Micro-structured black titania surfaces
Researcher at the Institut für Nanophotonik Göttingen e.V. have developed a microstructuring process for commercially available titania-containing glasses by excimer laser irradiation. Irradiation of commercial TiO2-containing glasses in ambient air with an excimer laser (ArF laser with 193nm wavelength and 20ns pulse duration) is able to create microstructures and thus darken the surface. Surface studies showed that upon illumination, phase separation into a silicon and titanium rich phase occurs near the surface. The dark appearance is due to light scattering from the resulting microstructure and the partial reduction of the titanium oxide. The markings can be realized with high resolution and high contrast while using comparatively low laser intensity below the ablation threshold.
Challenge
Meanwhile, lasers are frequently used for processing glasses, for example, to make markings, change the wettability of materials, create self-cleaning surfaces or make optical adjustments such as anti-reflective coatings or waveguides. Specifically, laser-induced periodic surface structuring on glasses using femtosecond (fs) lasers is part of the state of the art in this context. To date only ordered mound-like structures of rutile crystalline phases could be generated on glasses using longer nanosecond (ns) laser pulses. However, this requires specially titanium oxide (TiO2)-coated surfaces. Additionally, for this processing an inert gas atmosphere and comparatively high laser intensity is necessary.
Our solution
The technology describes a marking technique of titanium oxide-containing glasses using excimer laser radiation (ArF laser with 193nm wavelength and 20ns pulse duration) in ambient air. Specifically, the irradiation of the glasses takes place in an optical setup that images a predetermined mask onto the surface of a sample. Laser pulses that are only nanoseconds long and have intensity or fluences below the material dependent ablation threshold are used to induce phase separation on the surface of the glass. The dark appearance is due to light scattering from the resulting microstructure and the partial reduction of the titanium oxide. In this way, microstructures can be created on the surface of the glass that contrast with the rest of the unirradiated material and are thus suitable for implementing a wide variety of markings.
(left) Scanning electron microscope image of a modified surface irradiated with an ArF excimer laser (1000 pulses at 250 mJ/cm²) on N-F2 glass, (right) Microscope images of a QR code made by laser modification of N-SF11 glass (laser parameters (193nm, 300 mJ/cm², 200 pulses/pixel): (top) direct view, (bottom) backside view through the glass (source: Institut für Nanophotonik Göttingen e.V.)
Advantages
- High contrast marking technique
- Compact and easy to build up setup
- No inert gas necessary
- Comparably low laser power necessary
Applications
- Marking or inscription of any type of glass or coating containing titanium oxide, e.g. lenses (glasses) or beverage glasses with the purpose of identification, product traceability and as a quality feature
- Markings serving as crosshairs or scales
- Decorative purposes
- Marking of self-cleaning building facades which use titanium oxide coatings on glass
- Disinfection of the glass surface via photocatalytic effect of structured titanium oxide coated glasses (decomposition of viruses and bacteria)
Development status
Proof of concept shown in the lab
Patent status
Institut für Nanophotonik Göttingen e.V.
E102022107151.0 (filed)
References
Contact
Dr. Markus Muchow
Patentmanager Physics, Technology and Software
E-Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Tel.: +49 551 30724 159
Reference: MM-2337-LLG
Tags: Laser physics and optics, Physics and Technology & Software
