## 1 Introduction  
Silicon carbide (SiC) is a strong, covalent bond compound with high strength, high wear resistance, an excellent low coefficient of thermal expansion and corrosion resistance, and is often used for high-precision structural components, such as bearings, rotors, space telescopes [1; 2; 3]. In addition, due to its large band gap width, strong radiation resistance, and high breakdown field strength, silicon carbide is also used in the production of optical and electronic devices [4; 5]. However, owing to its high hardness and brittleness, silicon carbide is a difficult material to machine into the desired structural components with high surface quality and dimensional accuracy by conventional processing method, especially for the processing of microstructures [6; 7; 8]. Laser processing is a non-traditional processing method that uses high energy lasers to melt or vaporize material to produce components. Compared with traditional processing, laser processing is very suitable for processing hard and brittle materials, and has the additional advantages of no tool wear, no cutting force and high processing efficiency. Microstructures, such as microholes and microgrooves, have been successfully processed on silicon carbide using laser processing [9; 10; 11]. In the laser processing of silicon carbide, the temperature of the workpiece surface rises rapidly after absorbing laser energy, and silicon carbide is melted and sublimated under high temperature [12; 13; 14]. The ablation mechanism of silicon carbide in laser processing has been studied by many scholars. [PERSON] et al. processed the 3C-SiC material using a femtosecond pulsed laser, and their results showed that the ablation mechanisms were correlated with pulse energy, higher pulse energy generated significant amounts of recast oxide layers and damaged fragments, and the leading material removal mechanismswere photomechanical fragmentation, ultrafast melting, and vaporization with appropriate energy density [15]. [PERSON] et al. investigated the femtosecond pulsed laser micro-processing of the 4H-SiC material, and they proposed several material removal mechanisms for 4H-SiC in femtosecond laser ablation, which included normal melting, thermal vaporization, phase explosion, and photomechanical fragmentation [16]. [PERSON] et al. studied the thermal ablation behavior of C/SiC material processed by a high repetition frequency femtosecond laser, and found that material oxidation was an obvious defect caused by the thermal effect of the laser that seriously affected the processing quality of microstructures [17]. [PERSON] et al. reported that melting, sublimation, and solidification was observed in the nanosecond laser processing of C/SiC material, and serious defects, such as recast oxidation, debris, and residuals, were formed at the edge of processing area, and the ablation surface quality could be improved by optimizing the parameters [18]. The above research shows that the generation of oxidation products in the laser processing of silicon carbide cannot be ignored, as it has a negative effect on the processing quality of microstructures on silicon carbide surfaces. Many methods have been trialed that could improve the feasibility of laser processing microstructures on silicon carbide. [PERSON] et al. processed silicon carbide material in water by laser processing, and they found that the oxide products were not formed, and that microstructures with good quality were processed by controlling the laser parameters and water flow velocity [19]. [PERSON] et al. drilled silicon carbide by laser in water, and found that the auxiliary of water could reduce defects on hole surfaces, such as debris, cracks, and heat affected zones, but the processing efficiency was reduced due to the laser energy loss in water [20]. [PERSON] et al. used a combination of laser and acid etching to machine through holes on silicon carbide material, and they found that the acid etching could effectively remove laser affected zones and improve the processing quality [21].