The manufacturing and application challenges of wavelength band-selected CO₂ lasers

Five-layer film cutting using SR 25 AOM 9μm
Five-layer film cutting using SR 25 AOM 9μm

The need for wavelength selection

Both speed and heat affected zone (HAZ) can determine the choice of wavelength for certain materials that can only be machined using band selection optics. In thin films that are less than or equal to 100µm, speed can be greatly enhanced using the correct wavelength. In substrates that are greater than or equal to 250µm, HAZ is the determining factor in choosing to move from a 10.6µm operation.

Band selection method in 80-450W rated Luxinar CO2 lasers

Isotopic gas fill is used however there may be issues with this method, such as killing out neighbouring branches and the fact that availability and cost of isotopic gas is variable.

Band-selected cavity optics need robust coatings with a high flux density, proximity to RF discharge and the ability to suppress the neighbouring branch without reducing gain at the required wavelength. Niche coating designs can lead to lower yields and longer lead times.

Manufacturing challenges

Polarisation, absorption in air and loss are the main integration challenges for wavelength band-selected CO2 lasers in a manufacturing setting.

Standard 10.6µm dielectric mirrors can depolarise circular polarised light whereas isolation mirror solutions are lambda specific. At 9.3µm, especially at high powers, lens effects due to absorption distort the beam; these can be removed by nitrogen purging or by moving dry air. Loss per surface on standard 10.6µm AR or AR transmissive optics is approximately 3-5% at 9.3µm operation and can cause back reflections or heating of optic mounts. Loss on standard 10.6µm dielectric folding mirrors are not generally an issue.

Integration of wavelength band-selected CO2 lasers in a manufacturing setting
Integration of wavelength band-selected CO2 lasers in a manufacturing setting

Application challenges

Luxinar’s OEM series and SR series 9.3µm sealed CO2 lasers are both ideally suited to these applications. The SR and OEM series provide a higher quality cutting edge compared to standard pulsed CO2 lasers. For specific materials, the SR and OEM series give a faster cutting speed at 9.3µm when compared with standard 10.6µm lasers.

Paper cutting using OEM series 9.3μm CO2 laser

Summary

Luxinar offers 10.6, 10.25 and 9.3µm sealed CO2 laser sources that are 80 to 450W rated for use on materials that can only be machined using band selection optics. Manufacture and characterisation of these optics require collaboration and planning between Luxinar and the optics supplier.

The OEM and SR series from Luxinar provide a solution at 9.3µm however integration can be more involved than at the standard 10.6µm wavelength.

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