The chalcogenide phase-change material Ge2Sb2Te5 (GST) is paramount for developing next-generation reconfigurable photonic devices, yet its performance is critically dependent on thin-film quality. This work presents a systematic investigation into the influence of radio-frequency (RF) magnetron sputtering parameters-specifically argon (Ar) working pressure and substrate temperature-on the structural, chemical, optical, and kinetic properties of GST thin films. Films were deposited on SiO2/Si substrates under varying Ar pressures (0.4-3.0 Pa) and substrate temperatures (Room Temperature-160 degrees C). Comprehensive material characterization was performed using a suite of advanced analytical techniques. Results indicate that increasing Ar pressure leads to the formation of films with lower density and higher porosity, as confirmed by scanning electron microscopy analysis. This porous microstructure facilitates a lower crystallization temperature and faster crystallization dynamics, with switching times on the order of tens of picoseconds observed via time-resolved pump-probe reflectivity. However, this enhancement in switching speed is accompanied by a significant reduction in the optical contrast, a key figure of merit for photonic applications. Conversely, elevating the substrate temperature to an optimal 80 degrees C during deposition produces dense, pore-free amorphous films with a density of 6.16 g/cm3, only 1.5% lower than the crystalline phase. These films exhibit superior thermal stability and a maximized refractive index contrast (Delta n) at telecommunication wavelengths. X-ray photoelectron spectroscopy confirmed that a protective capping layer is essential to prevent the rapid surface oxidation of Ge. These findings establish a clear process-structure-property-performance relationship, providing a crucial framework for tuning GST film properties to meet the divergent demands of high-speed, low-power optical memories versus high-performance, low-loss tunable photonic components.

Objective The rapid advancement of high-power laser technology has led to the emergence of minute and morphologically complex damages on optical thin film components under intense laser irradiation. This issue not only constrains the development of laser systems toward higher power and energy but also directly impacts the stability and operational lifetime of their components. Traditional methods for detecting optical thin film damage, such as microscopy and scattered light detection, possess unique advantages and can identify damage to a certain extent. However, they are hampered by limitations including insufficient detection accuracy, a single dimension of information, and difficulty in revealing the micro-processes of damage formation. Consequently, these methods fail to meet the urgent demand for online, precise detection in high-power laser systems. In recent years, convolutional neural networks (CNNs) have demonstrated exceptional performance in object recognition and image segmentation. The U-Net model, with its symmetric encoder-decoder architecture and skip-connection mechanism, excels at multi-scale feature fusion and is widely used in fine-grained segmentation tasks like medical imaging. Nevertheless, when applied to high-resolution images of optical thin film damage, the basic U-Net exhibits limited detection accuracy, insufficient localization of damage edges, and a high propensity for missed and false detections of minute damage regions. To address these shortcomings, this paper introduces an innovative framework that integrates an error prediction sub-network and a dynamic feature fusion module at the end of the U-Net decoder. Combined with a novel loss function incorporating edge loss and an error prediction auxiliary loss, this approach enables adaptive attention and fine-grained correction of error-prone regions, thereby suppressing noise interference while significantly enhancing the segmentation accuracy of minute damage. Methods The methodology of this study encompasses three stages: damage image acquisition, image preprocessing, and the design and implementation of the improved U-Net model. First, a self-developed laser damage detection apparatus is used to conduct laser irradiation experiments on SiO (2), HfO (2), and TiO2 thin film samples. An optical microscope is employed to capture 1000 raw damage images, from which 750 typical samples are selected and manually annotated to construct a specialized dataset for this research. Second, a zero-shot deconvolutional network (ZS-DeconvNet) is utilized for noise suppression and resolution enhancement of the damage images, which clarified the details of damaged areas and made minute damage more discernible. Finally, in the design phase of the improved U-Net, two novel synergistic modules are introduced at the end of the decoder: an error prediction sub-network and a dynamic feature fusion module. These are combined with a multi-component loss function, including edge loss and an error prediction auxiliary loss, to progressively learn the feature distributions of error-prone areas, such as damage edges and minute defects. This allows for targeted optimization of these specific pixel regions during segmentation to achieve fine-grained, pixel-level results. Results and Discussions To comprehensively evaluate the effectiveness of the improved U-Net in the segmentation of optical thin film damage, comparative and ablation experiments are conducted against the basic U-Net using the same dataset and experimental strategy. Compared to the basic U-Net, the improved model demonstrates a significant increase in mean pixel accuracy (MPA) on the test set from 0.9801 to 0.9919, a leap in mean intersection-over-union (mIoU) from 0.7221 to 0.8658, a substantial rise in precision from 0.8212 to 0.9435, and an increase in recall from 0.9527 to 0.9531 (Table 1). The confusion matrix results indicate that the improved U-Net reduces misclassified pixels (false positives) by 72.49% and decreases missed detections (false negatives) by 0.85% (Table 2). This significant quantitative improvement is visually corroborated by the segmentation results (Fig. 11), which shows accurate segmentation of minute damage areas and effective avoidance of background noise interference. Furthermore, the ablation study reveals that the error prediction-guided dynamic feature fusion mechanism (DFFM+auxiliary loss function L-aux) is the key to the model's performance breakthrough, contributing 58.5% of the total improvement (Table 4), further validating the overall efficacy of the proposed model. Notably, this substantial enhancement in performance is achieved without sacrificing computational efficiency. The increases in model parameters and computational load are both below 3%, while the frame rate (FPS) is maintained above 154 frame/s, indicating no speed bottlenecks for online detection workflows (Table 3). Conclusions This study addresses the challenges of detecting minute features, complex edge morphologies, and severe noise interference in optical thin film damage images by proposing an improved U-Net segmentation method based on error prediction and dynamic feature fusion. By introducing an error prediction sub-network and a dynamic feature fusion module at the decoder stage and applying the constraints of edge loss and an error prediction auxiliary loss function to damage boundaries and error-prone regions, the method achieves adaptive attention and fine-grained correction of these difficult areas. Experimental results conclusively demonstrate that the improved U-Net achieves significant enhancements across all key evaluation metrics compared to the basic U-Net, particularly in mIoU (+19.90 % ) and precision (+14.89 % ). The proposed model not only segments minute and low-contrast damage with greater precision, effectively reducing the miss rate, but also significantly suppresses over-segmentation caused by background noise, thereby drastically lowering the false detection rate. Moreover, the improved U-Net accomplishes high-precision segmentation while maintaining low computational overhead and high-speed inference capabilities, showcasing its strong generalization ability and significant potential for practical application.

