Micro Markings inside Transparent Materials

Micro Structure in Sapphire - Logo structured inside sapphire, width approx. 1 mm and height 1 mm Copyright: Fraunhofer ILT Micro Structure in Sapphire - Logo structured inside sapphire, width approx. 1 mm and height 1 mm

Markings inside transparent materials are fabricated by micro structuring with femtosecond lasers. Three dimensional micro markings are possible in glasses, crystalls and polymers.

Micro Markings in the Volume
By focusing femtosecond laser radiation in the volume of transparent materials (sapphire, glass, polymers) local changes of the structure are induced. Thereby the refractive index of the material is locally changed. By focusing with objectives with large numerical aperture a high resolution (dot size ~ 1 m) is obtained. Furthermore, by using a large numerical aperture micro cracks in the material can be avoided. Therefore, the mechanical properties of the material remain unchanged.

Colored marking inside glass - Colorful in-volume marking in a microscope slide, dimension 9.6mm each Copyright: Fraunhofer ILT Colored marking inside glass - Colorful in-volume marking in a microscope slide, dimension 9.6mm each

Using a high speed scanning system and a laser with high repetition rate a large writing velocity (> 100 mm/s) and high precision (100-400 nm) are achieved. Potential applications include markings in the volume of parts for identification or adjustments as well as decoration.