The main oscillator power amplifier, commonly referred to as MOPA, is one of the most recent innovations in fiber laser technology.
Its ability to color mark stainless steel materials and engrave on plastic without firing has attracted a great deal of attention.
With the advent of MOPA laser technology in engraving applications, it has become the second most commonly used pulsed fiber laser technology, the first being gain modulation.
This article details the MOPA fiber laser technology, including its operation, applications, advantages and disadvantages.
In the last sections, I have compared the MOPA fiber laser technology with the most commonly used goodness modulation fiber laser technology.
What is MOPA and how does it work?
MOPA is an abbreviation for Master Oscillator Power Amplifier.
The name refers to its two gas discharge chambers, the master oscillator and the op amp.
First, a laser beam is generated by the reference laser/generator. Then, the generated laser beam is amplified by the optical power amplifier.
The amplified laser signal is then directed to a galvo head (mirror galvanometer) in MOPA laser marking machines to manipulate the laser beam path for high-speed engraving.
With a galvo head, laser machines can engrave at very high speeds.
As a result, Galvo heads are commonly used in portable laser engravers.
In MOPA fiber lasers, the main laser source is a fiber laser, and optical amplification is accomplished using magnifying lenses.
These lenses can make the laser beam oscillate and amplify the laser power up to four times.
The MOPA fiber laser has a variable pulse duration, made possible by two gas discharge chambers.
It can be controlled to adjust the pulse width of the laser beam from 2 ns to 200 ns.
Application of MOPA laser technology
The main application of the MOPA laser is color engraving of metals, especially stainless steel, and black marking of anodized aluminum. On stainless steel, it can engrave 16 or more colors.
It engraves each color separately because the laser beam causes a chemical reaction on the stainless steel material, creating a surface permanent marking.
MOPA laser marking can be used on plastic material surfaces requiring limited melt burn. Engravings made on dark plastic with the MOPA laser are also clearly visible.
This can be an alternative to expensive UV lasers used for engraving plastic.
However, it cannot be considered a cheaper alternative, MOPA is more expensive than most other fiber laser engravers that can perform engraving operations on plastic.
You only need to purchase a MOPA laser engraver if your application requires color engraving of metals and black marking of anodized aluminum.
A standard fiber laser is more than sufficient for most other engraving applications.
Advantages and disadvantages of MOPA fiber laser technology
The main advantage of using a MOPA laser is its ability to mark colors by oxidizing the surface and its adjustable pulse duration.
Because the frequencies, pulse duration and energy of the MOPA laser are adjustable, you will have much more control over the engraving.
The short duration is especially useful when marking on plastic materials because it provides high contrast with low or no burn-through and low foaming.
The low heat generation of metal parts when engraving with MOPA lasers limits corrosion and ensures clear markings.
MOPA fiber laser technology also offers all the advantages of a standard fiber laser.
It features high accuracy, low power consumption, powerful beam, high marking speed, long life, air-cooled, high optical quality and maintenance-free.
The main disadvantage of MOPA fiber laser technology is its high price. They are more expensive than most other fiber laser engravers on the market.
MOPA also lags behind in terms of engraving speed. The color engraving process is slower than the average speed of conventional fiber laser engravers.
This will be a problem if you plan to process thousands of metal parts with color engraved logos in a single day.
Why is MOPA technology so expensive?
MOPA fiber laser technology is new to the market, and research is constantly being conducted to improve its efficiency and materials capabilities.
It requires many sensitive internal components (optical and electrical) to create a laser that can operate at low and high frequencies and has an adjustable pulse frequency mechanism.
All of this adds to the cost of developing MOPA technology. When the machine reaches the customer, additional fees such as taxes, shipping costs, customs clearance, maintenance fees, etc., further increase the price of the machine.
An ideal example of the combination of laser fiber marker and MOPA here