Objective With the rapid advancement of high-power laser technology, optical components are increasingly challenged by severe thermal loads, among which the thermal lens effect has become a key physical phenomenon limiting beam quality and system performance. Although previous studies have identified that thermal lensing primarily arises from the temperature dependence of the refractive index and thermally induced stress, and have explored various mitigation strategies such as material optimization and structural compensation, most existing research remains focused on phenomenological observation and parameter optimization. A systematic and quantitative analysis linking the temperature field, stress field, refractive index distribution, and beam propagation characteristics (such as spot radius and focal position) is still lacking. This theoretical gap restricts the precise prediction of thermal damage and the active control of beam behavior in high-power laser systems. Therefore, this study takes fused silica as the representative optical material and aims to establish and solve a coupled multi-physics model. The objective is to elucidate the dynamic evolution mechanism of thermal lensing and its modulation of beam transmission characteristics, providing a solid theoretical foundation for the design optimization and lifetime evaluation of optical components in high-power laser systems. Methods A three-dimensional thermo-mechanical coupling model of fused silica under Gaussian beam irradiation is developed. The research methodology integrates theoretical modeling and numerical simulation. Theoretically, based on the first law of thermodynamics and thermoelastic theory, the governing equations and boundary conditions describing the transient temperature and stress fields inside the optical component are established, incorporating the temperature dependence of material parameters. By solving these equations, the total refractive index variation caused by both temperature gradients and thermal stress is derived, followed by a theoretical formula for the equivalent focal length of the thermal lens. Numerically, the finite element software COMSOL Multiphysics is employed to perform simulations with bidirectional coupling between ray tracing and solid mechanics. The optical component is subjected to continuous laser irradiation with powers ranging from 500 W to 3000 W. The model evaluates the spatial distributions of temperature, structural deformation, stress, and beam propagation within and beyond the optical medium. Realistic boundary conditions and nonlinear material behaviors are fully considered to ensure the accuracy and physical fidelity of the results. Results and Discussions From an innovation perspective, this study systematically reveals the spatial characteristics of the laser-induced temperature and stress fields. The results show that the temperature gradient is highly localized in the irradiated region, and the peak temperature at the beam center increases nonlinearly with laser power-from 466.43 K at 500 W to 522.06 K at 3000 W. Under mechanical constraints, thermal expansion produces an outward convex deformation in the central surface region (with the maximum deformation rising from 0.146 mu m at 500 W to 0.195 mu m at 3000 W and generates pronounced compressive stress concentration at the clamped edges. Moreover, the thermal lensing-induced focusing effect is quantitatively characterized. As the incident power increases, the beam spot radius on the observation plane monotonically decreases while the peak power density significantly increases, confirming the enhanced positive lensing behavior. The equivalent focal length of the optical element, derived from simulation data, exhibits a nonlinear reduction from approximately 695 mm at 500 W to 127 mm at 3000 W, showing excellent agreement with theoretical predictions. A further innovative contribution of this study lies in its microscopic analysis of refractive index gradient-induced beam modulation. It is found that laser irradiation generates a radial gradient of refractive index-higher at the center and lower toward the edge. By integrating the simplified Fresnel law with the derived refractive index gradient model, a theoretical framework is established to describe the continuous angular deflection of light rays as they traverse the graded refractive medium. The refracted angle incrementally increases through successive micro-layers, ultimately approaching normal emergence near the exit surface. Under higher laser power, the steeper refractive index gradient leads to stronger beam bending and a shorter focal length, thereby elucidating the physical origin of the nonlinear dependence of focal length on input power. Conclusions This study investigates the thermal stress distribution and beam transmission characteristics of fused silica optical components under continuous-wave laser irradiation of varying powers. Through multi-physics coupling simulations based on a three-dimensional axisymmetric thermodynamic model, the dynamic correlations among thermally induced refractive index gradients, spatial power deposition, and equivalent focal length are systematically explored. The results demonstrate that nonuniform thermal elevation caused by continuous laser irradiation induces a radial refractive index gradient, forming an equivalent thermal lens structure. This thermally driven optical distortion significantly alters the effective focal length and focal spot characteristics of the optical component. Furthermore, a bidirectional coupling mechanism between the refractive index gradient and power density distribution is elucidated: changes in the refractive index not only modulate the beam propagation path but also alter the energy deposition characteristics of the optical field, which in turn affects the evolution of the temperature field. Consequently, the irradiated region behaves analogously to an optical lens, exhibiting power-dependent focusing or defocusing effects. This work provides a comprehensive theoretical framework for understanding thermally induced beam distortions in high-power laser systems and offers guiding insights for the thermal stability design of optical components operating under extreme laser irradiation conditions.

