The Master Oscillator Power Amplifier (MOPA) refers to a system that is made up of a 'master' laser and an optical amplifier to boost the output power. Alternatively, conventional fiber lasers are powered using Q-Switch technology, which creates laser beam pulses that last mere billionths of a second. Thus, because the energy from the laser is emitted in such a brief period of time, the energy is concentrated into very powerful pulses. A MOPA laser is able to generate a higher pulse repitition rate than their Q-Switch powered counterparts. Furthermore, the pulse frequency range of a MOPA laser is much larger than that of a Q-Switch laser.
When you engrave metals with a laser, sometimes these materials react with their environment and rust will form, which is caused by the degree of heat applied to the surface of the metal and subsequent burning/melting of the edge area. MOPA lasers produce less heat, reducing this damage to the metal and thus increasing the corrosion resistance of the final product.
Annealing is a process that does not remove material during processing. The creation of colours when laser marking stainless steel with the annealing method is caused by heat application. Whilst the possibility of creating colours with a laser machine has been around for a long time, the capability to accurately precisely mark colours and to reproduce them is a newer advantage provided by a MOPA laser source.
The top layer of anodised aluminium is usually removed by a laser to reveal a white mark. A mark of this kind is particularly visible and clear on coloured anodized surfaces, but on natural, silver anodised aluminium, a white mark is not as clear. With a MOPA laser source, you can set very short pulse durations and so the anodised layer is not removed, simply repainted. Whilst the process of black marking is completely different from the production of reproducing colours on stainless steel, a comparable result is created.
The flexibility of the pulse duration on a MOPA laser is also very useful for producing high contrast marks on plastic materials. Typically, marking plastic with a fiber laser produces foaming and melting which compromises the quality of the mark. With less heat being applied, less foaming and unintentional melting occurs and a more uniform mark is achieved.
A laser with a MOPA source also comes with the advantage of a long life span and low levels of maintenance that you get with a regular fiber laser. If you're looking to mark a range of different surfaces and apply coloured marks to metals, then laser engraving machine with a MOPA source is definitely worth considering.