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Fused-silica-based microlens array (MLA) has excellent stability in the harsh environment. However, it is still a challenge to efficiently prepare superhydrophobic quasi-periodic MLA and keep the optical performance of the microlens. In this paper, we proposed spatial modulated picosecond laser parallel processing method to prepare a superhydrophobic quasi-periodic MLA on fused silica. By using a spatial light modulator, the picosecond laser was shaped to multi-focal spots and line-shape beam, respectively, which improved the fabrication efficiency. The line-shape beam was the key to induce micro-nanostructures on the smooth MLA and keep the optical performance of the microlens. The results showed that the surface roughness of the microlens region was less than 100 nm. Combing with shaping picosecond laser processing and chemical treatment, the superhydrophobic MLAs showed the excellent anti-fogging and self-cleaning properties. The average contact angle of the superhydrophobic MLAs was 162.3°. The superhydrophobic MLA showed low adhesion to water droplet (<10 μN) and low contact angle hysteresis (2.1° ± 0.7°). We believe shaping picosecond laser parallel processing method is a flexible and low-cost approach to prepare superhydrophobic micro-optical elements on fused silica. [ABSTRACT FROM AUTHOR]

• Aspherical concave microlens is prepared by shaping picosecond laser induced multi-step wet-etching. • The size, vertex curvature radius and cone coefficient of the microlens can be readily controlled. • The morphology of the concave microlens can be adjusted to sphere, ellipsoid, paraboloid and hyperboloid. • The ratio of maximum focal length and the minimum focal length is up to 9.53. Fused-silica-based microlens array (MLA) with different focal lengths is a significant optical element for multi-layer optical imaging. In this paper, we propose shaping picosecond laser-induced multi-step wet-etching to control the morphology of the MLA. A spatial light modulator (SLM) was employed to shape the Gaussian picosecond laser into multiple focal spots with different focal depths. The multiple focal spots induced the ablation regions with different depths inside the fused silica. As a result, the morphologies of the MLA could be controlled from the spherical surface to the aspheric surface. The diameter, sag height, vertex curvature radius, and cone coefficient of the aspheric surface could be readily controlled by the average pulse energy and the focal depths of each focal spot. The ratio between maximum vertex focal length and minimum vertex focal length could be adjusted between 1 and 9.52. Moreover, the patterned MLAs were used for multi-layer imaging and 3D code, which can be applied in optical storage or anti-fake. We believe that shaping picosecond laser induced multi-step wet-etching is a highly efficient and flexible approach to fabricate the micro-optical elements on fused silica. [ABSTRACT FROM AUTHOR]

The preparation of fused silica glass with microstructural patterns has attracted considerable interest, and the process chain of using nano-silica powders mixed with organic polymers to prepare composites for molding, degreasing, and sintering provides a good solution. However, the potential negative effects of organic residues cannot be avoided. In this study, a pattern stencil replication method with silica gel using high-purity quartz fibers as reinforcement is proposed for preparing micropatterned fused silica glass. The microscopic morphology and mechanical properties before and after silica gel drying and the optical properties of fused silica glass obtained by sintering were evaluated via transmission electron microscopy), three-point bending strength test, scanning electron microscopy, X-ray diffraction spectrum analysis, ultraviolet–visible and infrared measurements. The results showed that quartz fiber as a reinforcer could shorten the drying time of the gel and did not degrade the quality of the fused silica glass obtained by sintering. Laser confocal test results showed that microlens arrays were generated by template replication, demonstrating the feasibility of molding fused silica lens arrays with small feature sizes and providing new ideas for the preparation of bulk fused silica glass or micropatterned glass. [ABSTRACT FROM AUTHOR]

GNSS-related activities qualify as ʻspace activities', and it thus make international space law applicable. However, it is quite reticent to broadly interpret GNSS signals under the term ʻspace object', due to the lack of material and physical properties. The discussions on whether GNSS damage qualifies as indirect damage, and whether the Liability Convention cover that indirect damage, are irrelevant to the applicability of GNSS damage to the outer space treaties. GNSS damage may apply Article VII of the Outer Space Treaty and the Liability Convention as long as the causal link between the damage and GNSS satellites (not GNSS signals) is unbroken, logical, foreseeable and not too remote under the sense of general international law. [ABSTRACT FROM AUTHOR]

As the service provision to Asia-Pacific region and the construction of global constellation are being pushed forward step by step, the lack of soft power on the governance and management over BDS, including institutional, policy and legal arrangements, is clipping the wings of the deployment, development, exploration and application of BDS, and constraining its further popularization at both the domestic and global level. Therefore, it is necessary to propose a comprehensive legal framework for BDS to keep the sustainable development of BDS and to balance the interests of all stakeholders in the value chain of BDS. Bearing that in mind, this paper offers the whole thinking of shaping that legal framework based on the specific analysis on the legal regimes on the supervision mechanism, certification system, mandatory application, ownership, operation, cost of recovery, sovereign rights, liability regime, data and privacy protection as well as other legal issues in the context of BDS. [ABSTRACT FROM AUTHOR]