Laser cutting speed

[jancleynen]

Hello everyone,

 

As an engineering student at the University of Leuven (Belgium), I was given a task to determine the effect of the polarization of laser beams on the maximum cutting speed that can be reached with these beams. I haven't found anything that could help me out on the net, and specialized libraries only had more common books about lasers. So I'd be glad if someone could give me a little information on this subject. I was thinking in the direction of energy contained in polarized electromagnetic waves, but I suppose that's not the only factor...

 

Thanks already,

Jan

[Klaynos]

two beams that are identical in every way other than their polarisation will have the same energy.

 

The two questions I'd ask are:

 

How does a laser cut things? Heating to the point of vaporisation, breaking of bonds or what?

 

How is this effected by polarisation, is one polarisation state better at being absorbed and therefore heating than another on the thing I'm trying to cut? This will be highly material dependent.

[jancleynen]

Yes, I see what you mean. So my point doesn't hold.

So I'll have to look up whether circular polarisation is better than linear and so forth for he different materials? Or would you think I can consider all metals as one family that has the same properties concerning this subject?

Well then I'll have to continue the search. Thanks!

[Klaynos]

You can probably consider similar materials the same, so metals with similar energy bands.

 

I have read some stuff about this, But I think that that was only materials in magnetic fields...

[swansont]

Light reflecting off of a surface is usually polarized, so one might expect that the orthogonal polarization is more likely to be absorbed and cut more efficiently.

 

From a conceptual point you might want to read up on Brewster's angle.

[jancleynen]

Oh well just one more question, is a beam off a laser always polarized?

[YT2095]

all the ones I`ve used have been yes.

although I had a small HeNe that seemed to be a little Less so.

[Klaynos]

Oh well just one more question, is a beam off a laser always polarized?

 

No, but some are.it also depends on how polarised you consider polarisation to be, as there's obviousely an error, for example the polarisers I use for my experiments cost £800 each for a useable area of about 1cm square. But they are amazingly good, as we are trying to measure differences in polarisation of milla degrees.

[swansont]

It depends on the type of laser, but in many one polarization will dominate and often internal components will be added to further suppress the other orientation (e.g. a Brewster plate). Some lasers are not considered as being polarized, but are not truly unpolarized, i.e. the polarization is not truly random, and any polarization present will fluctuate.

 

http://www.rp-photonics.com/polarization_of_laser_emission.html

[jancleynen]

Ok thank you all very much, I found a study from the University of Bern ("Laser microhole drilling using Q-switched radially and tangentially polarized beams") where they compare drilling speeds for radially and tangentially polarized beams. The conclusion:

-Tangential polarization exhibited a significantly higher

drilling speed compared to radial polarization.

-We assume that the observed higher drilling rates utilizing

tangential polarization are due to more energy being

deposited at the bottom of a microhole.

 

I wonder how I can generalise this to cutting (which is essentially a large collection of holes)?

 

They also state this:

Radial polarization might possibly enable more efficientlaser cutting (1,2)

 

With:

 

[1] V.G.Niziev, A.V.Nesterov, Influence of beam polarization on cutting efficiency, J. of Physics D (Appl.Phys.), Vol. 32, pp. 1455-1461,

1999

 

[2] T. Moser , H. Glur, V. Romano, F. Pigeon, O. Parriaux, M. A. Ahmed and T. Graf, Polarization-selective grating mirrors used in the

generation of radial polarization, Applied Physics B, Vol. 80, No. 6, pp. 707-713, 2005

 

So they're not yet sure of it?