We identify that the inhomogeneous phase differences between the scattering components and reference field on the Fourier plane, in high numerical-aperture interferometric scattering microscopy and in imaging systems with aberration, severely distort the interferometric point-spread function (iPSF). We introduce the concept of Fourier-plane phase-difference synchronization, whereby all the scattering components share a fixed phase difference relative to the reference, to reshape the iPSF toward perfect circular symmetry and enhanced signal. In particular, synchronizing the phase differences to pi/2 between the scattered and reference components in the Fourier plane results in an axially antisymmetric iPSF, which we demonstrate to suppress the interferometric speckle background. Experimentally, Fourier-plane phase-difference synchronization is implemented using a photothermal spatial light modulator, producing 50% signal enhancement and an iPSF with almost-perfect circular symmetry. Experimental suppression of the speckle background enables reliable detection of 10 nm particles immobilized on a substrate that are otherwise indecipherable in the random background pattern. Our concept and the implementation technique provide a powerful asset for advanced optical microscopy.

Fluorescence blinking, often regarded as a limitation for stable emitters, can enable super-resolution localization microscopy and serve as a versatile reporter of the photophysical states of quantum emitters and their interactions with local environment. However, conventional blinking emitters are typically single quantum systems with Stokes-shifted fluorescence, making them susceptible to autofluorescence background, weak signal, and irreversible photodegradation under prolonged excitation. In contrast, single lanthanide-doped upconversion nanocrystals are effectively background-free anti-Stokes emitters and demonstrate robust resistance to photodegradation, yet they are generally considered non-blinking owing to the presence of a large ensemble of uncorrelated emitting lanthanide ions within a single nanocrystal. Here we report the discovery and control of collective blinking in the upconversion luminescence of thousands of lanthanide ions within a single nanocrystal. The blinking exhibits on-off intensity ratio exceeding 10, persists for over 15 hours (over 10,000 cycles) without discernible photodegradation, and can be reversibly controlled by adjusting the excitation power. We elucidate a universal, activator-independent upconversion blinking mechanism, whereby a single quencher, stochastically generated via a cooperative multi-ion process, can intercept delocalized excitation energy within the Yb3+ sensitizer network and darken the whole nanocrystal. Benefiting from the high-contrast, long-term photostable blinking and background-free emission, we achieve robust super-resolution localization microscopy that resolves individual nanocrystals in aggregates with 1.2 nm precision. This work establishes a general strategy to realize and control collective blinking in photostable multi-emitter nanosystems, opening new opportunities in nanoscience, bioimaging, and quantum technologies.

To address the challenges of poor formability, large springback, and low precision in the room-temperature V-bending of high-strength 2A97 Al-Li alloy, this study innovatively proposes a novel “metal matrix + rounded graphite” composite punch design for pulse current-assisted V-bending experiments. The effects of different mold structures and current paths on the temperature distribution, bending limit, forming precision, and microstructural evolution of 2A97 Al-Li alloy during forming were investigated. The results indicated that compared with room-temperature bending, the current-assisted bending process significantly reduces the bending load of 2A97 Al-Li alloy, increases the bending limit to 31° (whereas room-temperature bending results in fracture at only 115°), and improves forming precision. The “metal matrix + rounded graphite” composite punch enables precise local high-temperature control in the bending deformation zone, which enhances the plastic deformation capacity of the deformation zone and reduces the risk of cracking. Furthermore, this structure notably decreases the current density required for self-resistance heating of the alloy—only 11 A/mm² is needed to reach the target forming temperature of 400 °C, far lower than the 50 A/mm² required by traditional metal punches—and reduces the bending springback angle to 1°, corresponding to a 66