Their opto-thermo-mechanical response fundamentally constrains the reliability of dielectric metasurfaces under high-power laser irradiation. In this study, we systematically investigate the thermomechanical behavior of cylindrical fused silica metastructures under nanosecond pulsed laser irradiation using a fully coupled multiphysics finite element model. Our results reveal that the maximum temperature exhibits a nonlinear oscillatory dependence on the cylinder height, attributed to Mie-type optical resonances, while the maximum thermal stress decays with increasing height in accordance with Saint-Venant’s principle. These findings provide a theoretical basis for designing laser-resistant metasurfaces through geometric optimization.

The laser-induced damage threshold (LIDT) is a key measure of an optical component’s resistance to laser damage, making its accurate determination crucial. Following the ISO 21254 standards, we studied the measurement strategy and uncertainty fitting method for laser damage, establishing a calculation model for uncertainty. Research indicates that precise LIDT measurement can be achieved by using a small energy level difference and conducting multiple measurements. The LIDT values for the cylindrical grating are 15.34 ± 0.00052 J/cm2 (95% confidence) and 15.34 ± 0.00078 J/cm2 (99% confidence), demonstrating low uncertainty and reliable results. This strategy effectively measures the LIDT and uncertainty of various grating surface shapes, offering reliable data for assessing their anti-laser-damage performance.

