In industrial production, cleaning is a crucial process. Traditional cleaning methods, such as mechanical and chemical cleaning, can meet production needs to some extent, but they often suffer from low flexibility and environmental pollution. With the advancement of technology, laser cleaning has emerged. Featuring high efficiency, eco-friendliness, and non-contact operation, it has gradually become a rising star in the cleaning field. Among them, single-mode and multi-mode fiber pulsed lasers are the two most commonly used types. So, what are the differences between them? What are their respective advantages and disadvantages? And in which application scenarios are they suitable? This article will provide the answers.

What are single-mode and multi-mode?

The mode of a laser generally refers to the energy distribution state in the plane perpendicular to the propagation direction, which can be single-mode or multi-mode. Single-mode means that the laser only generates one mode during operation. Its energy intensity decreases gradually from the center to the edge, and the distribution follows a Gaussian curve, with the beam called a fundamental Gaussian beam. A single-mode laser beam is characterized by high beam quality, small beam diameter, small divergence angle, and energy distribution close to an ideal Gaussian curve. In addition, single-mode lasers have excellent focusing properties, producing small focal spots and stable mode output, making them suitable for strong removal applications such as rust cleaning.

A multi-mode laser beam, on the other hand, is composed of a combination of multiple modes, resulting in a more uniform energy distribution. The more modes there are, the more uniform the distribution becomes. This type of beam is often referred to as a flat-top beam. Compared with single-mode, multi-mode lasers have lower beam quality and larger divergence angles, requiring larger aperture optical systems, and their focal spots are bigger. However, multi-mode lasers can more easily achieve high single-pulse energy, high peak power, and high average power outputs. With uniform energy distribution, they are advantageous for applications that demand high efficiency and minimal damage, such as mold cleaning.

Advantages and disadvantages of single-mode and multi-mode laser cleaning

Due to their good beam quality, small focal spots, and high energy density, single-mode lasers are suitable for removing strongly attached contaminants such as copper rust, as well as cleaning thin or precision parts that are sensitive to heat input. However, because the energy of single-mode lasers is too concentrated, they may cause some damage to the base material during cleaning.

For applications such as mold cleaning, where the substrate must not be damaged, multi-mode lasers are the only choice. Multi-mode beams have uniform energy distribution and high peak power. By ensuring the peak power density is higher than the removal threshold of the contaminants but lower than that of the substrate, multi-mode lasers can effectively remove contaminants without damaging the surface structure. In addition, their larger focal spots allow for higher cleaning efficiency in scenarios where both single-mode and multi-mode can achieve similar results. However, for strongly attached contaminants, multi-mode lasers may be less effective.

Application scenarios of single-mode and multi-mode lasers

Based on their respective advantages and disadvantages, single-mode and multi-mode cleaning lasers are used in different applications.

Single-mode main applications:

1. Metal rust removal: The high energy density of single-mode lasers makes them ideal for rust removal, efficiently removing corrosion from metal surfaces. The higher the power, the stronger and faster the removal.

2. Weld oxide cleaning: During welding, high temperatures can produce oxides and debris around the weld, affecting quality and appearance. A 200–500W single-mode laser can precisely remove oxides, ensuring weld quality and appearance.

3. Precision parts cleaning: A 100–200W single-mode laser with QCS output delivers strong cleaning power with low heat input, minimizing deformation and thermal effects on the parts.

Multi-mode main applications:

1. Mold cleaning: During use, molds accumulate residues such as plastic, metal scraps, and dust, which can affect product quality and cause defects. Regular cleaning prevents corrosion and wear, extending mold life. Since the properties of mold substrates and contaminants differ significantly, flat-top beams can remove contaminants effectively without damaging the mold. A 500–1000W square-spot multi-mode laser achieves efficient and damage-free mold cleaning.

2. Perovskite solar cell edge cleaning: This process involves removing film layers from the edges of thin-film solar cells to create an insulating area for subsequent encapsulation. A square-spot laser with uniform energy distribution and high peak power can remove the film layer in one pass, leaving the glass undamaged and ensuring high efficiency.

3. Laser texturing: By roughening the surface with a laser, the adhesion of the material can be significantly improved. Depending on the roughness requirements, we can provide multi-mode lasers with different single-pulse energies, such as 5mJ, 15mJ, and 50mJ, ensuring both efficiency and customized roughness.

When choosing between single-mode and multi-mode cleaning lasers, customers should consider their actual needs and application scenarios. For fine parts or strongly attached contaminants such as oxides and coatings, single-mode lasers with high beam quality and small spot sizes deliver more precise and powerful cleaning. For larger cleaning areas or cases where substrate damage must be avoided, such as mold, rust, oil stains, and thin coatings, multi-mode lasers with higher energy and flat-top beams ensure higher efficiency and non-destructive cleaning.