Laser engraving is defined when material ablation (removal) occurs. In this case the laser engraving machine will vaporise some of the material to create some depth.

1. How Materials React to a Laser
There are generally three ways that a material can react to a
laser: Engrave, mark or cut.
Laser engraving is defined when material ablation (removal)
occurs. In this case the laser engraving machine will vaporise
some of the material to create some depth.
Some materials can only be laser engraved, such as wood for
example. In other words, the material cannot be exposed to the
laser without some ablation occurring, however, in this example
ablation is desirable because the perceived quality and value of
laser engraved wood is further enhanced when there is a
significant degree of ablation.
Some materials work well with minimal ablation but react
adversely when over-exposed to the laser. Cast acrylic is a good
example in this case where some ablation by a 10.6µm laser
creates a beautifully lustrous effect but when over-exposed the
engraving can become very powdery and tainted by an adverse
reaction to an excessive degree of thermal stress.
Laser marking constitutes the majority of laser applications and is
where the material reacts without ablation to show a contrast
between the area exposed to the laser and the area that has not
been exposed to the laser. Laser marking is usually some form of
colour change but can also include a reaction called ‘foaming’.
Foaming is a material specific phenomenon that occurs when the
laser marking machine heats the material to release gasses that
raise and then solidify above the surface of the material.
Polycarbonate is a good example of a plastic that if exposed to a
1µm laser will colour change and foam with a highly contrasting
and desirable effect.
Laser marking without ablation can provide for an incredibly
detailed result, at super-high speeds and with zero to minimal
adverse reactions from the base material.
Some materials can be laser marked or laser engraved according
to the system configuration used and the laser parameters set.
For example, a CO2 laser at the 10.6µm wavelength can only
mark the surface of anodised aluminium. Increasing the intensity
of the exposure can cause removal of the anodised surface but

2. this is not very noticeable. Using a solid state laser, like a fiber
laser at the 1µm wavelength, the same material can be surface
marked or ablated to a considerable depth.
Laser cutting occurs when the laser vaporises the entire thickness
of the material to create a void from upper to lower surface.
Solid, flat sheet materials are used for the vast majority of laser
cutting where highly accurate and detailed cuts can be made by
the laser that are impossible to produce by other forms of cutting
technology.
For example, laser cut acrylic provides for an instantly polished
edge and some textiles, such as silk for example, are heat-sealed
by laser cutter where they may otherwise fray.
For some applications a finely controlled cut takes place by the
laser. For example, ‘kiss-cutting’ of adhesive labels where the
adhesive surface is laser cut but the backing material is not and
also, the laser scoring of some materials to form a line that can
form a break point, for example for snapping-off labels out of a
sheet format.
At Lotus Laser Systems we manufacture a wide range laser
marking and engraving solutions ideally configured for laser
cutting, laser marking and laser engraving all types of materials.
Our experts would be happy to recommend which configuration
best suits your application.
Source: http://lotuslaser.blogspot.com/2016/04/how-materials-
react-to-laser.html