The Optics Side of the CO2 vs Fiber Laser Discussion
The Optics Side of the CO2 vs Fiber Laser Discussion

There are a number of articles that you can find on the web that discuss the comparisons of the CO2 performance to the fiber laser. It has been covered by a number of well-respected industry magazines. There is no longer a discussion about if fiber will be able to compete with CO2. Some of the OEMs have already reached the tipping point and are selling more fiber lasers than CO2.

Putting the sales pitch aside that the fiber is more efficient in delivering light than a CO2 laser, let us break that down to optical components. The CO2 laser has a series of optics. Some in the resonator which creates the power and some in the beam delivery system which adjusts the phase of the beam before the beam hits the final optic, the laser cutting lens. Any of the optics can at one point or another require replacement or at least cleaning, some more often than others. One of the major reasons to keep the manufacturing area clean in a laser cutting environment is that dirt of any kind is the enemy of good optics maintenance and that is the measure of the laser’s performance. Dirty optics won’t work and a machine that is not running is not making you any money.

The fiber laser machine can be solid state with diodes or disk or using the newer style large mode area (LMA) or even continuous-wave single-transverse-mode powers. The fact is that all the optics are located in the cutting head only. No mirrors, output couplers or water cooled copper in these machines.

But and it is a big “but”…the little discussed issue is that if the CO2 laser must be in a clean environment to perform better, the fiber laser must be kept clean on a whole new level of spotlessness.

The CO2 lens will continue to work if it is a little dirty. A fiber lens will not. A particulate, which is smaller than a virus microbe, will end the life of the fiber lens. The reason is, is that you are using a different light wave length. CO2 is in the IR (infrared) range. Fiber is in the visible light range.

In order to assist in keeping the laser lens in the fiber machine clean, you must use a protective window. The best protective windows are made of fused silica and have an AR (anti-reflective) coating on them. This allows the beam to pass through from the lens to the part you are cutting, but it prevents debris or dirt particles from getting back on to the lens. It is not just important; it is an essential part of the cutting process with high powered fiber lasers. And make no mistake; the quality of your window will affect the quality of your cut.

As the OEMs of fiber lasers kept increasing power, another major difference became apparent. When you had a fiber laser at 1K or 1.5K, the end user could easily change a lens. However once you started upping the power, to 3K and 4K the wheels fell off the wagon so to speak. Suddenly the end users were going through large numbers of lenses. That is when the OEMs recognized the issue of that speck of dust or dirt that got on the lens in the lens changing process. Where the average end user could easily change the lens of his CO2 laser, now he needed to have a clean room to accomplish the same task with fiber. That is why there are so many sealed heads in the industry today, to protect the optics.

In order to make the kind of changes that you need to cut different types of material, the beam needed to be expanded. So collimating optics were added into the cutting head of the fiber laser. Again the issue only became exacerbated by this addition. More optics that need protection!

All of this boils down to two major factors, quality and cleanliness. There is no way to get the best performance from the Fiber laser without understanding that the only really sensitive parts are in the laser head. That is the one area that will shut you down so fast that you will not believe it. That means that you must get the best lens to perform the task and best protection to protect the lens.

There is no substitute for quality. Coating quality is as different as the companies that make them. Making a good coating is part science and part magical. It takes a lot of experience to get it right. Testing and continually improving the process has made Ophir a leader in the coating industry for optics in lasers and infrared optics for night vision and a million other optical projects worldwide. The laser lenses for the fiber machines is absolutely the best lens in the industry. The windows to protect the fiber lenses are equally as good. The only way we can prove it, is to have you try it. I don’t think you will be disappointed.