The near-eye display feature in emerging spatial computing systems produces a distinctive visual effect of mixing virtual and real worlds. However, its application for all-day wear is greatly limited by the bulky structure, energy expenditure, and continuous battery heating. Here, we propose a lightweight holographic near-eye display system that takes advantage of solar energy for self-charging. To guarantee the collection of solar energy and near-eye display without crosstalk, we implement holographic optical elements (HOEs) to diffract sunlight and signal light into a common waveguide. Then, small-area solar cells convert the collected solar energy and power the system. Compact power supply components replace heavy batteries, thus contributing to the lightweight design. The simple acquisition and management of solar energy provide the system with sustainable self-charging capability. We believe that the lightweight design and continuous energy input solution will significantly promote the popularity of near-eye display in our daily lives.

Photoacoustic microscopy (PAM) operating within the 1.7-μm absorption window holds great promise for the quantitative imaging of lipids in various biological tissues. Despite its potential, the effectiveness of lipid-based PAM has been limited by the performance of existing nanosecond laser sources at this wavelength. In this work, we introduce a 1725-nm hybrid optical parametric oscillator emitter (HOPE) characterized by a narrow bandwidth of 1.4 nm, an optical signal-to-noise ratio (OSNR) of approximately 34 dB, and a high spectral energy density of up to 480 nJ/nm. This advanced laser source significantly enhances the sensitivity of photoacoustic imaging, allowing for the detailed visualization of intrahepatic lipid distributions with an impressive maximal contrast ratio of 23.6:1. Additionally, through segmentation-based analysis of PAM images, we were able to determine steatosis levels that align with clinical assessments, thereby demonstrating the potential of our system for high-contrast, label-free lipid quantification. Our findings suggest that the proposed 1725-nm HOPE source could be a powerful tool for biomedical research and clinical diagnostics, offering a substantial improvement over current technologies in the accurate and non-invasive assessment of lipid accumulation in tissues.

In this study, we developed a robust, ultra-wideband, and high-speed wavelength-swept distributed feedback (DFB) laser array with an 8×3 matrix interleaving structure with no movable or fragile optical components. This wavelength-swept laser (WSL) achieves a continuous (gap-free) wavelength sweeping range of 60 nm and a rapid sweeping speed of 82.7 kHz, marking the widest wavelength sweeping range reported to date for high-speed WSLs based on DFB laser arrays, to our knowledge. To achieve the high-precision mapping from the time domain to the frequency domain, a nonlinear wavelength and frequency variation measurement system based on dual Fabry–Perot (F-P) etalons is designed. The system accurately measures the dynamic relationship of frequency variations over time, enabling precise wavelength interrogation. The proposed WSL was applied to the fiber Bragg grating (FBG) sensor interrogation system. In the high-low temperature and strain experiments, the system performed real-time dynamic interrogation of FBGs for up to 3 h. The experimental results demonstrated good relative accuracy and excellent interrogation performance of the system. In the vibration experiment, the system achieved high-precision interrogation of FBG sensors for high-frequency sinusoidal vibrations up to 8 kHz. Furthermore, the system worked stably under strong vibrations and shocks. Thus, the proposed WSL is applicable to high-speed FBG sensing and optical coherence tomography applications.

Current synaptic characteristics focus on replicating basic biological operations, but developing devices that combine photoelectric responsiveness and multifunctional simulation remains challenging. An optoelectronic transistor is presented, utilizing a PMHT/Al2O3 heterostructure for photoreception, memory storage, and computation. This artificial synaptic transistor processes optical and electrical signals efficiently, mimicking biological synapses. The work presents four logic functions: “AND”, “OR”, “NOR”, and “NAND”. It demonstrates electrical synaptic plasticity, optical synaptic plasticity, sunburned skin simulation, a photoelectric cooperative stimulation model for improving learning efficiency, and memory functions. The development of heterostructure synaptic transistors and their photoelectric response enhances their application in neuromorphic computation.

Programmable photonic integrated circuits (PICs) have emerged as a promising platform for analog signal processing. Programmable PICs, as versatile photonic integrated platforms, can realize a wide range of functionalities through software control. However, a significant challenge lies in the efficient management of a large number of programmable units, which is essential for the realization of complex photonic applications. In this paper, we propose an innovative approach using Ising-model-based intelligent computing to enable dynamic reconfiguration of large-scale programmable PICs. In the theoretical framework, we model the Mach–Zehnder interferometer (MZI) fundamental units within programmable PICs as spin qubits with binary decision variables, forming the basis for the Ising model. The function of programmable PIC implementation can be reformulated as a path-planning problem, which is then addressed using the Ising model. The states of MZI units are accordingly determined as the Ising model evolves toward the lowest Ising energy. This method facilitates the simultaneous configuration of a vast number of MZI unit states, unlocking the full potential of programmable PICs for high-speed, large-scale analog signal processing. To demonstrate the efficacy of our approach, we present two distinct photonic systems: a 4×4 wavelength routing system for balanced transmission of four-channel NRZ/PAM-4 signals and an optical neural network that achieves a recognition accuracy of 96.2%. Additionally, our system demonstrates a reconfiguration speed of 30 ms and scalability to a 56×56 port network with 2000 MZI units. This work provides a groundbreaking theoretical framework and paves the way for scalable, high-speed analog signal processing in large-scale programmable PICs.

To adapt to the complex environment where low infrared emissivity and high infrared emissivity coexist, a radar stealth-infrared camouflage compatibility metasurface requires meta-atoms with customized infrared emissivity. Generally, the infrared emissivity is determined by the occupation ratio. However, the high occupation ratio will interfere with the scattering reduction function due to the Lorentz resonance from the metal patch. To address the problem, a method for decoupling Lorentz resonance is proposed in this paper. By shifting the resonant frequency of the metal patch to a high frequency, the Lorentz resonance is suppressed in the frequency band of scattering reduction. To verify the method, a single functional layer metasurface with microwave scattering reduction and customized infrared emissivity is designed. The scattering reduction at 3.5–5.5 GHz is realized through the polarization conversion. Meanwhile, the infrared emissivity of the metasurface can be gradient-designed by changing the occupation ratios of the meta-atoms. Compared with the initial design, the improved metasurface expands the infrared emissivity range from 0.60–0.80 to 0.51–0.80, and the scattering reduction effect remains unchanged. The experimental results agree with the simulated results. The work enriches the infrared emissivity function, which can be applied to camouflage in complex spectrum backgrounds.

Programmable metasurfaces are revolutionizing the field of communication and perception by dynamically modulating properties such as amplitude and phase of electromagnetic (EM) waves. Nevertheless, it is challenging for existing programmable metasurfaces to attain fully independent dynamic modulation of amplitude and phase due to the significant correlation between these two parameters. In this paper, we propose a radiation-type metasurface that can realize radiation space-time coding of the joint amplitude-phase. Hence, independent and arbitrary modulation of amplitudes and phases can be achieved for both x-polarized and y-polarized EM waves. For demonstration, the dynamic beam scanning with ultra-low sidelobe levels (SLLs) is validated. Moreover, we propose a strategy of stochastic coding and non-uniform modulation to suppress the harmonic energy, thereby obtaining the ultra-low sideband levels (SBLs). Prototypes were fabricated and measured, and all simulations and measurements demonstrated the superiority of the proposed strategy. In addition, the proposed strategy is optimization-free and highly integrated, which has unrivaled potential in the field of compact communication systems and radar systems.

Driven by advancements in artificial intelligence, end-to-end learning has become a key method for system optimization in various fields, including communications. However, applying learning algorithms such as backpropagation directly to communication systems is challenging due to their non-differentiable nature. Existing methods typically require developing a precise differentiable digital model of the physical system, which is computationally complex and can cause significant performance loss after deployment. In response, we propose a novel end-to-end learning framework called physics-guided learning. This approach performs the forward pass through the actual transmission channel while simplifying the channel model for the backward pass to a simple white-box model. Despite the simplicity, both experimental and simulation results show that our method significantly outperforms other learning approaches for digital pre-distortion applications in coherent optical fiber systems. It enhances training speed and accuracy, reducing the number of training iterations by more than 80%. It improves transmission quality and noise resilience and offers superior generalization to varying transmission link conditions such as link losses, modulation formats, and scenarios with different transmission distances and optical amplification. Furthermore, our new end-to-end learning framework shows promise for broader applications in optimizing future communication systems, paving the way for more flexible and intelligent network designs.

