Optical skyrmions represent a novel frontier in topological optics with diverse generation methods emerging recently, offering significant potential for robust optical information processing, high-density data storage, and other advanced photonic technologies. However, significant challenges persist in understanding their topological robustness under perturbations and in achieving flexible on-demand topologically controlled generation, both of which are essential for real-world applications. Here, we propose the theory of topological protection degrees to classify the robustness of the topological texture of optical skyrmions under perturbations, distinguishing between strong and weak protection. Then, we demonstrate the electrical generation of topologically tunable optical skyrmions through a controllable modulation scheme with common optical elements. Building upon this, we experimentally validate the proposed topological protection degrees under complex perturbations. Our work lays a foundational framework for future research on topological stability of optical skyrmions and paves the way for their applications in data transmission and storage.

Silicon carbide (SiC) has great potential for optomechanical applications due to its outstanding optical and mechanical properties. However, challenges associated with SiC nanofabrication have constrained its adoption in optomechanical devices, as embodied by the considerable optical loss or lack of integrated optical access in existing mechanical resonators. In this work, we overcome such challenges and demonstrate a low-loss, ultracompact optomechanical resonator in an integrated 4H-SiC-on-insulator (4H-SiCOI) photonic platform for the first time, to our knowledge. Based on a suspended 4.3-μm-radius microdisk, the SiC optomechanical resonator features low optical loss (<1 dB/cm), a high mechanical frequency fm of 0.95×109 Hz, a mechanical quality factor Qm of 1.92×104, and a footprint of <1×10-5 mm2. The corresponding fm·Qm product is estimated to be 1.82×1013 Hz, which is among the highest reported values of optomechanical cavities tested in ambient environment at room temperature. In addition, the strong optomechanical coupling in the SiC microdisk enables coherent regenerative optomechanical oscillations at a threshold optical dropped power of 14 μW, which also supports efficient harmonic generation at increased power levels. With such competitive performance, we envision a range of chip-scale optomechanical applications to be enabled by the low-loss 4H-SiCOI platform.

Neuromorphic photonic systems offer significant advantages for parallel, high-speed, and low-power computing, among which spiking neural networks emerge as a powerful bio-inspired alternative. This study demonstrates, to our knowledge, a novel approach to all-optical spiking processing and reservoir computing using passive silicon microring resonators (MRRs). A key innovation is the demonstration of deterministic optical spiking and spectro-temporal coincidence detection without the need for pump-and-probe methods, simplifying the architecture and improving efficiency. By leveraging injection of excitatory optical signals at negative wavelength detuning relative to the MRR’s cold resonances, the system delivers prompt and high-contrast optical spiking events, essential for effective chip-integrated photonic spiking neural networks. Building on this, a photonic spiking reservoir computer is implemented using a single silicon MRR. The system encodes input information through a novel spectro-temporal scheme and classifies the Iris-Flower dataset with 92% accuracy. This performance is achieved with just 48 reservoir virtual nodes, averaging only three spikes per flower sample, hence highlighting the system’s efficiency and sparsity. These findings unlock novel neuromorphic photonic frameworks with MRRs, enabling sparse all-optical spiking processing and reservoir computing, particularly promising to be adapted in future coupled MRR structures and with binary output weights for light-enabled edge computing and sensing applications.

Cholestatic liver diseases (CLD) lead to bile accumulation, hepatobiliary dysfunction, and progressive liver damage. Early, accurate evaluation of cholestasis is essential for improving prognosis. In this study, we developed a cross-scale, noninvasive optical imaging platform designed to evaluate both microstructure and metabolic functions in cases of intrahepatic cholestasis, such as primary biliary cholangitis, as well as extrahepatic cholestasis resulting from bile duct ligation. We employed high-resolution photoacoustic microscopy to assess changes in bile duct permeability, hepatic lobular architecture, and blood oxygen saturation following varying degrees of bile duct injury. Meanwhile, we utilized near-infrared-II fluorescence imaging to track the transport of indocyanine green, thereby mapping the absorption and excretion dynamics throughout the liver. Liver function reserve was monitored in situ using contrast-enhanced photoacoustic computed tomography. The imaging manifestations of microstructural alterations and functional impairments associated with cholestasis were quantitatively characterized, demonstrating a correlation with disease progression and validation of our findings. This platform enables dynamic, high-resolution assessment of small bile duct injury and hepatobiliary dysfunction, offering a promising tool for early diagnosis, monitoring, and therapeutic evaluation of CLD.

