Vanadium dioxide (VO2) is a promising candidate for intelligent optical limiting owing to its sharp and reversible metal-insulator transition (MIT). Here, we investigate the thermal-optical synergistic phase transition dynamics of epitaxial VO2 thin films under continuous-wave 3.8 mu m laser excitation. Thermal prebias is found to significantly reduce the optical activation threshold and compress the macroscopic optical response time scale by nearly 4 orders of magnitude. By performing spatially resolved transient measurements under Gaussian-beam illumination, we further reveal that the observed millisecond-scale response does not reflect the intrinsic speed of the phase transition but instead arises from a coupled process involving rapid local nucleation at the beam center and subsequent lateral propagation of the metallic phase across the illuminated area. While submillisecond phase nucleation is achieved locally under thermal-optical synergy, the effective optical limiting response is governed by beam-scale phase-front propagation. These results clarify the physical origin of the effective response time in VO2-based optical limiters and provide practical guidance for optimizing mid-infrared optical limiting through combined thermal biasing and spatial excitation engineering.

This study focuses on the two-dimensional semiconductor alpha-In2Se3, which exhibits excellent nonlinear optical response and tunable bandgap characteristics. It systematically investigates the evolution of its nonlinear optical properties and ultrafast carrier dynamics with thickness variation. A series of nanosheets with controllable thicknesses were fabricated via mechanical exfoliation. X-ray diffraction, Raman spectroscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy confirmed their high-quality 2Hphase crystal structure. Steady-state spectroscopic analysis revealed that the optical bandgap widens significantly from 1.57 eV to 2.13 eV as the thickness decreases, demonstrating a pronounced quantum confinement effect. Furthermore, micro-I-scan, transient absorption spectroscopy, and pump-probe techniques were employed to systematically study its third-order nonlinear optical response and ultrafast carrier relaxation behavior. The experiments revealed that the nonlinear absorption coefficient of the material exhibits a significant thickness dependence. This work reveals the thickness-tunable nonlinear optical properties and the defectdominated carrier relaxation mechanism in two-dimensional In2Se3. It also provides crucial experimental and theoretical support for designing and developing customizable nonlinear optoelectronic devices based on this material.

The development of synaptic devices capable of integrating optical sensing and long-term information storage remains a critical challenge in bio-inspired neuromorphic computing. To address the rapid decay of information in photoelectric synapses following cessation of illumination, we fabricated an artificial photoelectric synaptic device based on a small-angle (similar to 1.9 degrees) twisted bilayer MoS2 moir & eacute; superlattice structure and ReS2. By exploiting the cooperative effects of moir & eacute; potential wells and heterointerface charge trapping, our device achieves prolonged optical information retention (similar to 4.8 & times; 10(3) s) and demonstrates a "1 + 1 >> 2" synergistic enhancement effect. Based on techniques including Kelvin probe force microscopy (KPFM), scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and transient absorption, we elucidate the roles of moir & eacute; potentials and interfacial charge trapping in governing synaptic performance. The device successfully emulates essential neurobiological behaviors, including excitatory postsynaptic current, long/short-term memory transition, paired-pulse facilitation, Pavlovian conditioning, and handwritten digit recognition in neural network simulation. This work not only advances the understanding of moir & eacute;-regulated charge storage mechanisms but also establishes a promising platform for high-fidelity, high-performance neuromorphic hardware.

In recent years, the perfect vortex beam with independent wavefront spiral correlation has attracted extensive attention since its beam diameter is independent of topological charge. Perfect vortex beams are expected to make significant progress in optical fiber communications, particle manipulation, quantum information, and other areas. Traditional optical devices are difficult to integrate into the system due to their large size. In this paper, we design and realize a perfect vortex beam with a high reflection efficiency of 90.17% by an all-dielectric metasurface through a Pancharatnam-Berry (PB) phase modulation structure. The cross-polarization conversion efficiency measured by experiment is 89.81%. By modulating the parameter r(0) in the phase function, we can achieve flexible manipulation of topological charges and ring diameters. In addition, we also demonstrate the generation of a four-channel perfect vortex beam array based on the Dammann grating, with a beam uniformity of 40%. Our research will be of great significance for the realization of compact and multifunctional on-chip integrated photonic devices.

