Frequently Asked Questions
As the light from a laser is monochromatic, different types of laser are required to produce light across the ultra-violet, visible and infra red parts of the spectrum. These different wavelengths interact in different ways with different materials, and, as a result, many different laser types are found in materials processing applications. Other important features which generally determine the choice of laser for a particular application include:
- output power or energy and whether this is delivered to the workpiece continuously or in a form of pulses specifically tailored to the job in hand, and
- how the laser beam is controlled to achieve the correct energy distribution on the workpiece so that the process requirements are satisfied.
The above parameters will determine if the laser can be used for pyrolytic processing, i.e. heating, melting and vaporisation, or photolytic processing, such as ablation and steriolithography.
When considering deep penetration welding and thick section cutting of metals, only carbon dioxide gas lasers (ouput wavelength 20.6µm) and solid state lasers (Nd:YAG laser at 1.06µm and Yb:fibre laser at 1.07µm) are suitable. The situation is very different, however, when the precision processing of (usually) thin materials is considered, and several different types of laser are used. The processing capabilities of these lasers are related closely to the characteristics of the laser output. Note that once the laser wavelength drops below the 0.9µm of the diode laser, all lower wavelength lasers (apart from argon-ion) only operate in a pulsed mode. In the pulsed regime the pulse width, the pulse energy (or peak pulse power), and the laser wavelength are all factors used to determine the applied power density, which can now be as high as 1015 W/cm2 using the 'femto second' (10-15 seconds) pulses from the titanium sapphire laser. The pulse repetition rate capability of the particular laser then adds to the process efficiency.
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Further information
What is a solid state laser?
What is an excimer laser?
What is a laser?
What is an argon-ion laser?
What is a fibre laser?
Nd:YAG laser welding.