For next-generation 6.7 nm extreme ultraviolet lithography light sources, Gd2O3 thin films and Gd(OH)3 thinfilm target were fabricated via electrochemical deposition method. These gadolinium-based film targets enhance laser-coupling and function as mass-limited targets, effectively boosting EUV emission. It is shown that superior EUV spectral performance for both the thin-film targets. Specifically, the spectral intensity near 6.7 nm increases by a factor of 1.56 for Gd(OH)3 films and 1.25 for Gd2O3 films compared to pure Gd targets, respectively. while the spectral full width at half maximum was reduced by approximately one-third and one-fourth, respectively. The out-of-band(OOB) radiation measurements of the Gd2O3 thin-film target revealed that the thermal radiation intensity in the 325-385 nm and 435-500 nm wavelength ranges decreased to half compared to that of the metallic Gd target, thereby effectively mitigating OOB radiation spread in different directions. These results provide valuable insights for the development of next-generation EUV light-source targets.

To circumvent the inherent limitations of 2.94 & micro;m Er:YAG lasers in conventional Q-switched operation-specifically the low optical damage thresholds and the deleterious "self-termination effect"-we demonstrate a high-repetition-rate, high-energy mechanical rotating-mirror Q-switched laser integrated with FPGA-based precision synchronization. Theoretically, modified rate equations incorporating energy transfer upconversion (ETU), cross-relaxation (CR) nonlinearities, and a time-dependent dynamic loss function are developed to elucidate the physical mechanisms of multi-pulse generation and suppression in mechanical Qswitching. From a technical standpoint, a real-time rotation speed tracking loop, powered by a 200 MHz phaselocked loop (PLL) clock, achieves a 5 ns temporal resolution. This configuration suppresses the pulse peak timing jitter of the output laser to 8.58 ns (RMS), yielding sub-microsecond synchronization stability. Utilizing a dualmodule series-connected gain architecture, we achieve a single-pulse output of 82.5 mJ with a 126 ns pulse width at a 30 Hz repetition rate, maintaining energy stability better than 5 % and a beam quality factor M2 approximate to 3.8. At a reduced repetition rate of 5 Hz, the single-pulse energy scales to 328 mJ. This work significantly bolsters the temporal stability and extraction efficiency of mechanical Q-switched systems, providing a robust pathway for high-energy mid-infrared sources and demonstrating high potential for pumping gain-switched Fe:ZnSe lasers.

Polypropylene (PP) is widely used in high-cleanliness polymer assemblies because of its chemical stability, low density, processability, and mechanical flexibility. However, in semi-crystalline PP, the interfacial fusion zone often suffers from shrinkage mismatch and local stress concentration induced by distributed volumetric heat sources, undermining structural stability and mechanical reliability. Herein, an S-shaped scanning strategy was proposed to redistribute laser energy within the interfacial fusion zone, with a path-length correction factor ensuring comparison with the linear path at identical effective line energy. At Eeff = 1.0 J mm−1、A = 1.4 mm, the joint exhibits the highest apparent lap-shear strength of 26.8 MPa, 2.5 times that of linear scanning, with the failure mode shifting from interfacial-dominated cracking to more pronounced plastic energy-dissipative fracture. Infrared thermography and numerical simulations reveal that the S-shaped path markedly broadens the thermal band, mitigates the transverse temperature gradient, and suppresses local stress concentration, thereby enhancing interfacial structural continuity and load-transfer stability. XRD and DSC indicate that all interfacial fusion zones remain dominated by α-PP crystals, whereas the S-shaped path induces a stronger apparent recrystallization response, increasing the apparent cooling crystallinity from 41.2 % to 43.4 %. Combined Raman, HRTEM, and AFM-QNM analyses further demonstrate that the S-shaped path promotes more homogeneous local ordered-structure reconstruction and reduces micromechanical heterogeneity, yielding an average Derjaguin-Muller-Toporov (DMT) modulus of 2.77 ± 0.56 GPa and a coefficient of variation of 0.202. This work elucidates the relationship between pathway strategies, energy deposition, thermal history, structural evolution, and mechanical response, and provides an absorber-free, tunable approach for PP media-interface reinforcement.

This study designed a compact eight-pass folded resonant cavity structure based on a rectangular prism. Through the synergistic cooperation of rectangular prism and reflection mirror, the beam passed through the Tm: YLF gain medium eight times within a cavity length of 670 mm, enhancing mode selectivity and pump energy utilization efficiency. A 6.05 W laser output was obtained at a pump power of 90 W, with a slope efficiency of 27.6 %. The fast axis beam quality was My(2) = 1.59, and the slow axis beam quality was Mx(2) = 1.68, providing an effective and feasible optimization technology solution for the development of high-power and high beam quality mid infrared lasers.

