Ultrafast lasers can produce, beyond single-pulse mode locking, a multitude of robust multi-pulse dynamics, including optical soliton molecules. Based on recent experimental advances using smart fiber lasers, this commentary addresses the open question of using soliton molecules as symbols for digital optical information.

X-ray free-electron lasers (XFELs) have revolutionized ultrafast science with exceptional spatiotemporal resolution, yet attosecond-level beam diagnostics face critical challenges. The article comments on PolariX TDS, a polarization-tunable X-band deflector developed by CERN, DESY, and PSI, which overcomes these limits by enabling multidimensional phase-space characterization with sub-femtosecond resolution.

The rapid advancement of artificial intelligence (AI) has significantly impacted photonics, creating a symbiotic relationship that accelerates the development and applications of both fields. From the perspective of AI aiding photonics, deep-learning methods and various intelligent algorithms have been developed for designing complex photonic structures, where traditional design approaches fall short. AI’s capability to process and analyze large data sets has enabled the discovery of novel materials, such as for photovoltaics, leading to enhanced light absorption and efficiency. AI is also significantly transforming the field of optical imaging with improved performance. In addition, AI-driven techniques have revolutionized optical communication systems by optimizing signal processing and enhancing the bandwidth and reliability of data transmission. Conversely, the contribution of photonics to AI is equally profound. Photonic technologies offer unparalleled advantages in the development of AI hardware, providing solutions to overcome the bottlenecks of electronic systems. The implementation of photonic neural networks, leveraging the high speed and parallelism of optical computing, demonstrates significant improvements in the processing speed and energy efficiency of AI computations. Furthermore, advancements in optical sensors and imaging technologies not only enrich AI applications with high-quality data but also expand the capabilities of AI in fields such as autonomous vehicles and medical imaging. We provide comprehensive knowledge and a detailed analysis of the current state of the art, addressing both challenges and opportunities at the intersection of AI and photonics. The multifaceted interactions between AI and photonics will be explored, illustrating how AI has become an indispensable tool in the development of photonics and how photonics, in turn, facilitates advancements in AI. Through a collection of case studies and examples, we underscore the potential of this interdisciplinary approach to drive innovation, proposing challenges and future research directions that could further harness the synergies between AI and photonics for scientific and technological breakthroughs.

In general relativity, a gravitational “white hole” is a hypothetical region of space that cannot be entered from outside. It is the reverse of a “black hole” from which light and information cannot escape. We report an optical device exhibiting intriguing similarities to these objects. It will either totally absorb (optical black hole) or totally reject (optical white hole) light of any wavelength, depending on its polarization. The device’s functionality is based on the formation of a standing wave from the wavefront of spatially coherent incident radiation. Interaction of the standing wave with a thin absorber enables coherent perfect absorption and transmission, whereas polarization sensitivity arises from the geometrical phase of the interfering beams. We provide experimental proof-of-principle demonstrations and show that the device operates as a black and white hole for orthogonal polarizations of the incident light. From a remote point, it will look similar to a gravitational black or white hole depending on the polarization of light. In principle, the optical black and white hole device can operate as a deterministic absorber or rejector throughout the entire electromagnetic spectrum. Broadband absorbers and rejectors can be useful for energy harvesting, detection, stealth technologies, and redistribution of light.

Single-shot volumetric fluorescence (SVF) imaging offers a significant advantage over traditional imaging methods that require scanning across multiple axial planes, as it can capture biological processes with high temporal resolution. The key challenges in SVF imaging include requiring sparsity constraints, eliminating depth ambiguity in the reconstruction, and maintaining high resolution across a large field of view. We introduce the QuadraPol point spread function (PSF) combined with neural fields, an approach for SVF imaging. This method utilizes a custom polarizer at the back focal plane and a polarization camera to detect fluorescence, effectively encoding the three-dimensional scene within a compact PSF without depth ambiguity. In addition, we propose a reconstruction algorithm based on the neural field technique that provides improved reconstruction quality compared with classical deconvolution methods. QuadraPol PSF, combined with neural fields, significantly reduces the acquisition time of a conventional fluorescence microscope by ∼20 times and captures a 100-mm3 cubic volume in one shot. We validate the effectiveness of both our hardware and algorithm through all-in-focus imaging of bacterial colonies on sand surfaces and visualization of plant root morphology. Our approach offers a powerful tool for advancing biological research and ecological studies.

