4H-SiC Metalens: Mitigating Thermal Drift Effect in High-Power Laser Irradiation.

Enhancing energy density and efficiency in laser processing hinges on precise beam focusing, yet this often causes severe heat absorption and focus shifts in optical lenses. Traditional cooling methods increase cost and complexity, severely limiting versatility. Here, monolithic silicon carbide (SiC) metalens is introduced, which shows unparalleled thermal stability, integrated with a high-power laser. This metalens achieves diffraction-limited focusing with a numerical aperture (NA) of 0.5 and a focal length of 1 cm. Under a 1030 nm pulsed laser at 15 W for 1 h, it shows a minimal temperature rise of 3.2 °C and a tiny focal shift of 14 µm (0.1% relative), only 6% of the shift in conventional lenses. When used to cut a 4H-SiC substrate with the same laser, the metalens exhibit only an 11.4% change in cutting depth after 1 h of operation, correlating with the focal shift results. The results unveil a groundbreaking class of compact SiC photonics devices nearly impervious to heat absorption, representing a monumental leap for high-power laser systems and opening new horizons for their applications and efficiency.