As the support structure is in closest contact with 2D materials, substrates can significantly modulate the optical and electrical properties of 2D materials and are expected to become an effective regulatory approach to meet different device requirements. Here, the proximity doping effect of the substrate on 2D materials is confirmed through photoluminescence (PL) spectra, absorption spectra, Raman spectra, Kelvin probe force microscopy (KPFM), and X-ray Photoelectron Spectroscopy (XPS) spectra. Due to the proximity doping effect of the conductive substrate, the absorption and PL properties of MoS2 will be affected, which makes their optical behavior dominated by negatively charged excitons rather than excitons. Furthermore, through micro-area nonlinear optical, transient absorption measurement, and fluorescence lifetime imaging microscopy (FLIM), this effect can also prove to affect the recombination process of nonoptically active excitons and ultrafast carriers formed by band nesting. As an effective way to regulate the optical properties of 2D materials, this method is expected to have a profound impact on the optoelectronic properties of 2D materials and optoelectronic devices.

Optical manipulation of nanomachines demonstrates considerable promise in medicine and atomic physics owing to its non-contact and non-invasive nature. However, when the nanomachine is on dry van der Waals substrates, the interface friction increases significantly, and the substrate environment is more complicated, which makes the traditional optical manipulation face the challenge of excessive adhesion resistance. Herein, the controllable actuation of VSe2 nanosheets on dry substrates is focused, including their translation, rotation, and beam center trapping. The photoacoustic waves are detected, which strongly confirm the mechanism of the photoacoustic effect driving the nanosheet. Various characterization methods verify the non-destructive nature of the optical manipulation and highlight the significant impact of laser intensity distribution and substrate interaction on the process. Finally, combined with a program control strategy, automatic driving of the nanosheets is achieved. This precise and controllable particle optical manipulation technology has injected new impetus into the development of high-performance optoelectronic devices.

Memristors can modulate conductance, have multiple levels of storage, and have attracted significant attention in the field of artificial synapses. However, single-metal-electrode memristors are associated with the disadvantages of a low switching ratio and low stability, among others. Thus, herein, a metal/oxide bilayer electrode memristor device with the structure of Pt/La0.7Sr0.3MnO3/SrTiO3/Nb:SrTiO3 (Pt/LSMO/STO/NSTO) was fabricated by inserting a transition metal oxide electrode, LSMO, between a Pt metal electrode and the resistive material STO. Oxygen vacancies in the LSMO layer could reduce the barrier height (Phi) and barrier width (Wd) of the STO/NSTO interface, resulting in a higher on/off ratio (1.2 x 105), lower Vset (0.58 V) and higher stability (0.124/0.18) compared with a single-metal-electrode memristor without LSMO (on/off ratio = 9 x 103, Vset = 0.9 V, and sigma/mu = 0.23/0.25). In addition, it effectively simulated the features of artificial synapses and accomplished the function of a D-latch and decimal logic neuron computation. In particular, the convolutional neural network based on the metal/oxide bilayer memristor realized the high-precision recognition of traffic signals, demonstrating a high recognition rate of 95.4% for a traffic dataset, and its recognition accuracy remained above 80% even in 10% Gaussian noise.

Quantum communication is rapidly developing and is gradually being commercialized due to its technological maturity. Establishing dense communication links among multiple users in a scalable and efficient way is of great significance for realizing a large-scale quantum communication network. Here, we propose a novel scheme to construct a fully connected polarization-entangled network, utilizing the engineering of spontaneous four-wave mixings (SFWMs) and a path-polarization converter. It does not require active optical switches which limit the communication speed, or trusted nodes which lead to potential security risks. The required frequency channels in the network grow linearly with the number of users. We experimentally demonstrate a six-user fully connected network with on-chip SFWM processes motivated by four pumps. Each user in the network receives a frequency channel, and all fifteen connections between the users are implemented simultaneously. Our work opens up a promising scheme to efficiently construct fully connected large-scale networks.

