By: Dr Jack Gabzdyl

The new generation of ns fiber lasers offer a range of highly flexible compact beam sources with tailored beam quality options to give a further dimension for process enhancement. Combined with increases in peak powers and pulse energies new applications beyond the standard marking and micro-machining have opened. MOPA designs with directly modulated seeds also allow control of the pulse shape and duration using a range of preset pulse waveforms adding further flexibility.

The fundamental beam quality has a significant effect on many applications and beam quality should be taken in the context of fitness for purpose.

A comparative study clearly shows the impact of the spot size on marking and drilling applications. Marks made by single pulses on anodised aluminium and drilled holes in ceramic show strong correlation between spot size and focused spot diameters. Changing the M2 from 1.2 to 3.2 more than doubles the effective spot size and hence mark feature.

Additionally the beam quality can impact the depth and hole profile that is achieved. The single moded pulsed laser generates a narrow and deep high aspect ratio hole while the higher moded lasers generate progressively wider and shallower holes given the same number of laser pulses.

Other characteristics such as pulse energy and peak power are also prime requirements for applications such as deep engraving and processing reflective materials.

Deep metallic engraving has conventionally been an application dominated by the high pulse energy, low rep rate lamp pumped YAG laser. Fiber lasers lacked both the peak power and pulse energy required by this application, but with >20kW peak power and pulse energy >1.25mJ SPI’s 40W HM laser is well suited to this application. The higher mode does result in a larger spot size but can be mitigated by using higher beam expansion and this is more than compensated for by the additional pulse energy and peak power available. The requirements for deep engraved marks in the engineering industry are growing and typical examples are alphanumeric codes and 2D data matrices. Modest material removal rates of circa 3mm3/min are achievable.

The higher peak powers can also enable the processing of reflective metal such as copper and brass.

Nanosecond fiber lasers are maturing and elevating themselves from just simple marking lasers to far more capable micromachining tools.

The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here