To solve the difficulty in achieving that strong electromagnetic shielding and high infrared transmission of traditional square metal meshes, composite microstructures, i.e., circle-square, square-circle, hexagon-square, and honeycomb-square structures, exhibiting high electromagnetic interference shielding efficiency (EMI SE) comprising nonhomogeneous nested units have been constructed and demonstrated theoretically and experimentally. These composite microstructures, which are characterized by longer periods and wider line widths, are equivalent to square metal mesh with smaller structural parameters utilizing an equivalent period and line width model that resulted in enhanced EMI SE. Compared with single structures, composite microstructures exhibit a smaller dimensional span. Numerical simulation results demonstrate that an increase in the metal mesh within the composite microstructure reduces the local electric field value, thereby leading to an increased EMI SE value. Practical measurements indicate that, under conditions of comparable infrared transmittance, the average EMI SE values of the circle-square and honeycomb-square structures on a double-sided polished silicon substrate were 33.5 and 34.6 dB at 4-12 GHz, respectively, which are 3.3 and 4.4 dB higher than that of the traditional square structure. Thus, the constructed composite microstructures (circle-square and honeycomb-square) can realize enhanced EMI SE performance while maintaining comparable levels of infrared transmittance. The findings of this study are expected to be of considerable significance in terms of improving the comprehensive performance of graphical optical windows.

Traditional laser thin film optical components are specially designed layered structures made of two or more materials. However, as the number of layers increases, the anti-laser damage ability of the optical elements is significantly reduced. In this study, a single-layer structured surface is designed to have better optical transmittance than its homogeneous substrate. It also shows potential advantages in laser damage resistance applications. The transmittance and laser damage morphology of periodic cylindrical surfaces and their uniform substrates using a combination of experimental and simulation methods are examined. According to ISO21254, the laser-induced damage threshold (LIDT) of the structured surface and the uniform substrate were measured on a 1-on-1 irradiation of a 1,064 nm laser with a pulse width of 10 ns. The measured LIDT values were (15.3 ± 1.15) J/cm2 for the structured surface and (15.2 ± 1.09) J/cm2 for the uniform substrate. The damaged morphology of the structured surface was analyzed using a polarizing microscope to study its periodic distribution. Additionally, the electric field distribution on the surface of the structure and its uniform substrate was simulated using the finite element method. The results indicate that the damage characteristics of the structured surface are influenced by the surface structure, and the presence of the structure influences the energy distribution of laser deposition. This study serves as a valuable reference for further research into the laser damage mechanism of structured surfaces.

The stability, electronic structures and optical properties of g-ZnO/CdX (X = S, Se, Te) heterostructures are studied by density functional theory. It is found that the stable monolayers spacing of the corresponding heterostructure decreases with the increase of the X atomic radius in the CdX monolayers. The constructed g-ZnO/CdX heterostructures all belong to direct band gap, 2.12 eV, 2.09 eV and 1.99 eV, respectively. Electrostatic potential results show that the two monolayers form an internal electric field at the heterostructure interface, and can inhibit the recombination of photogenerated electron hole pairs, and effectively extend the carrier lifetime. Charge density difference analysis shows that charge redistribution mainly occurs in the interfacial region. The optical properties show that the absorption of g-ZnO in the visible range is achieved by heterostructure. In general, with the smallest band gap and the strongest built-in electric field, g-ZnO/CdTe could have the best carrier separation efficiency. And the optical property analysis proves that the g-ZnO/CdTe heterostructure system has the highest utilization ratio of visible light. The above results show that the electronic structure and optical properties of g-ZnO/CdTe heterostructure are the best, and it can be inferred that this heterostructure will be the most beneficial to improve the photocatalytic activity of g-ZnO, providing a new direction for its application in the field of photocatalysis.

The precision of testing the damage threshold of thin film lasers has always been a limiting factor in the advancement of high-power laser systems. The conventional plasma flash method sometimes fails to differentiate between film and air plasma flashes, resulting in significant errors in determining the film damage threshold. By distinguishing between the different durations of thin film and air plasma flashes, misjudgment can be eliminated. The aim of this article is to determine both the calculated and experimental values of the duration of air plasma flash near the surface of thin films (t c) and to analyze the factors that influence it. First, a model is established to calculate the theoretical value of t c. For a sample consisting of a single-layer hafnium oxide film, we assume that the incident laser wavelength, focal spot diameter, energy, and pulse width are 1,064 nm, 0.08 cm, 57.21 mJ, and 10 ns, respectively. The focal length of the lens positioned in front of the film sample is set at 350 mm, with a distance of 5 mm between the film sample and this lens. Under these conditions, the theoretical value for t c is calculated to be 4.24×10−6s4.24\times {10}^{-6}\hspace{.25em}s. Second, the device was used to conduct eight experiments to obtain experimental values of t c. The results are as follows: (1) An increase in incident laser energy leads to an increase in t c. (2) The length of t c is solely dependent on the incident laser energy, regardless of the sample material or placement (even when the sample is not placed and the laser directly acts on air). (3) When substituting experiment parameters into the model for calculating t c, there is good agreement between theoretical and experimental values. Third, it was observed that t c increases with increasing incident laser energy, pulse width, and focal length of the lens, while decreasing with an increase in distance between the film sample and the lens.