Abstract Optical field enhancement is an underlying mechanism for boosting various nanophotonic processes. At mid-infrared frequencies, polar dielectric nanogap structures are capable of generating greatly enhanced optical field thanks to optical phonon resonances. However, as a nanogap closes the field enhancement is predicted to diverge according to classical electromagnetic theory. The issue persists even when spatial nonlocality is considered. We recognize that the singularity should be regularized by accounting for the vibrational interactions between the atoms on the opposite sides of the nanogap, or effectively allowing for optical phonon tunneling. This insight leads us to propose a simple optical phonon tunneling model (OPTM) for approximating the phonon tunneling effect. We successfully demonstrate the regularization of the enhancement singularity by examining with the OPTM the optical response of silicon carbide nanosphere dimers. The systematic study further reveals that the phonon tunneling plays a more significant role for larger nanosphere dimers. Our work opens up possibilities for rational prediction of extreme optical field enhancement in delicate polar dielectric nanostructures.

different surface treatments-sandpaper polishing, chemical cleaning, and electrolytic polishing combined with chemical cleaning are employed to conduct hot compression bonding tests on 2024 aluminum alloy. The interface microstructure and the interface healing effect under different surface treatment conditions are investigated using characterization techniques such as OM ,SEM, and EBSD. The results reveal that under the three surface treatment conditions, the types of interfacial oxide elements are identical, while variations exist in the quantity and size of the oxides. After holding for 4 h, second-phase particles within the matrix precipitate extensively along grain boundaries and at the bonding interface. For the sandpaper-polished specimen, oxides and second-phase particles at the interface account for approximately 32% of the interface area; this proportion is about 42% for the chemically cleaned specimen, and roughly 28% for the specimen subjected to electrolytic polishing combined with chemical cleaning. Interface healing is achieved through the synergistic action of discontinuous dynamic recrystallization and continuous dynamic recrystallization. Based on the microstructural characteristics of the bonding interface, the interface healing rate is utilized to evaluate the degree of interface healing. After statistical calculations, the order of the interface healing rate is as follows: electrolytic polishing combined with chemical cleaning>sandpaper polishing>chemical cleaning.

This Letter focuses on a remarkable simulation tool for the photothermal properties of the metallic nanostructures. A fully coupled method is established based on Maxwell's equations and the law of heat conduction in the time domain. This method is different from the conventional co-simulation scheme with a steady-state optical field and a transient thermal field, offering a more versatile approach for analyzing photothermal characteristics. To effectively evaluate the photothermal coupling effect, the discontinuous Galerkin technique is utilized. Furthermore, the time-scaling approach is introduced to address the multiscale nature of the temporal responses between the light and heat fields. Thus, an efficient numerical solver for the photothermal properties of metallic nanostructures is developed. Numerical examples demonstrate the remarkable accuracy and efficiency of the proposed method. Therefore, this approach can provide an essential theoretical tool for designing dynamically reconfigurable nano-devices.

Abstract Mapping light fields and local density of optical states (LDOS) around nanostructured materials is instrumental for advancing both fundamentals and practical applications in nano-optics, nanomaterial science, and quantum technologies. In particular, LDOS governs key processes such as spontaneous emission, light scattering, van der Waals interactions, and nanoscale heat transfer, yet it remains inaccessible with conventional optical microscopy techniques. Here, we develop scanning-exciton optical nanoscopy to simultaneously map the light intensity and LDOS near plasmonic and dielectric photonic structures with a few-nanometer resolution. By grafting a rationally designed core–shell-shell quantum dot to a silica nanotip, we obtain an ultra-photostable and sensitive scanning quantum probe carrying excitons that are generated and decay at the rates proportional to the local light intensity and LDOS, respectively. We first demonstrate the correlative dual-parameter sensing capability using a model plasmonic structure, and subsequently apply it to uncover previously unobservable nanoscale coupling physics occurring in a plasmonic trimer. Furthermore, we report the first optical mapping of LDOS over a photonic-crystal nanocavity, visualizing the resonant nanocavity mode and its position-dependent coupling with a quantum emitter, essential for quantum photonic applications. Our work demonstrates a transformative technique towards bridging the gap between surface morphology and far-field optical response, and constitutes a platform for exploring light-matter interactions at deep-nanoscale and single-quanta level.

