Spatially-resolved characterization of absorptive defects on high-quality fused silica optical surfaces is demonstrated by combining laser thermal pumping with dynamic micro-interferometric imaging (LTP-DMI). Benefiting from array-CCD-based detection, the method enables spatially resolved imaging of defect distributions across a millimeter-scale field of view, offering higher efficiency and spatial resolution than conventional photothermal techniques. The consistency between thermally-induced deformation and photothermal absorption was validated using ion-implanted samples. An optimal LTP power density of 520 W/mm2 was identified. Four fused silica samples with different surface treatment levels were examined, revealing that improved defect control reduced deformation values, with a correlation coefficient of 0.99 at a fluence of 11 J/cm2. Finally, absorptive defect distribution models were constructed, showing that variations in defect type and distribution lead to distinct deformation behaviors. The resulting defect distribution models revealed distinct deformation behaviors associated with absorption centers, demonstrating the capability of LTP-DMI for sensitive and efficient assessment of ultra-low absorption features.

A multiphase nondestructive evaluation method based on energy-level transition mechanisms is proposed for fused silica optics after CO2-laser repair. The method integrates photothermal weak absorption associated with non-radiative transitions, together with steady-state confocal fluorescence and ultrafast fluorescence corresponding to radiative transitions, enabling complementary characterization of absorptive damage precursors within repaired pits. Photothermal weak absorption exhibits a clear qualitative correlation with laser damage behavior. Ultrafast fluorescence intensity exhibits a strong exponential correlation with the laser damage threshold (R2 = 0.98), reflecting the distribution of damage-relevant high-density defect states. In contrast, steady-state fluorescence shows a weaker correlation with damage behavior due to the contribution of slow radiative components that are not directly associated with damage precursors. Raman and fluorescence spectroscopy reveal distinct structural evolution and defect distributions at different repair states. In incomplete mitigation pits, three-fold and four-fold rings together with non-bridging oxygen and silicon dangling-bond defects are significantly enriched. In complete mitigation pits, defect contents are partially suppressed with spatial variability, yet the structure does not fully recover to the stable state of pristine fused silica. After dynamic chemical etching (DCE), the repaired regions exhibit microstructures that more closely approach the intrinsic state of the substrate. First-principles calculations demonstrate that chemical structural defects introduce localized electronic states and increase the density of states within the band gap, thereby enhancing sub-bandgap photon absorption and promoting both radiative and non-radiative transitions, which manifest as enhanced ultrafast fluorescence and photothermal signals.

Learning-based methods have garnered significant attention in indoor scene reconstruction tasks. However, researchers have often overlooked the crucial role of the surface prediction stage. Our study specifically focuses on this phase. According to our experiments and analysis, this phase primarily addresses spatial voxel occupancy and geometric structure maintenance. Simple structural designs are insufficient to effectively solve these problems. To address these challenges, we propose a hybrid model, which combines the strengths of Convolution Neural Networks and Transformer architectures for fine reconstruction. Additionally, we introduce several new techniques, including the Sparse Positional Attention mechanism, Sparse Channel Decoding Block, and Mixed Feature Fusion mechanism. These techniques, leveraging the characteristics of sparse computation, enhance feature utilization in both spatial and channel dimensions. With limited training and testing resources, our network achieves optimal results on the ScanNet dataset, improving accuracy and F-score by 2.1% and 1.6%, respectively, and reducing the Chamfer distance to 0.055m. To our knowledge, our model is the first use of hybrid structures in the surface prediction phase of an indoor scene reconstruction task. Moreover, we hope that our design and analysis can provide a new paradigm for task network design in this phase.

The fabrication of SSD-free fused silica optics is a crucial objective for high-power laser applications. To treat the surface of polished fused silica, a combination of RIE/RIBE and deep-controlled etch (DCE) techniques are typically employed. Currently, it is important to consider and study the ideal etching depth and precision while using combined etching techniques to remove the identified SSD. Herein, we present a novel approach to identify the distribution of SSD in fused silica, which corresponds to a specific grinding/polishing process condition. Our method involves using a mobile RIBE to perform cone cutting and remove material from the polished fused silica surface. Afterward, we etch the optical element’s surface with HF to visualize the subsurface cracks and understand their relationship with the RIBE depth. Through a systematic investigation of the combined etching technique, we establish a correlation between the depth of RIBE and DCE and the performance of laser damage. The combined etching technique can be implemented as a dependable approach to treat the surface/subsurface defects in fused silica and has the potential to improve laser damage resistance significantly.