This paper studies the Er:YLF laser under continuous laser diode end pumping, obtaining a mid-infrared radiation of 2.8 & micro;m, with a maximum output of 1.55W and a slope efficiency of 14.9%. The tunability of the laser was achieved by using F-P etalons with thicknesses of 0.025 mm, 0.5 mm and 1 mm, and the tuning ranges of 67 nm, 10 nm and 3 nm were obtained respectively. The tuning ranges of 145.17 nm and 111.31 nm were achieved by using birefringent filters with thicknesses of 2 mm and 4 mm. Continuous tuning of the 67 nm spectral width range was achieved in LD end-pumped Er:YLF lasers using the F-P etalon method, and for the first time, a birefringent filter was added to the Er(3+ )gain medium to achieve 145.17 nm spectral width range tuning, obtaining the broadest wavelength tuning range to date.

To mitigate channel-induced degradation in underwater wireless optical communication (UWOC), this study combines theoretical and experimental analyses to characterize 488 nm blue OAM beam propagation across varying temperatures, salinities, and distances. Under short-range conditions, received power decreases monotonically with increasing temperature (10 ∼ 30°C) and salinity (10 ∼ 35 PPT), though overall attenuation remains modest. Notably, salinity fluctuations exerted a more pronounced impact (0.167

This work presents a beam quality optimization approach for Tm: YLF slab lasers using a mode-shaping mirror (MSM) in a three-pass folded cavity. An equivalent thermal lens model is established to analyze transverse mode evolution. Experiments confirm that the optimized configuration (Lm = 10 mm, f = 200 mm, R = 500 mm) achieves M(2 )values of 1.70 and 1.58 along slow and fast axes. This compact and scalable design enables efficient high-quality output in mid-infrared lasers.

This paper reports a compact and efficient intracavity pumped 2 mu m laser. An average output power of 2.77 W at 2064 nm was achieved from a holmium laser in a 70 mm flat-concave cavity. Based on the dual-mode competition theory, this study conducted theoretical analysis and experimental verification of the wavelength variation of the 1.9 mu m pump light within the cavity. Without the use of external optical components, the wavelength of the 1.9 mu m pump light was effectively tuned, significantly improving the laser's conversion efficiency. Furthermore, the study emphasizes the critical role of integrating the absorption characteristics of holmiumdoped gain media and intracavity beam distribution in designing compact, high-efficiency laser systems.

This paper proposes a real-time active polarization imaging technology based on a color-and-polarization-encoded annular LED array. By replacing conventional monochromatic light sources with red, green, and blue (RGB) linearly polarized annular LED arrays and employing a standard color camera, our method achieves polarization image acquisition without requiring specialized polarization cameras. Each wavelength-specific light source integrates 0°, 45°, and 90° linear polarizers, with nested annular LED arrays enabling composite illumination that eliminates polarization errors inherent in dichroic mirror-based beam combining. The system demonstrates enhanced polarization feature retrieval through channel crosstalk correction and white balance algorithms. Experimental results reveal three key advantages: (1) spatial resolution shows a twofold improvement compared to commercial color-filter-based division-of-focal-plane (DoFP) polarization cameras; (2) measurement accuracy exhibits a maximum error of 4.7% against ground-truth images obtained by rotating polarizer methods, particularly for objects with wavelength-independent Mueller matrix variations; (3) imaging speed reaches 39.34 FPS at native 2448×2048 resolution through GPU-accelerated polarization computation. This technology establishes a novel framework for efficient polarization imaging of dynamic targets, demonstrating significant potential for industrial inspection and biomedical applications.

This paper is based on Semiconductor Saturable Absorber Mirror as passive mode-locking elements to construct a mode-locked laser, achieving stable continuous wave mode-locked laser output in the 2 mu m wavelength band through efficient end-pumping of Tm: YLF crystals. First, the continuous mode-locking threshold conditions are obtained through theoretical analysis and calculation, and the laser cavity length parameters are designed using ABCD matrix theory to control the astigmatism of the resonator and the distribution size of the transverse mode spot at each position. A 'W' shaped folded laser resonator was designed, and at a cavity length of 1.857 m, stable mode-locked laser output was obtained when the absorbed pump power exceeded 12.24 W. When the maximum pump power was 20.17 W, the maximum average output power of the mode-locked laser was 1.52 W. The pulse width was 1.716 ps with the repetition frequency of 81 MHz, and the beam quality M2 is 1.51. The results indicate that the Tm: YLF crystal can achieve relatively stable ultrashort pulse sequences, high-power output, and continuous mode-locked laser operation with high beam quality through rational design of the cavity structure.