The single-pixel imaging (SPI) technique illuminates the object through a series of structured light fields and detects the light intensity with a single-pixel detector (SPD). However, the detection process introduces a considerable amount of unavoidable white noise, which has a detrimental effect on the image quality and limits the applicability of SPI. In this paper, we combine the untrained attention U-Net with the SPI model to reduce noise and achieve high-quality imaging at low sampling rates. The untrained U-Net has the advantage of not requiring pre-training for better generalization. The attention mechanism can highlight the main features of the image, which greatly suppresses the noise and improves the imaging quality. Numerical simulations and experimental results demonstrate that the proposed method can effectively reduce different levels of Gaussian white noise. Furthermore, it can obtain better imaging quality than existing methods at a low sampling rate of less than 10%. This study will expand the application of SPI in complex noise environments.

In this manuscript, an automated optimization neural network is applied in Hadamard single-pixel imaging (H-SPI) and Fourier single-pixel imaging (F-SPI) to improve the imaging quality at low sampling ratios which is called AO-Net. By projecting Hadamard or Fourier basis illumination light fields onto the object, a single-pixel detector is used to collect the reflected light intensities from object. The one-dimensional detection values are fed into the designed AO-Net, and the network can automatically optimize. Finally, high-quality images are output through multiple iterations without pre-training and datasets. Numerical simulations and experiments demonstrate that AO-Net outperforms other existing widespread methods for both binary and grayscale images at low sampling ratios. Specially, the Structure Similarity Index Measure value of the binary reconstructed image can reach more than 0.95 when the sampling ratio is less than 3%. Therefore, AO-Net holds great potential for applications in the fields of complex environment imaging and moving object imaging.

Novel dual-trap and multi-trap optical tweezers are designed and analyzed, in order to enhance the particle trapping performance of optical tweezers in three-dimensional (3D) space. Firstly, controllable dual-trap optical tweezers are proposed based on metalens and the low-loss optical phase-change material Sb2S3. The horizontal and axial analysis of the optical force acting on two 250-nm-radius SiO2 particles are also carried out. The simulation results show that when Sb2S3 is in the crystalline state, the transverse optical trap stiffness \begin{document}$ {k}_{x} $\end{document} of two particles reaches about 25.7 pN/(μm·W) and 37.4 pN/(μm·W), respectively, and the axial optical trap stiffness \begin{document}$ {k}_{z} $\end{document} for each particle is about 10.0 pN/(μm·W). When the Sb2S3 is in the amorphous state, both \begin{document}$ {k}_{x} $\end{document} and \begin{document}$ {k}_{z} $\end{document} are about 1/10 of the counterpart of its crystalline state. As a result, the particle is not stably trapped in the z-direction, and thus enabling the controllability of trapping particles in 3D space. Furthermore, array-type multi-trap optical tweezers are proposed. By regulating the crystal state and noncrystal state of phase-change material Sb2S3, it is convenient to form different combinations of 3D trap schemes. These new optical tweezers can realize 3D space particle trap in various ways, thereby improving the flexibility of optical tweezers, and providing a series of new ways of implementing the metalens-based optical tweezers.