Beyond providing user access to the core network, the radio access network (RAN) is expected to support precise positioning and sensing for emerging applications such as virtual reality (VR) and drone fleets. To achieve this, fronthaul—the link connecting the central units/distributed units (CUs/DUs) to wireless remote units (RUs) in centralized RAN—must realize both high-capacity transmission and low-timing-jitter clock synchronization between RUs. However, existing solutions fall short of supporting these functions within one simple, cost-effective network. In this work, we propose a solution that simultaneously achieves picosecond-level timing jitter clock distribution and Tb/s data transmission with simplified DSP, using an electro-optic (EO) comb cloning technique to enable multifunctionality in fronthaul systems. Through the delivery of pilot comb lines, a 1 ps (integrated from 1 Hz to 40 MHz) low-timing-jitter 100 MHz clock is distributed by the beating of adjacent pilot comb lines and subsequent frequency dividing, realizing frequency synchronization between the CUs/DUs and RUs. Moreover, the delivery of pilot comb lines also facilitates self-homodyne structures through EO comb cloning, and supports wavelength division multiplexing (WDM) transmission with a line capacity of 2.88 Tb/s and a net capacity of 2.5 Tb/s. Thanks to the clock-synchronized and self-homodyne structure, DSP is streamlined, with digital timing recovery, carrier phase estimation, and frequency offset estimation all omitted. This work lays the technical foundation for implementing a 6G WDM fronthaul architecture that integrates ultra-wide wireless bandwidth with precise positioning and sensing.

Integrating distributed ultra-low-frequency vibration sensing and high-speed fiber optical communication can provide additional functionality under the current submarine telecommunication network, such as ocean seismic monitoring and geological exploration. This work demonstrates an integrated sensing and communication (ISAC) system utilizing the same wavelength channel over a 38 km seven-core fiber for concurrent large-capacity transmission and ultra-low-frequency distributed acoustic sensing. Specifically, the digital subcarrier multiplexing (DSM) signal and the chirped-pulse sensing signal are frequency division multiplexed at the same wavelength channel, under the condition of the optimal protection interval bandwidth, relying on the DSM flexibility in spectral allocation. As a result, we successfully achieve a sensitivity of both 3.89 nε/Hz@0.1 Hz and 0.18 nε/Hz@10 Hz under a spatial resolution of 20 m, under the framework of direct detection and cross-correlation demodulation. Meanwhile, a transmission capacity record of 241.85 Tb/s is secured for the ISAC when wavelength and space division multiplexed DP-16QAM DSM signals are successfully transmitted to reach the 20% soft-decision feedforward correction coding threshold of 2×10-2.

Neural networks (NNs), especially electronic-based NNs, have been rapidly developed in the past few decades. However, the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware, facing its bottleneck due to the slowdown of Moore’s law. Optical neural networks (ONNs), in which NNs are realized via optical components with information carried by photons at the speed of light, are drawing more attention nowadays. Despite the advantages of higher processing speed and lower system power consumption, one major challenge is to realize reliable and reusable algorithms in physical approaches, particularly nonlinear functions, for higher accuracy. In this paper, a versatile parametric-process-based ONN is demonstrated with its adaptable nonlinear computation realized using the highly nonlinear fiber (HNLF). With the specially designed mode-locked laser (MLL) and dispersive Fourier transform (DFT) algorithm, the overall computation frame rate can reach up to 40 MHz. Compared to ONNs using only linear computations, this system is able to improve the classification accuracies from 81.8% to 88.8% for the MNIST-digit dataset, and from 80.3% to 97.6% for the Vowel spoken audio dataset, without any hardware modifications.

The next generation of mobile communication is committed to establishing an integrated three-dimensional network that encompasses air, land, and sea. The visible light spectrum is situated within the transmission window for underwater communication, making visible light laser communication a focus of intense research. In this paper, we design and integrate a compact 5-λ transmission module based on five laser diodes with different wavelengths, utilizing a self-developed narrow-ridge GaN blue laser. With this transmitter, we have developed a polarization division multiplexing (PDM) 5-λ underwater visible light laser communication (UVLLC) system based on this transmission module. To enhance the transmission quality of the system, we designed a dual-branch ResDualNet network as a reciprocal differential receiver that incorporates common-mode noise cancellation and equalization functions for post-processing the received signals. With the combined contribution of the devices and algorithms, we achieved a total transmission rate of 170.1 Gbps, which represents a 16.1 Gbps increase compared to systems that do not utilize ResDualNet. To the best of our knowledge, this is the highest communication rate currently achievable in a UVLLC system using a single laser transmission module.

Single-molecule localization microscopy (SMLM) provides nanoscale imaging, but pixel integration of acquired SMLM images limited the choice of sampling rate, which restricts the information content conveyed within each image. We propose an upsampled point spread function (PSF) inverse modeling method for large-pixel single-molecule localization, enabling precise three-dimensional superresolution imaging with a sparse sampling rate. Our approach could reduce data volume or expand the field of view by nearly an order of magnitude, while maintaining high localization accuracy and greatly improving the imaging throughput with the limited pixels available in existing cameras.

Miniaturization of photoacoustic microscopy (PAM) to portable and wearable levels requires special design of scanning, detection, acquisition, and excitation units. Now the first three can be minimized to gram and millimeter levels, but the excitation sources usually remain bulky and also face different challenges, including low pulse energy, wide pulse width, limited wavelength, or high cost. Here, we propose a high-performance laser source specially designed for a miniature PAM system, that is, the pulse-pumped passively Q-switched solid-state laser (PQS-SSL). Its kilohertz repetition rate, nanosecond pulse width, microjoule pulse energy, and UV to NIR spectra are exactly within the requirements of functional PAM imaging, together with the merits of millimeter scale and low cost, originating from the all-crystal-based configuration. The pulsed pump technique empowers the laser with frequency lock and trigger-in ability for system synchronization, overcoming the conventional free-running drawbacks, and the senior multi-pulse pump is also feasible to further compress the laser size and cost. We showcase its PAM performance on the USAF1951, carbon fiber, zebrafish, and lipid (wavelength extension to ∼1.2 μm). The novel, to our knowledge, pulse-pumped PQS-SSL is not only promising for general PAM, but also paves the way to develop miniature PAM systems, such as hand-held or brain-wearable modalities.

Super-resolution (SR) imaging has been widely used in several fields like remote sensing and microscopy. However, it is challenging for existing SR approaches to capture SR images in a single shot, especially in dynamic imaging scenarios. In this study, we present a single-shot SR imaging scheme that leverages discernibility in the high-dimensional (H-D) light-field space based on a ghost imaging camera via sparsity constraints (GISC camera), which is capable of encoding H-D imaging information into a two-dimensional speckle pattern detected in a single shot. We demonstrate both theoretically and experimentally that while the resolution in the H-D light-field space, characterized by the second-order light-field correlation, remains limited by light-field diffraction, the single-shot spatial resolution is greatly improved beyond classical Rayleigh’s criterion by utilizing the discernibility in the H-D light-field space. We further quantify the effects of the sampling number, signal-to-noise ratio, and object sparsity on the resolution. Our results offer significant potential for the SR observation of high-speed dynamic processes.

With the recent development of diversity electro-optic sampling (DEOS), significant progress has been made in the range of applicability of single-shot EOS measurements, allowing broadband THz waveforms to be captured in a single shot over large temporal windows. In addition to the decrease in acquisition time compared to standard multishot data acquisition, this technique allows measurements on systems far from equilibrium with large shot-to-shot noise or with irreversible or poorly repeatable dynamics. Although DEOS has been demonstrated and verified for linearly polarized THz waveforms, we investigate the effects resulting from the presence of a secondary polarization component. This imposes new challenges for accurate waveform reconstruction, and opens the opportunity to measure out complex polarization states such as arbitrary elliptically polarized THz field. We demonstrate a single-shot diversity-electro-optic-sampling-based approach to capture both x- and y-THz fields simultaneously with a single (110)-cut EO crystal for THz polarimetry and ellipsometry over a wide range of frequencies.

Conventional frequency-sweep interferometry is unreliable for noncooperative or long-distance targets owing to scattering on the target surface. Hence, this paper proposes a laser frequency-swept carrier (LFSC) ranging method based on resonant cavity enhancement for long-distance noncooperative target measurements and weak-signal detection. Experimental verification revealed that for a target comprising an oxidized black aluminum plate at a distance of 16 m, the standard deviation of 10 measurements was less than 70 μm, measurement accuracy exceeded 27 μm, and system ranging resolution exceeded 0.13 mm when the target feedback light was very weak. This method is useful for measurements of noncooperative targets, e.g., large-scale component assembly, industrial measurement, and biomedical testing.