In this paper, the evolution of the beam from the double Hermite–Gaussian beam superposition state to the double Laguerre–Gaussian beam superposition state is realized based on the astigmatism conversion. Firstly, the tunable output of the double Hermite–Gaussian mode superposition state is realized by adjusting the off-axis pumping distance of the crystal. On this basis, an astigmatic mode converter is added to the back end of the resonant cavity output mirror. By utilizing it, the evolution from the double Hermite–Gaussian mode superposition state to the specific double Laguerre–Gaussian mode superposition state is realized. The evolution process of the double mode superposition state based on the astigmatic mode is analyzed theoretically. The light field change of the evolution process is demonstrated experimentally.

The refractive index of seawater is one of the essential parameters in ocean observation, so it is necessary to achieve high-precision seawater refractive index measurements. In this paper, we propose a method for measuring the refractive index of seawater, based on a position-sensitive detector (PSD). A theoretical model was established to depict the correlation between laser spot displacement and refractive index change, utilizing a combination of a position-sensitive detector and laser beam deflection principles. Based on this optical measurement method, a seawater refractive index measurement system was established. To effectively enhance the sensitivity of refractive index detection, a focusing lens was incorporated into the optical path of the measuring system, and simulations were conducted to investigate the impact of focal length on refractive index sensitivity. The calibration experiment of the measuring system was performed based on the relationship between the refractive index of seawater and underwater pressure (depth). By measuring laser spot displacement at different depths, changes in displacement, with respect to both refractive index and depth, were determined. The experimental results demonstrate that the system exhibits a sensitivity of 9.93×10−9 RIU (refractive index unit), and the refractive index deviation due to stability is calculated as ±7.54×10−9 RIU. Therefore, the feasibility of this highly sensitive measurement of seawater refractive index is verified. Since the sensitivity of the refractive index measurement of this measurement system is higher than the refractive index change caused by the wake of underwater vehicles, it can also be used in various applications for underwater vehicle wake measurement, as well as seawater refractive index measurement, such as the motion state monitoring of underwater navigation targets such as AUVs and ROVs.

In this paper, the Laguerre–Gaussian (LG) mode superposition is obtained by using the technology of double-end off-axis pumping Tm:YLF crystal, and the LG mode superposition is achieved by combining the extra-cavity conversion method. The impact of changing the off-axis distance on the order of Hermite–Gaussian (HG) mode and the topological charge of LG mode is studied. The results show that when the off-axis distance of the pump source at both ends is tuned, when the off-axis distance is in the range of 260 μm~845 μm, the single-ended 0~10 order HG mode can be obtained. Subsequently, the mode converter is placed to obtain the LG mode beam, and the double-end simultaneously pumps the crystal to obtain the superimposed LG mode. The tuning off-axis quantity changes the topological charge number. When P = 0, l1=l2, the superimposed LG mode is a single-ring spot, and the vortex beam center’s dark hollow area increases with the topological charge number. When P = 0, l1=−l2, the superimposed LG mode is a petal-like spot. The number of petals differs from the topological charges of two opposite numbers. Finally, in the case of changing the topological charge number of the double-ended LG mode, the output of the vortex array structured beams of the tuning mode order 1.9 μm Tm:YLF is completed in the case of conversion and superposition.

Perovskite light-emitting diodes (PeLED) owns the great potential for the further commercial application, while deep blue emitting and stability issue of PeLED should get more attention. In this paper, we investigated the simple strategy to tailor the color by tuning the precursor ratio, with more concentration of Cl element, the deeper blue we could achieved. The EL peak could be tuned from 520 nm to 478 nm when the Cl:Br was 0:10 and 9:1, respectively. At the same time, the effects of drive mode for the stability of PeLED was also explored. The PeLED demonstrated no distinct color change when driven by AC mode at 8 V for 3 min. While under DC mode for 3 min, the spectrum demonstrated significant red-shift. In this study, the influence of halied element to EL peak was investigated, the EL peak blueshifted with the increasement of Cl element. Furthermore, we confirmed the lift time of PeLED was enhanced under with AC mode.

The seawater refractive index is an essential parameter in ocean observation, making its high-precision measurement necessary. This can be effectively achieved using a position-sensitive detector-based measurement system. However, in the actual measurement process, the impact of the jitter signal measurement error on the results cannot be ignored. In this study, we theoretically analysed the causes of long jitter signals during seawater refractive index measurements and quantified the influencing factors. Through this analysis, it can be seen that the angle between the two windows in the seawater refractive index measurement area caused a large error in the results, which could be effectively reduced by controlling the angle to within 2.06°. At the same time, the factors affecting the position-sensitive detector’s measurement accuracy were analysed, with changes to the background light, the photosensitive surface’s size, and the working environment’s temperature leading to its reduction. To address the above factors, we first added a 0.9 nm bandwidth, narrow-band filter in front of the detector’s photosensitive surface during system construction to filter out any light other than that from the signal light source. To ensure the seawater refractive index’s measuring range, a position-sensitive detector with a photosensitive surface size of 4 mm × 4 mm was selected; whereas, to reduce the working environment’s temperature variation, we partitioned the measurement system. To validate the testing error range of the optimised test system, standard seawater samples were measured under the same conditions, showing a reduction in the measurement system’s jitter signal from 0.0022 mm to 0.0011 mm, before and after optimisation, respectively, as well as a reduction in the refractive index’s deviation. The experimental results show that the refractive index of seawater was effectively reduced by adjusting the measurement system’s optical path and structure.

