how to make a beam thinner?

[Dark_Horse]

You cannot have both low divergence and small beam diameter. You must sacrifice one for another, either low divergence with a fatter beam (At aperture), or higher divergence with a thinner beam (At aperture).

Yes,
This is true, but I would choose to say compromise rather than sacrafice. It depends on what your application/preferance is. I do not see many people modifying thier 532nm/green to have larger beams, even though they have much smaller beam with much more divergance than our DVD/Aixiz modules. I would not want any of my "greens" to have a fatter beam, but any thinner, and the beam would get to big at much distance, so a compromise is struck.
I like the Aixiz beam-profile for burning, but I want a "thinner" beam in my BR builds, this is very possible, I have just not found a 2-lense set-up as convienent as an aixiz. Perhaps I am the only one who would like more control over my beam profile, but "diameter versus divergance" is not an either-or senario, although it is often presented as thinning a beam any, will lead to horrible divergance. You will alway have some of each, just a matter of proportions for your application/preferance. I have seen laser advertised as having a 1mm beam with 1mr divergance, (helium neons), this is exceptional but not against physics.
Just my 2-cents,
Dark Horse

 

[likewhat]

Here is a graph that shows you divergence vs beam diameter over the range most people are interested in. Note that this is for purely gaussian beam and beam diameter refers to the minimum spot size, not necessarily the size the beam is when it comes out of the laser.

 

[pwnstar]

Thanks, thats good to have.

 

[GooeyGus]

[quote author=GooeyGus link=1206062220/0#13 date=1207726573]Heres a three element module from meredith. It might be worth looking into!

http://www.mi-lasers.com/cgi-bin/sh...hstart=0&template=Templates/SearchResult.html

Focus lenght: .315", 8.0mm.
Back Focal lenght: .059", 1.50mm.
Numerical aperture: .6
Beam diameter: .275", 7.0mm

Hmm. Has any one gotten that befor?
Beam diameter 7mm isnt that bad?[/quote]

7mm isn't great at all... Hmm... You would think with all those lenses in there, that they would be there specifically for making a tighter beam. Oh well... Its worth trying!

 

[steve001]

Here is a graph that shows you divergence vs beam diameter over the range most people are interested in. Note that this is for purely gaussian beam and beam diameter refers to the minimum spot size, not necessarily the size the beam is when it comes out of the laser.

What this graph shows is the beam divergence after it passes beyond the Rayleigh range

 

[likewhat]

What this graph shows is the beam divergence after it passes beyond the Rayleigh range


Yeah, by definition the beam divergence is the asymptotic behavior far from the waist.

 

[Dark_Horse]

Here is a another good guide for Gaussian beam properties:http://www.mellesgriot.com/products/optics/gb_1.htm
Dark Horse