Recently, a research team from Shanghai Institute of Optics and Fine Mechanics (SIOM) of the Chinese Academy of Sciences (CAS) found that femtosecond laser can selectively remove the irregularly distributed Si layer on the surface, effectively and quickly reduce the surface roughness, and obtain a high-quality surface, according to the difference between the ablation thresholds of silicon (Si) phase and silicon carbide (SiC) phase in Reaction-bonded silicon carbide (RB-SiC). The results were published in Optical Materials Express on March 16, 2022.

Compared with traditional diamond abrasive polishing, femtosecond laser can effectively improve the polishing efficiency. The research results expand the polishing method of RB-SiC and provide a novel idea for femtosecond laser processing of complex phase materials.

Based on different ablation thresholds of Si and SiC phases in RB-SiC, proposing a femtosecond laser selective polishing technique to selectively remove the raised Si burrs on the surface to reduce the roughness. The femtosecond laser multi-pulse ablation thresholds of SiC and Si were obtained through the dual-temperature model and experimental fitting calculations. After optimization of the femtosecond laser polishing process between the two-phase ablation thresholds, the surface topography and roughness at different scan time were analyzed. Through parameter optimization, the surface roughness can be quickly reduced from about 35nm to about 11nm, which greatly improves the polishing efficiency compared to traditional polishing methods.

This selective polishing technique can be employed to guide the femtosecond laser processing of other multiphase materials as well as stepped materials.

Fig.1 Experimental Results of Femtosecond Laser Selective Polishing. (Image by SIOM)