Polarization detection is essential for various applications, ranging from biological diagnostics to quantum optics. Although various metasurface-based polarimeters have emerged, these platforms are commonly realized through spatial-division designs, which restrict detection accuracy due to inherent factors such as crosstalk. Here, we propose, to our knowledge, a novel strategy for high-accuracy, broadband full-Stokes polarization detection based on the analysis of a single vector beam, whose polarization profile varies sensitively and exhibits a one-to-one correspondence with the incident polarization. Based on this, the incident polarization is completely encoded into the field profile of the vector beam, which avoids crosstalk in principle, and results in high-accuracy polarization detection without any calibration process. As a proof of concept, a geometric-phase metasurface-based grafted perfect vector vortex beam (GPVVB) generator was designed and fabricated. Experimental results demonstrate that our method achieves polarization detection with an average relative error of 2.25%. Benefiting from the broadband high transmittance exceeding 95% of the metasurface due to the femtosecond laser-induced birefringence process, our method operates across a wavelength range of 450–1100 nm. Furthermore, the detection capability of the vector beam polarization profile was validated using a GPVVB-generating array. These results highlight the potential of our approach for transformative applications in polarization detection, including optical communication and machine vision.

Circular dichroism (CD) spectroscopy, widely used for chiral sensing, has been limited by the detection sensitivity. Enhancing optical chirality in the light fields interacting with chiral molecules is crucial for achieving ultrasensitive chiral detection. Here, we present a new paradigm for ultrasensitive chiral detection by creating accessible chiral hotspots using a toroidal dipole Fabry–Perot bound state in the continuum (TD FP-BIC) metasurface. BIC resonance is achieved by controlling the coupling between the TD resonance and its multilayer reflector-induced perfect mirror image. This method enables unprecedented local maximum and average optical chirality enhancements of up to 6×104-fold and 2×103-fold, respectively, within non-structured regions, resulting in an 866-fold increase in CD signals compared to chiral molecules alone without nanostructures. Our results pave the way for enhanced light–matter interactions and ultrasensitive enantiomeric operation.

Two-dimensional second-order spatial differentiation metasurfaces with different numerical apertures (NAs) were designed by the spatial-frequency Trust-Region algorithm, which can be directly embedded into existing optical imaging systems to efficiently extract edge information of the observed targets. The spatial-frequency Trust-Region algorithm was implemented by integrating the Fourier modal method (FMM) with the Trust-Region algorithm to perform inverse optimization of the metasurface nanostructure. The fabricated metasurface with high-resolution functionality achieved a resolution of 1.2 μm and numerical aperture of 0.87, while the high-contrast one obtained a root-mean-square (RMS) contrast higher than that of the first with a numerical aperture of 0.26. Embedded in an optical microscope, the high-resolution differentiation metasurface, with more high-spatial-frequency components in the transfer function, was utilized to extract fine structures of unstained, even transparent, cell images, providing a new avenue for image segmentation, such as in magnetic resonance imaging. The high-contrast counterpart, due to its high transmission efficiency, was employed to detect edges in dynamic images of paramecia and Brachionus without motion smear, offering potential for application in microsurgical procedures involving real-time image analysis.

Symmetry plays a fundamental role in topological photonic crystals, and topological phase transitions induced by disorder have also been extensively explored in recent years. However, in this work, we find anisotropy can be induced by reducing symmetry in a C2v symmetry triangular photonic crystal. We investigate that anisotropy-induced interfaces profoundly affect edge states and enable the realization of slow light dispersion. Numerical simulations reveal a transition from gapless chiral edge modes to gapped flat band dispersion. Furthermore, we observe higher-order corner states in corner structures constructed by anisotropic interfaces. The corner states can be induced and localized at different lattice positions, thereby realizing multiple types of higher-order topological states. We demonstrate the significance of anisotropic geometry in topological photonics. These findings open new possibilities for steering wave transport in multiple dimensions and offer, to our knowledge, a novel research perspective on the transformation of topological states induced by anisotropic lattices.