Phase is an intrinsic property of light, and thus a crucial parameter across numerous applications in modern optics. Various methods exist for measuring the phase of light, each presenting challenges and limitations—from the mechanical stability requirements of free-space interferometers to the computational complexity usually associated with methods based on spatial light modulators. Here, we utilize a passive photonic integrated circuit to spatially probe phase and intensity distributions of free-space light beams. Phase information is encoded into intensity through a set of passive on-chip interferometers, allowing conventional detectors to retrieve the phase profile of light through single-shot intensity measurements. Furthermore, we use silicon nitride as a material platform for the waveguide architecture, facilitating multi-spectral utilization in the visible spectral range. Our approach for fast, multi-spectral, and spatially resolved measurement of intensity and phase enables a wide variety of potential applications, ranging from microscopy to free-space optical communication.

Bending optofluidic waveguides are essential for developing high-performance fluid-based photonic circuits and systems. The combination of femtosecond (fs)-laser-assisted etching of high-precision microchannels and vacuum-assisted liquid-core filling allows the controllable fabrication of low-loss optofluidic waveguides in fused silica. However, to form high-performance bending optofluidic waveguides in fused silica, facile fabrication of long, homogeneous microchannels with arbitrary shapes remains challenging due to the polarization-dependent limitations of conventional fs-laser-assisted etching. Here, we demonstrate the rational fabrication of homogeneous curved microchannels in fused silica using polarization-independent fs-laser-assisted etching enabled by a low-pulse-overlap scheme. An etching rate exceeding 350 μm/h can be reliably achieved at a pulse overlap of 10 pulses μm-1 regardless of the variation of the laser polarization. Highly interconnected nanocracks are observed along the laser writing direction in the laser-modified regions. Using the polarization-independent fs-laser-assisted etching combined with spatial beam shaping and carbon dioxide laser irradiation, uniform and smooth curved microchannels with centimeter lengths, flexible configurations, and nearly circular cross-sections are initially produced. Subsequently, single-mode bending optofluidic waveguides and beam splitters are created by filling tunable refractive index liquid-core solutions into the channels. The proposed method enables efficient processing of arbitrarily oriented homogeneous microchannels, paving the way for the development of large-scale, complex microfluidic photonic circuits.

We propose and numerically test, to our knowledge, a novel concept for asymmetric vortex beam generation in a degenerate vertical external cavity surface emitting laser (DVECSEL). The method is based on a phase-locking ring array of lasers created inside a degenerate cavity with a binary amplitude mask containing circular holes. The diffraction engineering of the mask profile allows for controlling the complex coupling between the lasers. The asymmetry between different lasers is introduced by varying the hole diameters corresponding to different lasers. Several examples of masks with non-uniform or uniform circular holes are investigated numerically and analytically to assess the impact of non-uniform complex coupling coefficients on the degeneracy between the vortex and anti-vortex steady states of the ring laser arrays. It is found that the in-phase solution always dominates irrespective of non-uniform masks. The only solution to make one particular vortex solution dominant over other possible steady-state solutions consists of imprinting the necessary phase shift among neighboring lasers in the argument of their coupling coefficients. We also investigate the role of the Henry factor inherent to the use of a semiconductor active medium in the probabilities to generate vortex solutions. Analytical calculations are performed to generalize a formula previously reported [Opt. Express30, 15648 (2022)OPEXFF1094-408710.1364/OE.456946], for the limiting Henry factor to cover the case of complex couplings.

Stimulated Brillouin scattering (SBS)-induced mode distortion (MD) in high power narrow linewidth fiber amplifiers has been implemented, and the origin has been investigated from the aspect of the evolution of the optical spectrum, spatial beam profiles, and temporal-frequency domain characteristics. It is shown that, following the onset of the backward giant pulses generated by SBS, forward giant pulses were generated, which reached multi-kilowatt level peak power and triggered the onset of stimulated Raman scattering (SRS). After the onset of SRS, the beam quality starts to degrade, and the beam profiles deteriorate obviously. It reveals that the SBS-induced MD is a two-stage physical process: SBS-induced forward giant pulses trigger the SRS effect, and then the SRS effect causes the beam deterioration of the signal laser, which means that SRS is the origin of the MD observed after the onset of SBS. To the best of our knowledge, this is the first revelation of SBS-induced mode distortion in high power narrow linewidth fiber amplifiers, which can facilitate the in-depth understanding and effective suppression of the complicated mode evolution phenomena.

The complexity of multi-dimensional optical wave dynamics arises from the introduction of multiple degrees of freedom and their intricate interactions. In comparison to multimode spatiotemporal mode-locked solitons, expanding the wavelength dimension is also crucial for studying the dynamics of multi-dimensional solitons, with simpler characterization techniques. By inserting a section of zero-dispersion highly nonlinear fiber (HNLF) into a passively mode-locked fiber laser, two heteronuclear dichromatic soliton compounds with different group velocities (GVs) are formed within the resonant cavity of the laser. The cross-phase modulation effect leads to the formation of a robust fast-GV compound (FGC), consisting of a partially coherent dissipative soliton bunch (PCDSB) and dispersion waves (DWs), while a conventional soliton (CS) and a narrow spectral pulse (NSP) form a slow-GV compound (SGC). Multiple SGCs can further interact to form an SGC loosely bound complex. These two types of compounds with different GVs continuously collide and exchange energy through the four-wave mixing (FWM) effect in the HNLF, promoting the annihilation, survival, and regeneration of the SGC complex. This exploration of interactions between asynchronous compounds broadens the study of soliton dynamics in multi-dimensions and offers insights for potential applications in areas such as high-throughput optical communication and optical computing.

Introducing topological lattice defects, such as dislocations, into topological photonic crystals enables the emergence of many interesting phenomena, including robust bound states and fractional charges. Previous studies have primarily focused on the realization of dislocation modes within a single band gap, which limits the number of dislocation modes and their applications. Here, we design a topological photonic crystal with two topologically non-trivial band gaps. By introducing a dislocation defect into this system, we observe the emergence of localized dislocation modes in both band gaps. Furthermore, we demonstrate a two-channel add-drop filter by coupling two dislocation modes with topological edge modes. These findings are rigorously validated through full-wave numerical simulations and experimental pump-probe transmission measurements. Our results provide a foundation for further exploration of dislocation modes and unlock the potential for harnessing other topological defect modes in dual-band-gap systems.

The integrated quantum interferometer has provided a promising route for manipulating and measuring quantum states of light with high precision, requiring negligible optical loss, broad bandwidth, robust fabrication tolerance, and scalability. In this paper, a rapid adiabatic coupler (RAC) is presented as a compelling solution for implementing the integrated quantum interferometer on a thin-film lithium niobate (TFLN)-based platform, enabling a compact, broadband, and low-loss optical coupler. The TFLN-based RACs are carefully designed by manipulating a curvature along the structures with consideration of inherent birefringence as well as fabrication-induced slanted sidewalls. The high extinction ratio over 20 dB of the RAC-based Mach–Zehnder interferometer (MZI) is achieved in the wavelength range from 1500 to 1600 nm. The beam splitter (BS) with the balanced splitting ratio is exploited for observation of on-chip Hong–Ou–Mandel (HOM) interference with high visibility of 99.25%. We believe TFLN-based RACs hold great potential to be favorably utilized for integrated quantum interferometers, enabling widespread adoptions in myriad applications in integrated quantum optics.

Unidirectional guided resonances (UGRs) in planar photonic lattices are distinctive resonant eigenstates that emit light in a single direction. A recent study has demonstrated that UGRs can be utilized to implement ultralow-loss grating couplers for integrated photonic applications. In this study, we investigate the formation and radiation of UGRs in two types of L-shaped gratings, type I and type II, which exhibit both broken up-down mirror symmetry and broken in-plane C2 symmetry. In type I gratings, quasi-UGRs are readily identified in the lower band, whereas in type II gratings they appear in the upper band. We demonstrate that, as the relevant grating parameters are gradually varied, these quasi-UGRs evolve into genuine UGRs in the lower band for type I gratings and in the upper band for type II gratings. In type I gratings, UGRs produce negative-angle emission because their Poynting vectors are oriented antiparallel to their wavevectors, while in type II gratings, UGRs yield positive-angle emission due to the parallel alignment of their Poynting vectors and wavevectors. Moreover, the position and emission angle of UGRs can be systematically controlled by varying the lattice parameters. Our findings offer valuable insights for developing high-efficiency optical interconnects that leverage UGRs.

