Light, science & applications最新文献

Single-pixel imaging (SPI) has long been recognized for its potential in spectral regions where conventional imaging sensors fall short, such as the near-infrared spectrum. Yet, despite its sensitivity, SPI and its complex-field variants have faced critical bottlenecks in speed and throughput, hindering their adoption for real-time applications. A recently proposed approach-frequency-comb acousto-optic coherent encoding (FACE)-places an important step in overcoming these barriers, delivering an unprecedented space-bandwidth-time product. By showcasing its versatility through several compelling proof-of-concept demonstrations in real-time complex-field microscopy, this advance paves the way for transformative progress in optical imaging beyond the visible spectrum. We discuss here advantages, challenges and potential future directions for scaling up this technology.

Gas sensing technology is widely applied in various fields, including environmental monitoring, industrial process control, medical diagnostics, safety warnings, and more. As a detection element, the quartz tuning fork (QTF) offers advantages such as high-quality factor (Q-factor), strong noise immunity, compact size, and low cost. Notably, its resonant characteristics significantly enhance system signal strength. Two spectroscopic techniques based on QTF detection, Quartz-enhanced photoacoustic spectroscopy (QEPAS) and light-induced thermoelastic spectroscopy (LITES), are currently research hotspots in the field of spectral sensing. This paper provides a comprehensive and detailed review and highlights pivotal innovations in these two QTF-based spectroscopic techniques. For QEPAS, these encompass high-power excitation methods, novel excitation sources, advanced QTF detection elements, and acoustic wave amplification strategies. Regarding LITES, the researches on optical cavity-enhanced approaches, modified QTF improvement mechanisms, integration with heterodyne demodulation technique, and combination with QEPAS were analyzed. These advances have enabled quartz-enhanced laser spectroscopy to achieve detection limits ranging from parts-per-billion (ppb) to parts-per-trillion (ppt) levels for trace gases such as methane (CH₄), acetylene (C₂H₂), carbon monoxide (CO), and so on. Additionally, prospects for future technological developments are also discussed in the concluding section.

Optical computing holds promise for high-speed, energy-efficient information processing, with diffractive optical networks emerging as a flexible platform for implementing task-specific transformations. A challenge, however, is the effective optimization and alignment of the diffractive layers, which is hindered by the difficulty of accurately modeling physical systems with their inherent hardware imperfections, noise, and misalignments. While existing in situ optimization methods offer the advantage of direct training on the physical system without explicit system modeling, they are often limited by slow convergence and unstable performance due to inefficient use of limited measurement data. Here, we introduce a model-free reinforcement learning approach utilizing Proximal Policy Optimization (PPO) for the in situ training of diffractive optical processors. PPO efficiently reuses in situ measurement data and constrains policy updates to ensure more stable and faster convergence. We validated our method through both simulations and experiments across a range of in situ learning tasks, including targeted energy focusing through a random diffuser, image generation, aberration correction, and optical image classification, demonstrating in each task better convergence and performance. Our strategy operates directly on the physical system and naturally accounts for unknown real-world imperfections, eliminating the need for prior system knowledge or modeling. By enabling faster and more accurate training under realistic experimental constraints, this in situ reinforcement learning approach could offer a scalable framework for various optical and physical systems governed by complex, feedback-driven dynamics.

X-ray scattering has been an indispensable tool in advancing our understanding of matter, from the first evidence of the crystal lattice to recent discoveries of nuclei's fastest dynamics. In addition to the lattice, ultrafast resonant elastic scattering of soft X-rays provides a sensitive probe of charge, spin, and orbital order with unparalleled nanometre spatial and femto- to picosecond temporal resolution. However, the full potential of this technique remains largely unexploited due to its high demand on the X-ray source. Only a selected number of instruments at large-scale facilities can deliver the required short-pulsed and wavelength-tunable radiation, rendering laboratory-scale experiments elusive so far. Here, we demonstrate time-resolved X-ray scattering with spectroscopic contrast at a laboratory-based instrument using the soft-X-ray radiation emitted from a laser-driven plasma source. Specifically, we investigate the photo-induced response of magnetic domains emerging in a ferrimagnetic FeGd heterostructure with 9 ps temporal resolution. The achieved sensitivity allows for tracking the reorganisation of the domain network on pico- to nanosecond time scales in great detail. This instrumental development and experimental demonstration break new ground for studying material dynamics in a wide range of laterally ordered systems in a flexible laboratory environment.

