In industrial production, cleaning is a crucial step. Traditional cleaning methods, such as mechanical cleaning and chemical cleaning, although can meet production needs to a certain extent, often have problems such as low flexibility and environmental pollution. With the advancement of technology, laser cleaning technology has emerged as a new favorite in the cleaning field due to its high efficiency, environmental friendliness, and non-contact characteristics. Among them, single-mode and multi-mode are the two most commonly used laser types in fiber pulse lasers. So, what are the differences between them? What are their respective advantages and disadvantages? What application scenarios are applicable? This article will reveal them one by one for you.
1. What are single-mode and multi-mode
The mode of laser usually refers to the energy distribution state of the laser in the plane perpendicular to the propagation direction, which can be divided into single-mode and multi-mode. Single mode refers to a laser that produces only one mode of laser output during operation. The energy intensity of a single-mode gradually decreases from the center to the outer edge, and the energy distribution forms a Gaussian curve. Its beam is called a fundamental mode Gaussian beam. The single-mode output laser beam has the characteristics of high beam quality, small beam diameter, small divergence angle, and energy distribution close to the ideal Gaussian curve. In addition, single-mode has good focusing characteristics, with a small focused spot and strong mode stability, making it suitable for cleaning scenarios that require strong removal, such as rust.
Schematic diagram of single-mode energy distribution
The output spot of a multi-mode laser is often composed of multiple modes, and the energy distribution inside the spot is relatively uniform. The more modes there are, the more uniform the energy distribution is. Its beam is also known as a flat top beam. Compared with single-mode lasers, multi-mode lasers have poorer beam quality, larger divergence angles, require optical systems with larger apertures for transmission, and have a larger focused spot than single-mode lasers. However, multi-mode is easier to achieve single pulse energy, high peak power, and high average power output, and the energy distribution is uniform, which is more advantageous for cleaning scenarios that require minimal damage and high efficiency, such as molds.
Schematic diagram of multi-mode energy distribution
2. What are the advantages and disadvantages of single-mode and multi-mode laser cleaning
Single mode lasers, due to their good beam quality, small focused spot, and high energy density, are suitable for removing strong adhesion pollutants such as rust, as well as for cleaning thin materials and precision parts that are sensitive to heat input. However, due to the excessive concentration of single-mode energy, it may cause certain damage to the substrate material during cleaning.
For scenarios such as molds that require no damage to the substrate after cleaning, a multi-mode laser must be selected. The multi-mode beam has uniform energy distribution and high peak power, which can control the peak power density to be higher than the damage threshold of pollutants and lower than the substrate. Therefore, it can effectively remove pollutants during cleaning without damaging the structure of the material surface. In addition, the focus spot of multi-mode is larger, and for scenarios where single-mode and multi-mode can achieve the same cleaning effect, the cleaning efficiency of multi-mode is usually higher. However, for strongly attached pollutants, multi-mode laser cleaning may not be effective.
3. Application scenarios of single-mode and multi-mode lasers
Based on the advantages and disadvantages of single-mode and multi-mode cleaning lasers, their applicable application scenarios are also different.
Single mode main application scenarios:
Metal rust removal: The high energy density of single-mode lasers makes them an ideal choice for metal rust removal, which can efficiently remove the rust layer on the metal surface. The higher the laser power, the stronger and more efficient the rust removal ability and efficiency. Guangzhi has launched a 1000W high-power single-mode pulse laser with QBH output that is easy to integrate and has the advantages of strong cleaning ability and high efficiency.
Weld oxide cleaning: During the welding process, due to the high processing temperature, oxides and material precipitates are easily formed in the weld and surrounding areas, affecting the welding quality and appearance. A 200-500W single-mode laser can be used to accurately remove oxides and ensure the appearance and quality after welding.
Precision component cleaning: With a light output of 100-200W single-mode laser and QCS output, it has strong cleaning ability, low thermal output, minimal material deformation and thermal impact after cleaning.
Multi mode main application scenarios:
Mold cleaning: During the use of molds, residues such as plastic, metal fragments, dust, etc. may accumulate, which can affect the surface quality of the product and cause product defects. Regular cleaning of molds can prevent corrosion and wear, thereby extending their service life. Due to the significant differences in the characteristics of mold substrates and pollutants, using a flat top beam can effectively remove pollutants without damaging the mold. Guangzhi has launched a 500-1000W square spot multimode laser, which has high cleaning efficiency for molds and no damage to the substrate.
Perovskite cell edge cleaning: refers to cleaning the film layer at the edge of thin film solar cells to create an insulating area that facilitates subsequent packaging work. Guangzhi has launched the YFPN-1000-GMC-H50-F laser, which has a square spot output, uniform energy distribution, high peak power, and can clean the film layer in one go. The glass is undamaged and the efficiency is high.
Laser roughening: Using laser to roughen the surface of materials can significantly improve the adhesion of the material surface. According to different requirements for roughening, Guangzhi can provide multi-mode lasers with different single pulse energies of 5mJ, 15mJ, and 50mJ, ensuring roughening efficiency while achieving different roughness requirements.
Source: GZTECH
