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

Hybrid laser processing of micro-lens arrays

Femtosecond lasers process glass with high precision, but throughput has long been the limiting factor for industrial use. Burst mode addresses that limit, and has opened applications single-pulse operation could not reach.

In burst mode, a single high-energy pulse is divided into multiple lower-energy pulses, which uses the available laser power more efficiently. This prevents excessive energy deposition, which would otherwise degrade processing quality. The high intra-burst repetition rate, from MHz to GHz, means every pulse contributes to material removal.

Illustration of burst mode operation.

Illustration of burst mode operation.

Bottom-up milling focuses the beam at the bottom of the sample, so ablation debris leaves through the backside and high aspect ratio geometries can be formed in glass.

A micro-lens array was fabricated with hybrid laser processing: burst mode combined with bottom-up milling. The device base was first cut from a thick fused-silica plate, the lens array was then ablated on its surface, and CO₂ laser polishing brought it to optical quality. The same three-step route applies to other custom micro-optical elements.

Illustration of TDM and BUM.

Illustration of TDM and BUM.

Micro-lens array fabricated with hybrid laser processing method using the FemtoLux 30.

Micro-lens array fabricated with hybrid laser processing method using the FemtoLux 30.

Courtesy of FTMC.

Publications

Hybrid Laser Processing of Micro-Lens Arrays Using the FemtoLux 30
D. Andriukaitis, https://ekspla.com/wp-content/uploads/Open-Publications/Hybrid-Laser-Processing_FX.pdf.

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.
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.
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