Beam Diameter ?'s

[jbrussell93]

I have a few specific questions about beam diameter pertaining to burning and brightness.

Burning:
I realize that a smaller beam diameter will burn better due to the more focused dot but how much of a difference will there be as far as burning power between a 1.5mm and 2mm beam for say... a 200mw laser.

Beam visibility:
I am also aware that a beam with a larger diameter has a better visibility but is there much of a difference between a 1.5mm and 2mm?

I guess the main question I'm asking is does a 0.5mm difference in beam diameter really make that much of a difference? Also, is burning or brightness more affected by beam diameter.

Thanks for all who reply

 

[MassLaserGuy]

Given that burning power roughly correlates with beam intensity, a laser with a 1.5mm beam will have approximately 78% greater intensity than a laser of the same power with a 2mm diameter beam. The intensity goes with the reciprocal of the square of the diameter. So, a 200 mw laser with a 1.5mm diameter will have the same burning ability as a 355 mw laser with a 2mm diameter. Size matters!

 

[Deleted member 10578]

I have a few specific questions about beam diameter pertaining to burning and brightness.

Burning:
I realize that a smaller beam diameter will burn better due to the more focused dot but how much of a difference will there be as far as burning power between a 1.5mm and 2mm beam for say... a 200mw laser.

Beam visibility:
I am also aware that a beam with a larger diameter has a better visibility but is there much of a difference between a 1.5mm and 2mm?

I guess the main question I'm asking is does a 0.5mm difference in beam diameter really make that much of a difference? Also, is burning or brightness more affected by beam diameter.

Thanks for all who reply

The burning power/ concentration of energy is determined by area and are = Pi X radius squared.
a 1.5mm diameter beam will have an area of 1.767 sq mm and a 2mm diameter beam will have an area of 3.1415 sq mm. That's a 77.8 percent increase in the area, so burning power would be ~ 77.8% less with the 2mm diameter than the 1.5mm diameter.

As for beam visibility vs. beam diameter, the beams visibility is determined mostly by how much particulate matter is in the air for beam to reflect off of. If the air is perfectly pure, no beam would be visible under any amount of power output. If the air is dirty then a very low power beam will be very visible.

If they were side by side under the same conditions with some particluate matter, the 2mm beam would be striking more particles to reflect off of, but it would be a weaker beam density, so I think it would be a wash.

 

[jbrussell93]

thank you both bootleg and MassLaserGuy!
Both of you were very helpful

 

[MassLaserGuy]

The burning power/ concentration of energy is determined by area and are = Pi X radius squared.
a 1.5mm diameter beam will have an area of 1.767 sq mm and a 2mm diameter beam will have an area of 3.1415 sq mm. That's a 77.8 percent increase in the area, so burning power would be ~ 77.8% less with the 2mm diameter than the 1.5mm diameter....

Actually, a 77,8% increase in area would be a 43.8% decrease in burning power. If area increases by 77.8%, then intensity goes down to 56.2% of the original. That is a 43.8% decrease in intensity, not a 77.8%.

Numbers are fun! Numbers are my life. In real life, I hold a PhD in engineering. :beer:

 

[Cyparagon]

There's also the factor of how much heat is dissipated through the material. You'll have a hell of a time burning anything with a pointer no matter how small the point gets.