Annoying question

Hello everyone,

I'm trying to build a burning laser pointer for a school project. Nothing serious, basic stuff (light a match, burn black paper, pop a balloon, etc.)

Now, I know you guys must get this question a lot, but I've searched for a little while, and I've gotten some somewhat ambiguous results. I've read the "I want to build a laser" threads, and they've been very helpful, however, there is one thing I still haven't found.

What is the minimum mW to be able to do the things I've specified? What should I get. If this has already been answered and I missed it, please link me there!

Thanks!
RabidBurn

Hello Rabid!

At least 100mW should get you easily what you want. They can be purchased for about $90 at most "Trusted Companies". Just check out Livinloud's thread :beer:

You do realize you can instantly blind someone right?

Yes safety should be emphasized first. Any laser that will burn things will easily fry a layer of your retina off of your eyeball. That said...

50mW can pop a balloon, 80mW can light a darkened match. Burn black paper I'm not so sure about, are you referring to lighting a sheet of darkened paper, or lighting flash paper? You would need around 300mW to light black paper on fire. Note that these are more conservative power estimates, 100mW-120mW would be well capable of popping balloons and lighting matches.

Another thing to consider: doing these thermal tricks is more dependent upon the diameter of the beam of your laser than the power output. A big round spot of light, even at 200mW, will not do anything, whereas 50mW of finely focused light will easily light a match. Usually, a green laser will have a small beam diameter than red or violet lasers, due the green lasers using crystals to create green light from IR light. This also makes green lasers more expensive and more sensitive. Not to mention, cheap green lasers (eBay is a famous example) have serious hazards to IR light leakage, which can burn a hole in your vision without you even knowing since you can't see IR light and you don't have pain receptors in your retinas

Focusable 100-200mw. Red would probably be your best bet because the diodes are fairly cheap at that power, so its not the end of the world if you kill one. Have fun building, be sure to post pictures, and be sure to wear safety glasses/use your laser responsibly.

Welcome to the forum!

NO4H99 said:

Focusable 100-200mw. Red would probably be your best bet because the diodes are fairly cheap at that power, so its not the end of the world if you kill one. Have fun building, be sure to post pictures, and be sure to wear safety glasses/use your laser responsibly.

Welcome to the forum!

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Remember NO4H, Red isn't best for burning :tsk:

Tha Greenlander said:

Remember NO4H, Red isn't best for burning :tsk:

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He's not looking for the best. He's looking for something that will get the job done.

I think a 405nm build would get the job done best... just set the driver lower than you normally would so you get around 150-200mW instead of 500mW.

FlutterPie said:

He's not looking for the best. He's looking for something that will get the job done.

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Well I would like the OP to get the best wavelength for burning and not have ot spend more $ to get another wavelength which requires more power.

Tha Greenlander said:

Well I would like the OP to get the best wavelength for burning and not have ot spend more $ to get another wavelength which requires more power.

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650nm is pretty cheap. 405nm would also be a good choice, maybe a 6x diode.

So I just tried it out for you with a few lasers.

100mw green - matches, balloons, and cuts/smokes black paper slowly.
240mw red - matches, balloons, and quickly cuts/burns black paper
400mw purple - matches, balloons, and quickly cuts black paper. Same when focused to infinity too.
2.5w blue - Hehehe (sets fire to the paper only when on full power)

Time to get out the CO2 :lasergun:

Thanks for all the replies! I'll be sure to post pictures of it when I finish building it, whether it works or not.

RabidBurn

Good luck :beer:

hwang21 said:

Time to get out the CO2 :lasergun:

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Do you have any pictures of your collection? It sounds awesome... just sayin.

Soon :eg: btw hi from WL's forum

Don't forget to buy the special laser safety glasses for everyone who will be in room during a
demonstration.