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Green Divergence. Most power single element

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scottsevenn

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I want a powerful 520nm laser. I don't want one that cannot reach the cloud cover. So what is my best option? I have yet to see a viable way to get a good infinity beam from one of the 1 watt 520nm diodes.
 





From my experience even with 100 mW greenie you can reach lower clouds to see the "dot" clearly (maybe even lower power). It depends on many parameters as well as further suggestion what laser you should get.

Do not forget the beam does not end untill it hits something. Even if you see it seemingly ending some few hundred meters in the middle of air, it is just reflected radiation from dust, humidity, etc. in the lower dense atmosphere layer. The beam goes further and can hit aircraft or something (you really do not want police to arrest you and put you into jail for years/life for hitting aircraft or cause some accident). Safety is needed in any laser use.

Specify your intended purpose as much as possible, the community here cannot give you good advice without that information.
 
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scottsevenn said:
I want a powerful 520nm laser. I don't want one that cannot reach the cloud cover. So what is my best option? I have yet to see a viable way to get a good infinity beam from one of the 1 watt 520nm diodes.
Click to expand...

What do you mean by "a good infinity beam"?
 
If a 520 nm laser pointer cannot put a dot on a 5,000 foot high cloud layer, I don't want it.

To do so, the divergence should be 1.5 mRad or less at 75-100 milliwatts output, but if you use a single mode laser diode which has a lens to produce a divergence of less than 1 mRad, you can detect a dot at about half that amount of power. Weather a dot can be viewed on a cloud base has variables; how high and dense the clouds are as well as how dark the surrounding area is at night. City lights can illuminate a cloud layer so brightly, it may be harder to see a dot on a cloud base.
 
Alaskan said:
If a 520 nm laser pointer cannot put a dot on a 5,000 foot high cloud layer, I don't want it.

To do so, the divergence should be 1.5 mRad or less at 75-100 milliwatts output, but if you use a single mode laser diode which has a lens to produce a divergence of less than 1 mRad, you can detect a dot at about half that amount of power. Weather a dot can be viewed on a cloud base has variables; how high and dense the clouds are as well as how dark the surrounding area is at night. City lights can illuminate a cloud layer so brightly, it may be harder to see a dot on a cloud base.
Click to expand...

I cannot rep you again, Alaskan, but well said.

I think OP should mention more about the purpose and learn laser basics of divergence, dot size, lasers (diode + DPSS in this case), illumination of materials, powers, etc. A lot to study. Luckily we can help him including safety stuff, we just need to know more about the purpose. Just pointing clouds for fun will become boring soon, so it is considerable if OP wants to put $$$ at least into lasers. There might be even reason for Optotronics RPL-I (which puts down of the sky even Death Star :crackup:), but I doubt so far.
 
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I was so disappointed in the divergence of a NDG7475 1 watt 520 nm green laser diode using one of our ~6 mm G2 lenses to be able to do just that, I put a five inch wide plano-convex lens on it to collimate the beam so I could spot a cloud, it sure does the job now. The divergence using a 6 mm lens was fairly high, probably close to 2.5 mRad, only producing a rake of light in the sky after 1000 feet which just disappears into the distance. Put a 3x expander on this diode and it's divergence is reduced so much it's a nice tight pointer, but in my opinion, terrible with a small 6 mm diameter collimate lens. All if the high power multimode laser diodes behave this wave, their emitters are so large they diverge a lot and need a larger diameter lens than our tiny 6 mm ones, a three element lens helps with a longer focal length because in effect, it expands the beam more than a G2, but some of the multimode diodes have their output truncated or blocked with a three element lens.
 
As long as you are not close to an airport and aim the beam vertically, there is little to no chance of it interfering with aircraft. Of course you need to be aware of low flying helicopters. You can hear those unless it's too noisy, though.
 
steve001 said:
What do you mean by "a good infinity beam"?
Click to expand...

Hello,
Thank you for responding. I need to brush up on technical terminology.
What I mean is a small dot at a distance. A fine beam that is as much round as is possible. This as opposed to a rectangular beam that paints a rectangular spot the size of a truck on a building 3 blocks away. I love power. I love a precise beam more. I am ready after a couple years of playing with smaller 50mw 532nm lasers to spend some money and get a quality higher power 520nm. I am planning to do my ordering with DTR. Still shopping hosts. There are so many here. My problems are from what I have seen here the G 2 and even the 3 element lenses just are not able to create a beam that goes for much distance without fading away to nothing. I always appreciate any feedback and let me thank you in advance for your time.
Scott
 
steve001 said:
What do you mean by "a good infinity beam"?
Click to expand...

Hello,
Thank you for responding. I need to brush up on technical terminology.
What I mean is a small dot at a distance. A fine beam that is as much round as is possible. This as opposed to a rectangular beam that paints a rectangular spot the size of a truck on a building 3 blocks away. I love power. I love a precise beam more. I am ready after a couple years of playing with smaller 50mw 532nm lasers to spend some money and get a quality higher power 520nm. I am planning to do my ordering with DTR. Still shopping hosts. There are so many here. My problems are from what I have seen here the G 2 and even the 3 element lenses just are not able to create a beam that goes for much distance without fading away to nothing. I always appreciate any feedback and let me thank you in advance for your time.
Scott
 
Hey, Scott. Do you see that "edit" icon on the bottom right of your posts? That is there to keep you from double and triple posting; one after another in a few minutes. That is highly frowned on here, so you can clean that up by deleting the last two posts and putting that information in the first post.
 
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scottsevenn said:
Hello,
Thank you for responding. I need to brush up on technical terminology.
What I mean is a small dot at a distance. A fine beam that is as much round as is possible. This as opposed to a rectangular beam that paints a rectangular spot the size of a truck on a building 3 blocks away. I love power. I love a precise beam more. I am ready after a couple years of playing with smaller 50mw 532nm lasers to spend some money and get a quality higher power 520nm. I am planning to do my ordering with DTR. Still shopping hosts. There are so many here. My problems are from what I have seen here the G 2 and even the 3 element lenses just are not able to create a beam that goes for much distance without fading away to nothing. I always appreciate any feedback and let me thank you in advance for your time.
Scott
Click to expand...

There's one way to achieve a round or nearly round beam, Use at least two beam shaping optics. That will circularize the beam and collimate it also. Once that is done use a long focal length lens plano-convex that does not truncate the beam or use a beam expander. I think one problem you'll have to solve is adding lenses requires custom machining of new parts.
 
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