A novel current-assisted heat treatment die with “metal body + rounded graphite” structure was proposed to suppress the bending springback of TA15 titanium alloy. Results indicate that the die of metal–graphite rounded corner die with 316L lower die (Die #2) achieves targeted heating at 680 ℃, reducing the springback angle from 4° to 0.2° and basically eliminating springback. The thermo-electric coupling effect promotes stress relaxation and static recovery, decreasing dislocation density and residual stress significantly. Theoretical calculations indicate that dislocation motion acceleration is primarily governed by the local hot spot effect, with the electron wind effect negligible upon ignoring thermal conduction and other heat losses. This work provides a high-efficiency and low-energy method for precision bending of TA15 alloy.

Photonic technologies continue to drive the quest for new optical materials with unprecedented responses. A major frontier in this field is the exploration of nonlocal (spatially dispersive) materials, going beyond the local, wavevector-independent assumption traditionally adopted in optical material modeling. The growing interest in plasmonic, polaritonic, and quantum materials has revealed naturally occurring nonlocalities, emphasizing the need for more accurate models to predict and design their optical responses. This has major implications also for topological, nonreciprocal, and time-varying systems based on these material platforms. Beyond natural materials, artificially structured materials-metamaterials and metasurfaces-can provide even stronger and engineered nonlocal effects, emerging from long-range interactions or multipolar effects. This is a rapidly expanding area in the field of photonic metamaterials, with open frontiers yet to be explored. In metasurfaces, in particular, nonlocality engineering has emerged as a powerful tool for designing strongly wavevector-dependent responses, enabling enhanced wavefront control, spatial compression, multifunctional devices, and wave-based computing. Furthermore, nonlocality and related concepts play a critical role in defining the ultimate limits of what is possible in optics, photonics, and wave physics. This Roadmap aims to survey the most exciting developments in nonlocal photonic materials and metamaterials, highlight new opportunities and open challenges, and chart new pathways that will drive this emerging field forward-toward new scientific discoveries and technological advancements. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

The microstructure of 40CrMnMoA during hot forging determines its macroscopic mechanical properties. Dynamic recrystallization (DRX) behavior is commonly used to refine grains and improve the microstructure of materials; therefore, it is important to be able to predict mechanical behavior during hot forging and the microstructure evolution during dynamic recrystallization. In order to accurately determine the DRX model parameters of 40CrMnMoA steel, an inverse optimization method is proposed in this work. The uniaxial isothermal compression experiment of 40CrMnMoA steel was carried out on a Gleeble-1500D thermal simulation tester (Dynamic Systems Inc. (DSI), Poestenkill, NY, USA) under the temperature range of 900~1200 °C and the strain rate range of 0.005 to 5 s−1. Based on the true stress–strain data obtained by a compression test, the DRX model of 40CrMnMoA was initially established using the traditional averaging method. Subsequently, the DRX model parameters calculated by the conventional averaging method were used as the initial values, the mean-square error between the experimental and calculated values of the DRX volume fraction was set as the objective function, and the DRX model parameters were optimized by the adaptive simulated annealing (ASA) algorithm. By comparing the correlation coefficient R, average absolute relative error (AARE), and the root mean square error (RMSE) of the predicted DRX percentage with the experimental values before and after optimization, it was found that the optimized model achieved an R-value of 0.992, with AARE and RMSE decreased by 34% and 2%, respectively, which verified the accuracy of the optimized DRX model. Through the program’s secondary development, the optimized DRX model of 40CrMnMoA was integrated into finite element software Forge® 3.2 to simulate the isothermal compression process. The comparison between grain size from the central region of simulation results and actual samples revealed that the relative error is less than 3%. This result demonstrated that the inverse optimization method can accurately identify the DRX model parameters of 40CrMnMoA alloy steel.

