Beam Shaping by Stacked Nonlinear Moiré Metasurfaces.

Moiré phenomena provide a versatile platform for creating tunable lattices with variable symmetries and periodicities, making them a focal topic in recent photonics research. Moiré photonic devices fused with metasurfaces have demonstrated numerous novel functionalities, yet fabricating moiré metasurfaces, particularly in stacked configurations, poses significant challenges. In this paper, we present an innovative nanofabrication approach for stacked nonlinear moiré metasurfaces, using a focused ion beam-assisted nanostructure transfer-welding technique.

Nonuniform Wave Momentum Band Gap in Biaxial Anisotropic Photonic Time Crystals.

Photonic time crystals (PTCs) host momentum band gaps, enabling intriguing nonresonant light amplification in propagating waves, but opening substantial band gaps demands refractive index changes too extreme for conventional nonlinear optics. Here, we introduce momentum band gaps for nonuniform waves, including evanescent and ghost types, by extending PTCs to biaxial anisotropic photonic time crystals that periodically alternate between uniform biaxial anisotropy and isotropic media over time. We show that ghost waves, unlike evanescent waves, sustain only momentum band gaps, opening wide band gaps at even the smallest modulation depths.

Smith-Purcell Radiation in Two Dimensions.

Smith-Purcell radiation (SPR) is an electromagnetic radiation generated by the motion of free electrons in close to a periodic structure. Over the past 70 years, there has been significant interest in the generation of light in three-dimensional (3D) free space through SPR. Here, by using the interaction between moving electrons and a designed metallic nanoaperture array, the observation of two-dimensional (2D) SPR, e.

Topological orbital angular momentum extraction and twofold protection of vortex transport.

Vortex phenomena are ubiquitous in nature. In optics, despite the availability of numerous techniques for vortex generation and detection, topological protection of vortex transport with desired orbital angular momentum (OAM) remains a challenge. Here, by use of topological disclination, we demonstrate a scheme to confine and guide vortices featuring arbitrary high-order charges.

Lithium niobate thin film electro-optic modulator.

The linear electro-optic effect offers a valuable means to control light properties via an external electric field. Lithium niobate (LN), with its high electro-optic coefficients and broad optical transparency ranges, stands out as a prominent material for efficient electro-optic modulators. The recent advent of lithium niobate-on-insulator (LNOI) wafers has sparked renewed interest in LN for compact photonic devices.

High Defect Tolerance Breaking the Design Limitation of Full-Spectrum Multimodal Luminescence Materials.

With the development of optical anti-counterfeiting and the increasing demand for high-level information encryption, multimodal luminescence (MML) materials attract much attention. However, the discovery of these multifunctional materials is very accidental, and the versatile host suitable for developing such materials remains unclear. Here, a grossite-type fast ionic conductor CaGaO, characterized by layered and tunnel structure with excellent defect tolerance, is found to meet the needs of various luminescent processes.

Nonlinear optical physics at terahertz frequency.

Terahertz (THz) waves have exhibited promising prospects in 6G/7G communications, sensing, nondestructive detection, material modulation, and biomedical applications. With the development of high-power THz sources, more and more nonlinear optical effects at THz frequency and THz-induced nonlinear optical phenomena are investigated. These studies not only show a clear physics picture of electrons, ions, and molecules but also provide many novel applications in sensing, imaging, communications, and aerospace.

Study on the optical mechanism of photorefractive resistance in Zr-doped lithium niobate crystals from first-principle calculations.

Lithium niobate on insulator (LNOI) has attracted widespread interest due to the excellent optical performance of lithium niobate crystals and the integration characteristics of thin film devices. With the improvement of the integration level of photonic integrated chips and the increase in light intensity inside the chip, the impact of optical damage in LNOI on-chip performance has attracted attention. One effective way to suppress the optical damage of lithium niobate is to dope it with Zr to form LiNbO (LiNbO:Zr), which is famous for its high resistance to optical damage from ultraviolet to visible spectrum.

Abruptly autofocused electron beam generation through electron-plasmon interactions.