Tungsten oxide (WO3) electrochromic devices are obtaining increasing interest due to their color change and thermal regulation. However, most previous work focuses on the absorption or transmission spectra of materials, rather than the optical parameters evolution in full spectrum in the electrochromic processes. Herein, we developed a systematic protocol of ex situ methods to clarify the evolutions of subtle structure changes, Raman vibration modes, and optical parameters of WO3 thin films in electrochromic processes as stimulated by dosage-dependent Li+ insertion. We obtained the below information by ex situ spectroscopic ellipsometry. (1) Layer-by-layer Li+ embedding mechanism demonstrated by individual film thickness analysis. (2) The details of its optical leap in the Brillouin zone in the full spectral. (3) The optical constants varied with the Li+ insertion in the ultraviolet, visible, and near-infrared bands, demonstrating the potential for applications in chip fabrication, deep-sea exploration, and optical measurements. (4) Simulated angular modulation laws of WO3 films for full spectra in different Li+ insertion states. This ex situ method to study the optical properties of electrochromic devices are important for monitoring phase transition kinetics, the analysis of optical leaps, and the study of ion diffusion mechanisms and the stoichiometry-dependent changes in optical constants over the full spectral. This work shows that electrochromic films in Li+ surface permeation can be applied in the field of zoom lenses, optical phase modulators, and other precision optical components. Our work provides a new solution for the development of zoom lenses and a new application scenario for the application of electrochromic devices.

The study of underwater vehicle wake detection is of significant importance within the field of target detection, localisation, and tracking of underwater vehicles. Given that propellers are the propellers of modern ships and underwater vehicles, the propeller wake field represents the principal target source for wake detection in underwater vehicles. The objective of this paper is to propose a method for measuring the wake of an underwater propeller based on a position-sensitive detector. A theoretical model of the relationship between the laser spot displacement and the change in the refractive index of the wake field is established on the basis of the principle of laser beam deflection. A prototype experimental setup for underwater propeller wake measurement was constructed based on the aforementioned optical measurement method. Furthermore, the simulation of the propeller wake flow field with strong density stratification and linear density stratification was conducted based on the experimental setup. Furthermore, experiments were conducted to detect the flow field of a propeller wake. The experimental results indicate that the wake dissipation times of the propeller in a strong density-stratified water environment are approximately 800 s and 750 s. Following the stabilisation of the wake field density, the laser spot position is observed to be stable at 0.341 mm and 0.441 mm, respectively, with a corresponding refractive index change of 2.99 × 10−6 RIU (refractive index unit) and 3.87 × 10−6 RIU, respectively. These experimental results are found to be in general agreement with the simulation results of the propeller wake field. A comparison of the experimental wake measurements based on the device with the wake measurements based on a CTD (conductivity–temperature–depth) device reveals a consistent trend. The realisation of this detection technique is of great significance for the advancement of research in the field of optical detection of underwater vehicle wake streams.

In this paper, the multi-transverse mode competition rate equation model of the Tm:YLF slab laser is established based on the cavity structure of multi-pass gain. As the pump power increased, the changing trend of the number of particles in each mode is analyzed. The direction of beam quality change is also mastered, verified by the three-pass gain laser with the evolution of pump power. Due to the limited compression capacity of the x-axial output spot of the three-pass gain laser, the output spot changes significantly under different cavity lengths and output mirror curvatures. By discussing the output spot evolution, it is known that the large curvature output mirror and the appropriate cavity length can optimize the output spot. Finally, under the pump power of 72 W, the four-pass gain laser obtains a laser output of 1.8 W. It’s beam quality is MX2 = 1.77;MY2 = 1.99, the optical–optical conversion efficiency is 2.5 %, and the slope efficiency is 15 %. The beam quality of a three-pass gain laser is MX2 = 2.67; MY2 = 1.70, the optical–optical conversion efficiency is 3.2 %, and the slope efficiency is 11 %. It is verified that the compression of the four-pass gain laser is stronger than that of the three-pass gain laser on the x-axis, laying the foundation for developing a compact multi-pass gain laser.