Inhomogeneous uniaxial strain-induced lattice deformations result in the Dirac point shift, leading to a strong synthetic pseudomagnetic field. The chiral edge state in the Haldane model and the antichiral edge state in the modified Haldane model can be realized in gyromagnetic photonic crystals, immersed in external real magnetic fields. Here, the interplay of the real- and pseudo-magnetic fields is investigated based on the onsite magnetization modulation and the uniaxial strain within gyromagnetic photonic crystals, thereby resulting in photonic band deformations including the shift of the chiral edge states and the lift of the degenerate antichiral edge states. The experiment is further performed to observe the imbalanced transport of these edge states on two opposite sides. Our findings can help to deeply explore rich and significant physics of synthetic gauge fields, and facilitate designs of photonic functional devices, such as the proposed unidirectional multichannel waveguide.

We demonstrate that a moiré superlattice nanocavity constructed in a photonic crystal slab promises strongly enhanced nonlinear optics, which is beneficial from the high-quality factor and high coupling efficiency of the flat-band mode with zero group velocity. From a silicon moiré superlattice nanocavity integrated with few-layer gallium selenide (GaSe), the second-harmonic generation (SHG) of GaSe is enhanced by over 10,000 times, and the third-harmonic generation (THG) is enhanced by 8500 times. Our results suggest the moiré superlattice nanocavity could be considered as a promising platform for developing high-efficiency nonlinear photonic devices.

Visible light communication plays an essential role in the next-generation 6G network due to its extremely high bandwidth and ultrafast transmission speed. Incorporating position sensing functionality into the communication system is highly desired for achieving target-oriented beamforming and accommodating high-speed data service. However, an efficient solution to integrated sensing and light communication remains challenging. Here, we demonstrate an integrated system that concurrently accomplishes high-precision sensing and high-speed data transmission by spatio-temporal modulation of the illumination and computational reconstruction. We developed a compressive angular projection imaging scheme to achieve rapid three-dimensional localization with high resolution, and a jointly optimized waveform design ensures slight sacrifice in the transmission data rate on the integrated system. We experimentally demonstrated a resolving resolution of 1 mm in lateral and 4 cm in depth within 0.6 m×0.6 m×0.6 m volume over 2 m distance at the sensing speed of 39 Hz in both static and dynamic conditions. This capability enables adaptive beamforming, which significantly enhances the data rate by 184% to permit errorless transmission of high-throughput virtual reality videos. Our work offers a promising route for intelligent wireless light communication systems with spatial perception capability, presenting the possibility of cable-free, immersive virtual reality experiences.

There is growing global interest in establishing free-space optical (FSO) communication links, such as ground-satellite links (GSLs) of at least hundreds of kilometers, intersatellite links of thousands of kilometers, and future deep space links of much greater dimensions. Enabling outdoor wireless FSO communication systems to be utilized during daylight hours can increase their availability in space-air-ground networks; however, this is usually accompanied by incoherent background radiation that impairs the signal-to-noise ratio (SNR) and bit error rate (BER). Therefore, a preliminary review of the background noise is required before constructing ground terminals with a suitable SNR in a harsh environment with high levels of solar noise. Herein, we evaluated the background noise that sunlight provides to ground terminals and quantitatively examined its impact on the SNR, communication performance, and beacon detection accuracy of the developed all-free-space ground terminal. Furthermore, we present the results of a daytime demonstration of a 7-km terrestrial free-space optical communication link by employing our ground terminal that was designed based on these analyses. The results verified that 2.5-Gbps data transmission up to 7 km is feasible, even in expected daytime satellite tracking scenarios with high background noise, by the developed system with spectral and spatial filtering to achieve an acceptable SNR. The background noise results of our research are anticipated to further the research on quantum communication networks, light detection and ranging (LiDAR), and green energy technologies.

Miniaturized spectrometers with high resolving power and cost-effectiveness are desirable but remain an open challenge. In this work, we repurpose a fiber generated by the catastrophic fuse effect and ingeniously harness it for a speckle-based computational spectrometer. Without complex disorder engineering, the axially random micro-cavities in the fused fiber enhance the wavelength sensitivity of multimode interference, enabling a 10 cm fiber to achieve a spectral resolution of 0.1 nm. This performance exhibits sixfold improvement over a common multimode fiber configuration of the same length. Furthermore, we develop a spectral reconstruction method that combines a weighted transmission matrix with automatic differentiation, which reduces the reconstruction error by approximately half and enhances the peak signal-to-noise ratio by 6.12 dB compared to traditional Tikhonov regularization. Spectra spanning a 40 nm range, exhibiting both sparse and dense characteristics, are accurately reconstructed. To the best of our knowledge, this represents the first application of fused fiber in computational spectrometers, demonstrating its potential for a wide range of spectral measurement scenarios.