Femtosecond laser filamentation has attracted significant attention due to its applications in remote sensing of atmospheric pollutants and artificial weather intervention. Nitrogen is the most abundant gas in the atmosphere, and its stimulated ultraviolet emission is remarkably clean, distinctly different from the fluorescence obtained through electron impact or laser breakdown. While numerous experiments and mechanism analyses have been conducted on its characteristic fluorescence excited by laser filamentation, they predominantly focused on short-distance filamentation (less than 1 m). Contrary to previous reports, we find that at long distances (30 m), the fluorescence intensity of neutral nitrogen molecules excited by linearly polarized laser pulses is approximately 7 times that excited by circularly polarized pulses with the same energy. This enhancement is caused by the enhanced tunneling ionization rate, 3.7 times that under circular polarization, and the elongated filament length, 1.85 times that under circular polarization, when using linear polarization. Additionally, after comparing existing theories for N2(C3Πu)) excitation, the dissociation-recombination model is found to be more appropriate for explaining the formation of N2(C3Πu)) excited states during long-distance filamentation.

Mass detection plays an indispensable role in many fields like medical targeted therapy, biological cytology, and nanophysics. However, traditional mass detection faces the challenge of a complex system, expensive instruments, and long testing time. Here we report an all-fiber-optic mass sensor based on a nanofilm resonator. Using resonant frequency shifts as the readout of analyte mass, the sensor achieves the mass sensitivity of 0.920 kHz/pg with a mass resolution of 1.9×10-14 g, for the first-order mode in the mass range up to 372 pg at room temperature. In this work, we transfer the excitation laser and detection laser to the micro-cavity structure at the end of the optical fiber. Combined with optical fibers, the sensor can be made extremely integrated, making it more stable and collimation-free compared with traditional bulky optical setups. Its good biocompatibility and anti-electromagnetism disturbance ability also make this mass sensor potentially a beneficial tool for cell biology and basic physics measurements.

This study pioneers a high-performance UV polarization-sensitive photodetector by ingeniously integrating non-centrosymmetric metal nanostructures into a graphene (Gr)/Al2O3/GaN heterojunction. Unlike conventional approaches constrained by graphene’s intrinsic isotropy or complex nanoscale patterning, our design introduces asymmetric metal architectures (E-/T-type) to artificially create directional anisotropy. These structures generate plasmon-enhanced localized electric fields that selectively amplify photogenerated carrier momentum under polarized UV light (325 nm), synergized with Fowler-Nordheim tunneling (FNT) across an atomically thin Al2O3 barrier. The result is a breakthrough in performance: a record anisotropy ratio of 115.5 (E-type, -2 V) and exceptional responsivity (97.7 A/W), surpassing existing graphene-based detectors by over an order of magnitude. Crucially, by systematically modulating metal geometry and density, we demonstrate a universal platform adaptable to diverse 2D/3D systems. This study provides a valuable reference for developing and practically applying photodetectors with higher anisotropy than ultraviolet polarization sensitivity.

In this paper, an efficient Ge25Sb10S65 (GeSbS)-loaded erbium-doped lithium niobate waveguide amplifier is demonstrated. By dimensional optimization of the waveguide, an internal net gain of approximately 28 dB and a maximum on-chip output power of 8.2 dBm are demonstrated upon 1480 nm bidirectional pumping. Due to the improved optical mode field distribution within the active erbium-doped lithium niobate film and the mode overlap ratio between the pump and signal sources, a 15% high conversion efficiency can be achieved at a modest pump power of 45 mW. Furthermore, the noise figure of the amplifier can be maintained below 6 dB for low-input-signal power levels. Compared to state-of-the-art erbium-doped waveguide amplifiers (EDWAs), this heterogeneously integrated device shows superior gain performance at the desired optical C-band while avoiding the complex plasma etching process of lithium niobate, providing an inspirative solution for power compensation in the optical telecommunications.

Optical fiber magnetic field sensors play a crucial role in aerospace and medical fields due to their high sensitivity, fast response time, and resistance to electromagnetic interference. Most current research primarily focuses on detecting magnetic field intensity; however, the magnetic field is a vector field with both intensity and direction, making vector magnetic field measurement significantly important in various fields. Here, we experimentally demonstrated a vector magnetic field sensor using a magnetic fluid (MF) enabled hexagonal fiber grating. Such a specialty optical fiber device features strong asymmetric evanescent field distribution along the index perturbed area, from which the overcoated MF can sense the external magnetic field. When the fiber magnetometer operated at the dispersion turning point, a maximum sensitivity of 10.48 nm/mT was achieved within a range of 0–20.7 mT, which is one order of magnitude greater than that of conventional fiber grating sensors. Utilizing the polygon optical fiber, our demonstrated device simultaneously achieves a maximum orientation sensitivity of 1.17 nm/deg within a range of 0°–30°. This hexagonal fiber grating as an excellent vector magnetic field sensor may be used in military, aerospace, medical sectors, etc.

Advanced technologies such as autonomous driving, cloud computing, Internet of Things, and artificial intelligence have considerably increased data demand. Real-time interactions further drive the development of high-speed, high-capacity networks. Advancements in communication systems depend on developing high-speed optoelectronic devices. Optical communication systems are rapidly evolving, with data rates advancing from 800 Gbps to 1.6 Tbps and beyond, driven by the development of high-performance photodetectors, high-speed modulators, and advanced RF devices. Avalanche photodetectors (APDs) are used in long-distance applications owing to their high internal gain and responsivity. This paper reviews the structural designs of APDs based on various materials for high-speed communication and provides an outlook on developing APDs based on advanced materials.

High-performance infrared emitters hold substantial importance in modern engineering and physics. Here, we introduce graphene/PZT (lead zirconate titanate) heterostructure as a new platform for the development of infrared source structure based on an electron–phonon coupling and emitting mechanism. A series of electrical characterizations including carrier mobility [11,361.55 cm2/(V·s)], pulse current (30 ms response time), and cycling stability (2000 cycles) modulated by polarized film was provided. Its maximum working temperature reaches ∼1041 K (∼768°C), and it was broken at 1173 K (∼900°C) within ∼1.2 s rise time and fall time. Based on Wien’s displacement law, the high temperature will lead to near–mid–far thermal infrared when the heterostructure is applied to external voltages, and obvious bright white light could be observed by the naked eye. The changing process has also been recorded by mobile phone. In subsequent infrared emitting applications, 11 V bias voltage was applied on the PZT/graphene structure to produce the temperature change of ∼299 to 445 K within ∼0.96 s rise time and ∼0.98 s fall time. To demonstrate its optical information transmission ability, we exhibited “N, U, C” letters by the time-frequency method at 3 mm×3 mm@20 m condition. Combining with spatial Morse code infrared units, alphabetic information could also be transmitted by infrared array images. Compared with the traditional infrared emitter, the electron–phonon enhancing mechanism and high-performance emission properties of the heterostructure demonstrated a novel and reliable platform for further infrared optical applications.

Single-shot multi-frame phase imaging plays an important role in detecting continuous extreme physical phenomena, particularly suitable for measuring the density of media with non-repeatable changes and uncertainties. However, traditional single-pattern multiplexed imaging faces challenges in retrieving amplitude and phase information of multiple frames without sacrificing spatial resolution and phase accuracy. In this study, we demonstrate single-shot common-path encoded coherent diffraction imaging with orbital angular momentum (OAM) multiplexing. It employs a sequence of vortex illumination fields, combined with encoding wavefront modulation and a vortex multiplexing phase retrieval algorithm, to achieve the retrieval of complex amplitudes from dynamic samples in single shots. Our experimental validation demonstrated the capability to achieve 9-frame high-resolution phase imaging of the dynamic sample in a single diffraction pattern. The spatial resolution and phase accuracy improve to 9.84 μm and 4.7% with this lensless multiplexed imaging system, which is comparable to single-mode imaging. This technology provides a multiplexed dimension with orbital angular momentum and holds potential in the study of transient continuous phenomena.

The enantiospecific detection of the chirality of substances at the nanoscale has attracted significant attention due to its importance in materials science, chemistry, and biology. This study presents, to our knowledge, a novel method for chirality detection based on transverse optical torque (OT), which leverages the transverse rotation of achiral particles induced by the transfer of chirality from the chiral particle within interference fields formed by the incident light without spin angular momentum (SAM). We demonstrate, both numerically and analytically, that by modulating the chirality of the chiral particle within a dimer system, it is possible to achieve the transfer of local SAM to the gold particle, thereby generating a transverse OT perpendicular to the light propagation direction. Furthermore, by adjusting the orientation of linear polarization in the excitation field, the respective contributions of electric and magnetic responses to the chirality-transfer-induced transverse OT can be exclusively observed separately, providing deeper insights into the underlying physical mechanisms. More importantly, the transverse OT exhibits an approximately linear dependence on the chirality parameter of the chiral particle, enabling enantiospecific detection of nanosamples. By replacing gold nanoparticles with suitable high-refractive-index dielectric materials such as germanium, the induced transverse magnetic dipolar OT can be further enhanced by more than two orders of magnitude, significantly improving the sensitivity of chirality detection and making it possible to detect weak chiral signals with exceptional precision. This work broadens the application scope of OTs in chirality detection and highlights the potential of chirality transfer mechanisms for advanced optical manipulation and the identification and analysis of chiral substances.

