Mastering MOPA Fiber Lasers: A Quick 3-Minute Guide

What is MOPA Fiber Laser？

A MOPA (Master Oscillator Power-Amplifier) laser refers to a laser structure comprising a laser oscillator and an amplifier cascaded together. In the industrial realm, a MOPA laser specifically denotes a unique, more "intelligent" nanosecond pulsed fiber laser consisting of a semiconductor laser seed source driven by electric pulses and a fiber amplifier. Its "intelligence" primarily lies in the independently adjustable output pulse width (ranging from 2ns to 500ns) and a repetition frequency that can reach up to megahertz.

The MOPA fiber laser allows for independent adjustment of the output pulse width. The pulse width of a MOPA fiber laser is arbitrarily adjustable within a range of 2ns to 500ns. A narrower pulse width results in a smaller heat-affected zone, leading to higher processing precision. The MOPA laser can achieve high-frequency output up to MHz, implying higher processing efficiency. Even at high frequencies, MOPA can maintain high peak power characteristics.

 

Applications of MOPA fiber lasers

The parameters of MOPA fiber lasers have a wide adjustment range. Therefore, besides covering conventional nanosecond laser processing applications, they can also be utilized for unique precision processing applications due to their narrow pulse width, high frequency, and high peak power. For example:

• Surface removal application of alumina thin plates: As modern electronic products become thinner, many devices like mobile phones, tablets, and computers employ thin alumina as their outer casing material. When using a Q-switched laser to mark conductive paths on thin aluminum plates, there is a risk of material deformation and the formation of protrusions on the back surface, which directly affects aesthetics. However, employing parameters with smaller pulse widths using a MOPA laser can prevent material deformation, resulting in finer and brighter patterns. This is because the use of smaller pulse width parameters in MOPA lasers reduces the time the laser stays on the material while still providing sufficient energy to remove the anodized layer. Therefore, for surface removal of anodized layers on thin alumina plates, a MOPA laser is the preferred choice.

• Anodized alumina blackening application: Laser marking black logos, models, and text on anodized aluminum surfaces is increasingly common in electronic products' casings by manufacturers like Apple, Samsung, and LG. Currently, only MOPA lasers are capable of processing such applications. Due to their wide range of pulse width and frequency adjustments, MOPA lasers can achieve black marking effects on the surface. Different combinations of parameters can produce markings of various grayscale intensities.

• Color laser marking: Color laser marking is a novel laser marking technique. Currently, only MOPA lasers can produce colored patterns on metal materials such as stainless steel, chromium, and titanium. When marking colors on stainless steel, adjusting the laser beam can change the surface layer's color, resulting in different decorative effects. For the stainless steel products industry, adding colored markings enhances product aesthetics, provides versatility in designing various patterns, is environmentally friendly and pollution-free, increases marking speed, significantly enhances product added value, and strengthens product competitiveness.

• Precision processing applications in electronics, semiconductors, and ITO: Precise line applications are often required in electronics, semiconductors, and ITO precision processing. Q-switched lasers, due to their inherent architecture, cannot adjust pulse width parameters, resulting in less precise lines. In contrast, MOPA lasers, with their flexible pulse width and frequency parameter adjustments, can produce finer lines with smooth edges.

In summary, MOPA fiber lasers offer independently adjustable pulse widths and frequencies, as well as a wide range of adjustment parameters, resulting in fine processing with low thermal effects. They excel in applications such as marking alumina, blackening anodized alumina, and color marking stainless steel, offering effects that Q-switched fiber lasers cannot achieve. While Q-switched fiber lasers have advantages in strong marking intensity and deep engraving of metals, their marking effects tend to be rougher. In common marking applications, the main characteristics of MOPA and Q-switched fiber lasers are compared as shown in the table below. Users can choose the appropriate laser based on their actual needs for marking materials and effects.

Application	Q-switched Fiber Laser	MOPA Fiber Laser
Surface removal of alumina thin plates	Material prone to deformation, forming protrusions, rough patterns	Using small pulse width, low residual heat, no material deformation, fine and bright patterns
Blackening of anodized alumina	Limited quality blackening	Different shades of blackening and graying can be achieved through wide parameter settings
Metal deep engraving	Strong intensity, suitable for deep engraving, rough patterns	Weak engraving depth, but fine patterns, small taper, can be brightened
Color marking on stainless steel	Requires defocusing, difficult to control the effect	Various colors can be achieved by adjusting pulse width and frequency combinations
ABS plastic processing, etc.	Yellowing effect, heavy feel, fast speed	No yellowing, fine processing, smooth finish
Peeling paint off translucent plastic buttons	Difficult to clean thoroughly	Easy to clean, clear edge contours, better transparency, high efficiency
PCB board marking of barcodes, QR codes	High single pulse energy, but epoxy resin is sensitive to laser energy	Clearer barcodes, QR codes with small pulse width, moderate frequency, difficult to remove, easy to scan

 

Performance characteristics of MOPA laser marking machine

MOPA laser marking machine belongs to the category of laser marking machines. It adopts a fiber laser based on the direct electric modulation semiconductor laser (MOPA) scheme as the seed source. Compared with Q-switched fiber lasers, the pulse frequency and width of MOPA fiber lasers are independently controllable. Through the adjustment and coordination of these two laser parameters, constant high peak power output and applicability to a wider range of marking substrates can be achieved via a high-speed scanning mirror system. It features high-quality laser beams, low operating costs, maintenance-free for 100,000 hours, and is suitable for marking applications such as blackening of alumina, coloring of 304 stainless steel, stripping anodes, stripping coatings, semiconductor and electronic industries, plastics, and other sensitive materials marking, and PVC plastic pipe industry, marking patterns and fonts are environmentally friendly and comply with ROHS standards.

However, many customers expect MOPA laser marking machines to have the same processing speed as ordinary fiber laser marking machines, which is clearly not the case. These two technologies are different. When engraving color effects, the machine needs to mark at high frequencies with minimal shadow effects, resulting in high resolution but slower engraving speeds. Additionally, in deep metal engraving, MOPA laser marking machines may not have an advantage in terms of single pulse energy, but they excel in fine effects compared to regular laser marking machines. Therefore, customers need to understand the advantages and disadvantages of this type of laser marking machine before purchasing.

The MOPA laser marking machine is suitable for precision marking processes on both metal and non-metal materials. It can be used for a wide range of applications including laser engraving of digital product components, mobile phone back covers, iPads, blackening aluminum, marking phone buttons, transparent plastic buttons, electronic components, integrated circuits (ICs), electrical appliances, communication products, sanitary ware, tool accessories, knives, eyewear, watches, jewelry, automotive parts, luggage accessories, kitchenware, stainless steel products, and more.

Finally, the Monport laser marking machine product line offers a wide range of machines with power ranging from 20 to 100 watts. These machines come equipped with powerful features such as automatic focusing, MOPA color marking, and more. They offer great value for money, assured quality, and are backed by professional technical support with free after-sales assistance. For further details, please visit monportlaser.com.