First, place a piece of anodized aluminum on the working table to protect the table from the laser. Alternatively, you can also work with the honeycomb table. Then, set the mirror with the glass side facing up, mirror coating side down. You can engrave the mirror reflective side up through the glass with the fiber laser. Glass does not react with the fiber laser, and only the mirror layer is removed. The glass itself is not scratched because it reacts only to the wavelength of the CO₂ laser source.