X-ray free-electron lasers (FELs) are cutting-edge research instruments employed in multiple scientific fields capable of analyzing matter with unprecedented time and spatial resolutions. Time-resolved measurements of electron and photon beams are essential in X-ray FELs. Radiofrequency (RF) transverse deflecting structures (TDSs) with a fixed streaking direction are standard diagnostics to measure the temporal properties of the electron beams. If placed after the undulator of the FEL facility, TDSs can also be employed to reconstruct the power profile of the FEL pulses. We present measurements of an X-band RF TDS system with variable polarization with a resolution below one femtosecond. We show FEL power profile measurements with associated root mean square pulse durations as short as 300 attoseconds. The measurements have been carried out at Athos, the soft X-ray beamline of SwissFEL. Measurements with variable polarization and attosecond resolution are essential to characterize and optimize the electron beams in all its dimensions for all types of X-ray FEL experiments, in particular for ultrafast X-ray applications.

A fundamental challenge in endoscopy is how to fabricate a small fiber-optic probe that can achieve comparable function to devices with large, complicated optics. To achieve high resolution over an extended depth of focus (DOF), the application of needle-like beams has been proposed. However, existing methods for miniaturized needle-beam designs fail to adequately correct astigmatism and other monochromatic aberrations, limiting the resolution of at least one axis. Here, we describe an approach to realize freeform beam-shaping endoscopic probes via two-photon polymerization three-dimensional (3D) printing. We present a design achieving <8μm lateral resolution with a DOF of ∼800 μm. The probe has a diameter of <260 μm (without the torque coil and catheters) and is fabricated using a single printing step directly on the optical fiber. The probe was successfully utilized for intravascular imaging in living diabetic swine at multiple time points, as well as human atherosclerotic plaques ex vivo. To the best of our knowledge, this is the first report of a 3D-printed micro-optic for in vivo imaging of the coronary arteries. These results are a substantial step to enable the clinical adoption of both 3D-printed micro-optics and beam-tailoring devices.

Single-shot ultrafast multidimensional optical imaging (UMOI) combines ultrahigh temporal resolution with multidimensional imaging capabilities in a snapshot, making it an essential tool for real-time detection and analysis of ultrafast scenes. However, current single-shot UMOI techniques cannot simultaneously capture the spatial-temporal-spectral complex amplitude information, hampering it from complete analyses of ultrafast scenes. To address this issue, we propose a single-shot spatial-temporal-spectral complex amplitude imaging (STS-CAI) technique using wavelength and time multiplexing. By employing precise modulation of a broadband pulse via an encoding plate in coherent diffraction imaging and spatial-temporal shearing through a wide-open-slit streak camera, dual-mode multiplexing image reconstruction of wavelength and time is achieved, which significantly enhances the efficiency of information acquisition. Experimentally, a custom-built STS-CAI apparatus precisely measures the spatiotemporal characteristics of picosecond spatiotemporally chirped and spatial vortex pulses, respectively. STS-CAI demonstrates both ultrahigh temporal resolution and robust phase sensitivity. Prospectively, this technique is valuable for spatiotemporal coupling measurements of large-aperture ultrashort pulses and offers promising applications in both fundamental research and applied sciences.

