Overview: Surface-enhanced Raman scattering (SERS) affords a rapid, highly sensitive, and nondestructive approach for label-free and fingerprint diagnosis of a wide range of chemicals. This technique has been applied in explosives detection, pre-cancer diagnosis, food safety, and forensic analysis, where a small number of hazardous substances can seriously affect health of human beings. Thus, it is of great significance to prepare high-performance SERS sensors. In general, the signal intensity of SERS is determined by the following three factors: 1) The enhancement effect of surface nanostructure on local electric fields; 2) The number of molecules to be detected in hot spots; 3) Performance of the Raman spectrometer. Therefore, in order to achieve high-performance SERS detection of trace molecules, current research focuses on how to increase the density of hot spots and the number of analyte molecules in the detection area. An ultrafast laser has an ultra-short pulse width and ultra-high peak power, so it can interact with the majority of materials with high processing accuracy and excellent controllability. Meanwhile, it can rapidly construct a variety of large-area micro/nano-structures on material surfaces based on facile digital programming strategies. In addition, combined with multi-beam parallel fast scanning technology, low-cost and high-efficiency machining can be realized without a special requirement for the machining environment. Based on the above advantages, the ultrafast laser has become one of the important means for the fabrication of micro/nano-structures. This is important for the commercial preparation of high-performance SERS sensors. In this paper, we focus on two aspects to introduce the ultrafast laser preparation of high-performance SERS sensors, including how to increase the density of hot spots and the number of analyte molecules in the detection region. Ultrafast lasers can prepare micro/nano-structures with local field enhancement effects by both "bottom-up" and "top-down" processing strategies. The first is based on the "bottom-up" principle, where the reduction, deposition or polymerization of atoms, molecules or other nanoparticles is controlled by ultrafast lasers to achieve additive manufacturing of micro/nano-structures. The other is based on the "top-down" principle, where materials are removed by the ultrafast laser ablation to rapidly achieve hierarchical micro/nanostructures. These structures provide abundant active hot spots for SERS detection. In particular, the superhydrophobic surfaces prepared by the ultrafast laser are one of the most effective methods to achieve the enrichment of analyte molecules. Raman scattering can be excited more effectively by enriched molecules, which is conducive to obtaining higher detection limits and realizing ultra-trace detection. Finally, a prospect for the development of laser-prepared SERS substrates is provided.

Overview: With the development of industry, laser fabrication has become one of the important technologies for welding, cutting, surface processing, and other advanced manufacturing areas. At the same time, the pursuit of structures miniaturization, devices integration, and high precision has put forward more stringent requirements for laser fabrication technologies. Due to the advantages of stable mechanical and chemical properties and unique photoelectric properties, hard and brittle materials have been widely used in aerospace, the photoelectric industry, et al. Laser fabrication is an ideal technology for hard and brittle materials processing due to its high precision, high energy, and non-contact properties. In order to achieve the removal of hard and brittle materials, high laser energy is usually required, resulting in low fabrication accuracy and poor surface quality. As an improved laser processing method, liquidassisted laser fabrication can effectively improve fabrication accuracy and surface quality. The processing characteristics and material removal principles of three different liquid-assisted laser processing technologies are summarized in this review. According to the different functions of the medium through which the laser penetrates and the kinds of liquid, liquid-assisted laser fabrication technology can be divided into Laser ablation in liquid (LAL), laser-induced backside wet etching (LIBWE), and etching-assisted laser modification (EALM). The auxiliary liquid of Laser ablation in liquid is mostly water, which mainly plays the role of cooling and removing debris. The auxiliary liquids used by laser-induced backside wet etching include organic solvents, acid-base solutions, inorganic salts, and other liquids, which play different roles according to different liquids. The etching-assisted laser modification mainly uses an acid or alkaline solution as an auxiliary liquid to remove laser-modified materials. Different methods and auxiliary liquids have different mechanisms in the methods. Therefore, almost any material can be processed by choosing suitable methods and auxiliary liquids, including photosensitive glass, silicon crystal, sapphire, and other transparent hard brittle materials. Here, we summarize the fabrication technologies and fabrication parameters for different materials. The development and applications of liquid-assisted laser fabrication technologies in the fields of micro-optical components, microfluidic devices, and drilling and cutting are introduced. Finally, the challenges of the technology are discussed.

通过光刻工艺和热熔法，制备了形貌均匀、尺寸可控的微透镜阵列，通过反应离子刻蚀技术制备用于改善光提取性能的纳米光栅结构，成功制备出高效光提取的微透镜/纳米光栅组合的微纳复合结构。研究了等离子体处理对纳米光栅形貌的影响规律、纳米光栅的形成机理以及微透镜/纳米光栅微纳复合结构光提取性能。实验结果表明，通过改变等离子体处理工艺条件，可实现纳米光栅周期与深度的调控，从而得到不同尺寸的微透镜/纳米光栅复合结构。当微透镜高度约为19.6 μm，纳米光栅尺寸约为周期600±50 nm、深度20±5 nm时，微透镜/纳米光栅微纳复合结构可以在不改变绿光有机电致发光二极管器件电学特性的前提下，有效提高有机电致发光二极管器件的外量子效率，比单纯的有机电致发光二极管器件提高33%。

三维微纳米台阶光学显微测量信息为多维形貌数据，其数据量庞大复杂、多维相关性低、表征难度大，且通常存在测量坏点影响关键尺寸表征精度。本文提出了一种三维微纳米台阶高精度光学显微测量量化表征方法。首先，针对三维微纳米台阶的结构特征选取测量系统并设计测量方法，获取其三维形貌点云数据信息；其次，建立三维形貌实测数据维度重构方法，将复杂的多维面形数据降维至有序二维空间；基于K-means聚类算法和数据映射，创建台阶高度参数量化表征模型，实现识别离群值的同时将二维数据点集中的质心距离映射为台阶高度值；最后，通过迭代收敛设计，进一步提高算法表征的准确度和鲁棒性。对两种微纳台阶标准物质进行实验，结果表明，在测量存在离群值等坏点情况下，本方法能够高精度表征出台阶高度参数，与校准值比对，误差小于1.5%。