Free-space optical communication (FSOC) enables high-speed, secure, and scalable data transmission, with great potential for space-ground networks. However, existing FSOC systems predominantly employ point-to-point transmitters, each requiring bulky beam steering devices with complex control mechanisms, which severely limits their feasibility for multi-node micro-platform applications. Here, to address such a challenge, we propose a novel point-to-multipoint FSOC scheme based on reconfigurable SiC gratings, which are directly fabricated in stretchable PDMS films via femtosecond laser-induced carbide precipitation. The reconfigurable SiC transmission gratings are with good transparency (~91.9% at 1550 nm), dynamic beam steering capability (hundred-milliradian level), and an ultralightweight design (single grating: 0.4 g). The SiC fringes are specially fabricated within the internally symmetric region of the PDMS film to mitigate the structure distortion during stress regulation, significantly enhancing the long-range transmission capability in degraded atmospheric channels. The system supports 1-to-7 and 1-to-9 dynamic optical communication for 1D and 2D configurations, respectively. In a state-of-the-art 225-meter outdoor experiment, the system achieves reliable 10 Gbps transmission for each node. This portable FSOC system overcomes the limitations of conventional systems, enabling scalable and flexible multibeam steering. This approach establishes a robust foundation for long-range, multinode, and high-capacity FSOC networks among spatial micro-platforms such as unmanned aerial vehicles and micro-satellites.

Cavity electro-optic (EO) modulation plays a pivotal role in optical pulse and frequency comb synthesis, supporting a wide range of applications including communication, computing, ranging, and quantum information. The ever-growing demand for these applications has driven efforts in enhancing modulation coupling strength and bandwidth towards advanced pulse-comb synthesis. However, the effects of strong-coupling and high-bandwidth cavity EO modulation remain underexplored, due to the lack of a general, unified model that captures this extreme condition. In this work, we present a universal framework for pulse-comb synthesis under cavity EO modulation, where coupling strength and modulation bandwidth far exceed the cavity's free spectral range (FSR). We show that, under such intense and ultrafast driving conditions, EO-driven frequency combs and pulses exhibit rich higher-order nonlinear dynamics, including temporal pulse compression and comb generation with arbitrary pump detuning. Leveraging this framework, we reveal a direct link between the higher-order dynamics of EO pulse-comb generation and the band structure of synthetic dimension. Furthermore, we demonstrate arbitrary comb shaping via machine-learning-based inverse microwave drive design, achieving a tenfold enhancement in cavity EO comb flatness by exploring the synergistic effects of high-bandwidth driving and detuning-induced frequency boundaries. Our findings push cavity EO modulation into a new frontier, unlocking significant potential for universal and machine-learning-programmable EO frequency combs, topological photonics, as well as photonic quantum computing in the strong-coupling and high-bandwidth regimes.

Building a sensitive magnetic field sensor is non-trivial; building a more sensitive one by adding extra loss to the sensor is counterintuitive, but with innovative ideas from non-Hermitian physics like an exceptional point, a new magnetic field sensor first of its kind paves the way for broader applications of similar techniques.

With the rapid advancement of the information age, the demand for multi-dimensional light information detection has significantly increased. Traditional Fourier-transform infrared (FTIR) spectrometers and pooptical power, andlarimeters, due to their bulky structure, are no longer suitable for emerging fields such as medical diagnostics, secure communications, and autonomous driving. As a result, there is a pressing need to develop new miniaturized on-chip devices. The abundant two-dimensional (2D) materials, with their unique light-matter interactions, offer the potential to construct high-dimensional spatial mappings of incident light, paving the way for the development of novel ultra-compact multi-dimensional deep optical sensing technologies. Here, we review the interconnections of multi-dimensional information and their relationship with 2D materials. We then focus on recent advances in the development of novel dimensional detectors based on 2D materials, covering dimensions such as intensity, time, space, polarization, phase angle, and wavelength. Furthermore, we discuss cutting-edge technologies in multi-dimensional fusion detection and highlight future technological prospects, with a particular emphasis on on-chip integration and future development.

Orbital angular momentums (OAMs) of light can be categorized into longitudinal OAM (L-OAM) and transverse OAM (T-OAM). Light carrying time-varying L-OAM, known as self-torqued light, was recently discovered during harmonic generation and has been extensively developed within the context of optical frequency combs (OFCs). Meanwhile, ultrafast bursts of optical pulses, analogous to OFCs, are sought for various light-matter interaction, spectroscopic and nonlinear applications^1-6. However, achieving transiently switchable T-OAM of light on request, namely spatiotemporal vortex pulse bursts, with independently controlled spatiotemporal profile of each comb teeth, remains unrealized thus far. In this work, the experimental generation of spatiotemporal vortex bursts featured with controllable time-dependent characteristics is reported. The resultant bursts comprised of spatiotemporal optical vortex comb teeth have picosecond timescale switchable T-OAMs with defined arrangement. We also show ultrafast control of T-OAM chirality, yielding pulse bursts with staggered azimuthal local momentum density, resembling Kármán vortex streets. This approach enables the tailoring of more intricate spatiotemporal wavepacket bursts, such as high-purity modes variation in both radial and azimuthal quantum numbers of spatiotemporal Laguerre-Gaussian wavepackets over time, which may facilitate a host of novel applications in ultrafast light-matter interactions, high-dimensional quantum entanglements, space-time photonic topologies as well as spatiotemporal metrology and photography.