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

Bottom-up milling of glass

Conventional laser milling struggles to achieve high aspect ratio geometries: ablation debris accumulates within the ablation area, prevents further material removal and saturates the ablated depth. In bottom-up milling the laser beam is focused at the bottom of the sample instead, so all ablation products leave through the backside and high aspect ratio geometries can be formed in glass.

The FemtoLux GHz burst function combined with bottom-up milling raises process throughput. Precise, flexible control of the burst energy and the number of pulses in the burst sets the thermal stress generated in the glass substrate. With the right parameters the removal process switches to laser-induced fracture, and the glass leaves in particle form.

With 25 pulses in a GHz burst, the material removal rate reaches 600 mm³/min. Bottom-up milling is also taper-free, and forms holes and channels with depths of tens of millimeters.

Schematic of top-down milling (TDM) and bottom-up milling (BUM) techniques.

Schematic of top-down milling (TDM) and bottom-up milling (BUM) techniques.

Manufacturing examples

Glass nozzle fabrication by using multi-step bottom-up milling.

Glass nozzle fabrication by using multi-step bottom-up milling.

Courtesy of FTMC.

Bottom-up milling of 100 µm diameter taper-free channels in glass.

Bottom-up milling of 100 µm diameter taper-free channels in glass.

Courtesy of FTMC.

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.

Bottom-up milling of fused-silica glass.

Bottom-up milling of fused-silica glass.

Courtesy of FTMC.

Bottom-up milling of fused-silica glass.

Bottom-up milling of fused-silica glass.

Courtesy of FTMC.

Bottom-up milling of fused-silica glass.

Bottom-up milling of fused-silica glass.

Courtesy of FTMC.

Recommended products

FemtoLux
Industrial Femtosecond Lasers
  • 50 W / >300 µJ at 1030 nm
  • 20 W / >50 µJ at 515 nm
  • 10 W / >25 µJ at 343 nm
  • < 400 fs – 1 ps
  • Single shot to 4 MHz (AOM controlled)
  • MHz, GHz, MHz+GHz burst modes

Similar applications

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