Recently, spatiotemporal optical vortices (STOVs) with transverse orbital angular momentum have emerged as a significant research topic. While various STOV fields have been explored, they often suffer from a critical limitation: the spatial and temporal dimensions of the STOV wavepacket are strongly correlated with the topological charge. This dependence hinders the simultaneous achievement of high spatial accuracy and high topological charge. To address this limitation, we theoretically and experimentally investigate a new class of STOV wavepackets generated through the spatiotemporal Fourier transform of polychromatic Bessel–Gaussian beams, which we term as perfect spatiotemporal optical vortices. Unlike conventional STOVs, perfect STOVs exhibit spatial and temporal diameters that are independent of the topological charge. Furthermore, we demonstrate the generation of spatiotemporal optical vortex lattices by colliding perfect STOV wavepackets, enabling flexible manipulation of the number and sign of sub-vortices.

Crystalline undulator radiation (CUR) is emitted by charged particles channeling through a periodically bent crystal. We show that entangled high-energy photons of the order of 100 MeV can be generated from CUR and obtain the quantum entanglement properties of the double-photon emission of CUR with a nonperturbative quantum field theory. We demonstrate that the crystalline undulator (CU) can induce a 3D free-electron lattice with premicrobunched electrons, and the resulting free-electron lattice can enhance the entangled high-energy photon emission for certain angles by phase matching. We also examine the effects of demodulation and dechanneling during the electron beam channeling process, and show the dependence of the dechanneling and demodulation lengths on the undulator parameters.

Photonic multi-dimensional storage capabilities and the high storage efficiency of multiplexed quantum storage devices are critical metrics that directly determine the entanglement distribution efficiency of quantum networks. In this work, we experimentally demonstrate a high-efficiency storage for multi-dimensional photonic states in path, polarization, and orbital angular momentum (with vector beams serving as the photonic dimensional carriers of polarization and orbital angular momentum) in laser-cooled Rb87 atom ensembles with cigar shapes. We achieve path-multiplexed storage of two-channel vector beams at the single-photon level, with storage efficiency exceeding 74% for first-order vector beams and 72% for second-order vector beams. Additionally, the storage fidelity surpasses 89% for both types. Furthermore, we achieve a storage time of approximately 7 μs for two-channel vector beams, and the spatial structure and phase information are preserved during storage through performed projection measurements. The results confirm that our system has the capability for optical storage in photon polarization and orbital angular momentum, as well as in a multi-dimensional photon path. These results show significant potential for advancing large-scale repeater-based quantum networks and distributed quantum computing.

A GeSn nanostrip grown by the rapid melting growth method has gradient Sn content along the strip, a very attractive approach for making an infrared broad-spectrum light source. In this work, by applying the Sn content distribution strategy, GeSn shortwave infrared light-emitting diodes (LEDs) arrays with a size of 3 μm×2 μm were fabricated on Si substrate, and the active layer Sn content increased from 2.1% to 5.2% to form a broadband light source. The GeSn LEDs show perfect rectifying behavior about 106 for ±1 V, and room temperature electroluminescence (EL) from the direct bandgap was achieved. The super-linear dependence between the injected current and EL intensity confirms the band-to-band radiative recombination. By utilizing Sn content gradient technology, the EL spectra of Sn gradient GeSn LED arrays can cover from 1600 to 2200 nm with a full width at half-maximum of about 340 nm. These results show a novel method for preparing broad-spectrum shortwave infrared light emitters on a Si chip.

Infrared spectroscopy has wide applications in the medical field, industry, agriculture, and other areas. Although the traditional infrared spectrometers are well developed, they face the challenge of miniaturization and cost reduction. Advances in nanomaterials and nanotechnology offer new methods for miniaturizing spectrometers. However, most research on nanomaterial-based spectrometers is limited to the visible wavelength or near infrared region. Here, we propose an infrared spectrometer based on diffraction gratings and colloidal quantum dot (CQD) homojunction photodetector arrays. Coupled with a Fabry-Perot cavity, the CQD photodetector covers the 1.4–2.5 μm spectral range, with specific detectivity 4.64×1011 Jones at 2.5 μm at room temperature. The assembled spectrometer has 256 channels, with total area 2.8 mm×40 mm. By optimizing the response matrix from machine learning algorithms, the CQD spectrometer shows high-resolution spectral reconstruction with a resolution of approximately 7 nm covering the short-wave infrared.

Imaging in the solar blind ultraviolet (UV) region offers significant advantages, including minimal interference from sunlight, reduced background noise, low false-alarm rate, and high sensitivity, and thus has important applications in early warning or detection of fire, ozone depletion, dynamite explosions, missile launches, electric leakage, etc. However, traditional imaging systems in this spectrum are often hindered by the bulkiness and complexity of conventional optics, resulting in heavy and cumbersome setups. The advent of metasurfaces, which use a two-dimensional array of nano-antennas to manipulate light properties, provides a powerful solution for developing miniaturized and compact optical systems. In this study, diamond metalenses were designed and fabricated to enable ultracompact solar-blind UV imaging. To prove this concept, two representative functionalities, bright-field imaging and spiral phase contrast imaging, were demonstrated as examples. Leveraging diamond’s exceptional properties, such as its wide bandgap, high refractive index, remarkable chemical inertness, and high damage threshold, this work not only presents a simple and feasible approach to realize solar-blind imaging in an ultracompact form but also highlights diamond as a highly capable material for developing miniaturized, lightweight, and robust imaging systems.

Metasurfaces offer innovative approaches for manipulating electromagnetic waves at subwavelength scales. Recent advancements have focused on toroidal dipole (TD) and quasi-bound state in the continuum (quasi-BIC) modes, which are particularly attractive due to their capacity to enhance light-matter interaction. However, most metasurfaces with TD and quasi-BIC modes exhibit passive electromagnetic responses after fabrication, limiting their practical applications. This study presents both numerical and experimental investigations that demonstrate the active control of TD and quasi-BIC modes through the integration of symmetric and asymmetric aluminum dumbbell aperture arrays with the phase-change material Ge2Sb2Te5 (GST). The symmetric hybrid dumbbell aperture array shows a pronounced TD response within the terahertz frequency range. In contrast, modifying the geometric parameters to disrupt the structural symmetry induces a quasi-BIC mode in the asymmetric hybrid dumbbell aperture array. Furthermore, as GST undergoes a phase transition from its amorphous to crystalline state, both TD and quasi-BIC modes become dynamically tunable, driven by changes in the conductivity of GST. Notably, significant modulation of the transmitted terahertz wave occurs around the frequencies corresponding to the TD and quasi-BIC modes during the GST phase transition. Symmetric and asymmetric hybrid dumbbell aperture arrays provide a versatile platform for generating tunable TD and quasi-BIC modes, with promising applications in terahertz modulators and filters.

The precise spatiotemporal characterization of broadband ultrafast laser beams is essential for accurate laser control and holds significant potential in photochemistry and high-intensity laser physics. Existing methods for spatiotemporal characterization, such as frequency-resolved optical gating (FROG) and compressed ultrafast photography (CUP), are often spatially averaged or suffer from limited spatial resolution. Recent advances in imaging techniques based on multiplexed ptychography have enabled high-spatial-resolution diagnostics of ultrafast laser beams. However, the discrete spectral assumption inherent in multiplexed ptychographic algorithms does not align with the continuous spectral structure of ultrafast laser pulses, leading to significant crosstalk between different wavelength channels (WCs). This paper presents a method to reduce the bandwidth of each wavelength channel through spectral modulation, followed by the discretization of the continuous spectrum using interference techniques, which significantly improves the convergence and accuracy of the reconstruction. Using this method, the experiment accurately measured chromatic dispersion, spatial chirp, and other spatiotemporal coupling effects in femtosecond laser beams, achieving a spatial resolution of 9.4 μm, close to the pixel size resolution limit of the angular spectrum method.

Due to the high-dimensional characteristics of photon orbital angular momentum (OAM), a beam can carry multiple OAMs simultaneously thus forming an OAM comb, which has been proved to show significant potential in both classical and quantum photonics. Tailoring broadband OAM combs on demand in a fast and accurate manner is a crucial basis for their application in advanced scenarios. However, obtaining phase-only gratings for the generation of arbitrary desired OAM combs still poses challenges. In this paper, we propose a multi-scale fusion learning U-shaped neural network that encodes a phase-only hologram for tailoring broadband OAM combs on-demand. Proof-of-principle experiments demonstrate that our scheme achieves fast computational speed, high modulation precision, and high manipulation dimensionality, with a mode range of -75 to +75, an average root mean square error of 0.0037, and a fidelity of 85.01%, all achieved in about 30 ms. Furthermore, we utilize the tailored broadband OAM combs in conducting optical convolution calculation, enabling vector convolution for arbitrary discrete functions, showcasing the extended capability of our proposal. This work opens, to our knowledge, new insight for on-demand tailoring of broadband OAM combs, paving the way for further advancements in high-dimensional OAM-based applications.

