Laser-assisted 6H-SiC surface activation and electroless nickel-phosphorus plating for high-performance metallic mirror fabrication

Silicon carbide (SiC) has attracted growing attention in various high-tech industries such as advanced mirror systems, precision glass molding, and electronic devices, owing to its outstanding mechanical strength, thermal stability, and chemical resistance. However, achieving high-quality surface finishing on 6H-SiC substrates remains a significant challenge, limiting its broader application in ultra-precision optics. To address this issue, this study presents an innovative methodology for fabricating high-performance metallic mirror on 6H-SiC substrates by integrating laser-assisted surface activation, electroless Nickel-Phosphorus (Ni-P) plating, and precision machining. Laser activation, conducted at power levels of 8 W and 15 W with path distances of 1 μm and 0.1 μm, effectively modified the substrate surface by introducing High-Spatial-Frequency Laser (HSFL) induced periodic surface structures. These features enhanced surface wettability, reducing the Water Contact Angle (WCA) to as low as 22.1°, and promoted uniform electroless Ni-P deposition. The resulting plating exhibited a thickness range of 41.16±1.3 μm to 94.78±3.9 μm and hardness values between 506.9 ± 45.2 HV and 523.1 ± 39.2 HV, demonstrating superior adhesion, mechanical interlocking, and surface uniformity. The surface of the optimal workpiece was refined further through Single-Point Diamond Turning (SPDT), achieving a mirror-like finish with the surface roughness of Ra ∼2.41 nm. Reflectivity tests revealed excellent optical performance, with reflectance values ranging from 40% at 8 nm to 70% at 800 nm, significantly surpassing benchmarks from previous studies. This study provides a scalable and effective approach for developing durable and optically precise metallic mirrors, with potential applications in advanced optical systems.