Metalens with extended depth of focus (EDOF) can extend the mapping area of the image, which leads to novel applications in imaging and microscopy. Since there are still some disadvantages for existing EDOF metalenses based on forward design, such as asymmetric point spread function (PSF) and non-uniformly distributed focal spot, which impair the quality of images, we propose a double-process genetic algorithm (DPGA) optimization to inversely design the EDOF metalens for addressing these drawbacks. By separately adopting different mutation operators in successive two genetic algorithm (GA) processes, DPGA exhibits significant advantages in searching for the ideal solution in the whole parameter space. Here, the 1D and 2D EDOF metalenses operating at 980 nm are separately designed via this method, and both of them exhibit significant depth of focus (DOF) improvement to that of conventional focusing. Furthermore, a uniformly distributed focal spot can be maintained well, which can guarantee stable imaging quality along the longitudinal direction. The proposed EDOF metalenses have considerable potential applications in biological microscopy and imaging, and the scheme of DPGA can be promoted to the inverse design of other nanophotonics devices.

Achieving optically controlled nanomachine engineering can satisfy the touch-free and non-invasive demands of optoelectronics, nanotechnology, and biology. Traditional optical manipulations are mainly based on optical and photophoresis forces, and they usually drive particles in gas or liquid environments. However, the development of an optical drive in a non-fluidic environment, such as on a strong van der Waals interface, remains difficult. Herein, we describe an efficient 2D nanosheet actuator directed by an orthogonal femtosecond laser, where 2D VSe2 and TiSe2 nanosheets deposited on sapphire substrates can overcome the interface van der Waals forces (tens and hundreds of megapascals of surface density) and move on the horizontal surfaces. We attribute the observed optical actuation to the momentum generated by the laser-induced asymmetric thermal stress and surface acoustic waves inside the nanosheets. 2D semimetals with high absorption coefficient can enrich the family of materials suitable to implement optically controlled nanomachines on flat surfaces.

The solar-blind ultraviolet (UV) wavelength is particularly interesting within the range of 200 nm–300 nm. Here, we propose a focusing metalens, focusing vortex beam (VB) metalens and metalens array that specifically work in the UV band to focus a beam or VB. Firstly, a high numerical aperture (NA) focusing metalens working at a wavelength of 214.2 nm was designed, and the NA reached 0.83. The corresponding conversion efficiency of the unit structure reached as high as 94%, and the full width at half maximum was only 117.2 nm. Metalenses with large NA can act as optical tweezers and can be applied to trap ultracold atoms and molecules. Secondly, a focused VB metalens in the wavelength range of 200 nm–300 nm was also designed, which can convert polarized light into a VB and focus the VB simultaneously. Finally, a metalens array was developed to focus VBs with different topological charges on the same focal plane. This series of UV metalenses could be widely used in UV microscopy, photolithography, photonics communication, etc.

Limited by the number of illumination fields and the speed of a spatial light modulator, single-pixel imaging (SPI) cannot realize real-time imaging and fast classification of an object. In this paper, we proposed the circular harmonic Fourier single-pixel imaging (CHF-SPI) for the first time to realize fast imaging and classification of objects. The light field distribution satisfies the circular harmonic Fourier formula, and the light intensity values of the single-pixel detector are equivalent to the circular harmonic Fourier moments. Then the target can be reconstructed under low sampling ratio by inverse transformation. Through simulation and experimental verification, clear imaging can be performed at a sampling ratio of 0.9%. In addition, circular harmonic Fourier moments are used to construct multi-distortion invariant to classify objects with rotation and scale change. The scale change multiples of objects can be calculated and the objects can be classified by using 10 light fields. It is of great significance to classify objects quickly without imaging.

We propose a Fermat spiral laser array as illumination source in ghost imaging. Due to the aperiodic structure, the Fermat spiral laser array generates illuminating light field without spatial periodicity on the normalized second-order intensity correlation function. A single-pixel detector is used to receive the signal light from object for image reconstruction. The effects of laser array parameters on the quality of ghost imaging are analyzed comprehensively. Through experimental demonstration, the Fermat spiral laser array successfully achieves ghost imaging with high quality by combining with the compressive sensing reconstruction algorithm. This method is expected to be applied in remote sensing by combining with phased and collimated fiber laser array equipped with the high emitting power and high-speed modulation frequency.