What is the working principle of a fiber laser cutting machine?

A fiber laser is a solid-state laser that uses ytterbium-doped fiber as its laser medium. It emits laser light with a wavelength of 1.064 µm and transmits the beam directly to the cutting head via a sealed fiber optic cable—eliminating the need for exposed mirrors.

The laser medium itself is ytterbium-doped glass fiber. Ytterbium is a rare-earth element that emits laser light with a wavelength of 1064 nanometers when optically excited. This monolithically sealed beam transmission path is why fiber lasers require far less maintenance than CO2 lasers: no mirror cleaning, no bellows replacement, and no beam calibration are required.

The generation mechanism follows five steps:

Pump Diode Excitation—The pump laser diode emits light, which is captured by the reflective cladding fiber waveguide.

Cavity Entry and Dopant Excitation—Light enters the laser cavity, where ytterbium-doped ions are excited through cyclic electron excitation and relaxation.

Stimulated Emission—Stimulated ytterbium ions release photons through stimulated emission, amplifying the light within the fiber.

Fiber Bragg grating control—The fiber Bragg grating (an optical element used as an internal reflector and output gate within the fiber laser cavity) controls the resonance, defining the output wavelength at 1.064 µm.

Direct fiber transmission—The output beam is transmitted directly to the dicing head and workpiece via a sealed fiber optic cable, without an exposed mirror path.

Cut power ranges from 20 watts in low-power marking systems to 6000 watts in standard cutting platforms, while dedicated multi-kilowatt systems for research and heavy industrial applications can reach 1 megawatt. Some fiber laser architectures, such as TRUMPF's GT-Wave coupling scheme, connect the pump fiber and gain fiber for several meters, thus avoiding hot spots and producing a uniform gain distribution along the fiber length.

Fiber lasers have two core configurations, which affect beam quality and the ability to process thicker materials:

Single-mode fiber lasers use thin fiber cores to produce a near-Gaussian TEM00 (TEM00—the fundamental transverse mode, the purest beam shape achievable by a fiber laser) beam profile, providing the highest beam quality and precision—ideal for fine feature cutting and processing of fragile materials.

Multimode fiber lasers use thicker fiber cores to provide greater raw power, suitable for cutting thicker sheets, where beam power density is more important than spot precision when cutting sheets.

The term "laser"—Light Amplification by Stimulated Emission of Radiation—was first coined by Albert Einstein, and it applies equally to the working principles of fiber lasers and CO2 lasers. However, at the engineering level, the transmission architecture and laser medium completely separate these two technologies.