## 1 Introduction  
As a typical ultra-hard material (Vickers hardness \(\sim\)100 GPa), diamond is an ideal candidate for ultra-hard tool fabrication for its outstanding properties such as super high hardness, extreme low expansion coefficient, and so on. In addition to being directly used as blank materials for micro tool fabrication, another widespread application of diamond is to deposit it on various tool surfaces to improve their working performance. Especially with the development of chemical vapor deposition (CVD) technology, that technology has become the preferred method to prepare high-quality diamond film with high efficiency and low cost. The usage of CVD diamond films as performance-enhancing coatings has already been extensively adopted in various complex shape tools [1], wire drawing dies [2; 3], and other important components, and it exhibits outstanding performance and promising prospects for future development. However, the limitations of its traditional machining in efficiency, accuracy, and flexibility may pose an obstacle to the further application of diamond tools. The mentioned problems can be effectively solved by adopting femtosecond (fs) laser processing technology in the machining of diamond tools. At present, fs laser processing technology has been successfully applied across various industries for its material versatility [4; 5; 6; 7; 8] and found its place in ultra-precision machining owing to its ultra-short pulse width and high spatial resolution. In addition, the excellent geometric flexibility of laser machining makes it possible to fabricate complex micro or nano three-dimensional structures by fs laser processing. The past decade has seen a wide application of fs laser processing technology on the fabrication of various micro ultra-hard tools, such as the binder-less polycrystalline diamond micro-milling tool [1], the nano-twinned cubic boron nitride micro cutting tool [9], the positive rake angled single-crystal diamond (SCD) grinding tool [10], and so on. Besides bulk processing, surface modification of diamond is another hot research spot. A large number of researchers have studied the influence of fs laser parameters [11; 12; 13] and the pattern of surface textures [14; 15; 16; 17; 18; 19] on tool processing performance. It has been proved that the fabrication of surface micro-textures is favorable to the tribological properties and lubrication behaviors of tools [20; 21]. Since fs laser processing technology has great advantages in diamond-made tool bulk processing and surface modification, it is necessary to understand the mechanism and pattern of fs laser-diamond interaction, thus further expanding the application field of fs laser processing technology. Recently, there have been many reports on the exploration of fs laser-diamond interaction mechanisms. [PERSON] et al. [22] have proposed a numerical model to predict the width of the ablated channel and calculate the fs laser ablation threshold of materials. The predicted results are close to the experimental results with a negligible error. [PERSON] et al. [11] obtained the single femtosecond pulse ablation threshold of diamond-like carbon (about 0.35 J/cm\({}^{2}\)) by observing the radius variation of irradiated spots. [PERSON] et al. [12] calculated the single femtosecond pulse ablation threshold of the SCD to be 8.80 J/cm\({}^{2}\) by the ln\(\varphi\)-\(D^{2}\) fitting method, and they also figured out the optimum fs laser processing parameters according to the experimental results. With respect to the polycrystalline diamond(PCD) material, many researchers have investigated the influence of ultrashort laser-induced ablation on its surface roughness [23; 24] and dimension(depth and width) [24; 25] in the nanosecond, picosecond, and femtosecond regimes. It can be concluded from those works that a shorter pulse duration, lower laser power (or single pulse energy), higher scanning speed and pitch can achieve a higher surface quality.