Is P-Polarization Essential for Effective Laser Cutting on Target Surfaces?

[Amany Gouda]

if I have laser beam irradiated normally on the target surface and in the same time time it is p- polarized. under these conditions, we will have the electric field which is completely parallel to the target surface and have a great effect on the target surface.
my questions is;
is this statement correct physically. if yes, which law or equation can confirm this statement

 

[mfb]

Is the electric field not parallel to the target surface for other polarizations?

How do you quantify "great effect"?

 

[Amany Gouda]

if you have laser beam with oblique incidence then you will not get electric field parallel to the surface especially in s- polarized beam.

 

[Domullus]

Please clarify what you have in mind "normally on the target" and "p-polarized".Polarization state is defined in reference to the laser incident plane, so if your beam falls perpendicularly to the target your polarization state is in degenerate state (p-and s- polarization are the same). Are you performing some ablation/laser cutting experiments?

 

[Amany Gouda]

Please clarify what you have in mind "normally on the target" and "p-polarized".Polarization state is defined in reference to the laser incident plane, so if your beam falls perpendicularly to the target your polarization state is in degenerate state (p-and s- polarization are the same). Are you performing some ablation/laser cutting experiments?

yes, you are true. this is related to ablation experiment. and the choice of the p-polarized is done by my boss and I am try to understand why that happen by adding some physical explanation.

 

[mfb]

if you have laser beam with oblique incidence then you will not get electric field parallel to the surface especially in s- polarized beam.

The first post was about a normal angle of incidence.

For other angles: yeah, I can imagine that the right polarization maximizes ablation.

 

[Amany Gouda]

The first post was about a normal angle of incidence.

For other angles: yeah, I can imagine that the right polarization maximizes ablation.

now I am try to find the required law to ensure the difference between p-polarization and s- polarization for my case

 

[Domullus]

I understand your problem. I guess you use polarization perpendicular to laser cutting direction. This is indeed p-polarized beam. Why? Imagine that you move laser beam and ablate a narrow channel. When you translate laser beam second time along this channel, you can distinguish separate polarizations, because your incidence angle is not perpendicular anymore (your reference plane is the walls of the channel). As channel is rather steep, you are close to Brewster angle at this stage, therefore with p-polarized beam you will get lower reflection from the walls. If you use s-polarized light (parallel to cutting direction), greater amount of light will be reflected from the walls. Usually with p-polarized beam you will get more regular cut, but with s- polarized - deeper cut.

 

[Amany Gouda]

I understand your problem. I guess you use polarization perpendicular to laser cutting direction. This is indeed p-polarized beam. Why? Imagine that you move laser beam and ablate a narrow channel. When you translate laser beam second time along this channel, you can distinguish separate polarizations, because your incidence angle is not perpendicular anymore (your reference plane is the walls of the channel). As channel is rather steep, you are close to Brewster angle at this stage, therefore with p-polarized beam you will get lower reflection from the walls. If you use s-polarized light (parallel to cutting direction), greater amount of light will be reflected from the walls. Usually with p-polarized beam you get more regular cut, but with s- polarized - deeper cut.

wonderful explanation, is there any official resource (books, articles,..etc) to explain this fact.

 

[Domullus]

I am not sure. It is rather basic effects and you can refer to any optics textbook (Fresnel equation, Brewster angle, polarization). There are myriads of papers on laser cutting experiments where you can read about polarization effects :)

 

[Amany Gouda]

I am not sure. It is rather basic effects and you can refer to any optics textbook (Fresnel equation, Brewster angle, polarization). There are myriads of papers on laser cutting experiments where you can read about polarization effects :)

thank you very much.