Questions about Lasers. Beginner's guide.

Hi to all. New to this field and i just want to learn some things about lasers.

•1)What is the difference between a green laser and a red laser?
OK one obvious difference is the wave length/frequency but what exactly does this implies? Human eye is more sensitive to green than red but apart from this how green-red compares?
-Can anyone describe all the advantages and disadvantages of the red-green debate.
Except for the price, as i'm aware about the higher manufacturing prices of green versus red lasers.

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•2)Some sites advertise/say that green lasers of some power(e.g 50 mW) are 60 times stronger than red lasers of the same power. Is this true? If so, stronger in what sense? In visibility or what?

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•3)The following site-1 advertises a green laser of power 100 mW saying that it has an active beam of a range of 12 km!!  I have seen in the site-2 to advertise that one of their products, a true green laser with 100 mW power has a range of 6000 ft or about 2 km. And generally in other sites i have seen that green lasers of about 50-200 mW power have a range of about 2 km.
So what is the actual range of these lasers? Can it be really 12 km? Can the ending dot of the beam reach so far? And what about the whole beam?

site-1: globalimport.gr/catalog/product_info.php/cPath/139/products_id/373
site-2: dealextreme.com/products.dx/category.911

(I have removed the http from the sites since this forum does not allow me yet to post links.)

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•4)Can anyone recommend me 3-4 top sites for buying common medium price( 30-500 $ or €) lasers? I'm aware of dealextreme.com that i have heard some good recommendations(are they true?), but what about others?

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•5)What are IR filters about? I have heard that one has to prefer lasers with IR filters, but why? Also if a powerful laser does not have these IR filters i have read that it is dangerous to watch the beam without special protection glasses since eye has no pain receptors and also the IR wavelength light that is emitted is invisible to human eye. What i don't understand in this is what "to watch the beam" means. It is dangerous to watch only the ending dot of the beam or it is dangerous even to watch the produced whole beam even from sideways?

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•6)I have seen in different sites the prices for let's say a 100 mW green laser, that range very widely and i can't understand why. I have seen prices to range from $20 to 500$.

For example look at the following 3 sites that advertise a green laser of power 100 mW:
-globalimport.gr/catalog/product_info.php/cPath/139/products_id/373  
-wickedlasers.com/lasers/Elite_Series-69-0.html
-dealextreme.com/details.dx/sku.1372

The first has a price of $100, the second of $500 and the 3rd of $37.
Why this oddity in prices?  I mean $37 for a good true green laser from dealextreme.com that is supposed to have quality products, and $500 for a similar power green laser from another site???? Something is definitely wrong here. :-/

And what is the normal price one can expect for a good quality green laser with power of 100 mW? And what about a similar power red laser?


Thanks in advance.

Read SAM'S LASER FAQ , on GOOGLE. It's a good QUESTIONS ABOUT LASERS GUIDE. rob

phoenix77 said:

Read SAM'S LASER FAQ , on GOOGLE. It's a good QUESTIONS ABOUT LASERS GUIDE.   rob

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Many thanks for this FAQ, very interesting read, but unfortunately does not answer most of my questions.

Nice formatting.

•1)What is the difference between a green laser and a red laser?

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There is no "debate" on wavelength. Choose whatever you want/need.

Higher frequencies (i.e. lower wavelengths) have higher energy, meaning that a green laser technically burns better than a red laser. Not by much though. If you're looking for low cost burning lasers, go with a blu-ray (405nm).

•2)Some sites advertise/say that green lasers of some power(e.g 50 mW) are 60 times stronger than red lasers of the same power. Is this true? If so, stronger in what sense? In visibility or what?

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The authors of those sites know absolutely nothing about lasers so you probably shouldn't buy anything from them if they're selling anything. There are two factors here: power and apparent visibility.

Power is power. A 250mW red laser has just as much power as a 250mW green laser.

Apparent visibility is just what it sounds like. The eye is more sensitive to green than red, so green is a more visible wavelength. That's why a 250mW green laser appears much more visible than a red laser of the same wavelength.

The range is a factor of power and how well focused the beam is. If the divergence of the beam is too high, it won't go very far.

•4)Can anyone recommend me 3-4 top sites for buying common medium price( 30-500 $ or €) lasers? I'm aware of dealextreme.com that i have heard some good recommendations(are they true?), but what about others?

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DealExtreme is good for any laser under 100mW (if you live outside of the US). After that, you will not get what you pay for. If you're looking for cheap laser pointers, also try LEDshoppe.com.

For higher power lasers, there are a lot of options that are often discussed here. I can only vouch for SkyLasers.net; I have a 300mW green portable from them.

•5)What are IR filters about?

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Green lasers emit IR due to leakages from the DPSS process. IMO, it isn't really as big of an issue what some sites say it is in terms of safety. The bigger issue is whether your laser is being rated for power with or without an IR filter. If you buy a 300mW green laser and it was rated without an IR filter, you're really only getting less than 300mW of green output.

Why this oddity in prices? I mean $37 for a good true green laser from dealextreme.com that is supposed to have quality products, and $500 for a similar power green laser from another site???? Something is definitely wrong here. undecided

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Some sites will overcharge lasers, but give you good quality products.
Some sites will have really inexpensive lasers, but they will be underspec and generally bad.
And some sites (like WickedLasers) will overcharge ridiculously and then sell you really, really underspec lasers and then laugh at you for wasting your money on their products.

And what is the normal price one can expect for a good quality green laser with power of 100 mW? And what about a similar power red laser?

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You might try a green laser from DX, but I don't think you'll get 100mW out of it. Day hosted a group buy about a week ago that included high power lasers, so you might want to check that out in the group buy section. However, he probably won't be doing another order soon.

There are tons of threads in the reviews and green/red lasers boards. Look at them for company ideas.

I can answer it all. READ..READ..READ then build your own. It's cheaper and you can build a better quality one than you could buy. And if it breaks you have the know how to fix it without having for buy another complete unit. Start with the links in my sig.

To add on to what JWC has said...

There is also a difference in how red and green lasers are constructed.
Reds use a single laser diode and greens use an infrared diode to "pump" crystals which produces green light (search DPSS).
There are also DPSS red lasers but those are not too common in the hobbyist community.

Range means nothing. Divergence, atmospheric conditions, and power determine how visible your laser will be at large distances.

Novalasers is a good company. They have top quality products at good prices. The X-100 is $210 and if you use the discount code WARP5 at checkout you get 5% off.
Dragonlasers sells similar products at equally good prices.
Laserglow is a bit more expensive but still very good. These three companies use IR filters in their DPSS lasers.
Techlasers, Wickedlasers, and Warnlaser are a few companies that you want to avoid.

Thanks everyone for the answers. All were, honestly, very informative!
Especially jwc for the very detailed answer, many thanks!