How do Fiber Lasers work?

While many of our clients know that they have need of a laser, many don’t actually know how a fiber laser works! So whether you’re new to the industry, or you’re just looking to brush up on your knowledge and learn something new on how fiber lasers work, then this article is for you!

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What is a Fiber Laser?

A fiber laser is a laser where the active medium being used is an optical fiber that has been doped in rare elements; typically, erbium, ytterbium, neodymium, thulium, praseodymium, holmium or dysprosium. While you don’t need to worry too much about which rare-earth elements have been used, the main thing to note is that it is fiber that is being used at the centre of this laser machine.

This is different to the two other main types of laser, which are gas lasers (typically uses helium-neon or carbon dioxide) and crystal lasers (using Nd:YAG). Fiber lasers are the newest type of laser to hit the market, with many arguing that it is the more beneficial of the three types.

An example of a crystal laser

An example of a crystal laser

So how does a fiber laser work?

As mentioned earlier, the fiber used as the central medium for your laser will have been doped in rare-earth elements, and you will most often find that this is Erbium. The reason this is done is because the atom levels of these earth elements have extremely useful energy levels, which allows for a cheaper diode laser pump source to be used, but that will still provide a high output of energy.

For example, by doping fiber in Erbium, an energy level that can absorb photons with a wavelength of 980nm is decayed to a meta-stable equivalent of 1550nm. What this means is that you can use a laser pump source at 980nm, but still achieve a high quality, high energy and high power laser beam of 1550nm.

The Erbium atoms act as the laser medium in the doped fiber, and the photons that are emitted remain within the fiber core. To create the cavity in which the photons remain entrapped, something known as a Fiber Bragg Grating is added.

A Bragg Grating is simply a section of glass which has stripes in it – which is where the refractive index has been altered. Any time that light passes across a boundary between one refractive index and the next, a small bit of light is refracted back. Essentially, the Bragg Grating makes the fiber laser act like a mirror.

The internal Bragg Grating acts like a set of mirrors inside the core

The internal Bragg Grating acts like a set of mirrors inside the core

The pump laser is focused into cladding that sits around the fiber core, as the fiber core itself is too small to have a low-quality diode laser focused into it. By pumping the laser into the cladding around the core, the laser is bounced around inside, and every time that it passes the core, more and more of the pump light is absorbed by the core.

Why does all of this make a fiber laser so useful?

While the above may have been a bit science-heavy, we thought we’d share with you some of the benefits that come with the way that a fiber laser works. One of the biggest benefits that a fiber laser offers to its users is that it is extremely stable.

Other normal lasers are very sensitive to movement, and should they get knocked or banged, the whole laser alignment will be thrown off. If the optics themselves get misaligned, then it can require a specialist to get it working again. A fiber laser, on the other hand, generates its laser beam on the inside of the fiber, meaning that sensitive optics aren’t required to have it working properly.

Another huge benefit in the way that a fiber laser works is that the beam quality that is delivered is extremely high. Because the beam, as we’ve explained, remains contained within the core of the fiber, it keeps a straight beam that can be ultra-focused. The dot of the fiber laser beam can be made incredibly small, perfect for applications such as laser cutting.

While the quality remains high, so too does the level of power that the fiber laser beam delivers. The power of a fiber laser is constantly being improved and developed, and we now stock fiber lasers that have a power output over 6kW (#15). This is an incredibly high level of power output, especially when it is super focused, meaning it can easily cut through metals of all kinds of thicknesses.

Another useful aspect in the way in which fiber lasers work is that despite their high intensity and high power output, they are extremely easy to cool while remaining highly efficient at the same time.

Many other lasers will typically only convert a small amount of the power that it receives into a laser. A fiber laser, on the other hand, converts somewhere between 70%-80% of the power, which has two benefits.

The fiber laser will remain efficient by using near-to 100% the input that it receives, but it also means that less of this power is being converted into heat energy. Any heat energy that is present is evenly distributed along the length of the fiber, which is usually quite long. By having this even distribution, no part of the fiber gets too hot to the point where it causes damage or breaks.

Finally, you’ll also find that a fiber laser works with low amplitude noise, is also extremely resistant to heavy environments, and has low maintenance costs. Generally, an SPI fiber laser will require no servicing as they are built with our ‘fit and forget’ technology. However, for the rare occurrence maintenance should ever be required costs are typically around 50% less than other lasers.

Fiber lasers require very little maintenance

Fiber lasers require very little maintenance

Find out more about our fiber lasers

We hope that this brief article has given you some deeper insight into what a fiber laser is, how it works, and the benefits that this provides to anyone using it. If you want to discuss this further, please read our FAQs guide and get in contact with us here.

 

Image credit: Jason Miller, Len dela Cruz and Clker-Free-Vector-Images

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