Free-space strong-field terahertz (THz) pulses, generated via optical rectification of femtosecond lasers in nonlinear crystals, are pivotal in various applications. However, conventional Ti:sapphire lasers struggle to produce high-average-power THz sources due to their limited output power. While kilowatt ytterbium lasers are increasingly adopted, their application in THz generation faces challenges: low optical-to-THz conversion efficiency (attributed to long pulse duration and low energy) and crystal damage under high pumping power. Here, we report a high-average-power strong-field THz source using a lithium niobate crystal pumped by a 1030 nm, 570 fs, 1 mJ, 50 kHz ytterbium femtosecond laser with tilted pulse front pumping (TPFP). By systematically optimizing TPFP implementations and comparing grating- and echelon-type configurations, we achieve a THz source with 64.5 mW average power at 42 W, 50 kHz pumping, and focused peak electric field of 525 kV/cm at 0.83 mJ, 1 kHz operation. Additionally, we observe Zeeman torque signals in cobalt-iron ferromagnetic nanofilms. This high-repetition-rate, high-average-power THz system, combined with its potential capabilities in high signal-to-noise ratio spectroscopy and imaging, promises transformative impacts in quantum matter manipulation, non-destructive testing, and biomedicine.

We present a high-power and broadband terahertz (THz) time-domain spectroscopy setup utilizing the nonlinear organic crystal MNA both as an emitter and a detector. The THz source is based on optical rectification of near-infrared laser pulses at a central wavelength of 1036 nm from a commercial, high-power Yb-based laser system and reaches a high THz average power of 11 mW at a repetition rate of 100 kHz and a broad bandwidth of more than 9 THz without a significant power fall-off in the higher THz frequency components. The conversion efficiency is high (0.13%) in spite of the high excitation average power of 8 W. We validate the high dynamic range and reliability of the source for applications in linear spectroscopy by measuring the broadband THz properties of χ(2) nonlinear crystals up to 8 THz. This new high-repetition-rate source is very promising for ultra-broadband THz spectroscopy at high dynamic range and/or reduced measurement time.

In complex environments, infrared camouflage within the long-wave infrared range is essential for modern defense and surveillance applications, requiring precise control over both radiative and scattering properties of military targets. For practical implementation, developing surfaces that integrate dynamic emissivity control, low specular reflectance, and scalable fabrication processes remains a significant challenge. Here, a novel infrared camouflage device is proposed to simultaneously achieve low specular reflectance (<0.1) and dynamic infrared camouflage. The device seamlessly blends into backgrounds with temperatures ranging from 35°C to 45°C by tuning the emissivity of the device, which is attained by controlling the Ge2Sb2Te5 phase change. In addition, it reflects almost no surrounding thermal signals compared with the conventional low-emissivity smooth surface. The thermal camouflage remains effective and stable across observation angles ranging from 20° to 60°. This work proposes a novel approach to simultaneously reducing specular reflection and dynamic emissivity control, potentially inspiring future research and applications in multispectral camouflage and stealth technology.

Upconversion nanoparticles (UCNPs) have attracted considerable interest due to their large anti-Stokes shift, offering promising applications in lasing. Here, multi-wavelength upconversion whispering gallery mode (WGM) lasing is demonstrated in silica microspheres coated with NaYF4@NaYbF4:1%Tm3+@NaYF4 nanoparticles and coupled with tapered fibers. Under continuous-wave 980 nm pumping, low-threshold lasing is achieved across Tm3+ transitions from near-infrared to visible, with an ultra-low threshold of 0.61 μW for the H43→H36 transition. Additionally, upconversion laser output can also be achieved in Er3+- and Ho3+-activated microspheres. These results establish tapered fiber coupling as a versatile approach for enhancing upconversion microlasers.