In vivo microscopic imaging inside a biological lumen such as the gastrointestinal tract, respiratory airways, or within blood vessels has faced significant technological challenges for decades. A promising candidate technology is the multimode fiber (MMF) endoscope, which enables minimally invasive diagnostics at a resolution reaching the cellular level. However, for in vivo imaging applications deep inside a biological lumen, sample-induced aberrations and the dynamic dispersion in the MMF make the MMF endoscope a chaotic system with many unknowns, where multiple minor fluctuations can couple and compound into intractable problems. We introduce a dynamically encoding, cascaded, optical, and ultrathin polychromatic light-field endoscopy (DECOUPLE) to tackle this challenge. DECOUPLE includes an adaptive aberration correction that can accurately track and control MMF behavior in the spatial-frequency domain to compensate for chaos introduced during complex dynamic imaging processes. We demonstrate the flexibility and practicality of DECOUPLE for noninvasive volumetric imaging in two colors for light passing through various highly aberrating samples including 120-μm-thick onion epidermal slices and 80-μm-thick layers of fat emulsions. To summarize, we represent a significant step toward practical in vivo imaging deep within biological tissue.

Metasurfaces, with their capability to control all possible dimensions of light, have become integral to quantum optical applications, including quantum state generation, operation, and tomography. We utilize a metasurface to generate polarization–hologram hybrid entanglement between a signal–idler photon pair to construct a quantum hologram. The properties of the quantum hologram can be revealed by collapsing the polarization degree of freedom of the idler photon, inducing interference between two holographic states of the signal photon as a meaningful and selective erasure of the holographic content. On the contrary, interference disappears when the idler photon is detected without observing polarization. This process can be further interpreted as a quantum holographic eraser, where the erasing action is visualized with erased contents in holograms. Our construction of a polarization–hologram hybrid entangled state with metasurfaces will be useful for quantum communication with enhanced robustness, anticounterfeiting applications through the additional quantum degrees of freedom or phase difference between two holographic states, and as an emerging platform for exploring fundamental quantum concepts for entanglement and nonlocality.

Flexible manipulation of chiral terahertz electromagnetic waves holds substantial potential for a wide range of applications, such as terahertz circular dichroism spectroscopy in biomaterials analysis, ultrafast electron bunch manipulation, high-speed wireless communication, and imaging. However, the development of tunable terahertz polarization modulation has been impeded by the lack of terahertz flexible manipulation measures at room temperature. We demonstrate an innovative element based on patterned spintronic terahertz sources, which can achieve efficient and great flexibility in polarization adjustment. The contributory effect of built-in electric fields on chiral terahertz waves is experimentally revealed by arranging different periodical microscale stripes, and swift polarization switching among linear, elliptical, and circular states is achieved by rotating ferromagnetic heterostructures. Notably, the ellipticity of the circle polarization state remains above 0.85 over a broadband terahertz bandwidth (from 0.74 to 1.66 THz). Furthermore, various polarization states dependent on geometry and azimuth angles provide insight into the physical mechanism of terahertz modulation by the built-in electric field. These findings contribute to the development of novel multifunctional terahertz devices, which pave the way to implement on-chip tunable terahertz polarization spectroscopy applications in biomedical detection and high-speed communication.

Distributed acoustic sensors (DASs) can effectively monitor acoustic fields along sensing fibers with high sensitivity and high response speed. However, their data processing is limited by the performance of electronic signal processing, hindering real-time applications. The time-wavelength multiplexed photonic neural network accelerator (TWM-PNNA), which uses photons instead of electrons for operations, significantly enhances processing speed and energy efficiency. Therefore, we explore the feasibility of applying TWM-PNNA to DAS systems. We first discuss processing large DAS system data for compatibility with the TWM-PNNA system. We also investigate the effects of chirp on optical convolution in complex tasks and methods to mitigate its impact on classification accuracy. Furthermore, we propose a method for achieving an optical full connection and study the influence of pruning on the full connection to reduce the computational burden of the model. Experimental results indicate that decreasing the ratio of Δλchirp / Δλ or choosing push–pull modulation can eliminate the impact of chirp on recognition accuracy. In addition, when the full connection parameter retention rate is no less than 60%, it can still maintain a classification accuracy of over 90%. TWM-PNNA provides an innovative computational framework for DAS systems, paving the way for the all-optical fusion of DAS systems with computational systems.