Ultrafast laser welding of transparent materials has been widely used in sensors, microfluidics, optics, etc. However, the existing ultrafast laser welding depths are limited by the short laser Rayleigh length, which makes it difficult to realize the joining of transparent materials in the millimeter depth range and becomes a new challenge. Based on temporal shaping, we realized Burst mode ultrafast laser output with different sub-pulse numbers and explored the effect of different Burst modes on the welding performance using high-speed shadow in situ imaging. The experimental results show that the Burst mode femtosecond laser (twelve sub-pulses with a total energy of 28.9 μJ) of 238 fs, 1035 nm and 1000 kHz can form a molten structure with a maximum depth of 5 mm inside the quartz, and the welding strength can be higher than 18.18 MPa. In this context, we analyzed the transient process of forming teardrop molten structures inside transparent materials using high-speed shadow in situ imaging detection and systematically analyzed the fracture behavior of the samples. In addition, we further reveal the Burst femtosecond laser welding mechanism of transparent materials comprehensively by exploring the difference in welding performance under the effect of Burst modes with different sub-pulse numbers. This paper is the first to realize molten structures in the range of up to 5 mm, which is expected to provide a new welding method for curved surfaces and large-size transparent materials, helping to improve the packaging strength of photoelectric devices and the window strength of aerospace materials.

Around the world, a large number of stone artifacts have been exposed to air for long periods of time, showing multiple types of deterioration that have attracted widespread attention. Among them, there is an often overlooked deterioration of stone artifacts, i.e., black stains on the surface of the calcareous stone, which are tightly bonded to the substrate as a result of the long-term deposition of air pollution. However, due to the current lack of a clear understanding of the black stains, people often tend to use the wrong cleaning and conservation methods, which is not conducive to sustainable conservation. Therefore, there is an urgent need to comprehensively recognize the black stains in terms of material properties and environmental sustainability to guide scientific sustainable conservation methods. To this end, in this paper, we take the black stains observed on marble buildings in the Xianling Tomb, China, as an example, and for the first time, we aim to create a comprehensive understanding of black deposition from the aspects of material properties and environmental characteristics. Multi-analytical approaches, including polarized light microscopy, X-ray fluorescence (XRF), and scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), were employed to discern the differences between the substrate and black stains. The results revealed that the formation of black stains was attributed to prolonged exposure to various air pollutants (PM, SO₂, NO₂, CO, and O₃). Subsequently, observational data from 2015 to 2023 were utilized to investigate the temporal evolution of local air pollutants and their coupled resonances. Multi-scale variations (annual, seasonal, monthly, weekly, and daily) of pollutant concentration sequences were identified, which helps us to have a clearer perception and to proactively control air pollutants in the region from different cycles. In addition, wavelet coherence (WTC) demonstrated significant time-scale dependency in correlation with air pollutants, which provides effective data support for the coordinated control of air pollutants. This study reveals the mechanism of black stain deterioration on stone artifact surfaces, provides data support for the control and prediction of air pollutants oriented to the sustainable conservation of stone artifacts, and provides a novel and comprehensive approach to the scientific knowledge and sustainable conservation of stone artifacts.

The Mount Wudang architectural complex, recognized as a UNESCO World Cultural Heritage site, extensively utilizes green schist as the building material in its rock temple structures. Due to prolonged exposure to weathering and moisture, effective surface protection of these stones is crucial for their preservation. Inspired by the lotus leaf, femtosecond laser fabrication of bioinspired micro/nanostructures offers a promising approach for imparting hydrophobicity to stone surfaces. However, green schist is a typical heterogeneous material primarily composed of quartz, chlorite, and muscovite, and it contains metal elements, such as Fe and Ni. These pronounced compositional differences complicate laser–material interactions, posing considerable challenges to the formation of stable and uniform micro/nanostructures. To address this issue, we performed systematic femtosecond laser scanning experiments on green schist surfaces using a 100 kHz, 40 μJ laser with a 30 μm spot diameter, fabricating microgrooves under various process conditions. Surface morphology and EDS mapping analyses were conducted to elucidate the ablation responses of quartz, chlorite, and muscovite under different groove spacings (100 μm, 80 μm, 60 μm, and 40 μm) and scan repetitions (1, 2, 4, 6, 8, 10). The results revealed distinct differences in energy absorption, material ejection, and surface reorganization among these minerals, significantly influencing the formation mechanisms of laser-induced structures. Based on optimized parameters (60 μm spacing, 2–6 passes), robust and repeatable micro/nanostructures were successfully produced, yielding superhydrophobic performance with contact angles exceeding 155°. This work offers a novel strategy for interface control in heterogeneous natural stone materials and provides a theoretical and technical foundation for the protection and functional modification of green schist in heritage conservation.

The ancient building complex in Wudang Mountain, China, is known as the “Museum of Ancient Chinese Architectural Accomplishments”. However, the valuable stone components are preserved in open or semi-open environments and environmental factors such as rain seriously threaten its sustainable conservation. In this context, a femtosecond laser processing method has been demonstrated to be able to prepare hierarchical micro-nano structures on the stone surface to regulate its wettability, achieving the purpose of sustainable conservation. In this paper, the processing mechanism and performance of the femtosecond laser on green schist, a local stone material in the Wudang Mountain, are systematically investigated. It is found that green schist, as a typical non-homogeneous material, exhibits significant differences in its absorption of femtosecond laser with different compositions. Among them, quartz, chlorite, and muscovite are the three main compositions, and they are mainly characterized by cold ablation, thermal melting, and expansion under the irradiation of the femtosecond laser (238 fs, 100 kHz, 40 μJ, 33 μm, 500–40,000 pulses), respectively, and it is difficult to achieve a uniform and stable surface structure. Based on this, we prepared grooves with a spacing of 100–400 μm by scanning the femtosecond laser. Through the characterization of surface morphology, elemental composition, and three-dimensional structure, the processing mechanism of the hierarchical micro-nano structures of green schist under the irradiation of the femtosecond laser is comprehensively revealed. Finally, the wettability modulation result of water contact angle up to 147° is achieved by processing the grooves with an optimal spacing of 400 μm. The results of this research are of guiding significance for the sustainable conservation of ancient buildings and cultural relics.