The excellent electrical and optical properties of graphene provide the possibility for its application in transparent electromagnetic shielding films. The multi-layer graphene films were designed and prepared, and the average transmittances of 1–4 layers graphene in the 3–5 μm band were 97.19

The laser-irradiated grating exhibits a unique damage morphology, and its surface geometry and period distribution significantly affect the laser-induced damage threshold (LIDT). Understanding the formation mechanism of this damage morphology can help in achieving higher LIDT gratings. The laser-induced damage threshold (LIDT) of the grating was measured to be 15.3 J/cm2 under 1064 nm, 10 ns pulsed laser irradiation according to the ISO 21254 standard. Through finite element analysis, we simulated the ensuing temperature and thermal stress fields. The results identify interfacial thermal stress as the primary driver of damage. The model qualitatively reproduces the characteristic hexagonal damage morphology observed in experiments, revealing a thermo-mechanical shaping process. These findings provide critical insight into the damage evolution in nanostructured surfaces and offer guidance for the design of high-LIDT optical gratings.

For the optical components in the optical system, it is not only required to have good optical transmittance, but also to achieve the shielding of the electromagnetic wave band. Traditional metal materials suppress the light transmission performance while shielding electromagnetic waves. Carbon-based materials have become the first choice for mesh structure shielding materials due to their special physical and chemical properties and excellent electromagnetic shielding properties. In this paper, the copper metal plane structure is designed as a mesh structure, and a graphene layer is added to the copper mesh structure to establish a multi-layer copper-based graphene composite mesh structure model. In the range of 12 similar to 18 GHz electromagnetic frequency band, HFSS simulation software is used to simulate the electromagnetic shielding effectiveness of copper-based graphene multilayer composite mesh structure model by waveguide method. The linewidth parameters of the basic mesh structure are changed, and the electromagnetic shielding characteristics are simulated and experimentally studied. The absorption loss SEA and reflection loss SER of different structures are calculated to further explore the electromagnetic shielding mechanism of the new structure. The results show that in this electromagnetic frequency range, with the increase of electromagnetic wave test frequency, the electromagnetic shielding effectiveness SE of all structures shows a downward trend. When the same structure is at low frequency of electromagnetic wave, the shielding material has relatively poor permeability and propagation ability to electromagnetic wave, strong blocking ability to electromagnetic wave, and high electromagnetic shielding effectiveness SE. The electromagnetic shielding effectiveness of the three copper-based graphene multilayer composite mesh structures is improved compared to the single copper mesh structure. Among them, the double-sided superimposed graphene layer structure in the copper mesh structure is the best structure of the electromagnetic shielding effect in the three composite structures compared with the copper mesh structure. The relationship between the electromagnetic shielding effectiveness of the three composite structures is consistent with the theoretical calculation. The electromagnetic shielding effectiveness of this structure with double-sided graphene layer is more than 1.7 dB higher than that of a single copper mesh structure, and the absorption loss of electromagnetic wave is increased by 4.81 dB. Due to the superposition of graphene layers in the three composite structures, the absorption of electromagnetic waves by graphene is increased, so that the overall structure has a certain absorption effect on electromagnetic waves. While improving the overall electromagnetic shielding effectiveness of the structure, the composite structure also significantly improves the absorption loss of electromagnetic waves. Under the same electromagnetic frequency range, when the material properties of the composite structure and the mesh period are constant, the line width parameters of the basic mesh structure are changed. With the increase of the mesh line width, the electromagnetic shielding effectiveness of the composite structure is also increasing, while the mesh transmittance is decreasing. It is concluded that for the mesh substrate structure, there is a mutually restrictive relationship between electromagnetic shielding effectiveness and light transmittance. The electromagnetic shielding characteristics of three kinds of multi-layer composite structure samples designed by simulation are tested to verify the accuracy and feasibility of the simulation in this study. The experimental results show that the electromagnetic shielding effectiveness of the three multi-layer composite structure model samples is higher than that of the copper mesh structure model samples. The experimental results are almost consistent with the simulation and theoretical calculations, and the trend of the electromagnetic shielding effectiveness curve is consistent, which further verifies the feasibility of the simulation and the accuracy of the data results. The results of this study have certain reference value and reference significance for improving the electromagnetic shielding characteristics of metal materials and the electromagnetic shielding characteristics of metal and non-metal composite structures.

