Light, science & applications最新文献

Recent work on Al₂O₃:Cr³⁺ introduces a compelling mechanoluminescence platform based on a simple oxide, highlighting dopant-localized emission driven by stress-induced carrier dynamics at Cr centers. This advances a shift from bulk-mediated processes to dopant-centered carrier dynamics, enabling more rational and precise materials design. However, the origin of carrier separation required for dopant ionization remains to be clarified, particularly regarding the role of interfacial and heterojunction-induced fields; addressing these aspects may rapidly establish a more comprehensive understanding of the coupled mechanisms involving localized excitation and field-assisted carrier modulation.

Optically addressable solid-state spin defects are essential platforms for quantum sensing and information processing. Recently, single spin defects with combined S = 1 and S = ½ spin transitions were discovered in hexagonal boron nitride (hBN). In this work we unveil their excitation dynamics. In particular, we study the effects of the excitation wavelength on the spin-dependent fluorescence and the spin dynamics of these peculiar quantum spin defects. We find that changing the excitation wavelength leads to a threefold enhancement in both the optically detected magnetic resonance (ODMR) contrast and the corresponding magnetic field sensitivity. In addition, we find that the excitation wavelength has a strong impact on the photodynamics of spin complex emitters. Our work presents valuable insights to the mechanistic understanding of spin complex emitters in hBN and highlights the importance of excitation wavelength for optimising their performance in quantum sensing and quantum technologies.

Extending the excitation and emission wavelengths into the red or even near-infrared region is a highly challenging yet scientifically valuable research topic in the field of organic afterglow materials. To solve this issue, we put forward a twisted intramolecular charge transfer dopant molecule design strategy, in which long-lived electron-deficient dopant is decorated with electron-rich substituent. In this way, the orbital energy level of the dopant can be lowered while maintaining the compatibility with the host. Benefiting from the twisted molecular conformation and small energy gap, the obtained dopant (CN) shows visible-light-excited afterglow with various performance (decay path, lifetime, emission wavelength) when doped into different matrices. Particularly, the maximum excitation wavelength extends to 567 nm and tails to 700 nm when CN is doped into benzophenone matrix. More importantly, the maximum emission wavelength of the afterglow extends to 725 nm (τ = 67.82 ms). We also successfully apply this material in autofluorescence-free bioimaging. This work provides a viable molecular design strategy for developing red-light-excitable near-infrared afterglow materials and demonstrates their potential for in vivo bioimaging.

Organic emitters with narrowband emission characteristics demonstrate significant advantages and application potential in ultra-high-definition displays and multiplexed fluorescence imaging. However, the obstinate spectral broadening phenomenon upon aggregation limits the practical application of organic narrowband emissive materials. Here, a referable strategy on conformation engineering is proposed in a central 8π-electron system with narrowband emissions in both solution and aggregate. Owing to the synergistic effect of strain-release-driven conformational planarity in ground state and excited-state aromaticity-driven planarity, PDBP-b,i exhibits minimal structural change between the S₀ and S₁ states, resulting in narrowband emission in solution with a full width at half maximum (FWHM) of 35 nm/0.24 eV. While in aggregate, the cross dipole stacking mode further confines molecular conformation and restricts high-frequency vibration, additionally narrowing with a record-small FWHM of 13 nm/0.08 eV. The concept of aggregation-induced ultra-narrowband emission is proposed, which also offers advantages in electroluminescence to exhibit a small FWHM of 13 nm and remaining stable as the concentration increases. These results provide new insights and instructive guidance for the design of organic narrowband emitters.

3D image display is essential for next-generation volumetric imaging; however, dense depth multiplexing for 3D image projection remains challenging because diffraction-induced cross-talk rapidly increases as the axial image planes get closer. Here, we introduce a 3D display system comprising a digital encoder and a diffractive decoder, which simultaneously projects different images onto multiple target axial planes with high axial resolution. By leveraging multi-layer diffractive wavefront decoding and deep learning-based end-to-end optimization, the system achieves high-fidelity depth-resolved 3D image projection in a snapshot, enabling axial plane separations on the order of a wavelength. The digital encoder leverages a Fourier encoder network to capture multi-scale spatial and frequency-domain features from input images, integrates axial position encoding, and generates a unified phase representation that simultaneously encodes all images to be axially projected in a single snapshot through a jointly-optimized diffractive decoder. We characterized the impact of diffractive decoder depth, output diffraction efficiency, spatial light modulator resolution, and axial encoding density, revealing trade-offs that govern axial separation and 3D image projection quality. We further demonstrated the capability to display volumetric images containing 28 axial slices, as well as the ability to dynamically reconfigure the axial locations of the image planes, performed on demand. Finally, we experimentally validated a two-plane optical prototype using a single-layer physical decoder, demonstrating close agreement between the measured results and the target images. These results establish the diffractive 3D display system as a compact and scalable framework for depth-resolved snapshot 3D image projection, with potential applications in holographic displays, AR/VR interfaces, and volumetric optical computing.