Electron Airy beams and electron vortex beams are commonly generated using phase masks that imprint a transverse modulation on the particle wave function. Plasmons sustained by nanostructured conductors facilitate substantial interactions with free electrons, enabling considerable transverse modulation of the electron wave function. Consequently, electron Airy and vortex beams can also be produced through interactions between electrons and structured plasmonic fields.

High-efficiency second-harmonic generation in reverse-polarization dual-layer lithium niobate waveguides.

Second-harmonic (SH) generation is an important way to generate short-wavelength light sources. Thin-film lithium niobate (TFLN) resonators and waveguides featuring tight light confinement are flexible to realize mode- or quasi-phase-matching (MPM or QPM) and thus efficient SH generation. Here, we report an efficient SH with an absolute conversion efficiency of 45% in a reverse-polarized double-layer TFLN waveguide.

Super-resolution microscopy unveils the nanoscale organization and self-limiting clustering of CD47 in human erythrocytes.

The transmembrane protein CD47, an innate immune checkpoint protein, plays a pivotal role in preventing healthy erythrocytes from immune clearance. Our study utilized stochastic optical-reconstruction microscopy (STORM) and single-molecule analysis to investigate the distribution of CD47 on the human erythrocyte membrane. Contrary to previous findings in mouse erythrocytes, we discovered that CD47 exists in randomly distributed monomers rather than in clusters across the human erythrocyte membrane.

Electro-Optic Response of Polymer-Stabilized Cholesteric Liquid Crystals with Different Polymer Concentrations.

Polymer-stabilized cholesteric liquid crystals (PSCLCs) have emerged as promising candidates for one-dimensional photonic lattices that enable precise tuning of the photonic band gap (PBG). This work systematically investigates the effect of polymer concentrations on the AC electric field-induced tuning of the PBG in PSCLCs, in so doing it explores a range of concentrations and provides new insights into how polymer concentration affects both the stabilization of cholesteric textures and the electro-optic response. We demonstrate that low polymer concentrations (≈3 wt.

Optical vortex ladder via Sisyphus pumping of Pseudospin.

Robust high-order optical vortices are much in demand for applications in optical manipulation, optical communications, quantum entanglement and quantum computing. However, in numerous experimental settings, a controlled generation of optical vortices with arbitrary orbital angular momentum remains a challenge. Here, we present a concept of "optical vortex ladder" for the stepwise generation of optical vortices through Sisyphus pumping of pseudospin modes in photonic graphene.

Giant Kerr nonlinearity of terahertz waves mediated by stimulated phonon polaritons in a microcavity chip.

Optical Kerr effect, in which input light intensity linearly alters the refractive index, has enabled the generation of optical solitons, supercontinuum spectra, and frequency combs, playing vital roles in the on-chip devices, fiber communications, and quantum manipulations. Especially, terahertz Kerr effect, featuring fascinating prospects in future high-rate computing, artificial intelligence, and cloud-based technologies, encounters a great challenge due to the rather low power density and feeble Kerr response. Here, we demonstrate a giant terahertz frequency Kerr nonlinearity mediated by stimulated phonon polaritons.

Bulk photovoltaic effect in ferroelectric nematic liquid crystals.

The bulk photovoltaic (BPV) effect in ferroelectric liquid crystals is of increasing scientific interest owing to its great potential for light-energy conversion. The ferroelectric nematic phase exhibits a huge spontaneous polarization that can be aligned to a preferred direction. In this Letter, we investigate the tensorial properties of the BPV effect in the planarly aligned ferroelectric nematic phase of the liquid crystalline material RM734.

Omni-polarized Faraday isolator based on non-Hermitian Faraday system.

Non-Hermitian systems have recently attracted significant attention in photonics due to the realization that the interplay between gain and loss can lead to entirely new and unexpected features. Here, we propose and demonstrate a non-Hermitian Faraday system capable of non-reciprocal omni-polarizer action at the exceptional point. Notably, both forward and backward propagating light with arbitrary polarization converge to the same polarization state.

