how to achieve a wide beam? how to achieve a long beam?

[n3wb]

Greetings,

I have been reading this forum for about a few months, trying to learn about lasers, specifically about building one (in my case 2). I need to build a laser that will be seen 2 km away when the operator is pointing it up, basically as a signal.

I have seen a few beam expanders and they look like they might do the trick. I wonder though how much less distance will the laser shine with a beam expander. As to the colour it is going to be green but unsure of the specific wavelength and wattage. And this laser will not be used for burning, but i am open to the idea.

so i have a few questions before I build this;

1. from how far away will a normal beam be visible to the naked eye? (if the operator is poinintg it up, not at the observer)

2. beam expander vs no beam expander - how long is the beam when compared to with and without?

3. how long can a laser shine assuming unlimited battery/power supply?


any reference to specific posts/info will be greatly appreciated , thnx

 

[Sta]

Welcome to the forum! A lot of your questions need more detail to be accurately answered. What's your budget? And what do you mean by "a normal beam"?
The idea that immediately popped into my head was 2 Sanwu Spiker 520nm 1W lasers and 2 Sanwu beam expanders. Here's a link: https://www.sanwulasers.com/product/spiker
and the expander: https://www.sanwulasers.com/product/x3beamexpander

That'll cost you almost exactly $1000.

1. I can't answer this one without knowing more about 'a normal beam', but I can tell you a 1W 520nm will almost certainly be visible from 2km with a beam expander.

2. With a *X beam expander, it can be seen from a distance X times further away, possibly a bit less.

3. This has to do with the duty cycle of the laser. The Sanwu Spiker that I mentioned has practically unlimited duty cycle, because of its excellent heatsinking.

 

[Pi R Squared]

Won't a beam expander make it less visible when pointed straight up but more visible at greater distance when pointed in someone's direction? Maybe Alaskan will comment here, he is an expert on beam expanders. A 1W 520nm without a beam expander should easily be visible from more than 2 kilometers. I remember a YouTube video of some 532nm from 8 or 9 kilometers at night and it was visible even when pointing up, this would of course depend greatly on atmospheric conditions, humidity and particulate matter in the air.

Alan

 

[n3wb]

Thank you guys for your input
I apologize, by normal beam I meant a beam with no expander.

My budget is around 800.

I was also wondering how effective would it be if I get 4 cheaper lasers and strap them together to make a wide beam.

 

[hakzaw1]

^^^^ yes VERY effective.. do that;; not the other
3 pointerpens 9$ on ebay add together for ~150 to 200 mW!!

very 'wide' beam too..

be safe!!!