Holographic optical elements (HOEs) are integral to advancements in optical sensing, augmented reality, solar energy harvesting, biomedical diagnostics, and many other fields, offering precise and versatile light manipulation capabilities. This study, to the best of the authors’ knowledge, is the first to design and fabricate an HOE mutli-waveguide system using a thermally and environmentally stable photopolymerizable hybrid sol-gel (PHSG) for sensing applications. Using a 476.5 nm recording wavelength, 60% diffraction efficiency PHSG holographic waveguides of spatial frequency of 1720 lines/mm were successfully fabricated to function as in- and out-couplers at 632.8 nm and 700 nm wavelength, respectively. The waveguides were integrated into a polydimethylsiloxane (PDMS) microfluidic system, guiding excitation light of 632.8 nm wavelength into and extracting fluorescence light signal peaking at 700 nm from a location filled with methylene blue water solution. Further, to demonstrate the potential of the proposed optical system, four holographic waveguides were recorded by peristrophic and angular multiplexing in the same location of the material and the input beam was delivered into four spatially separated channels by total internal reflection in the sol-gel layer, thus, successfully highlighting the capabilities and advantages of HOE waveguides for parallel interrogation of multiple locations in a wearable sensor. This study demonstrates the efficiency and versatility of PHSG-based HOE waveguides, underscoring their potential to enhance photonic device design and performance across various optical applications.

Ranging is indispensable in a variety of fields, encompassing basic science, manufacturing, production, and daily life. Although traditional methods based on the dispersive interferometry (DPI) in the frequency domain provide high precision, their measurement speed is slow, preventing the capture and measurement of dynamic displacements. Here, we propose a fast and precise ranging method based on the dispersion-controlled dual-swept laser (DCDSL), which allows the dynamical displacement measurement of the target under test. Due to the slight frequency sweeping speed difference between the signal and reference lights, there is a zero-frequency point of the oscillation (ZPO) generated in the interference signal, whose position in the time domain is linearly related to the relative delay between the signal and reference lights. Utilizing phase demodulation of the interference signal from the DCDSL and the fitting algorithm, the time-domain position of ZPO is accurately found, which precisely maps to the displacement of the target in real time without direction ambiguity. The fast frequency sweeping rate ensures fast ranging with the MHz order refresh frame. We have experimentally demonstrated its capabilities for precise measurement of static distances and the capture of dynamic displacement processes through simulations and experiments, with the measurement range encompassing the entire interference period (56 mm). Compared to a calibrated motorized displacement platform, the residual error for full-range distance measurements is within 10 μm, and the error in average speed during dynamic processes is 0.46%. Additionally, the system exhibits excellent stability, achieving a minimum Allan deviation of 4.25 nm over an average duration of approximately 4 ms. This method ensures high precision while maintaining a simple system, thereby advancing the practical implementation of ultrafast length metrology.

Optical transfer delay (OTD) is essential for distributed coherent systems, optically controlled phased arrays, fiber sensing systems, and quantum communication systems. However, existing OTD measurement techniques typically involve trade-offs among accuracy, range, and speed, limiting the application in the fields. Herein, we propose a single-shot OTD measurement approach that simultaneously achieves high-accuracy, long-range, and high-speed measurement. A microwave photonic phase-derived ranging with a nonlinear interval microwave frequency comb (MFC) and a discrete frequency sampling technique is proposed to conserve both frequency and time resources, ensuring high-accuracy and ambiguity-free measurements. In the proof-of-concept experiment, a delay measurement uncertainty at the 10-9 level with a single 10 μs sampling time is first reported, to our knowledge. The method is also applied to coherently combine two distributed signals at 31.8 GHz, separated by a 2 km optical fiber. A minimal gain loss of less than 0.0038 dB compared to the theoretical value was achieved, corresponding to an OTD synchronization accuracy of 0.3 ps.

Dispersive optical phased arrays (DOPAs) offer a method for fast 2D beam scanning for solid-state LiDAR with a pure passive operation, and therefore low control complexity and low power consumption. However, in terms of scalability, state-of-the-art DOPAs do not easily achieve a balanced performance over the specifications of long-range LiDAR, including the number of pixels (resolvable points) and beam quality. Here, we experimentally demonstrate the pixelated DOPA concept, which overcomes the scaling challenges of classical (continuous) DOPAs by introducing a new design degree of freedom: the discretization of the optical delay lines distribution network into blocks. We also present the first demonstration of the unbalanced splitter tree architecture for the DOPA distribution network, incorporated in both the continuous DOPA and the pixelated DOPA variations. The small-scale demonstration circuits can scan over a field of view of 15°×7.2°, where the continuous DOPA provides 16×25 pixels, while the pixelated DOPA provides 4×25 pixels, for a 1500 to 1600 nm wavelength sweep. The pixelated DOPA exhibits a side lobe suppression ratio with a median of 7.6 dB, which is higher than that of the continuous version, with a median of 3.6 dB. In addition, the ratio of the main beam to the background radiation pattern is 11 dB (median value) for the pixelated DOPA, while for the continuous DOPA, it is 9.5 dB. This is an indication of a higher beam quality and lower phase errors in the pixelated DOPA. The degree of discretization, combined with other design parameters, will potentially enable better control over the beam quality, while setting practical values for the number of pixels for large-scale DOPAs.

Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties. However, its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors. Recently, lithium tantalate, another piezoelectric and nonlinear material, has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction, faster electro-optic response relaxation, higher optical damage threshold, wider transparency window, and lower birefringence compared with lithium niobate. Here, we developed an ultralow-loss lithium tantalate integrated photonic platform, including waveguides, grating couplers, and microring cavities. The measured highest optical Q factor of the microring cavities is beyond 107, corresponding to the lowest waveguide propagation loss of ∼1.88 dB/m. The photorefractive effect in such lithium tantalate microring cavities was experimentally demonstrated to be 500 times weaker than that in lithium niobate microcavities. This work lays the foundation for a lithium tantalate integrated platform for achieving a series of on-chip optically functional devices, such as periodically poled waveguides, acousto-optic modulators, and electro-optic modulators.

Spatial photonic Ising machines, as emerging artificial intelligence hardware solutions by leveraging unique physical phenomena, have shown promising results in solving large-scale combinatorial problems. However, spatial light modulator enabled Ising machines still remain bulky, are very power demanding, and have poor stability. In this study, we propose an integrated XY Ising sampler based on a highly uniform multimode interferometer and a phase shifter array, enabling the minimization of both discrete and continuous spin Hamiltonians. We elucidate the performance of this computing platform in achieving fully programmable spin couplings and external magnetic fields. Additionally, we successfully demonstrate the weighted full-rank Ising model with a linear dependence of 0.82 and weighted MaxCut problem solving with the proposed sampler. Our results illustrate that the developed structure has significant potential for larger-scale, reduced power consumption and increased operational speed, positioning it as a versatile platform for commercially viable high-performance samplers of combinatorial optimization problems.

Mode-locked fiber lasers are excellent platforms for soliton generation. Solitons exhibit distinct distribution and evolution characteristics depending on the net dispersion of the laser cavity. Here we propose an experimental scheme to reconstruct the intracavity dynamics of solitons within a mode-locked fiber laser. The proposed scheme is facilitated by disposing multiple output ports at different positions throughout the cavity, thereby enabling in-depth observation and manipulation of soliton evolution along the dispersion map. The experimental results verify corresponding simulations and explain some phenomena from the perspective of soliton evolution. Our results offer a pathway for comprehensive analyses of intracavity pulse dynamics, fostering advancements in nonlinear and ultrafast optics.

Hollow-core-fiber (HCF) gas lasers (GLs) have garnered significant interest as a novel approach for generating mid-infrared lasers, owing to their inherent benefits of rich emission wavelength, high beam quality, and high output power potential. However, they are mostly achieved by a free-space coupling structure, which has a major drawback of being prone to vibrations and other environmental variations. Here, we devise and implement an all-fiber-structure gas-filled HCF amplified spontaneous emission (ASE) source at 3.1 μm based on the reverse tapering and angle-cleaved fusion splicing techniques. By optimizing the C2H2 gas pressure, a maximum mid-infrared output power of 6.59 W was obtained, corresponding to a slope efficiency of 19.74% and near-diffraction-limited beam qualities of Mx2=1.03 and My2=1.06. Furthermore, with a similar all-fiber configuration, a CO2-filled HCF ASE source at 4.3 μm with output power exceeding 1.4 W was generated. To the best of our knowledge, the proposed all-fiber-structure HCF gas light source demonstrates the longest wavelength and highest power reported to date. The development of mid-infrared HCF gas light sources in an all-fiber configuration represents a significant step toward miniaturized HCF lasers, which hold promise as powerful new tools for application in laser medicine, space communication, and other scientific research.

