Light, science & applications最新文献

Superradiance, an enhanced radiation phenomenon stemming from the phase synchronization of emitters, features a radiation intensity proportional to the number of emitters squared. The pursuit of superradiance from free electrons has long been a goal for generating intense radiation across a broad spectrum, from terahertz (THz) to the X-ray regime. However, achieving superradiance in the THz spectral range has been hindered by the lack of effective microbunching techniques. Here, we demonstrate an ultra-widely tunable superradiant THz free-electron laser (FEL) driven by high-peak-current electron microbunch trains. The emission efficiency is substantially improved as the ultra-short electron microbunches emit in phase and engage in strong interactions with the generated THz waves within the undulator. We further demonstrate that the implementation of a tapered undulator configuration leads to a two-fold enhancement in emission intensity compared to the non-tapered case, elevating the pulse energy of the narrow-band THz radiation to the millijoule level in a one-meter-long undulator. This experimental breakthrough represents a critical step toward realizing a compact, high-power, narrow-band THz source capable of fully bridging the 'THz gap' and will unlock numerous opportunities across a wide range of scientific disciplines.

Mott insulators are a unique class of materials whose insulating state originates from strong electron-electron correlations: the interactions localize charge carriers, and the resulting on-site Coulomb repulsion opens a charge gap, fundamentally different from conventional insulators, making these systems an exceptional platform for exploring exotic physical phenomena. Significantly, the interplay between strong correlations and charge transfer not only stabilizes the antiferromagnetic ground state but also endows the material with enriched properties, particularly in optics. Herein, we demonstrate a 2D antiferromagnetic charge-transfer Mott insulator, Vanadium Oxychloride (VOCl), which shows giant third-harmonic generation (THG) anisotropy (ρ_THG = I_x/I_y, where I_x and I_y represent the THG intensities corresponding to the excitation polarization parallel to crystal's x- and y-axes), with ρ_THG reaching up to 187 at 1280 nm excitation wavelength. Notably, it is the highest THG anisotropic ratio within the van der Waals materials family. The nonlinear anisotropy is further modulated across a broadband infrared (IR) excitation wavelength range from 2028 to 1280 nm, during which ρ_THG rises from 2.6 to 187, corresponding to a 72-fold enhancement relative to its value at 2028 nm. Additionally, VOCl demonstrates layer-independent third-order susceptibilities (χ⁽³⁾ ~ 10^-19 m²/V²) and band structures attributed to its extremely weak interlayer electronic coupling. Moreover, the colossal THG anisotropic ratio in 2D VOCl can be ascribed to the synergistic effect of the correlated charge-transfer Mott insulator behavior and intrinsic C₃ symmetry breaking, as supported by theoretical calculations. The colossal nonlinear optical anisotropy in 2D VOCl positions it as an excellent candidate for nanophotonic and optoelectronic applications, enabling next-generation nanodevices based on 2D correlated Mott insulators.

Inspired by the snake pit organ's remarkable ability to perceive mid-wave infrared (MWIR) radiation, researchers have developed a biomimetic artificial vision system that integrates infrared-to-visible upconverters with CMOS sensors. Operating at room temperature, this platform enables direct visualization of both short-wave infrared (SWIR) and MWIR, marking a pioneering demonstration of broadband infrared imaging with high resolution. Such a breakthrough paves the way for low-cost and flexible applications in night vision, agricultural monitoring, industrial inspection, and beyond.

GeS₂, a layered a wide bandgap van der Waals material, is now found to exhibit record-high refractive index and extreme optical anisotropy across blue and near-ultraviolet bands, promising bright future for short-wavelength photonics.

Narrow linewidth stabilized lasers are central to precision applications that operate across the visible to short-wave infrared wavelengths, including optical clocks, quantum sensing and computing, ultra-low noise microwave generation, and fiber sensing. Today, these spectrally pure sources are realized using multiple external cavity tabletop lasers locked to bulk-optic free-space reference cavities. Integration of this technology will enable portable precision applications with improved reliability and robustness. Here, we report wavelength-flexible design and operation, over more than an octave span, of an integrated coil-resonator-stabilized Brillouin laser architecture. Leveraging a versatile two-stage noise reduction approach, we achieve low linewidths and high stability with chip-scale laser designs based on the ultra-low-loss, CMOS-compatible silicon nitride platform. We report operation at 674 and 698 nm for applications to strontium neutral and trapped-ion clocks, quantum sensing and computing, and at 1550 nm for applications to fiber sensing and ultra-low phase noise microwave generation. Over this range we demonstrate frequency noise reduction from 1 to 10 MHz resulting in 1.0-17 Hz fundamental and 181-630 Hz integral linewidths and an Allan deviation of 6.5 × 10^-13 at 1 ms for 674 nm, 6.0 × 10^-13 at 15 ms for 698 nm, and 2.6 × 10^-13 at 15 ms for 1550 nm. This work demonstrates the lowest fundamental and integral linewidths and highest stability achieved to date for stabilized Brillouin lasers with integrated coil-resonator references, with over an order of magnitude improvement in the visible wavelength range. These results unlock the potential of integrated, ultra-low-phase-noise stabilized lasers for precision applications and further integration in systems-on-chip solutions.