Mid-infrared spectroscopy enables biochemical sensing by identifying vibrational molecular fingerprints, but it faces limitations in instrumentation portability and analytical sensitivity. Optical metasurfaces with strong mid-infrared photonic resonances provide an attractive solution towards on-chip spectrometry and sensitive molecular detection, yet their static nature hinders their anticipated impact. Here, we introduce and demonstrate dynamically tunable silicon membrane metasurfaces exhibiting high-Q transmissive resonances in the fingerprint region. By harnessing silicon's thermo-optical properties, we achieve continuous modulation of coupling-induced transparency (CIT) modes that emerge upon the interference of quasi-bound states in the continuum (q-BICs) and surface lattice modes (SLMs). We measure a spectral tuning rate of 0.06 cm^-1 K^-1 by continuously sweeping the sharp CIT resonances over a 23.5 cm^-1 spectral range across a temperature range of 300-700 K. In the current proof‑of‑concept implementation, the dynamic transmission control enables non-contact chemical analysis of polymer films by detecting characteristic absorption bands of polystyrene (1450 and 1492 cm^-1) and poly(methyl methacrylate) (1730 cm^-1) without requiring conventional spectrometers. When analyte molecules fill the metasurface-generated photonic cavities, we demonstrate vibrational strong coupling between the poly(methyl methacrylate)'s carbonyl band and the CIT mode, manifested in a Rabi splitting of ~43 cm^-1. Our results establish a new photonic platform that unites spectral precision, strong field enhancement, and reconfigurability, offering diverse potential for compact mid-infrared spectroscopy, molecular sensing, and programmable polaritonic photonics.

When light propagates through a flowing transparent fluid, the refractive index it experiences depends on its propagation direction relative to the flow direction. This leads to different phase delays for light traveling along or against the flow. The moving effect, which results from the cross-coupling between electric and magnetic responses in a specific way, is only detectable over a considerable distance within the moving medium, because the fluid's velocity is much smaller than the speed of light c in realistic systems. In the context of metamaterials - artificial subwavelength structures - it may be possible to manipulate electromagnetic fields to mimic the moving medium without physical motion. Here we demonstrate a passive metamaterial that achieves a significant synthetic moving effect. The metamaterial is composed of artificial metallic structures and gyromagnetic materials, and is meticulously designed based on symmetry and electromagnetic considerations to achieve significant pure bianisotropic moving coupling. Our experiment reveals for the first time a gigantic moving response of the metamaterial with an effective velocity reaching 0.3c. The inherent strong non-reciprocity of this moving response opens the door to a variety of photonic devices, like polarization-independent gyrators and isolators.

Capturing transient events on ultrafast time scales demands imaging at up to trillions of frames per second (Tfps). Yet leading methods, including compressed sensing-based photography, time-resolved shadowgraphy, and other active approaches, are limited by bulky optics, high cost, and repeated measurements. Here, we propose angular spectrum-encoded single-shot ultrafast photography (ASUP). ASUP combines the time-wavelength mapping of a chirped-pulse probe with dispersion-encoded angular spectrum information. The latter is realized by a multilayer dielectric thin-film photonic chip, inversely designed using a deep Q-network (DQN) reinforcement-learning framework. This chip performs pixel-level encoding without the need for bulky dispersive optics. An enhanced residual convolutional neural network with Transformer blocks then decodes the measurements to reconstruct high-fidelity ultrafast dynamics. In experiments, ASUP achieves 0.83 Tfps with six frames in a single exposure and captures picosecond laser-induced damage and plasma dynamics in metal films. ASUP delivers performance comparable to state-of-the-art ultrafast photography while remaining compact, highly integrated, and cost-effective. It overcomes key limitations of existing ultrafast imaging and offers a scalable solution for high-speed optical diagnostics, laser-matter interactions, and transient phenomena studies.

Optical fibres, owing to their ultra-low transmission loss, underpin global telecommunications. However, this remarkable low-loss performance has not been extended to integrated photonic devices, which are increasingly critical for data-intensive communications in the era of artificial intelligence (AI). Here, we translate the widely adopted mass-production process for fibre manufacturing-flame hydrolysis-to wafer-scale integrated photonics, and demonstrate ultrahigh-Q integrated microresonators. By leveraging high GeO₂ doping, the deposited germano-silicate (Ge:silica) films achieve full densification at moderate thermal budgets, while also allowing for a post-processing furnace-reflow technique that has the capability to both repair any etch-induced defects and enhance optical Q, leading to a high degree of process tolerance. When combined with deep-UV lithography, these films form microresonators exhibiting ultrahigh Q factors of up to 566 million at 1064 nm, corresponding to a waveguide propagation loss as low as 0.07 dB m^-1. Like their fibre counterparts, these devices exhibit a broad transmission window with Q factors surpassing 100 million demonstrated from the telecommunications band to the violet spectrum. Moreover, the width dependence of Q factor and a two-order-of-magnitude Q recovery enabled by the furnace reflow process are also demonstrated. This work extends high-quality, high-rate flame hydrolysis deposition (FHD) from optical fibre manufacturing to integrated photonics, establishing a scalable route towards fibre-level loss in photonic integrated circuits.