Glass processing

Glass is transparent and brittle: conventional and thermal methods chip it, crack it, and leave tapered walls. Femtosecond laser pulses deposit energy faster than heat can spread, so glass can be drilled into high-aspect-ratio vias, milled and cut with smooth walls, scribed kerf-free by Bessel beams, or modified for selective chemical etching.

Material processing
Material processing Glass Metal Polymer Other materials
Glass

Through-glass vias (TGVs) fabrication

Forming high-aspect-ratio holes in glass substrates is becoming more important, especially in the semiconductor field. Femtosecond lasers can form low-taper, high-aspect-ratio TGVs in glass at high quality, with low chipping, no cracking, and a smooth inner hole wall.

FemtoLux 30 operating in GHz burst mode produces high-aspect-ratio TGVs in glass substrates by percussion drilling. Splitting the single high-energy pulse into 50 pulses in a GHz burst achieves aspect ratios above 1:80 and controls the hole’s depth to a resolution of 0.1 µm by tuning the burst configuration. The technology was validated for AN100, BK7, BF33, D263, EXG, fused silica and soda-lime glass.

Combining a long GHz burst with beam shaping narrows the vias further: a single 180 µJ burst forms 1 µm diameter TGVs through 0.5 mm glass, an aspect ratio of 1:500, in one laser shot. Because each via needs only one burst, thousands can be formed per second.

TGVs can also be formed by combining MHz+GHz burst mode with bottom-up milling. Bottom-up milling gives zero-taper structures and the MHz+GHz burst raises throughput; together they produced a matrix of 200 µm diameter holes in BF33 and D263 glass.

GHz burst assisted percussion drilling of high aspect ratio holes in EXG glass.

GHz burst assisted percussion drilling of high aspect ratio holes in EXG glass.

Courtesy of Akoneer.

Manufacturing examples

GHz burst assisted percussion drilling of high aspect ratio holes in EXG glass.

GHz burst assisted percussion drilling of high aspect ratio holes in EXG glass.

Courtesy of Akoneer.

GHz burst assisted percussion drilling of high aspect ratio holes in EXG glass.

GHz burst assisted percussion drilling of high aspect ratio holes in EXG glass.

Courtesy of Akoneer.

Bottom-up milling of 200 µm holes in SCHOTT BF33/D263 glass.

Bottom-up milling of 200 µm holes in SCHOTT BF33/D263 glass.

Courtesy of FTMC.

Selective laser etching (SLE) of through-glass vias in glass.

Selective laser etching (SLE) of through-glass vias in glass.

Courtesy of WoP.

Selective laser etching (SLE) of through-glass vias in glass.

Selective laser etching (SLE) of through-glass vias in glass.

Courtesy of WoP.

Selective laser etching (SLE) of through-glass vias in glass.

Selective laser etching (SLE) of through-glass vias in glass.

Courtesy of WoP.

Publications

TGVs formation FemtoLux
Formation of through-glass vias (TGVs) in glass substrates using femtosecond laser operating in MHz/GHz burst mode
D. Andriukaitis, V. Stankevič, E. Kažukauskas, and P. Gečys, in Lasers in Manufacturing Conference 2025, (WLT, 2025).

Similar applications

UVFS milling.
Glass milling in GHz burst mode

Femtosecond milling of glass gives high quality but limited throughput. GHz burst mode on the industrial femtosecond laser FemtoLux splits one high-energy pulse into a train of sub-pulses, and 70 pulses at a 2 GHz intra-burst rate deliver sevenfold throughput over single-pulse mode.
Bottom-up milling of 200 µm holes in SCHOTT BF33/D263 glass.
Bottom-up milling of glass

Conventional laser milling struggles to achieve high aspect ratio geometries, because ablation debris accumulates in the ablation area and prevents further material removal. Bottom-up milling focuses the laser beam at the bottom of the sample, so all ablation products leave through the backside and deep, taper-free geometries can be formed in glass.
Micro-lens array fabricated with hybrid laser processing method using the FemtoLux 30
Hybrid laser processing of micro-lens arrays

A micro-lens array is fabricated with hybrid laser processing: burst mode combined with bottom-up milling. The device base is cut from a thick fused-silica plate, the lens array is ablated on its surface, and CO₂ laser polishing brings it to optical quality. The same route suits other custom micro-optical elements.
Laser-based Bessel beam scribing of 4.8 mm soda-lime glass.
Laser-based Bessel beam scribing

Conventional glass cutting removes material and leaves a kerf. Bessel beam scribing does not: a single femtosecond laser pass writes a line of voids inside the glass, and the part then separates mechanically or thermally. On 4.8 mm soda-lime glass, sidewall roughness stays below 0.5 µm at 80 mm/s.
300 µm hole drilling in thin borosilicate glass.
Thin glass cutting

Glass thinner than 0.5 mm cracks easily, and conventional cutting loads it thermally. Femtosecond pulses keep thermal accumulation low enough that thin substrates survive: borosilicate, fused silica and cover slips are cut, milled and drilled with minimal chipping and no cracking.
Femtosecond laser-induced selective etching of various-diameter holes in fused silica.
Femtosecond laser-induced selective etching

Femtosecond laser-induced selective etching is a two-step process: focused pulses modify the material structure, and a chemical etch then removes only the modified regions. It produces taper-free 3D features in transparent materials, with surface roughness in the hundreds of nanometers, and it works at wafer scale.
All applications