Generation of the LASER
The most important part of how laser marking machines works is the generation of the LASER responsible for the marking process. The intricate details of laser generation depend on the type of machine you are talking about. Nevertheless, every machine follows a general template based on the laser generating tube.
In turn, the laser generating tube comprises three important components:
· Lasing Medium
The lasing medium can be solid (neodymium-doped yttrium aluminum garnet or YAG lasers), liquid (organic dyes), or gas (CO2 laser). Aside from that, they can be geometric shapes, the commonest being fiber laser marking machines. It determines the wave position and the type of excitation energy they get. Â
Note: Most laser markers’ names come from the lasing medium.
· Pump Source
The pump source introduces energy into the laser medium. Consequently, the atoms of the lasing medium become excited, emitting photons through spontaneous or stimulated emission. On the one hand, spontaneous emission is when an atom is excited, emits a photon, and returns to the ground state. On the other hand, stimulated emission is when the atom is excited, collides with a photon, returns to the ground state, and emits an identical photon.
The choice of pump source depends on the laser medium. For example, CO2 laser markers use electric excitation, while solid ones like YAG lasers use infrared. Furthermore, the pump source should be capable of exciting about half of the laser mediums (also known as population inversion). Increasing the number of excited atoms will increase the chance of photons colliding with them, creating the LASER (Light Amplification by Stimulated Emission of Radiation).
· Laser Medium
The resonator is made of reflective (high reflector) and partially reflective (output coupler) mirrors and functions by reflecting the produced light in the laser medium. This amplifies the produced light due to stimulated emission, superimposition, and constructive/destructive overlap of light.
In some lasers, it is possible to have more than two mirrors, with some sophisticated laser marking machines having four. The design and placement of the mirror determine the wavelength of the generated light.
The optical resonator can also contain other things, such as a modulator, q-switch, etc., each altering the properties of the generated laser beam.