Figure 1

Optical and scanning electron microscopy of the QR codes in diamond (a–c) and sapphire (d–f). Yellow squares represent selected area for the SEM analysis shown in the subsequent figure to the right. (a) Optical image of the QR code written in diamond obtained with a 100x magnifying set of lenses in the reflection mode. Laser energy was 4 μJ (b) SEM image with a magnification of 800x and (c) SEM image with a magnification of 7000x. (d) Optical image of the QR code written in sapphire obtained in the reflection mode. Laser energy was 3 μJ. (e) SEM image with a magnification of 1500x and (f) SEM image with a magnification of 8000x.