"Gaussian"
As we all know, the energy distribution of the fiber laser excitation beam is close to the "Gaussian distribution", so it is also called "Gaussian".
Compare multiple pictures to help you understand "single-mode" and "multi-mode" fiber lasers in seconds (Figure 1)
Compare multiple pictures to help you understand "single-mode" and "multi-mode" fiber lasers in seconds (Figure 2)
Energy distribution of Gaussian beam
Theoretical explanation
Let’s take a brief look at the principle and structure of the fiber laser. It is composed of a pump source, a multimode coupler (beam combiner), a fiber grating, an active fiber, a beam calibration output module, and a passive fiber (energy output fiber). . When there is only one pump module inside the laser, it is called a single-mode laser, and multiple pump modules are combined together to allow multiple beams of pump light to enter the active fiber through a beam combiner, so that higher power can be obtained Beam, this multi-module combination laser is a multi-mode laser. Therefore, among the mainstream fiber laser products, most single-mode lasers are small and medium-power, while most high-power products are multi-mode lasers.
Compare multiple pictures to help you understand "single-mode" and "multi-mode" fiber lasers in seconds (Figure 3)
Fiber laser construction
The difference
Through the structure of fiber lasers, it is easier for us to understand the difference between multimode and single-mode: the single-mode fiber core is thinner and emits a typical Gaussian beam with very concentrated energy, similar to a steep mountain. The beam quality is also better than that of multi-mode fiber lasers. Mode; multi-mode is equivalent to a combination of multiple Gaussian beams, so the energy distribution is similar to an inverted cup, which is relatively average. Of course, the beam quality is worse than that of single-mode.
Compare multiple pictures to help you understand "single-mode" and "multi-mode" fiber lasers in seconds (Figure 4)
Comparison of 1500W single mode (top) and 1500 multimode (bottom)
Application
Based on these characteristics, the application directions of single-mode and multi-mode are also different. For example, in cutting stainless steel/carbon steel sheets of 1mm and below, the processing efficiency of single-mode is significantly better than that of multi-mode (single-mode is 15%~20% faster ), and the cutting quality is similar; in thick plate cutting of 2mm and above, high-power multi-mode lasers perform better in terms of quality and efficiency. Also in the field of welding, in thermal conduction welding, single-mode lasers can produce more uniform and smooth welds, so single-mode lasers are used for welding some thin materials, such as the overlapping welding of tabs when soft-pack power batteries are assembled; while in deep In fusion welding, multi-mode lasers can obtain welds with a better aspect ratio, such as the welding of square power battery pack Bus-Bar.
Single mode heat conduction welding
Multi-mode deep penetration welding
Summarize
The single-mode and multi-mode characteristics of lasers are an important basis for selecting fiber lasers. After understanding these differences of lasers, in future activities such as procurement, production and processing, and process testing, different core diameters can be reasonably selected based on these differences. /Multi-mode and power-sized fiber lasers.