Optical edge-enhanced imaging is an effective method for boundary extraction, and it is also a cutting-edge technology for object detection in image processing. With the rapid development of metamaterial and metasurface fields, the miniaturization and lightweight of optical devices have reached a new scale. At present, the experimental research of optical edge-enhanced imaging using metasurface is insufficient and lags behind the theoretical research. In this paper, we propose optical edge-enhanced imaging based on a Huygens phase metasurface in the near-infrared (NIR). The entire optical edge-enhanced process is simulated, and the feasibility of the method is verified theoretically. Then, the edge-enhanced of numbers, letters, and biological tissues is carried out experimentally, and the results are consistent with the simulation results. This study proposes a near-infrared dielectric metasurface-based edge-enhanced imaging that can find important applications in compact optical platforms such as image processing.

Three-dimensional (3D) plasmonic metamaterials have become a trend in the application of nanophotonic devices. In this paper, a convenient and inexpensive method for the design of 3D multilayer plasmonic metamaterials is constructed using a one-step self-shielded reactive-ion-etching process (OSRP) and a thermal evaporation system, which provides an efficient and low-cost method for the preparation of surface-enhanced Raman spectroscopy (SERS) substrates. The near-field enhancement of the 3D plasmonic metamaterials provides highly efficient electromagnetic resonance, and highly sensitive and uniform SERS sensing capabilities. The SERS detection results of rhodamine B (Rh. B) and rhodamine 6G (R6G) on this substrate show that the detection limit could reach 10–13 mol/L, and the signal could give expression to excellent uniform stability. The results show that high sensitivity and high robustness SERS substrates can be prepared with high efficiency and low cost.

Optical metasurfaces are two-dimensional arrays of nano-scatterers that modify optical wavefronts at subwavelength spatial resolution.They achieve the effect of focusing through phase control under a subwavelength scale,and are called metalenses.They are poised to revolutionize optics by enabling complex low-cost systems.However,there are severe monochromatic aberrations in the metasurfaces.In this paper,the coma of the long-wave infrared optical system is elimi-nated through a single-layer metasurface.By changing the phase function,this metalens has a numerical aperture of 0.89,a focal length of 150 μm and a field of view of 120°(0.4@60 line pairs/mm)that enables diffraction-limited monochromatic imaging along the focal plane at a wavelength of 10.6 μm.The designed metasurface maintains a favorable value of the modulation transfer function at different angles.This equipment can be widely used in imaging and industrial processing.

Fused silica optics are highly susceptible to rear-surface damage under irradiation by ultraviolet pulsed laser with high energy density, which seriously affects the reliability of high-power ultraviolet pulsed laser facilities. Comprehensively analyzing the related research progress in China and abroad, this paper systematically expounds the damage characteristics of the surface of fused silica optics under high-energy ultraviolet pulsed laser irradiation, including typical initial damage and characteristics of damage growth behaviors. Subsequently, it outlines the types and distribution characteristics of the defects on the surface of fused silica optics, and the intrinsic mechanism of damage induced by ultraviolet pulsed laser. Then, commonly used surface processing methods and defect control technologies for fused silica are summarized. Finally, an overview of the research progress on new non-destructive detection technologies for defects on the surface of fused silica and damage-resistant performance testing technologies is presented.

A photo-thermal absorption distribution probability curve based on a normal distribution model was proposed to describe the distribution of absorptive defects on fused silica surfaces under different processing conditions. Simultaneously, the maximum distribution probability absorption coefficient (MPA) and absorption distribution deviation (ADD) were used to quantitatively describe the overall absorption level and the uniformity of the absorption distribution on the fused silica surface. Based on this, the MPA (μ) and ADD (δ) were used to establish a statistical numerical relationship with the surface damage density of fused silica. The results showed that when μ ≤ 0.095 ± 0.015 and δ ≤ 0.045 ppm, the fused silica optics met the manufacturing process requirements for high laser-induced damage performance. Thus, a non-destructive approximate evaluation of the laser-induced damage density on the fused silica surface was achieved. This evaluation method provides a new, to the best of our knowledge, technology for evaluating the manufacturing process quality related to the damage performance of fused silica optics in high-power solid-state laser facilities and is an important supplement to popular destructive laser-induced damage testing methods.

