, are reviewed.

Giant spin-selective asymmetric transmission in multipolar-modulated metasurfaces.

Spin-selective manipulation of optical waves is widely utilized in various optical techniques and plays a key role in modern nanophotonics. While numerous efficient approaches have been applied in metasurfaces to realize spin-selective manipulation of optical waves, the implementation of giant spin-selective asymmetric transmission remains a challenge. Here, we propose an all-dielectric metasurface to realize giant tri-band spin-selective asymmetric transmission in the near infrared regime.

Energy-Tailorable Spin-Selective Multifunctional Metasurfaces with Full Fourier Components.

Compact integrated multifunctional metasurface that can deal with concurrent tasks represent one of the most profound research fields in modern optics. Such integration is expected to have a striking impact on minimized optical systems in applications such as optical communication and computation. However, arbitrary multifunctional spin-selective design with precise energy configuration in each channel is still a challenge, and suffers from intrinsic noise and complex designs.

Ultrastiff, Strong, and Highly Thermally Conductive Crystalline Graphitic Films with Mixed Stacking Order.

A macroscopic film (2.5 cm × 2.5 cm) made by layer-by-layer assembly of 100 single-layer polycrystalline graphene films is reported.

From Single-Dimensional to Multidimensional Manipulation of Optical Waves with Metasurfaces.

Metasurfaces, 2D artificial arrays of subwavelength elements, have attracted great interest from the optical scientific community in recent years because they provide versatile possibilities for the manipulation of optical waves and promise an effective way for miniaturization and integration of optical devices. In the past decade, the main efforts were focused on the realization of single-dimensional (amplitude, frequency, polarization, or phase) manipulation of optical waves. Compared to the metasurfaces with single-dimensional manipulation, metasurfaces with multidimensional manipulation of optical waves show significant advantages in many practical application areas, such as optical holograms, sub-diffraction imaging, and the design of integrated multifunctional optical devices.

Ultrahighly Saturated Structural Colors Enhanced by Multipolar-Modulated Metasurfaces.

Colors with high saturation are of prime significance for display and imaging devices. So far, structural colors arising from all-dielectric metasurfaces, particularly amorphous silicon and titanium oxide, have exceeded the gamut of standard RGB (sRGB) space. However, the excitation of higher-order modes for dielectric materials hinders the further increase of saturation.

Hybrid graphene heterojunction photodetector with high infrared responsivity through barrier tailoring.

The graphene/Si heterojunction is attractive for high gain and broadband photodetection through photogating effect. However, the photoresponsivity in these devices are still limited to under 1 A W if no narrowband absorption-enhanced nanostructures were used. In this paper, the effects of barriers on photoresponse are systematically studied at 1550 nm wavelength.

Conductivity mapping of graphene on polymeric films by terahertz time-domain spectroscopy.

Fast inline characterization of the electrical properties of graphene on polymeric substrates is an essential requirement for quality control in industrial graphene production. Here we show that it is possible to measure the sheet conductivity of graphene on polymer films by terahertz time-domain spectroscopy (THz-TDS) when all internally reflected echoes in the substrate are taken into consideration. The conductivity measured by THz-TDS is comparable to values obtained from four point probe measurements.

Folding Large Graphene-on-Polymer Films Yields Laminated Composites with Enhanced Mechanical Performance.

A folding technique is reported to incorporate large-area monolayer graphene films in polymer composites for mechanical reinforcement. Compared with the classic stacking method, the folding strategy results in further stiffening, strengthening, and toughening of the composite. By using a water-air-interface-facilitated procedure, an A5-size 400 nm thin polycarbonate (PC) film is folded in half 10 times to a ≈0.