The impact ring of extra-large forgings, a core component of large marine hydraulic pile drivers, requires fracture defect control in its forging process. Therefore, considering the influence of temperature and strain rate, a coupled Normalized Cockcroft & Latham elevated temperature damage model was proposed to predict cracking in 35CrMo steel during hot forging process. Firstly, the Gleeble-1500D thermal simulation tester was used to conduct elevated temperature tensile tests on 35CrMo steel under deformation conditions of a temperature range of 900-1200 degrees C and a strain rate range of 0.01-5 s-1. Based on experimental data, a Normalized Cockcroft & Latham elevated temperature damage model on 35CrMo steel was established by introducing Zener-Hollomon parameter which accounted for temperature and strain rate. To obtain an elevated temperature damage model with high prediction accuracy, an inverse optimization method was put forward to determine model parameters. The genetic algorithm was employed as optimization algorithm, the critical damage value was used as optimization parameter, and the mean square error between the actual and simulated fracture displacement was used as objective function. The established model was modified through a subroutine modification and was embedded into the finite element code Forge (R) to simulate the process of elevated temperature tensile. The experimental and simulated fracture displacements were compared to verify the accuracy, the correlation coefficient R was 0.9706, and the root mean square error was 1.0305. The result showed that the proposed elevated temperature damage model could accurately predict the fracture behavior in elevated temperature forging process of 35CrMo steel.

The phase transformation kinetics of 35CrMo steel during heating have been harnessed to refine thermo-mechanical processing techniques, thereby ensuring the quality of heat-treated components. To accurately forecast the austenite phase transformation in 35CrMo steel, a non-isothermal diffusion-type Johnson–Mehl–Avrami–Kolmogorov (J–M–A–K) model was developed under continuous heating conditions. The phase transformation activation energy was determined to be Q = 1.097 × 106 J/mol, with kinetic parameters n = 0.6434 and k0 = 7.8316 × 1052. The adaptive simulated annealing (ASA) algorithm was employed to perform inverse estimation, optimizing the J–M–A–K model parameters to n = 0.6306 and k0 = 1.2 × 1053. Taking the cumulative error between the experimental and model values of austenite volume fraction as the objective function, with the minimization of this error as the identification strategy, the optimized model showed an improvement in the prediction correlation coefficient R by 0.285, while the average absolute relative error (AARE) and root-mean-square error (RMSE) decreased by 2.67

We introduce a Surface Response Model (SRM) to efficiently describe phonon nonlocal effects in polar dielectric nano-resonators within the framework of classical electromagnetism. While accurate, conventional nonlocal models introduce angstrom-scale longitudinal waves, which lead to two critical challenges: prohibitive computational costs due to the required mesh refinement, and a quasi-continuous quasinormal mode (QNM) spectrum that complicates modal analysis. Our SRM circumvents these issues by capturing the nonlocal physics entirely at the material's surface. This approach simplifies the modal landscape, allowing for the definition of a discrete and well-behaved set of QNMs, thereby unlocking the powerful toolbox of modal analysis. The validity of our model is demonstrated by accurately reconstructing the nonlocal optical response of nanostructures. Our SRM provides a framework that is both computationally efficient and physically transparent, enabling rapid and intuitive analysis of light-matter interactions in mid-infrared devices where nonlocality is significant.

The microstructure of metallic materials plays a crucial role in determining their performance. In order to accurately predict the dynamic recrystallization (DRX) behavior and microstructural evolution during the hot deformation process of GCr15 bearing steel, a microstructural evolution model for the DRX process of GCr15 steel was established by combining the level set (LS) method with the Yoshie–Laasraoui–Jonas dislocation dynamics model. Firstly, hot compression tests were conducted on GCr15 steel using the Gleeble-1500D thermal simulator, and the hardening coefficient k1 and dynamic recovery coefficient k2 of the Yoshie–Laasraoui–Jonas model were derived from the experimental flow stress data. The effects of temperature, strain, and strain rate on DRX behavior and grain size during the hot working process of GCr15 steel were investigated. Through secondary development of the software, the established microstructural evolution model was integrated into the DIGIMU® software. Metallographic images were imported in situ to reconstruct its initial microstructure, enabling GCr15 steel DRX microstructure finite element simulation of the hot compression process. The predicted mean grain size and flow stress demonstrated a strong correlation and excellent agreement with the experimental results. The results demonstrate that the established DRX model effectively predicts the evolution of the DRX fraction and average grain size during the hot forging process and reliably forecasts DRX behavior.

