Welcome back to the Thinklaser Lightblade blog, I apologise its been a few weeks since we last posted. Lets kick back off with a more detailed look into the science behind the beam by looking at Laser Beam Modes.

Before we crack on – this post is going to be a more detailed look at the beam, it’s an interesting subject to cover in more detail, we will revert to more tips and tricks for day to day production next week.

We have already covered in great detail the importance of beam alignment and optics cleanliness, if you need a refresher, please take a look at our earlier blogs. We have also taken a look at how the beam is created by excitation of the CO2 molecules in the laser gas mix.

Lets take a closer look at the laser beam mode – what that means in the real world.

Laser Beam Modes

The Lightblade is powered by a CO2 glass tube that produces a laser of beam wavelength 10,600nm producing a TEM00 or Gaussian beam mode.

This means that the beam “profile” if you were to look at it side on is like this:

Laser Beam Modes

This can be easily observed by firing the beam into a block of Acrylic as demonstrated by Russ in todays learning lab.

That’s wonderful I hear you say, but what use is that to me?

The beam mode defines the laser spot density or the energy density of the laser beam, the greater the energy density, the more effective the laser will be at punching through the material.

We discussed energy density a while back when we looked at focus, low energy density means you need a lot of force (energy) to penetrate the material – high energy density means you need less force (energy) to punch through the material.

When checking the laser tube – our engineers will often do a beam mode to check the health of the mode, ideally you want a nice peaky spike, not a dome.

I feel it might be worth peeking inside the can of worms here as beam mode and spot density are often referenced when comparing Fibre lasers and CO2 lasers.

The big difference between Fibre and CO2 is the way the laser is generated. A CO2 laser will excite a gas mix, whereas a Fibre laser will use a bank of LED diodes and then collimate (align all the light wavelengths in the same direction) the light and amplify it in a specially coated fibre optic cable.

Straight out of the can, both Fibre lasers and CO2 lasers both have a TEM00 beam mode, however the spot density of the Fibre is considerably higher – which is why on large scale industrial lasers they can cut thin material much faster with lower power.

Quite often you will hear suppliers of industrial CO2 laser systems discussing the donut beam – this is where manufacturers have developed clever optics to create a TEM01 beam mode:

Laser Beam Transverse Mode 1 E1700739764938

This is especially useful for cutting thicker materials, as often these systems will use an assist gas to help with the cutting. The donut beam looks like this from in line:

Laser Beam Transverse Mode E1700739749658

The wider beam profile can help to get assist gas to the cutting face on thicker materials – it’s not something you’ll need to worry about with the Lightblade, but hopefully it helps to debunk some of the laser jargon floating in the ether.

There are a number of other differences between the two sources we will delve into in a later post as its an interesting subject to explore and can help to narrow down your machines choice if you are looking to cut or engrave certain materials.

So back to today and the use of the beam mode – it’s a useful engineering tool as it can give a fairly clear indication as to the health of a laser source and ties in with ensuring that you get the most from your laser.

And with that – I hand you over to Russ to explain in more detail.

Next week – more tips and tricks to keep your machine running in tip top condition.

If you have any questions regarding the topics covered in these posts or questions regarding any other laser application, please request a call back or, talk to one of our laser marking specialists by going to our contact page – link below.

Contact Us for Laser Engraving, Marking & Cutting Advice (thinklaser.com)

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