For many marking enthusiasts, having the right laser marking machine can separate a successful and quality marking from an unsuccessful one. Additionally, understanding how a laser marking machine works and its operation can help select the right machine.
Laser marking is the commonest marking system due to its accuracy, precision, speed, and material compatibility. It comprises many types, each working according to a general laser mechanism, although there can be a few additions. This article will show you how laser marking machines works.
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.
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.
Common Laser Marking Machines and How they Work?
The above is a general way of how laser marking machines work. However, each machine has its peculiarities or additions. Some can be based on the introduction of other laser marking components. Here, we will discuss how fiber and CO2 laser works as they are the most common laser markers.
How Fiber Laser Marking Machines Work
· Step 1: Generation of Light by the Laser Pump
Fiber laser markers use laser diodes as the pump source, which converts electricity to photons of light which they pump into the fiber optic cable. The laser diode is made of two semiconductors, positively and negatively charged. For them to meet, the electron on the negatively charged diode must be released as a photon. As electric current flows through them, the quantity of photons increases.
· Step 2: Guiding the Light in the Fiber-Optic Cable
Light travels in all directions. Therefore, the fiber-optic cables have a fiber core and cladding to ensure the generated light does not. The light travels through the core made from silica glass, while the cladding ensures the light stays in the core and undergoes total internal reflection.
· Step 3. Light Amplification
Light enters the laser cavity, which contains the lasing medium (a doped fiber optic cable). Doping can be using rare earth elements such as Ytterbium. When the atoms that make up the cable interact with the laser diode light, they become excited and release photons or light.
The laser cavity is also the optical resonator. Here, light bounces through the fiber Bragg gratings similar to the reflective (high reflector) and partially reflective (output coupler) explained under the general mechanism of laser generation. As a result, this creates the LASER light
The laser light wavelength depends on the doping material. For example, Ytterbium-doped fiber lasers can generate a wavelength of 1064 nm. As a result, they are applicable in laser marking and cleaning machines.
· Step 4: Shaping and Release
The laser beam generated by fiber lasers is well collimated because of the fiber’s light-guiding properties. As a result, they might be unsuitable for some laser applications. To remove this limitation, the laser manufacturers introduce several components, such as the lenses, and beam expanders, to shape the beam before releasing it.
How CO2 Laser Marking Machines Work
· Step 1: Generation of Light by the Laser Pump
The lasing medium of the CO2 laser comprises carbon dioxide, nitrogen, hydrogen, and helium. Nitrogen is crucial here because it can hold its excitation long. While holding its excitation, the resulting vibration excites the CO2 molecules. The excited nitrogen atoms then produce light by coming in contact with cold helium atoms.
· Step 2: Light Amplification
Light enters the optical resonator and bounces according to the reflective (high reflector) and partially reflective (output coupler) like the above. As a result, this creates the LASER light, which is invisible and in the far infrared range of the light spectrum.
· Step 3: Shaping and Release
CO2 laser manufacturers introduce several components, such as the lenses, and beam expanders, to shape the beam before releasing it.
Pulsed Laser vs Continuous Lasers
Laser markers can be pulsed or continuous, each with unique features arising from the excitation of the lasing medium. Below is a simple comparison between both lasers.
Continuous lasers: They follow the normal population inversion protocol. As long as the pump source is working on exciting the lasing medium, the laser will be produced
Pulsed lasers: They use a Q-switch to stop the photons generated from the lasing medium from creating a chain reaction. As a result, they have two modes: lasing mode for uninhibited chain reactions and the pumping mode where the chain reaction is inhibited. Furthermore, the pumping mode makes it possible to excite the lasing medium completely. Consequently, pulsed lasers can have monstrous peak powers.
Get the Best Laser Marking Machine and Laser Accessories
Understanding how laser marking machines work can help with the selection process. Therefore, this article introduced how laser markers work. Are you looking for a laser marking machine or accessories? Then, kindly check our laser marking machines and accessories or get in contact with us.