Transient cavity-cavity strong coupling at terahertz frequency on LiNbO chips.

Terahertz (THz) microcavities have garnered considerable attention for their ability to localize and confine THz waves, allowing for strong coupling to remarkably enhance the light-matter interaction. These properties hold great promise for advancing THz science and technology, particularly for high-speed integrated THz chips where transient interaction between THz waves and matter is critical. However, experimental study of these transient time-domain processes requires high temporal and spatial resolution since these processes, such as THz strong coupling, occur in several picoseconds and microns.

Collective Cell Radial Ordered Migration in Spatial Confinement.

Collective cells, a typical active matter system, exhibit complex coordinated behaviors fundamental for various developmental and physiological processes. The present work discovers a collective radial ordered migration behavior of NIH3T3 fibroblasts that depends on persistent top-down regulation with 2D spatial confinement. Remarkably, individual cells move in a weak-oriented, diffusive-like rather than strong-oriented ballistic manner.

Electro-Optical Comb Envelope Engineering Based on Mode Crossing.

Resonator-enhanced electro-optical (EO) combs could generate a series of comb lines with high coherence and stability. Recently, EO comb based on thin-film lithium niobate (TFLN) has begun to show great potential thanks to the high second-order nonlinearity coefficient of lithium niobate crystal. Here we demonstrate that EO comb envelope engineering based on mode crossing induced a quality factor reduction in the TFLN racetrack microcavity both in the numerical simulation and experiment.

Frequency modulation of terahertz microcavity via strong coupling with plasmonic resonators.

Tunable terahertz (THz) microcavities are crucial for the compact on-chip THz devices, aiming to future cloud-based computing, and artificial-intelligence technologies. However, the solutions to effectively modulate THz microcavities remain elusive. Strong coupling has been widely demonstrated in many configurations at different ambient conditions to date and may serve as a promising tool to modulate THz microcavities.

Electrically Tunable Two-Color Cholesteric Laser.

Two-color lasing emission from an asymmetric structure, consisting of two dye-doped cholesteric liquid crystal (DD-CLC) layers separated by a transparent interlayer, is demonstrated. The DD-CLC mixtures have different reflection bands with long-wavelength band edges located at the green and red wavelengths of the visible spectrum, respectively. For the laser action, the CLC hosts provide the feedback, and the fluorescent laser dyes represent the active medium.

Equilibrium Dynamics of Mutually Confined Waves with Signed Analogous Masses.

We report the first experimental realization of equilibrium dynamics of mutually confined waves with signed analogous masses in an optical fiber. Our Letter is mainly demonstrated by considering a mutual confinement between a soliton pair and a dispersive wave experiencing opposite dispersion. The resulting wave-packet complex is found robust upon random perturbation and collision with other waves.

4D Additive-Subtractive Manufacturing of Shape Memory Ceramics.

The development of high-temperature structural materials, such as ceramics, is limited by their extremely high melting points and the difficulty in building complicated architectures. Four-dimensional (4D) printing helps enhance the geometrical flexibility of ceramics. However, ceramic 4D printing systems are limited by the separate processes for shape and material transformations, low accuracy of morphing systems, low resolution of ceramic structures, and their time-intensive nature.

Photonic Realization of a Generic Type of Graphene Edge States Exhibiting Topological Flat Band.

Cutting a honeycomb lattice (HCL) ends up with three types of edges (zigzag, bearded, and armchair), as is well known in the study of graphene edge states. Here, we propose and demonstrate a distinctive twig-shaped edge, thereby observing new edge states using a photonic platform. Our main findings are (i) the twig edge is a generic type of HCL edge complementary to the armchair edge, formed by choosing the right primitive cell rather than simple lattice cutting or Klein edge modification; (ii) the twig edge states form a complete flat band across the Brillouin zone with zero-energy degeneracy, characterized by nontrivial topological winding of the lattice Hamiltonian; (iii) the twig edge states can be elongated or compactly localized at the boundary, manifesting both flat band and topological features.