We introduce and experimentally implement Fourier-plane phase synchronization for optical microscopy, and demonstrate its performance with interferometric scattering microscopy. By combining a photothermal phase plate and laser beam scanning, we realize a synchronized phase for all scattering components on the Fourier plane of high numerical-aperture microscopes, where the evanescent waves and optical aberration normally produce highly inhomogeneous phase distributions. We achieve an almost perfect point spread function, exhibiting a tighter focus with 50% enhancement of the signal and ideal circular symmetry. Particularly, by synchronizing the phase to π/2, we demonstrate the background speckles exhibit an anti-symmetric dependence on axial defocus, enabling the effective suppression of the speckles via defocus integration and thus the detection of 10 nm particles immobilized on the substrate. The concept and technique of seamless dynamic phase control on the Fourier plane constitute a key asset for modern optical microscopy.

On-chip integration of independent channels of indistinguishable single photons is a prerequisite for scalable optical quantum information processing. This requires separate solid-state single-photon emitters to exhibit identical lifetime-limited transitions. This challenging task is usually further exacerbated by spectral diffusion due to complex charge noise near material surfaces made by nanofabrication processes. Here we develop a molecular quantum photonic chip and demonstrate on-chip Hong-Ou-Mandel quantum interference of indistinguishable single photons from independent molecules. The molecules are embedded in a single-crystalline organic nanosheet and integrated with single-mode waveguides without nanofabrication, thereby ensuring stable, lifetime-limited transitions. With the aid of Stark tuning, we show how 100 waveguide-coupled molecules can be tuned to the same frequency and achieve on-chip Hong-Ou-Mandel interference visibilities exceeding 0.97 for 2 molecules separately coupled to 2 waveguides. For two molecules with a controlled frequency difference, we unveil over 100-µs-long quantum beating in the interference, showing both excellent single-photon purity (particle nature) and long coherence (wave nature) of the emission. Our results showcase a possible strategy towards constructing scalable optical universal quantum processors and a promising platform for studying waveguide quantum electrodynamics with identical single emitters wired via photonic circuits.

This work investigated the microstructure evolution behavior of the Mg-2.0Y-2.0Zn-2.0Al-0.3Mn alloy within the initial plastic deformation zone, the plastic deformation zone prior to the die exit, and the non-plastic deformation zone after the die exit during the extrusion process. The results showed that in the initial plastic deformation zone, basal slip dominated the plastic deformation of the alloy, accompanied by a relatively high basal texture intensity. The alloy mainly consisted of larger deformed grains and smaller dynamically recrystallized grains, and the dynamically recrystallized grains mainly nucleated and grew through discontinuous dynamic recrystallization. From the initial plastic deformation zone to the plastic deformation zone prior to the die exit, non-basal slip gradually became activated and dominated the plastic deformation of the alloy. Meanwhile, continuous dynamic recrystallization gradually dominated the formation of dynamically recrystallized grains, and the increase in the recrystallization degree led to the weakening of the basal texture intensity. In the non-plastic deformation zone after the die exit, static recrystallization took place in the alloy, further reducing the basal texture. At the same time, grain boundary migration and grain growth caused a certain degree of deflection in grain orientation, and some grains with < 0001 > //ED orientation showed a relatively obvious growth advantage.

An efficient mixed-potential integral equation formulation is proposed for the analysis of 2-D periodic dielectric objects above the half-space. The spatial-domain half-space Green's functions are obtained from the corresponding spectral-domain Green's functions via the discrete complex image method (DCIM) combined with the matrix pencil method (MP) technique. Then, the Poisson summation formula is used to express the periodic Green's function via a combined summation of spectral and spatial terms. However, the half-space Green's function with 2-D periodicity is commonly expressed as spatial and spectral infinite series that leads to bad convergence. In order to effectively calculate the components of dyadic and scalar mixed-potential half-space periodic Green's functions, a novel acceleration method is proposed. In this work, the modified Ewald method is applied to the spatial series to accelerate periodic Green's functions convergence. Numerical results are provided to validate the efficiency of the proposed method. Compared with the traditional spatial method, the accelerated algorithm has faster convergent speed.