Non-Hermitian topology provides an emergent research frontier for studying unconventional topological phenomena and developing new materials and applications. Here, we study the non-Hermitian Chern bands and the associated non-Hermitian skin effects in Floquet checkerboard lattices with synthetic gauge fluxes. Such lattices can be realized in a network of coupled resonator optical waveguides in two dimensions or in an array of evanescently coupled helical optical waveguides in three dimensions. Without invoking nonreciprocal couplings, the system exhibits versatile non-Hermitian topological phases that support various skin-topological effects. Remarkably, the non-Hermitian skin effect can be engineered by changing the symmetry, revealing rich non-Hermitian topological bulk-boundary correspondences. Our system offers excellent controllability and experimental feasibility, making it appealing for exploring diverse non-Hermitian topological phenomena in photonics.

Spatiotemporal optical vortices (STOVs) exhibit characteristics of transverse orbital angular momentum (OAM) that is perpendicular to the direction of pulse propagation, indicating significant potential for diverse applications. In this study, we employ vanadium dioxide and photonic crystal plates to design tunable transreflective dual-channel terahertz (THz) spatiotemporal vortex generation devices that possess multipolarization adaptability. In the reflection channel, we achieve active tunability of the topological dark lines by utilizing circularly polarized light, based on the topological dark phenomenon, and observe variations in the number of singularities across the parameter space from different observational perspectives. In the transmission channel, we generate independent vortex singularities using linearly polarized light. This multifunctional terahertz device offers a novel approach for the generation and active tuning of spatiotemporal vortices.

Simultaneously increasing the spectral bandwidth and average output power of mid-infrared supercontinuum sources remains a major challenge for their practical application. We particularly address this issue for the long mid-infrared spectral region through experimental developments of short tapered rods made from selenide glass by means of supercontinuum generation in the femtosecond regime. Our simple post-processing of glass rods unlocks potentially higher-power and coherent fiber-based supercontinuum sources beyond the 10-μm waveband. By using a 5-cm-long tapered Ge-Se-Te rod pumped at 6 μm, a supercontinuum spanning from 2 to 15 μm (3–14 μm) with an average output power of 93 mW (170 mW) is obtained for 500-kHz (1-MHz) repetition rate. Additional experiments on other glass families (silica and tellurite) covering distinct spectral regions are also reported to develop and support our analyses. We demonstrate that ultra-broadband spectral broadenings over entire glass transmission windows can be achieved in few-cm-long segments of tapered rods by a fine adjustment of input modal excitation. Numerical simulations are used to confirm the main contribution of the fundamental mode in the ultrafast nonlinear dynamics, as well as the possible preservation of coherence features. Our study opens a new route, to our knowledge, towards the power scaling of high-repetition-rate fiber supercontinuum sources over the full molecular fingerprint region.

Femtosecond pulsed lasers offer significant advantages for micro-/nano-modifications in integrated photonics. Microring resonators (MRRs), which are essential components in photonic integrated circuits (PICs), are widely employed in various fields, including optical communication, sensing, and filtering. In this study, we investigate the modification mechanisms associated with femtosecond laser interactions with MRRs fabricated on a low-pressure chemical vapor deposition (LPCVD)-silicon nitride (SiN) photonic platform, with emphasis on the post-fabrication trimming of second-order microring filters and MRR-based four-channel wavelength-division multiplexing (WDM). We examine 10 MRRs located at different positions on a wafer and discovered resonance wavelength shifts exceeding 1 nm due to fabrication-induced variations. Interactions between femtosecond lasers and LPCVD-SiN films resulted in silicon nanoclusters, which significantly redshifted the resonance wavelength of the MRRs. Additionally, the extinction ratio of MRRs improved by over 11.8 dB within the conventional band after laser modification. This technique is employed to enhance the performance of second-order MRRs and the four-channel WDM configuration, thus providing critical experimental evidence for leveraging femtosecond lasers to optimize LPCVD-SiN PICs.

Pesticide residues in tea are an important problem affecting the sustainable development of the tea industry; thus, pesticide detection is the key to ensuring the quality and safety of tea. Here, a terahertz metasurface structure based on the quasi-bound state in the continuum is proposed, which consists of two copper microrods arranged periodically. This design in the metasurface provides strong local enhancement near the surface of the microstructure, significantly improving the interaction of light with the analyte, resulting in increased sensitivity. The simulated and experimental results show that the metasurface structure can be used to detect the refractive index of trace analytes with a high sensitivity and successfully detect low concentrations of chlorpyrifos in tea. This study provides a new idea for the detection of pesticide residues in tea.

The fast and accurate design of terahertz devices for specific applications remains challenging, especially for tailoring metadevices, owing to the complex electromagnetic characteristics of these devices and their large structural parameter space. The unique functionalities achieved by metadevices come at the cost of structural complexity, resulting in a time-consuming parameter sweep for conventional metadevice design. Here, we propose a general solution to achieve efficient inverse design for a terahertz metagrating via machine learning. Metagratings with different structural parameters were selected as illustrations to verify the effectiveness of this method. As proof-of-principle examples, the metagratings predicted via the inverse design model are numerically calculated and experimentally demonstrated. Initially, the physical modeling of a metagrating is performed via the finite element method (FEM). A spectrum dataset obtained from FEM simulation is prepared for the training of machine learning models. Then, trained machine learning models, including the Elman neural network (Elman), support vector machine (SVM), and general regression neutral network (GRNN), are used to predict probable structural parameters. The results of these models are compared and analyzed comprehensively, which verifies the effectiveness of the inverse design method. Compared with conventional methods, the inverse design method is much faster and can encompass a high degree of freedom to generate metadevice structures, which can ensure that the spectra of generated structures resemble the desired ones and can provide accurate data support for metadevice modeling. Furthermore, a metagrating tailored by an inverse design is used as a biological sensor to distinguish different microorganisms. The proposed data-driven inverse design method realizes fast and accurate design of the metagrating, which is expected to have great potential in metadevice design and tailoring for specific applications.

Multi-spectral and multi-functional optical components play a crucial role in fields such as high-speed communications and optical sensing. However, the interaction between different spectra and matter varies significantly, making it challenging to simultaneously achieve dynamic multi-spectral modulation capabilities. We designed a modulator based on a planar nested multiscale metasurface, incorporating silicon (Si) and perovskite as control materials, to modulate both microwave and terahertz (THz) ranges. Modulation of microwave and THz waves is achieved through visible light and near-infrared light pumping, with modulation depths of 94.03% and 90.77%, respectively. The modulator employs a planar nested multiscale metasurface, utilizing the odd-order nonlinear polarization properties of perovskite in the THz range and the linear absorption properties of Si in the microwave range to realize dual-frequency-range modulation. This research offers innovative insights for designing multi-spectral components applicable in all-optical coding metasurfaces and intelligent light windows.

Space division multiplexing (SDM) can achieve higher communication transmission capacity by exploiting more spatial channels in a single optical fiber. For weakly coupled few-mode fiber, different mode groups (MGs) are highly isolated from each other, so the SDM system can be simplified by utilizing MG multiplexing and intensity modulation direct detection. A key issue to be addressed here is MG demultiplexing, which requires processing all the modes within a single MG in contrast to MG multiplexing. Benefiting from the great light manipulation freedom of the diffractive optical network (DON), we achieve efficient separation of the MGs and receive them with the multimode fiber (MMF) array. To fully exploit the mode field freedom of the MMF, a non-deterministic mode conversion strategy is proposed here to optimize the DON, which enables high-efficiency demultiplexing with a much smaller number of phase plates. As a validation, we design a 6-MG demultiplexer consisting of only five phase plates; each MG is constituted by several orbital angular momentum modes. The designed average loss and crosstalk at the wavelength of 1550 nm are 0.5 dB and -25 dB, respectively. In the experiment, the loss after coupling to the MMF ranged from 4.1 to 4.9 dB, with an average of 4.5 dB. The inter-MG crosstalk is better than -12 dB, with an average of -18 dB. These results well support the proposed scheme and will provide a practical solution to the MG demultiplexing problem in a short-distance SDM system.

