The difference between single mode and multi-mode in laser cleaning machine​

When choosing laser cleaning equipment, you always hear about single-mode and multi-mode. Most people don’t understand the difference between them. Today we will analyze it.

First, from the definition, single-mode and multi-mode laser refers to the mode type of laser. In a laser, the propagation mode of the laser beam can be a single mode or a mixture of multiple modes.
Lasers with a single propagation mode are called single-mode lasers, while lasers with multiple propagation modes are called multimode lasers.
In a single-mode laser, there is only one mode of beam propagation, so the diameter of the beam and the energy distribution of the beam are Gaussian. In contrast, multimode lasers support multiple propagation modes simultaneously, so the diameter and energy distribution of the beam appear as the superposition of multiple wave packets, and its beam is similar to flat-top light.

In the application of laser cleaning, the difference between Gaussian light and flat top light is very important, especially for precision workpieces. You must first understand the cleaning requirements before choosing which laser.
What is Gaussian light? Gaussian light is similar to normally distributed light. Simply put, the laser energy is strong in the middle, weak at the edges, and the spot distribution is uneven. The advantage of this kind of spot is that the energy is concentrated and can be transmitted farther. The disadvantage is that it can easily damage the base material.
Flat-top light is named relative to Gaussian light. Its spot distribution is more uniform. When facing precision instruments, it can perfectly remove contaminants without damaging the base material.

In current actual cleaning applications, fiber laser is the mainstream laser.
Fiber lasers are divided into pulsed fiber lasers and continuous fiber lasers. Generally speaking, lasers are used to remove rust. Continuous fiber lasers are used to remove rust. Pulse fiber lasers are used to remove paint, clean aluminum, and clean molds.
Specific practical applications of single-mode and multi-mode are explained below through specific applications of continuous and pulsed lasers.

The power of continuous lasers （CW） currently used for actual rust removal is 1500W, 2000W and 3000W.
All lasers at this power level are single-mode, such as Raycus lasers and Chuangxin lasers. Only lasers with a power of more than 20,000 watts are multi-mode. 20,000-watt lasers are very expensive and are not currently used in the cleaning field.
Therefore, there is no need to worry about single-mode or multi-mode laser rust removal machines in current practical applications, because the machines on the market are all single-mode.

Pulse fiber lasers are currently used for laser cleaning of molds, paint removal, and aluminum cleaning. Pulse fiber lasers with power higher than 200 watts are divided into single-mode and multi-mode. The difference between single-mode and multi-mode pulse fiber lasers is obvious.
Among laser machines with the same power, multi-mode is slightly more expensive, but its cleaning efficiency is lower. The advantage of multi-mode is that it can clean the substrate without damaging it.
When single-mode laser control is excellent, there will be several micron-level damage. If you can accept micron-level damage, try to choose single-mode laser for cleaning, which is cheap and efficient. If the base material requires a certain roughness, you must choose single mode.

To summarize, the main difference between single-mode and multi-mode is the light spot. Single-mode is generally Gaussian light, and multi-mode is generally flat-top light. Therefore, their usage scenarios are different. If you need to texture the substrate surface when cleaning pollutants, choose Gaussian light. If the laser is required to be completely non-damaging to the base metal, you must use flat-top light.