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Question about cheap green lasers

danielbriggs

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Hi,

I really want to make a DVD laser burner, and I've orderd the stuff, but green sounds cooler - is there any way to cheaply get a powerful green diode, like the DVD-Reds? I know that there are shops in the US that sells them for $100's but, with shipping to the UK, etc, I can't afford it.

Also, why are laser diodes so expensive?


Dan :)
 



paper183

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When it comes to green lasers the diode isn't really expensive because the diode is a pump diode, basically it's a very high powered IR diode. The IR laser light goes through 2 different crystals which in the end changes the wavelength of the light to 532nm (green). Green lasers cost a lot because the crystals are rare and it takes a lot of time and precision to align everything perfectly. Red laser diodes are far less expensive, SenKat has a group buy going for red diodes from dvd burners, take a look at the Buy, Sell and Trade section.
 

danielbriggs

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Thanks, I did but one from SenKat, but I'm already thinking of making my next one! - Green
As I want to see the beam :) not just the dot.

What is the wattage needed to burn/pop/light most objects? How's the cheapest way to go about it with green lasers?

Also, on the red side: How about using a laser from a lightscribe 20x drive - now that should be powerful :-D (shouldn't it?? has anyone tried it?
 

pseudonomen137

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Lightscribe uses 780nm as I recall. The diode can handle something in the 100-300mW range, but at 780nm its not very impressive for more than burning.

There is no such thing as an effective green laser diode as of yet. All green lasers are made via a DPSS process, but I'll let you research that on your own  ;). Paper explained a good bit of it, and it won't be too hard to find the rest.

Because of that, you have to buy a green module. You can't just buy a green diode (although some modules are pretty dang small!). The cheapest way to go about getting a burning greenie, would be to buy one. No tricks or backdoors like harvesting red laser diodes unfortunately.  

The wattage for burning really doesn't matter much in the face of irradiance - the power per area. Consider 1mW in a 1mm diameter area. Now consider 10,000mW in a 10cm diameter area. The irradiance is the same in both cases, and irradiance is key to burning. Generally in a pen laser though you'll want to get into the 35mW+ range to easily pop balloons, and ~100mW to easily take out matches.
 

styropyro

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A green will take a lot more time than a red, and it will be more expensive. About the 20x drive, a lot of 20x burners I've heard have open can diodes, and if it is 780nm, it will be cheaper just to buy an 80mW 780nm module from AixiZ for $15. They are about as bright as those cheaper red pointers, but it is a deeper reddish color, really weird. But it's a good burner, lights matches pretty fast.
 

danielbriggs

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Oh right!
Cheers for all your replies... I thought that the diodes for lasers were like super-speical LED diodes that were doped with god-knows-what and you could get most colours under the sun. I didn't realise there were only a handful of colours, and you have to use prisms and stuff...

I'll mess with the cheapy red, and invest in a green later.

Also, I'm sure there is a table or list out there, but I couldn't find one on Wiki.

AFAIK:
(nomial sizes)

Red: 635nm ,650nm
Green: 532nm
IR: ???
Blue: ???

Could some one please write me a propper list with all the common nm sizes you talk about, so I can have it for reference. What's 780nm?
Are there 2 or 3 diodes in a lightscribe? (i.e. 1x CD, 1x DVD, 1x lightscribe) or (1x CD, 1x DVD/Lightscribe combo)

Thanks


Dan :)

Edit: Also, what's an Open diode? How do I make it a closed diode? :D
 

pseudonomen137

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as I undersand it, lightscribe uses a CD and DVD diode. The CD diode is on steriods and this is used for the lightscribe tech. 780nm is near-IR. Just barely visible in very high powers - not normally considered visible light.

I'm sorry, but what was your question about wavelengths?

Prisms don't really have anything to do with the range of wavelengths lasers can come in. Its just that we can only attain certain wavelengths with certain technologies. With diodes we now have viable semiconductor diodes in the 400-445nm range as well as from 635nm up to into the IR at least up to ~1600nm. Perhaps a little further but I'm not sure. DPSS (look it up! :D) allows more possibilities, some advantages, and some disadvantages. There are also gas lasers, chemical lasers, etc depending on the task.

Normally with laser diodes you find them in "c block", "5.6mm can", and "9mm can" forms, although ultimately the laser diode is a very tiny chip that can be incorporated in a multitude of packages if needed.
 

danielbriggs

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Thanks!
I'll read up on DPSS!

Lastly, as before: Could you write me a list of common nm and their translations in to English please!
e.g. 650 red (that's all I know!)

Dan ::)
 




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