Whispering gallery mode (WGM) resonators have been widely researched for their high-sensitivity sensing capability, but there is currently a lack of high-sensitivity real-time sensing methods for quasi-static measurement. In this paper, within the framework of dissipative coupling sensing, a new method for quasi-static sensing based on the self-modulation of lithium niobate (LiNbO3) resonators is proposed. The LiNbO3 resonator actively modulates the signal to be measured, solving the challenge of real-time demodulation of quasi-static signals. The noise background is upconverted to a high frequency region with lower noise, further enhancing the detection limit. In the demonstration of quasi-static displacement sensing, a customized LiNbO3 resonator with a Q-factor of 2.09×107 serves as the high frequency modulation and sensing element, while the movable resonator acts as the displacement loading unit. Experimental and theoretical results show that the sensing response can be improved to 0.0416 V/nm by dissipation engineering to enhance the resonator evanescent field decay rate and orthogonal polarization optimization. The Allan deviation σ demonstrates a bias instability of 0.205 nm, which represents the best result known to date for microresonator displacement sensing in the quasi-static range. Our proposed scheme demonstrates competitiveness in high-precision quasi-static sensing and provides solutions for the high-precision real-time detection of low frequency or very low frequency acceleration, pressure, nanoparticles, or viruses.

In recent years, optical skyrmions have garnered increasing attention for their ability to introduce new degrees of freedom in manipulating optical fields. While most research has focused on creating innovative optical topological states such as merons and hopfions, there has been limited exploration into their manipulation, which hinders practical applications in this field. In this study, we utilize a hybrid multi-zone filter to induce a Hall effect-like splitting of optical Stokes skyrmions (HESSs), enabling effective separation and manipulation. By manipulating the horizontal phase gradient parameter, we independently control the separation angle of skyrmions. Additionally, we demonstrate control over the topological charge parameter to achieve symmetric and asymmetric HESSs. This effect not only enhances the manipulation capabilities of optical fields but also opens up potential applications for high precision displacement measurements and preservation quantum information.

Silicon photonics (SiPh) technology has become a key platform for developing photonic integrated circuits due to its CMOS compatibility and scalable manufacturing. However, integrating efficient on-chip optical sources and in-line amplifiers remains challenging due to silicon’s indirect bandgap. In this study, we developed prefabricated standardized InAs/GaAs quantum-dot (QD) active devices optimized for micro-transfer printing and successfully integrated them on SiPh integrated circuits. By transfer-printing standardized QD devices onto specific regions of the SiPh chip, we realized O-band semiconductor optical amplifiers (SOAs), distributed feedback (DFB) lasers, and widely tunable lasers (TLs). The SOAs reached an on-chip gain of 7.5 dB at 1299 nm and maintained stable performance across a wide input power range. The integrated DFB lasers achieved waveguide (WG)-coupled output powers of up to 19.7 mW, with a side-mode suppression ratio (SMSR) of 33.3 dB, and demonstrated notable robustness against optical feedback, supporting error-free data rates of 30 Gbps without additional isolators. Meanwhile, the TLs demonstrated a wavelength tuning range exceeding 35 nm, and a WG-coupled output power greater than 3 mW. The micro-transfer printing approach effectively decouples the fabrication of non-native devices from the SiPh process, allowing back-end integration of the III–V devices. Our approach offers a viable path toward fully integrated III–V/SiPh platforms capable of supporting high-speed, high-capacity communication.

Reconfigurable silicon microrings have garnered significant interest for addressing challenges in artificial intelligence, the Internet of Things, and telecommunications due to their versatile capabilities. Compared to electro-optic (EO) and thermo-optic (TO) devices, emerging micro-electromechanical systems (MEMS)-based reconfigurable silicon photonic devices actuated by electrostatic forces offer near-zero static power consumption. This study proposes and implements novel designs for fully reconfigurable silicon photonic MEMS microrings for high-speed dense wavelength division multiplexing (DWDM) elastic networks. The designs include an all-pass microring with a 7 nm free spectral range (FSR) and full-FSR resonance tuning range, an add-drop microring with a 3.5 nm FSR and full-FSR tuning range, and an add-drop double-microring with a 34 nm FSR, wide-range discrete resonance tunability, and flat-top tunability. These advancements hold promise for practical applications.

Thermal quenching has been known to entangle with luminescence naturally, which is primarily driven by a multi-phonon relaxation (MPR) process. Considering that MPR and the phonon-assisted energy transfer (PAET) process may interact cooperatively plays a critical role in conducting the thermal response of luminescence thermometry. Herein, an energy mismatch system of Yb3+/Ho3+/Er3+ co-doped β-NaLuF4 hollow microtubes was delicately proposed to combat thermal quenching of near-infrared (NIR)-II luminescence of Ho3+ via premeditated Er3+-mediated PAET processes under 980 nm excitation. Meanwhile, the mechanism of anti-thermal quenching is attributed to the Er3+ as an energy trap center to facilitate the PAET process, thereby enabling a considerable energy transfer efficiency of over 80% between Er3+ and Ho3+ without Yb3+ ions as sensitizers. Leveraging the accelerated PAET process at increased temperature and superior emission, the phonon-tuned NIR-II ratiometric thermometers were achieved based on fluoride beyond the reported oxide host, enabling excellent relative sensitivity and resolution (Sr=0.57% K-1, δT=0.77 K). This work extends the significant effect of PAET on overcoming the notorious thermal quenching, and offers a unique physical insight for constructing phonon-tuned ratiometric luminescence thermometry.

Moiré meta-devices facilitate continuous and precise modulation of optical properties through the alteration of the relative alignment, such as twisting, sliding, or rotating of the metasurfaces. This capability renders them particularly suitable for dynamic applications, including zoom optics and adaptive imaging systems. Nevertheless, such designs often sacrifice more complex functionalities, such as polarization manipulation, in favor of simplicity and tunability. Here, we propose and experimentally validate a design strategy for a twisted bilayer metasurface that exhibits both varifocal capabilities and polarization filtering properties. By selecting silicon pillars with polarization-maintaining properties for Layer I and polarization-converting properties for Layer II, the designed Moiré metasurface can become sensitive to specific polarization states. Experimental results demonstrate that the proposed design can generate on-demand terahertz (THz) focused beams, achieving an average focusing efficiency exceeding 35% under x-linearly polarized (x-LP) illumination. This is accomplished by systematically varying the twisting angles p and q of Layer I in relation to Layer II in increments of 30°. Additionally, we provide numerical evidence that the focal length of the transmitted vortex beam can be adjusted using the same approach. The Moiré meta-device platform, which is engineered to modulate optical properties via mechanical twisting, obviates the necessity for external power sources or active materials. This generalized design strategy has the potential to significantly expedite the commercialization of multifunctional metasurfaces, which can produce high-precision optics across various practical applications.

The finding of Snell’s law for anomalous reflection enables broad applications of metasurfaces in stealth, communication, radar technology, etc. However, some unavoidable high-order modes are inherently generated due to the super lattice of this local approach, which thus causes a decrease in efficiency and a limit in the reflected angle. Here, a novel, to our knowledge, low-profile wideband reflective meta-atom shaped like a four-leaf rose is proposed to achieve a phase coverage of full 360° by varying the length of the rose leaf. Then, the genetic algorithm is adopted for the first time to encode and optimize the topology of each meta-atom on the coding metasurface to achieve two-dimensional (2D) anomalous reflection with excellent performances through an inverse design. Numerical results show that our optimized coding metasurfaces achieve a high-efficiency (≥90%) and large-angle (θ≤70° and 0°≤φ≤360°) reflection under normal incidence. For verification, far-field measurement is carried out and experimental results are consistent with the numerical ones. Our work sets up a solid platform for utilizing algorithms, especially in artificial intelligence, in the future for arbitrary 2D anomalous reflection with high efficiency and a large angle.

A reconfigurable metasurface based on optical control provides a control paradigm for integrating multiple functions at the same aperture, which effectively expands the freedom of control. However, the traditional light control method requires the light source to directly illuminate the photosensitive device, which forces the metasurface to be placed only according to the light emitter position, and even to need to be integrated on the light emitter, limiting the application scenarios of light-controlled reconfigurable metasurfaces. In this work, a light control method based on optical fiber is proposed, which guides and controls the light propagation path through optical fiber. The metasurface can be flexibly deployed, breaking through the limitation of physical space. As a verification, photoresistors are embedded in the metasurface, and the active device is directly excited by the light source as a driving signal to realize the switching of a polarization conversion function. The experimental results show that the optical-fiber-controlled metasurface can achieve linear-to-linear polarization conversion in the light environment and linear-to-circular polarization conversion in the dark environment. This work paves a new way, to our knowledge, to achieve a light-controlled metasurface, which enriches the family of intelligent metasurfaces and has great potential in many fields.