Non-Hermitian chiral coalescence associated with polarization in optical scattering systems has been routinely realized and applied. However, the scattering exceptional points (EPs) associated with polarization obtained by modes with broadband response and high dissipation constrain its further application in narrowband optics. Here, as a scheme, distinct from the implementation pathway of traditional EPs, we introduce a quasi-bound state in the continuum based on a quadrupole mode as the response environment for EP generation, achieving an EP with high-quality-factor characteristics on a metasurface. Furthermore, we demonstrate the robustness of EPs as intrinsic features of non-Hermitian systems, independent of specific parameter choices. Finally, we present an example of direct chirality detection and display, showcasing the maximum spin-selective property induced by EPs. Our approach unveils the potential of scattering chiral EPs for applications in narrowband optics.

Optical topological quasiparticles with nontrivial topological textures, such as skyrmions and meron lattices, have attracted considerable attention due to their potential applications in high-dimensional optical data storage and communications. Most previous studies of optical topological quasiparticles have focused on the formation of topological structures in isotropic media, whereas in our work, we perform a comprehensive investigation into the formation, topological stability, and phase transitions of optical meron lattices at the metal/uniaxial crystal interface. Our theoretical studies show that by rotating the optical axis orientation of the uniaxial crystal, meron lattices constructed by electric-field vector undergo phase transitions from a topologically nontrivial to a topologically trivial state, whereas the skyrmion number of the spin meron lattices remains robust against such rotations. The findings offer new insights into the topological stability and phase transitions of topological quasiparticles under light–matter interactions and hold promise for applications in optical data storage, information encryption, and communications.

Nonreciprocal optical devices are key components in photonic integrated circuits for light reflection blocking and routing. Most reported silicon integrated nonreciprocal optical devices to date were unit devices. To allow complex signal routing between multiple ports in photonic networks, multi-port magneto-optical (MO) nonreciprocal photonic devices are desired. In this study, we report experimental demonstration of a silicon integrated 5×5 nonreciprocal optical router based on a magneto-optical phased array. By introducing different nonreciprocal phase shifts to planar photonic waveguides, the device focuses light to different ports for both forward and backward propagation directions. The device shows designable nonreciprocal optical transmission between 5×5 ports, achieving 16 dB isolation ratio and -18 dB crosstalk.

The high degree of freedom of multimechanism metasurfaces has greatly facilitated multifunction or even multiphysics design for practical applications. In this work, to achieve camouflages simultaneously in microwave, infrared, and optical regimes, we propose a multimechanism-empowered metasurface composed of four elemental indium-tin-oxide-based meta-atoms. Each meta-atom can modulate microwaves both in phase and magnitude through polarization conversion and resonance absorption, which can realize radar stealth at 8–14 GHz. The reflective amplitude is less than -10 dB. When the incident angle increases to 60°, the reflective amplitude is still less than -3 dB. The far-field scattering patterns of microwaves are modulated by destructive interferences of reflected waves, which results in diffusion-like scattering due to randomly distributed reflection phases on the metasurface. The superposition of microwave absorption and diffuse reflection enables broadband microwave scattering reduction of the metasurface. Meanwhile, the emissivity of four types of meta-atoms covers from 0.3–0.8 at 3–14 μm due to delicately designed occupation ratios. The infrared radiation of the metasurface exhibits the characteristics of digital camouflage in infrared imaging. To demonstrate this method, prototypes were fabricated and measured. The measured results are consistent with the simulated ones. The angular stability in the microwave range within 0°–60° was also demonstrated. This work presents an approach to achieving multispectrum functions with integrated multimechanisms in a single functional metasurface layer and offers a new methodology for custom-designing infrared performance. Moreover, the simplicity of the structure offers significant cost control and large-scale fabrication advantages.

Developing approaches for precise engineering of the optical response of plasmonic nanocavities at the post-fabrication stage is important for achieving enhanced and tunable light-matter interactions. In this work, we demonstrate selective enhancement/suppression of specific plasmonic modes by embedding nanocube-on-mirror plasmonic nanocavities into a poly(methyl methacrylate) (PMMA) layer with a controllable thickness. With the increase of the PMMA thickness from 0 to approximately 100 nm, the dominating out-of-plane plasmonic modes are significantly suppressed in the scattering spectra, while the in-plane plasmonic modes are greatly enhanced with a factor reaching 102±20. This enhancement is related to the variation of momentum matching between the plasmonic modes and the radiative fields, affecting both mode excitation and emission properties. In addition, the spectral positions of the in-plane and out-of-plane plasmonic modes shift up to 52±5 and 81±2 nm, respectively. These properties are important for matching and enhancing plasmonic and molecular resonances in a variety of applications.