Femtosecond Laser Glass Processing: Holes, Channels and Microfeatures

Glass can be transparent to a laser wavelength and still be processed under the right focusing and pulse conditions. Femtosecond laser processing opens routes to small features in glass and other transparent materials, but the material grade and manufacturing route matter as much as the intended geometry.

Direct ablation and selective etching are different routes

Direct laser ablation removes material during laser exposure. Selective laser-induced etching uses laser exposure to modify selected regions, followed by a separate chemical etching step that removes the modified material preferentially. Fraunhofer ILT describes this two-stage route for glass and sapphire microstructures. Its suitability depends on the material, laser modification and etching conditions.

That distinction matters when requesting a quotation. An internal channel may require a different process chain from an open surface groove. Ask which operations are included: laser exposure, etching, cleaning and inspection. A laser source alone does not constitute a complete selective-etching production line.

Identify the exact transparent material

“Glass” is not a complete material specification. Give the manufacturer's grade, thickness, coatings and surface finish. Distinguish fused silica from crystalline quartz; include crystal orientation where relevant. If the part is strengthened or contains residual stress, state this in the enquiry. Send samples from the actual intended material rather than a convenient substitute.

Specify quality beyond the visible opening

• Holes: entrance and exit diameters, taper, position and allowable edge chipping.
• Channels: cross-section, length, access openings, cleaning requirements and whether the channel must be enclosed.
• Optical surfaces: regions that must remain untouched and the inspection needed to detect damage.
• Finished parts: any strength, leak-tightness or optical performance requirement that follows processing.

Plan a trial that answers a manufacturing question

Begin with a small feature set covering the most demanding geometry. Agree on how to inspect both surfaces and, where necessary, the interior. A microscope image can show edge appearance, but it cannot by itself establish mechanical strength or leak-tightness. Select tests that reflect the final use of the component.

Ask the trial to separate demonstrated results from proposed next steps. For production planning, include sample handling, alignment, any wet processing and inspection in the cycle-time estimate. Consider whether the feature can be reached for cleaning and whether residues would affect the application.

Is crack-free processing guaranteed?

No. Define an acceptable damage limit and an inspection method for the specific material and geometry. The aim of a feasibility trial is to establish a usable process window and identify remaining risks before committing to a production design.

Discuss your application with DIY-Optics

DIY-Optics GmbH develops the PulseBrick ultrashort pulse laser platform in Switzerland and provides optical and laser engineering. For a feasibility discussion, sample-processing enquiry or potential jobshop project, send us your material-processing requirements. We will confirm the available process route, scope and timing before a trial is agreed.

Preparing an enquiry? Use our laser processing trial checklist, or explore laser and optical engineering services.