Sun Laser

[kristopher]

One of the coolest things I saw Re:this topic was something like this :
http://wildwoodsurvival.com/survival/fire/ice/rb/rbfirefromice1.html

 

[Switch]

[quote author=randomlugia link=1225885183/0#5 date=1225933581]

What exactly is the wavelength of sunlight?

Ha!

All of them.



Sunlight is coherent compared to an incandescent light bulb.
It can be made into a reasonably "parallel" beam, just not effectively as a laser.
The rays aren't scattered as with any other light source, they at least travel uniformly in one general direction.

I really don't see a point in making it into a parallel beam though.
A fresnel lens works just fine as is. Adding optics and mirrors just adds on to the cost and reduces power. And that defeats the purpose of having easily attainable, low cost, large area fresnel lenses.
And is all the frustrating alignment worth the seared flesh and corneas?

If you want to do some "long distance" burning with the sun, get a large parabolic mirror with a long focal length.


The End.
[/quote]
Yea but the mirror would have a fixed focal point and can't be turned in any direction you want. :

And yes sunlight has a pretty small divergence because of the distance, but it's still not coherent.1m[sup]2[/sup] of sunlight on the ground doesn't come just from one tiny spot on the sun, it comes from the whole surface at the same time. You can get a pretty good idea of the divergence with a tiny circular mirror projecting a dot.You can even calculate it if you want. BUT, even if the sun rays are nice enough to make a beam, after the fresnel lens all of that is lost.

 

[RA_pierce]

I'm not saying the sun is as "good" as a laser... :

I'm saying that it's better than a light bulb (The two are not even close when it comes to the degree of coherence), and you basically just restated what I said.

Yea but the mirror would have a fixed focal point and can't be turned in any direction you want.

But can the lens thing be turned in any direction you want? No. It all depends on the position of the sun.
And lenses have fixed focal points too.

 

[randomlugia]

Sunlight is not coherent, but it is a combination of all wavelengths. So shouldn't we be able to extract one on the wavelengths? For example, we could have it go through a lot of red lenses, or use dichros for every color but red. Then we could focus it like a red laser, and have a red laser from the sun. All we have to do is make it coherent, right?

 

[RA_pierce]

Sunlight is not coherent, but it is a combination of all wavelengths. So shouldn't we be able to extract one on the wavelengths? For example, we could have it go through a lot of red lenses, or use dichros for every color but red. Then we could focus it like a red laser, and have a red laser from the sun. All we have to do is make it coherent, right?

Sunlight is basically coherent. Just not monochromatic.
Yes you can put the beam through a prism or other optics to filter out specific wavelengths, but the reason it cannot be used like a laser is because the sun is too large of a light source for a small beam.
Laser diodes have a very small emitting area so can be focused to a very tiny point.

Besides that, it's not practical.

 

[artix]

Have fun with those beamshots.

 

[kristopher]

I hear the beamshots in the dark are the best! ;D