Working principle and construction of fiber laser

The most important element of this type of devices is active optical fiber doped with rare earth elements, inside of which the laser beam is created. It is a specific kind of fiber, which consist of three layers of materials, characterized by different refractive index:
the outer layer – it is a special cladding, characterized by the lowest refractive index. Its role is to reflect of its surface light, which is responsible for starting the machine’s work. At the same time

the cladding blocks the emission of radiation outside;

the middle layer – the outer layer of the core, which is created from a material characterized by higher refractive index in comparison to the outer cladding. Its goal is to initiate the work of the laser, as well as guarantee optimal transmission of the pumping energy;

the center: an active optical core – it is characterized by the highest refractive index of all of the layers.

Stage 1

Active fiber of the laser is finished with special diffraction gratings. One of them works as a mirror and provides complete refraction, while the other is an output mirror in an optical resonator. What is important, it is highly flexible, and at the same time it is characterized by very solid and compact construction, which allows to create thin and plastic laser rods of substantial length. On both sides of the fiber there are connectors, responsible for the transportation of the energy from pumping diodes to the external layer.

Stage 2

In the next step the beam, which is emitted by the core, is transferred to the collimator through the fiber. The beam itself is characterized by a very strong power and large divergence. It is transformed in the collimator into a beam with rays being transmitted in parallel to each other.


After the process is finished, the beam is transferred to the optical system, in which it is focused into a point of a required diameter. Naturally, its final size depends on the requirements of the user as well as technological conditions, necessary to precisely and effectively process the material.

A great advantage is the fact, that a thin construction of long beams makes its cooling process easier and more effective. At the same time the heating process, resulting from pumping the laser’s beam with energy, is minimal. These parameters influence the general efficiency of the devices, which in turn leads to achieving very high power conversion ratio (it is calculated by taking into account the ratio of the power of the beam, emitted by the active fiber, to the electrical power, which had to be used to generate the radiation).

How it works?

Technology based on such unique construction allowed to achieve 30% efficiency of the machines, which implement it. In comparison to traditional cutting and welding methods this result might not be the most impressive, but amongst laser technology solutions, this construction is second to none.