Viscosity is a crucial biomechanical factor in energy dissipation, mass transport, and non-equilibrium dynamics in living systems. Yet, quantifying local viscosity within deep, optically opaque tissues remains a formidable challenge due to strong light scattering. Here, we present the magnetically-twisted photoacoustic phase relaxation technique revealing the spatiotemporal heterogeneity of viscosity in deep tissue by introducing magnetoplasma Fe 3 O 4 /Au nanorotors. The viscosity-induced phase relaxation is extracted from the phase shift between the external magnetic field and the polarization-modulated photoacoustic readout. The depth-resolved, high-fidelity viscous mechanical information is converted into rotation-modulated ultrasound signals that are capable of propagating through strongly scattering tissues. Theoretically, we establish a quantitative relationship linking viscosity to the phase relaxation based on the overdamped angular momentum balance equation of the rotor and achieve a viscosity measurement uncertainty of up to 0.17 cp at a signal-to-noise ratio of 15 dB. Experimentally, we successfully capture the dynamic viscosity evolution during blood coagulation at a 2.4 mm tissue depth and map localized viscosity profiles during early zebrafish embryogenesis. This work provides a technical foundation for visualizing viscosity as an active physical field involved in morphogenesis and dynamical regulation in living systems.
Silicon photonics has benefited greatly from wafer-scale fabrication, with very-large-scale integration enabling systems for diverse applications, including data communications, LiDAR sensing, and quantum computing and sensing. However, the vast majority of these systems are fabricated on rigid and opaque substrates, precluding their use for applications such as transparent pliable displays (especially for augmented reality) and discreet wearable sensors. Prior demonstrations of photonic chips that are both transparent and flexible have been limited to fabrication processes on the individual device or chip scale, limiting scalability as well as the use of foundry-grade cleanroom tools, which can enable tighter fabrication tolerances and increased stack complexities. In this paper, we develop and experimentally characterize a 300-mm wafer-scale platform and fabrication process that results in optically transparent and mechanically flexible silicon-photonics wafers and chips. We demonstrate mechanical robustness to bending, as well as attractive optical properties relevant to transparency, such as low haze and distortion. This work introduces a scalable platform for the development of the next generation of transparent and flexible silicon-photonics systems, opening up applications for silicon photonics in areas including transparent pliable displays and discreet wearable sensors.
Non-contact monitoring of vital signs is critical for healthcare and emergency response but becomes especially challenging when the subject is hidden from direct view. Although electronic radar-based solutions have been validated, they encounter critical bottlenecks in detection range, resolution, and robustness against dynamic interference. Here, we report a photonic framework for hidden vital sign sensing to transcend these bottlenecks and explore its potential for intelligent respiration analysis via deep learning. Based on our developed picosecond-temporal-resolution, single-photon-sensitive LiDAR and specialized signal-processing algorithms, we achieve an order-of-magnitude improvement in detection range and resolution over previous radar-based methods and realize multi-target respiration monitoring, localization, and tracking under dynamic interference. Combined with deep learning, the system further identifies abnormal breathing patterns and issues timely alerts. These results demonstrate the strong potential of photonic sensing for continuous health monitoring and search-and-rescue, and motivate future clinical validation of the reported approach.
Super-resolution optical fluctuation imaging (SOFI) provides an accessible route to nanoscopy using conventional fluorophores and standard fluorescence microscopy platforms, but background signals can compromise reconstruction accuracy and structural consistency in densely labeled samples. Here, we show that out-of-focus fluorescence and photobleaching generate spatiotemporally correlated pseudo-fluctuations that bias cumulant estimation, particularly in high-order and three-dimensional reconstruction. We introduce ST-SOFI, a spatiotemporal joint correction framework that suppresses defocus-associated spatial background and photobleaching-associated temporal background while preserving molecular fluctuation statistics. Simulations and experiments demonstrate better weak-signal preservation, reduced intensity bias, enhanced contrast, and lower reconstruction error than conventional SOFI and two-step autocorrelation deconvolution. Combined with spin-SR imaging, ST-SOFI achieves second-order reconstruction with improved structural consistency and a lateral resolution of ∼76nm. These results establish a physically grounded and broadly compatible computational strategy for more reliable fluctuation-based super-resolution imaging and advance SOFI from resolution enhancement toward quantitatively consistent statistical imaging.