Meta-surfaces is a two-dimensional structure, which can completely control the amplitude, phase, and polarization of light. Different from metallic meta-surfaces, the silicon structure is favorable for high transmission, low loss, and compatibility with existing semiconductor technologies. However, these devices are usually made up of meta-atoms with a single morphology. In this paper, we put forward the conjecture that there is a certain internal relationship between different morphologies of meta-atoms of meta-surfaces. The property similarities of different-shape meta-atom are revealed through simulations. The geometric relationship between different morphologies was found by statistical method. Finally, By comparing the performance of the two meta-lenses composed of different-shape meta-atoms, it is proved that there is a perfect substitution relationship between the different morphologies of the meta-atoms. This discovery provides a very good new idea for designing meta-surfaces in the future.

A new method that combines scanning ion beam etching (IBE) and dynamic chemical etching (DCE) is proposed to tracelessly remove the subsurface damage (SSD) layer of fused silica optics to improve their laser-induced damage resistant performance. Several characterization techniques are employed to investigate the influence of the etching depth of each individual step on the optical properties of the treated sample surfaces, which helps to provide a guide for its implementation in practice as well as improve our understanding on the mechanism of the proposed combined method. The results indicate that traceless removing of SSD layer is accomplished with a shallow 0.3 mu m-IBE treatment. Nevertheless, secondary defects such as metal contaminations are introduced at the same time, which induces optical absorption even higher than that of the conventionally polished sample. These secondary defects can be effectively removed with a 3 mu m-DCE treatment, achieving high-quality surface with laser-induced damage threshold much higher than that of the 10 mu m-DCE etched sample and surface roughness as low as that of the virgin sample. The combined treatment of scanning IBE and DCE shows an excellent performance in improving the damage resistance of fused silica optics without deteriorating their surface quality.

The optical performance of fused silica optics used in high-power lasers is known to depend not only on their surface damage resistance, but also on their surface quality. Previous studies have shown that good fused silica damage performance and surface quality can be achieved by the use of reactive ion etching (RIE), followed by HF-based wet shallow etching (3 μm). In this study, two kinds of HF-based etchants (aqueous HF and HF/NH4F solutions) were employed to investigate the effect of HF-based etching on the optical performance of reactive-ion-etched fused silica surfaces at various HF-based shallow etching depths. The results showed that the addition of NH4F to HF solution makes it possible to produce a high-quality optical surface with a high laser-induced damage threshold, which is strongly associated with the surface roughness and fluorescence defect density. Additionally, changing the HF-based etching depth over the range from 1 μm to 3 μm can affect the surface damage resistance and absorption performance of RIE-treated fused silica. The light-scattering results indicate that the point defect density plays an important role in the determination of the HF-based etching depth. Understanding these trends can enable the advantages of the combined technique of RIE and HF-based etching during the fabrication of high-quality fused silica optics.

This paper proposes a novel model for an high-efficiency tunable broadband near-infrared absorber. The proposed absorber consists of an Al bottom mirror, SiO2-VO2 hybrid spacing layer, and certain MoS2 top nanostructures. Owing to the thermal tunability of the refractive index of VO2 materials, the near field coupling resonance in the multilayer metamaterials can be tuned by regulating the temperature, and henceforth, the efficiency of the absorber and the absorption band are also tunable. MoS2 has an excellent thermal-stability in the near-infrared range, which can nullify the influence of the temperature regulation of VO2. The results from our study demonstrated that the absorber achieved an average absorbance of 86.5% at 75 °C for a broadband range of 800–2350 nm. At 25 °C, the absorber attained an average absorbance of 96.6% for the wavelength range of 800–1160 nm, and a narrow-band absorption peak around 1489 nm. The absorber we have studied, which was based on tunable metasurfaces, displays tremendous potential for the applications such as camouflage coatings, solar energy, information sensing, and atmospheric environment monitoring.

