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A few questions about beam expanders

gozert

gozert

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Could someone explain to me if it is possible to use a 1064/532nm coated beam expander for a 520nm laser? I've been thinking about building a 520nm with a beam expander on it, but I can only find very few expanders that have a wide range of wavelengths that are usable.

Also, what exactly is the difference between 2x and 10x expansion? Does 10x get you a better divergence, or is the difference too small to notice?
 





gozert said:
Could someone explain to me if it is possible to use a 1064/532nm coated beam expander for a 520nm laser? I've been thinking about building a 520nm with a beam expander on it, but I can only find very few expanders that have a wide range of wavelengths that are usable.

Also, what exactly is the difference between 2x and 10x expansion? Does 10x get you a better divergence, or is the difference too small to notice?
Click to expand...

An expander for 532/1064 should work just fine - you'll lose a little more power than you would if you were using 532/1064 but it isn't going to be noticeable, not without an LPM anyway, and even then.

2x beam expansion will increase the beam diameter 2x and reduce the divergence by the same amount. A 10x beam expander will increase the beam diameter 10x and reduce the divergence by the same amount.

I.e, you have a 1mm at aperture beam with a divergence of 1mRad and you pass it through a 10x beam expander, at the other end of the expander you should have a 10mm beam with 0.1mRad divergence.
 
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Okay, I get it now. Thanks a lot! Time to search ebay for a nice expander.
 
Keep in mind to check entrance and your laser beam diameters before buying.

The expander for 532/1064 might have a small entrance aperture like 3 mm, while your 520 laser diode larger beam ~ 4-5 mm.
 
gozert said:
I currently am looking at a couple different expanders on ebay, but I'm not sure about the entrance aperture. Could you guys take a look for me at these?

YAG 1064nm/532nm 3x Beam Expander

ND:YAG 1064nm/Green 532nm Beam Expander

YAG 1064nm/532nm 7x Beam Expander


Thanks again guys.
Click to expand...


They all look fine aperture wise, I don't think I've seen any beam expanders like this with an aperture small enough to be a problem. Those expanders were probably intended to be used with a big YAG system which generally suggests a larger beam anyway.
 
That sounds good. Even if the expander required a smaller beam width, wouldn't I be able to just focus it to a smaller point with the lens that's already in front of the diode?
 
gozert said:
That sounds good. Even if the expander required a smaller beam width, wouldn't I be able to just focus it to a smaller point with the lens that's already in front of the diode?
Click to expand...

You could do that, but the output from the expander would be more divergent than if you had an already collimated beam entering. ;)
 
Makes sense, but with a 15x beam expander I doubt this will be significant, or will it?

Thanks again.
 
gozert said:
Makes sense, but with a 15x beam expander I doubt this will be significant, or will it?

Thanks again.
Click to expand...


It depends on how divergent your beam is really.

The apertures on the expanders you linked all look fairly large so I don't imagine you'd have any issues unless you're planning to use it with a CuBr or something like that.

You could bring down the beam diameter and collimate it again using some other optics before the expander, but that's a little pointless I'd say.
 
Alright. I believe one of them required a 2mm beam, but I'll just send them a message with some questions about it.
 
gozert said:
Alright. I believe one of them required a 2mm beam, but I'll just send them a message with some questions about it.
Click to expand...


That's the best option, they might be able to suggest something they have that suits your needs!
 
the divergence is great with a 10x i have a sinner cypreus 3 with his exspander in the hsot is a NDB7875 3+W diode running at 4.0A i have a post in the 445 section. 10x beam expander /445nm
 
For myself, a divergence of 1.2 mRad or less is great, 1.0 wonderful, lower awesome.
 
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