Compact and lightweight varifocal imaging systems are increasingly important for emerging applications such as portable sensing, wearable optics, and aerospace instrumentation. However, conventional varifocal architectures rely on mechanically complex axial or lateral translations of optical components, limiting their miniaturization and integration. Here, we present a hybrid refractive-metalens varifocal system that enables focal tuning through rotational modulation of cascaded freeform metalenses rather than component displacement. The proposed architecture combines the high imaging capability of refractive optics with the wavefront-engineering flexibility of metalenses, enabling continuous varifocal operation within a significantly reduced system footprint. To enable the practical design of such hybrid systems, a real-ray-tracing-based co-design strategy is developed, together with a multi-configuration optimization framework that suppresses parasitic zeroth-order diffraction while maintaining imaging performance across the full varifocal range. A fabricated prototype demonstrates continuous 2× zoom operation with stable aberration control and low distortion, showing good agreement between experimental measurements and theoretical predictions. These results validate both the proposed hybrid refractive-metalens architecture for compact translation-free varifocal imaging and the accompanying system-level co-design methodology, providing a practical framework for future hybrid refractive-metasurface optical systems in infrared sensing, AR/VR, aerospace instrumentation, compact cameras, and portable intelligent devices.
Holography enables quantitative access to complex-amplitude fields, supporting applications ranging from biological microscopy to industrial metrology. Although Kramers–Kronig (KK) holography offers an attractive route toward deterministic reconstruction, existing implementations rely on a lens-based 4 f system to construct the required half-plane-blocked spatial-frequency filter, limiting system miniaturization and reducing alignment tolerance. Here, we demonstrate lensless KK holography enabled by nonlocal flat optics, in which a 2 mm thick multilayer filter replaces the conventional 4 f system and directly provides the spatial-frequency filtering required for reconstruction. We recover amplitude and phase from artificial test targets and biological specimens over a 5.52 mm ×5.52 mm field of view with a 4.92 µm half-pitch resolution, while achieving a processing throughput of 1.94 megapixels per second on a laptop. Our approach combines the deterministic reconstruction capability of KK holography with a compact, large-FoV lensless architecture offering improved alignment tolerance, providing a route toward integrated and computationally efficient holographic imaging systems.
Coherent lidar recovers a scene's geometry and motion by measuring the time-of-flight and Doppler shift of backscattered light. However, conventional coherent lidar systems do not capture the full optical wavefield-comprising time-varying amplitude, phase, and polarization-and therefore forfeit access to an additional, rich source of scene information: surface material properties encoded in the polarization state of backscattered light and in the statistical properties of coherent polarization speckle. Prior approaches to full-wavefield sensing require complex benchtop optics for ultrafast modulation and detection, or do not address the modeling and recovery of the surface polarimetric response, which is scrambled by inter-reflections within the lidar's internal optics. Here, we introduce a polarimetric full-wavefield coherent lidar system that recovers a surface point's Jones matrix-encoding material and geometric surface properties as observed through the system's illumination and collection aperture-along with depth and velocity, all from a single measurement. We achieve this by (1) repurposing an off-the-shelf coherent optical modem-conventionally used for telecommunications-for ultrafast full-wavefield modulation and detection, and (2) developing a polarization-aware image formation model and inverse method that disentangles the system's optical response from that of a target surface. Overall, the approach delivers millimeter-accurate depth, robust velocimetry, and polarimetric surface properties, all with microsecond-scale exposures, eye-safe optical power, and insensitivity to ambient light. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Full-field transmission X-ray microscopy (TXM) is a powerful technique for nondestructive nanoscale imaging. In laboratory-based systems, high-resolution full-field TXM remains challenging due to the low brightness and polychromaticity of X-ray tubes. Here, we demonstrate a laboratory TXM instrument composed of a microfocus X-ray source with an integrated multilayer Montel mirror, high-resolution Fresnel zone plates (FZPs), and a charge-integrating direct conversion hybrid pixel detector (M & Ouml;NCH detector). The Montel mirror monochromatizes the X-ray beam and efficiently focuses it onto the sample. Importantly, the numerical aperture of the Montel mirror is matched to that of an FZP with an outermost zone width of 25 nm, thereby ensuring optimal performance in spatial resolution. A central innovation of our work is the replacement of traditional scintillator-based indirect detection schemes with a direct conversion hybrid pixel detector featuring higher detective quantum efficiency. This transition is enabled by the uniquely small pixel size of the M & Ouml;NCH detector (25 & micro;m) and its interpolation capabilities arising from charge sharing between contiguous pixels when an X-ray photon is detected. By integrating our tailored TXM design with the advanced interpolation capabilities of the M & Ouml;NCH detector, features with dimensions down to 34 nm were resolved. Furthermore, the microscope can be operated in Zernike phase-contrast mode, which was applied for imaging of an integrated-circuit chip. This work represents a significant step forward in laboratory-based TXM, introducing a combination of X-ray optics that brings nanoscale imaging in laboratory and industrial environments closer to synchrotron-level resolution. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Quantitative assessment of unresolved microstructural alterations remains a challenge for conventional X-ray imaging, limited by spatial resolution and dose constraints. While X-ray dark-field imaging with grating interferometry provides high sensitivity to sub-resolution microstructures and has demonstrated considerable promise in the diagnosis of pulmonary diseases, the absence of a rigorously established signal-to-structure relationship has restricted its clinical studies to semi-quantitative analysis. Here, using a naturally close-packed microsphere model, whose dark-field signal characteristics closely resemble those of pulmonary tissue, we establish a deterministic relationship between microsphere diameter and linear diffusion coefficient in the regime where the microsphere diameter substantially exceeds the auto-correlation length-a condition commonly encountered in clinical dark-field imaging systems. This enables resolving unknown microsphere sizes through linear superposition of two basis microspheres. Our investigation also reveals the inherent limitation of dual-energy techniques in achieving such structure decomposition, stemming from unavoidable linearly energy-dependent behavior of the material's linear diffusion coefficient. To address this, we present a quantitative framework featuring a single-energy (i.e., single energy spectrum) structure decomposition method. Experimental validation using 200 and 400 & micro;m diameter reference microspheres achieved precise diameter prediction (relative error of mean value < 2%) for 300 & micro;m test samples. To conclude, our approach forges a quantitative relationship between dark-field signal interpretation and clinically actionable microstructural quantification. Building on the fact that naturally packed microspheres serve as an established physical surrogate for alveolar structures, this framework demonstrates potential for objective staging of emphysema and other pulmonary disorders in which microstructural degradation dictates disease progression. Moreover, the proposed method can be extended to other medical applications, such as bone quality assessment, calcification, and kidney stone identification, as well as to metamaterial characterization in materials science. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Skyrmions, topological spin textures, have been extensively studied across disciplines, including particle physics, quantum fields, condensed-matter physics, and optics. Optical skyrmions have recently promised topologically enhanced light-matter interaction, sensing, and information processing. However, the generation of which typically requires complex structured media or intricate wavefront engineering. Here, we unveil that a well-known optical diffraction phenomenon-the Poisson spot-can host a rich variety of skyrmionic topologies simultaneously, which are constructed by multiple degrees of freedom of light, including optical spin, polarization Stokes vectors, and electric and magnetic fields. We also experimentally demonstrate the coexisting electric field, spin and Stokes skyrmions, and magnetic field skyrmions can be derived from electric field skyrmions via electromagnetic duality symmetry. Our approach is strikingly simple but enables tunable multidimensional topological control, overcoming the intrinsic complexity of electromagnetic fields. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Super-resolution structured illumination microscopy (SR-SIM) enables fluorescence microscopy beyond the diffraction limit at high frame rates. Compared to other super-resolution microscopy techniques, the low photon fluence used in SR-SIM makes it readily compatible with live-cell imaging. Here, we combine SR-SIM with electro-optic fluorescence lifetime imaging (EOFLIM), demonstrating super-resolved multiplexed imaging of spectrally overlapping fluorophores, enhanced contrast due to optical sectioning, and environmental sensing at a spatial resolution of 156 nm. The high photon detection throughput of EOFLIM enables a combination of lifetime precision, size of the field of view, spatial resolution, and speed, which, taken together, is unprecedented, enabling the super-resolved imaging of cellular dynamics. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
Achieving efficient microwave–optical transduction is a critical challenge for quantum networks where information is shared optically across disparate microwave systems and for coherent optical detection and manipulation of microwave states. Resonant electro-optic systems are being pursued as a means of efficiently bridging these frequencies. Here, we present a platform that employs a bulk lithium niobate crystal whose large dielectric constant creates wavelength-scale confinement of microwave photons. By incorporating this crystal within a high-finesse Fabry–Pérot optical cavity, microwave photons couple to optical photons through the electro-optic effect. We demonstrate the ability to tune our system into triply resonant operation, where microwave photons, optical pump photons, and upconverted optical photons are simultaneously resonant with high quality factor electromagnetic modes of the system. The device achieves photon-number conversion efficiency at the percent level, comparable to that of state-of-the-art devices at room temperature—sufficient to resolve the thermal occupation of the microwave mode—by taking advantage of the high-power handling, low loss, and low noise of all-dielectric devices. These results establish our all-dielectric devices as a promising platform for high-precision sensing of optically detected microwave fields and as a viable route toward single-photon-level microwave–optical quantum transduction.
Ghost imaging reconstructs an object by correlating two optical fields, even though the spatially resolved light used to form the image never directly interacts with the object. It has been demonstrated with both quantum and classical light sources. In classical thermal light ghost imaging, however, the two correlated beams are typically obtained by splitting a single beam and therefore remain wavelength degenerate, which limits its use when infrared illumination is desirable but visible-light detection is more efficient. Here, we demonstrate wavelength-transforming ghost imaging using a non-degenerate thermal light source. The scheme coherently transfers the spatial incoherence of infrared thermal light to a visible field through type-II second-harmonic generation, such that one photon in the thermal two-photon correlation is up-converted while the other remains in the infrared. Using this source, we reconstruct infrared-illuminated objects with a visible CCD camera and examine how source coherence affects image quality. These results establish a practical route to non-degenerate thermal ghost imaging and open new possibilities, to our knowledge, for infrared imaging with efficient visible-light detection.
Optical coherence elastography (OCE) enables label-free imaging of tissue mechanical properties, but conventional scanning implementations have limited volumetric acquisition speed. We present a full-field swept-source optical coherence elastography (FF-SS-OCE) system, based on compressive loading, that provides rapid volumetric imaging of strain at a rate of 2 volumes/s, enabled by an effective OCT A-scan rate of 4.2 MHz, corresponding to an order-of-magnitude increase in imaging speed over previous OCE demonstrations. The system achieves a shot-noise-limited phase sensitivity in volumetric imaging by combining highly parallel signal detection using a full-field configuration, implementation of a common-path interferometer to minimize the impact of environmental noise, a highly stable tunable laser, and active reduction of spatial coherence to reduce cross-talk noise. We demonstrate, for the same signal-to-noise ratio (SNR) of ∼20dB, that FF-SS-OCE provides 41% higher phase sensitivity and 35% higher strain sensitivity compared to a scanning OCT system. We validate the method using structured phantoms and freshly excised human breast tissue, demonstrating rapid visualization of mechanical contrast and showing its potential to discern between tumor and healthy tissue based on their distinct mechanical properties. These results establish FF-SS-OCE as a promising approach for high-speed, high-sensitivity volumetric elastography in biomedical tissue imaging.