To solve the difficulty in achieving that strong electromagnetic shielding and high infrared transmission of traditional square metal meshes, composite microstructures, i.e., circle-square, square-circle, hexagon-square, and honeycomb-square structures, exhibiting high electromagnetic interference shielding efficiency (EMI SE) comprising nonhomogeneous nested units have been constructed and demonstrated theoretically and experimentally. These composite microstructures, which are characterized by longer periods and wider line widths, are equivalent to square metal mesh with smaller structural parameters utilizing an equivalent period and line width model that resulted in enhanced EMI SE. Compared with single structures, composite microstructures exhibit a smaller dimensional span. Numerical simulation results demonstrate that an increase in the metal mesh within the composite microstructure reduces the local electric field value, thereby leading to an increased EMI SE value. Practical measurements indicate that, under conditions of comparable infrared transmittance, the average EMI SE values of the circle-square and honeycomb-square structures on a double-sided polished silicon substrate were 33.5 and 34.6 dB at 4-12 GHz, respectively, which are 3.3 and 4.4 dB higher than that of the traditional square structure. Thus, the constructed composite microstructures (circle-square and honeycomb-square) can realize enhanced EMI SE performance while maintaining comparable levels of infrared transmittance. The findings of this study are expected to be of considerable significance in terms of improving the comprehensive performance of graphical optical windows.

The thickness of a metal grid represents a significant factor in electromagnetic interference shielding effectiveness (SE), and the skin depth of the uniform metal surface does not represent the critical thickness of the metal grid. In this study, the influence of Cu grid thickness on the electromagnetic interference SE and critical thickness was assessed using a theoretical model, followed by simulation analysis. According to the equivalent circuit model theory, the skin depth in the equivalent resistance was replaced by the actual thickness of the grid, and the equivalent reactance was corrected by changing the coefficient. A physical field model was established, considering the effects of different grid structures on the SE, using the finite element method. The Cu grids were fabricated in line with the simulation results, and we found that the tested electromagnetic interference SE values of the Cu grids with different thicknesses were generally consistent with the equivalent circuit model when the thickness was less than the critical thickness. The simulation demonstrated that the critical thickness of the Cu grid was constant for different periods and line widths, and the critical thickness of the Cu grid was approximately 170 nm at 1–12 GHz. When the thickness of the Cu grid was 170 nm, the average electromagnetic interference SE was 24.8 dB at 1–12 GHz. In engineering applications, grid thickness greater than the critical thickness should be preferentially designed, and the period or line width should be optimized to further improve the electromagnetic interference SE of the target frequency band. In addition, the electromagnetic interference SE of a metal grid can be quickly estimated by the equivalent circuit model, thus guiding future design work.

The accurate testing of plasma temperature and electron density and shock wave pressure during an electroburst in a copper foil transducer is critical for the characterization of the detonation performance of its elements. In this paper, the sequence of interferograms during the detonation of a copper foil transducer is captured at a frame rate of 3×106 f p s in conjunction with Mach-Zehnder interferometry and high-speed photography, and the results clearly demonstrate the propagation of the shock wave wavefront and plasma. The phase differences disturbed by plasma are extracted using the Fourier transform method, and the refractive index distributions are reconstructed with the Abel algorithm. Subsequently, based on the refractive index models of the shock wave and plasma, the shock wave pressure and plasma temperature and electron density are partitioned and reconstructed. Results show that the maximum shock wave pressure in the detonation of the copper foil transducer element is 1.297 atm, the maximum plasma temperature is 16,280 K, and the maximum plasma electron density is 2.134×1017 c m -3. This study provides a theoretical and technical foundation for the detonation performance testing of pyrotechnic energy-conversion components.