Holography has emerged as a vital platform for three-dimensional displays, optical encryption, and photonic information processing, leveraging diverse physical dimensions of light such as wavelength, polarization, and orbital angular momentum (OAM) to expand multiplexing capacity. However, the exhaustive utilization of these intrinsic degrees of freedom has saturated the parameter space for holographic encoding, leaving no room for further scalability. Here, we demonstrate an OAM multiplication operator enabled holographic multiplexing. We engineer the operator-specific hologram that selectively responds to the predefined operator pathway. Subsequent validation of orthogonality between distinct operator pathways ensures the multiplexing ability, thereby enabling the parallel encoding of multiple holographic images. In the experiment, we have successfully demonstrated a ninefold capacity enhancement over conventional OAM holography and a 2-bit operator-multiplexed hologram for high-security optical encryption. This work introduces operators as a synthetic dimension beyond light's intrinsic properties into holography, unlocking a scalable and secure paradigm for ultrahigh-dimensional information technologies.

The anisotropy of perovskite nanoplatelets (PeNPLs) opens up many opportunities in optoelectronics, including enabling the emission of linearly polarized light. But the limited stability of PeNPLs is a pressing challenge, especially for red-emitting CsPbI₃. Herein, we address this limitation by alloying formamidinium (FA) into the perovskite cuboctahedral site. Unlike Cs/FA alloying in bulk thin films or nanocubes, FA incorporation in nanoplatelets requires meticulous control over the reaction conditions, given that nanoplatelets are obtained in kinetically-driven growth regimes instead of thermodynamically-driven conditions. Through in-situ photoluminescence (PL) measurements, we find that excess FA leads to uncontrolled growth, where phase impurities and nanoplatelets of multiple thicknesses co-exist. Restricting the FA content to up to 25% Cs substitution enables monodisperse PeNPLs, and increases the PL quantum yield (from 53% to 61%), exciton lifetime (from 18 ns to 27 ns), and stability in ambient air (from ~2 days to >7 days) compared to CsPbI₃. This arises due to hydrogen bonding between FA and the oleate and oleylammonium ligands, anchoring them to the surface to improve optoelectronic properties and stability. The reduction in non-radiative recombination, improvement in the nanoplatelet aspect ratio, and higher ligand density lead to FA-containing PeNPLs more effectively forming edge-up superlattices, enhancing the PL degree of linear polarization from 5.1% (CsPbI₃) to 9.4% (Cs_0.75FA_0.25PbI₃). These fundamental insights show how the stability limitations of PeNPLs could be addressed, and these materials grown more precisely to improve their performance as polarized light emitters, critical for utilizing them in next-generation display, bioimaging, and communications applications.

Plasmonic metasurfaces supporting high-quality (Q) resonances offer unprecedented ways for controlling light-matter interaction at the nanoscale, yet scalable fabrication of such sophisticated nanostructures still relies on expensive and multi-step fabrication routes, hindering their practical application. Here, we produced plasmonic metasurfaces composed of the regular arrangement of hollow protruding nanobumps via direct femtosecond laser patterning of thin gold films. By using comprehensive optical modeling, infrared spectroscopy and angle-resolved third harmonic generation experiments, we justified that such laser-printed nanostructures support symmetry-protected plasmonic quasi-bound states in the continuum (qBIC) with a measured Q-factor up to 20. Moreover, under critical coupling conditions that match the radiative and nonradiative losses of the high-Q mode, the metasurfaces demonstrate the third harmonic generation enhanced by a factor of ≈10⁵ as compared to the smooth Au film benchmark, proving structure efficiency for nonlinear conversion. Finally, by taking advantage of the simplicity and straightforward character of the laser printing process, we realized a field-effect transistor device with HgTe quantum dots as an active medium and qBIC-supporting plasmonic metasurface imprinted over drain and source electrodes. The resulting metasurface-empowered device operates at 200 K and 5 V bias voltage and demonstrates superior specific detectivity around 8.7 × 10¹¹ at the plasmonic-qBIC spectral region and fast response time, holding promise for the realization of advanced shortwave infrared photodetectors.

The first measurement of attosecond pulses in 2001 unleashed a new wave of exploration in the microcosmic world. The pulse width has since shrunk from an initial 650 to 43 as, and the flux, photon energy, and repetition rates have progressively been raised. The performance of attosecond pulses hinges upon the driving lasers, whose rapid development underlaid many advancements of attosecond technology. Yet the expansion of new applications in attosecond science demands driving lasers with ever better performance. Beginning with the fundamental principles of attosecond pulse generation and applications, this article reviews the evolution and trend of the driving lasers in terms of pulse energy, pulse width, wavelength, and repetition rate.

Integrated photonics has emerged as a promising alternative for data communication and computing, ferroelectric BaTiO₃ (BTO) stands out for its exceptional electro-optic response among candidate materials. However, direct epitaxial growth of BTO entails a fundamental trade-off: substrates with low refractive index are required for strong optical confinement, yet those with large lattice mismatch degrade film crystalline quality and electro-optic performance. We report a buffer-free, strain-engineered approach to integrate high-performance BTO thin films directly on LaAlO₃-Sr₂TaAlO₆ (LSAT) oxide-insulator substrates. By exploiting a self-buffer layer formed during the initial growth stage, we achieve periodic in-plane strain modulation that stabilizes a polymorphic phase boundary with orthorhombic polar nanoregions, yielding a Pockels coefficient exceeding 358 pm V⁻¹ and a Curie temperature raised to 200 °C. Leveraging this material platform, we demonstrate the first realization of a Mach-Zehnder modulator using epitaxial BTO on LSAT. The device exhibits a half-wave voltage-length product of 0.7 V cm at 1550 nm, which closely matches finite-element simulations, and supports a 6-dB electro-optic bandwidth of 28 GHz. Our results validate BTO on LSAT as a viable photonic platform for scalable, low-voltage and high-speed modulators.