Optical meta-surface element is a kind of two-dimensional ultra-thin device based on the regular arrangement of single-layer or multi-layer sub-wavelength nanostructure array. It can realize the sudden operation of optical amplitude, phase, polarization, the wavelength in a subwavelength scale. In this paper, we design a Huygens meta-surface based on low loss all-dielectric, which can approach the phase control of the outgoing beam after the parallel beam incident on the meta-surface. By the single-layer dielectric nanostructure array, so called Huygens surface, the abnormal transmission without reflection and low loss meta-atoms are realized. Five different beam deflectors were design by these meta-atoms. The different performance of five beam deflectors were discussed, and the effect of wavelength for different beam deflector was investigated next. The highest efficiency of beam deflector is around 85%. The largest deflection angle is 13.248˚ for one polymer grating. These silicon-based beam deflection meta-surfaces may be applied as blazed grating in the monochromator r, precision measurement, and laser shaping.

Randomly subwavelength structures (SWSs) were fabricated by reactive ion etching (RIE) process on the fused silica substrate, on the basis of an advanced metal nanodot induced one-step self-masking technology. Metal fluoride nanodots induce the deposition of fluorocarbon polymer stably. It acts as micromasks during the RIE process. With an increase in radio frequency (RF) power, the average sample height increases, the aspect ratio of the structure becomes greater and more uniform, and the average optical transmittance increases. Moreover, the maximum transmittance for single-sided SWSs can reach 95.5%. The theoretical simulation is in good agreement with the experiment results. The calculated results indicate that the profile of prepared structures may be close to a cylinder profile.

HF-based wet deep etching is an effective method for improving the laser damage resistance of fused silica optics. However, the fact that the etching process involves HF reaction makes the operation very unsafe. Potassium hydroxide (KOH) has recently shown great potential to outperform the more commonly used HF-acid as an etchant for the damage resistance enhancement of fused silica optical surface. In this paper, we present a detailed investigation into how the KOH-based shallow etching process affects the polished surface of fused silica. The results show that KOH-based etching does a good job at exposing the subsurface damage and increasing the laser damage threshold of fused silica while keeping the surface roughness nearly unchanged. Potential factors that limit the further increase in surface damage threshold of fused silica are also delved. The study offers an exciting option for fabricating high-quality fused silica optics with shallow wet etching under higher safety conditions that cannot be achieved with conventional HF-based wet etching approaches.

Laser-induced damage on fused silica surface is often ignited by absorbing impurities introduced by polishing processing. In order to analyze laser damage mechanism induced by Fe and Ce impurity on fused silica surface, this paper presents laser induced damage threshold of three types of fused silica surface dealed with traditional chemo-mechanical or magnetorheological finishing and carries out the surface impurity analysis, photo-thermal absorption analysis and gray haze damage mechanism analysis. The results show the significant different Ce and Fe impurities on the surface of the three kinds of samples. The two impurities both have a serious influence on laser-induced native damage. The analyses of photo-thermal absorption on the surface of optical element show that the haze damage pits morphology is related to the absorptivity of nanoparticles. The native surface damage threshold induced by Fe nanoparticle is lower than by Ce nanoparticle by analyzing atomic force microscopy images and scanning electron microscopy images. The conclusion is different from previous reports which believe Fe element shows a weak relation with laser-induced damage. This paper also analyzes the relationship between gray haze damage and native damage for the first time. The results are helpful to understanding laser induced damage of fused silica ignited by impurities.

Reactive ion etching (RIE) is crucial for fabricating high-quality fused silica optics since this technique can be used as a first step before dynamic chemical etching (DCE) for tracelessly removing the fractured defects in subsurface layer. The final quality of the optics is dramatically influenced by the plasma etching condition but still lacks sufficient information for practical application. In this work, combination of RIE and DCE was investigated deeply on polished fused silica surface by changing the gas type and flow rate. We show that the proper choice of fluorine-containing plasma condition during the RIE process allows the simultaneous occurrence of high surface quality and a low concentration of etching-introduced defects on fused silica. This leads to an ultrahigh laser-induced damage threshold at 355 nm while substantially keeping the surface roughness unchanged. This study paves the way for designing and developing a next-generation surface modification ability of high-quality fused silica with the great potential for high-power laser application.

The reactive ion etching (RIE) process of fused silica is often accompanied by surface contamination, which seriously degrades the ultraviolet laser damage performance of the optics. In this study, we find that the contamination behavior on the fused silica surface is very sensitive to the RIE process which can be significantly optimized by changing the plasma generating conditions such as discharge mode, etchant gas and electrode material. Additionally, an optimized RIE process is proposed to thoroughly remove polishing-introduced contamination and efficiently prevent the introduction of other contamination during the etching process. The research demonstrates the feasibility of improving the damage performance of fused silica optics by using the RIE technique.