Divergence?

[steve001]

Are you telling me i do, from what i said in my last post! or asking me?

Yes, that was a question. I asked you if you did because you said this.

i guess some divergence is important for a good beam

All light diverges. It's inescapable.

Another point that needs clarity is this.

Also that i read here somewhere that with a 2.0 divergence, it means that at 10 meters, the dot would be 2.2cm!!

What that means is this. The beam once it passes the Rayleigh Range will diverge 2 millimeters per meter of travel. It does not necessarily mean it will be 2 cm @ 10 meters

 

[waterface]

Well i think i do in that its the amount the beam spreads outwards once it leaves the aperture i think! & if it didn't spread out, then we wouldn't see any beam beyond a certain distance!!
This is what makes me think we all need a little to see a good beam!!
Focusing, i think, minimalises divergence & intensifies or concentrates the beam so burning can take place & the more focused the beam is, the further away burning can take place, i.e, smaller concentrated beam & the less focused the beam is, the closer the 'match stick' for example must be to light!
Thats my take on it all!, just like binoculars! :thinking:

 

[ElektroFreak]

Well i think i do in that its the amount the beam spreads outwards once it leaves the aperture i think! & if it didn't spread out, then we wouldn't see any beam beyond a certain distance!!
This is what makes me think we all need a little to see a good beam!!
Focusing, i think, minimalises divergence & intensifies or concentrates the beam so burning can take place & the more focused the beam is, the further away burning can take place, i.e, smaller concentrated beam & the less focused the beam is, the closer the 'match stick' for example must be to light!
Thats my take on it all!, just like binoculars! :thinking:

Actually, focusing is simply narrowing and moving the beam waist. Adjusting the focus narrows the beam waist to a fine point near the aperture, and moves this point closer or farther away from the aperture. The beam waist is the point at which the beam's energy is concentrated into the smallest space allowed by the optical configuration. All laser beams have a waist, even beams that are collimated to the lowest possible divergence have a waist (although it isn't a fine point when the beam is collimated for low divergence, but rather the narrowest point of the beam), which is actually part of why there is always some divergence.

Here's some good info on this: Encyclopedia of Laser Physics and Technology - beam divergence

 

[waterface]

I was reading your post & thinking of waste not waist lol, as in waste light escaping the main beam & spreading outwards, hence divergence!! like when you shine a torch!!.. Imagining a 'V' shape & the aperture being the bottom of the 'V' & the light gradually spreading!
I'm hoping i wasn't way out!!
On the video, he makes the dot smaller that he points at the bed, which i thought was narrowing the beam & therefore decreasing the divergence!
I'm thinking you can alter, by focusing, the distance from the aperture that you can actually burn!, more intense, smaller dot +better burn at greater distance, or is it the other way round grr!!

 

[ElektroFreak]

I'm thinking you can alter, by focusing, the distance from the aperture that you can actually burn!, more intense, smaller dot +better burn at greater distance, or is it the other way round grr!!

That's exactly right to a point. Once you get a ways away from the aperture, the waist doesn't focus down to as small a point. The farther away you try to focus, the larger the smallest possible spot size becomes. The best burning ability is up close and out to a few feet.

 

[waterface]

Unless your Han Solo hehe! Yes i understand that & obviously the more power in a laser, the further away its easier to focus & burn things!!
I'm trying now to see where waist & divergence connect!

 

[BKarim]

if the dot is too large you can't see it.
it is better when dot is thin and concentrate more light in one point.
even if the dot were microscopic sized you could see it far away because of the concentrated energy