The laser attenuation device has always been an important component of the LIDT system,the attenuation adjustment ability of the laser attenuation device directly affects the performance of the testing system.The continuous attenuation device of high energy laser is achieved by combining polarization cube with rotating half wave plate,when the angle of the rotating half wave plate changes from 0° to 45°, the transmissivity of the attenuator changes from 99.9% to 0.3%.This design scheme reduces the volume of the attenuation device while achieving continuous adjustment of the transmissivity.Adopting optical devices with large aperture and high damage threshold, the maximum single pulse energy that the system can withstand is 2J@1064nm. The attenuated energy is tested by using a Ophir PE50BF-DIF-C pyroelectric energy sensor,the results show that the laser energy transmissivity can be continuously adjusted within the range of [0.3%,99.9%]. Using Beamtech China SGR20 laser, it can work stably with the power density of 2J@1064nm whose experimental results meet the design re-quirements. Compared with the traditional optical variable attenuator,this design has the advantages of large dynamic regulation range, stable attenuation and continuous regulation.

TiO2 and SiO2 films with different porosity were prepared on quartz substrate and Si substrate respectively by sol-gel technique combined with spin coating method,and the optical and laser damage characteristics of both films were investigated.The optical band gap of the films was calculated based on the transmission spectral curves.It was found that the optical band gap increased with the increase of porosity,the optical band gap size of TiO2 films ranged from 3.75 eV to 3.97 eV,and that of SiO2 films ranged from 3.52 eV to 3.78 eV.The ellipsometry measurement results show that when the mass fraction of polyethylene glycol(PEG)was increased from 0,0.8%,4%to 8%at a wavelength of 1 064 nm,the porosity of TiO2 films increased from 11.5%,14.1%,30.9%to 38.7%,and the refractive index decreased from 2.063 5,2.016 5,1.748 1 to 1.640 9;the porosity of SiO2 films increased from 4.04%,4.6%,5.7%to 13.9%,and the refractive index decreased from 1.438 6,1.435 8,1.420 4 to 1.387 9.The extinction coefficients of all TiO2 and SiO2 film samples are better than 10-3 except for the TiO2 film with PEG mass fraction of 0.8%,which indicates that the absorption of the films is smaller.The laser induced damage threshold(LIDT)of the films is greatly influenced by the porosity,and the larger the porosity,the higher the LIDT of TiO2 films,with a value up to 16.7 J/cm2.However,the LIDT of SiO2 film is not improved compared with that without PEG,and when the PEG mass fraction increased from 0.8%to 8%,the LIDT of SiO2 film increased by 1.9 J/cm2.In summary,improving the porosity helps to improve the laser damage resistance of the film.

随着激光技术的不断发展,对应用于大功率、高能量激光系统,以及激光防护系统中的光学薄膜器件提出了高损伤阈值的要求.但目前在激光损伤阈值的测量上,还存在测量标准不统一、重复性不好、准确性差、相互结果难以比对等问题,其主要原因在于不同的材料及膜系适用于不同的损伤识别方法.对目前国内外在损伤识别方法方面的研究进行了总结,阐述了图像法、散射法、等离子闪光法,等离子体光谱法等多种不同的损伤识别方法,介绍了各种方法识别损伤的原理、特点,以及损伤识别的效果,期望对激光损伤阈值测试方面的研究具有参考和借鉴.

The infrared anti-reflection film is prepared by ion beam assisted thermal evaporation deposition technology. The film has good firmness and can meet the needs of wet transfer. By adjusting the number of layers of the graphene mesh, the electromagnetic shielding and optical transparency properties are simultaneously improved. The infrared anti-reflection film and graphene mesh are combined to design and prepare a compatible electromagnetic shielding infrared anti-reflection film device with sandwich structure. The test results of the device show that the peak transmittance of the graphene mesh/infrared film/substrate/infrared film combination structure in the 3 to 5 mu m band is 95.06%, and the average transmittance is 93.40%. The peak shielding effectiveness (SE) in the 12 to 18 GHz frequency band is 14.50 dB, and the average SE is 12.98 dB. It shows that the film device of this structure maintains the high transmittance of the infrared anti-reflection film and has good electromagnetic shielding effectiveness.