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UV, Violet, or IR which is best for burning?

DrSid

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It can be simplified as this: 1W diodes are only available at 445nm at the moment .. so for hand-held laser, 1W 445nm is best for burning. If you wanna go cheaper, go for 200mW focusable red. If you wanna go more expensive and forget hand-held, go for CO2.
 

chipdouglas

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ok, here is a more simple thing for the op.

what do you want to burn
from what distance are you looking to be able to burn?
 

LazyBeam

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Absorbed Power Density. Nothing else matters 99% of the time.

The single aspherical lenses we use don't reach the diffraction limit. So the greater theoretical focus limit of short wavelengths is a moot point. Plus, most of our burning happens at short ranges so diffent factors of raleigh scattering between wavelengths does not play much of a role easier. Power density is power density... for all practical purposes the color of the light doesn't matter.

The only thing you could really say is that more materials readily absorb the shorter wavelengths so it might be easier to find "burnable targets" for you laser. Said otherwise, when considereing "best burning" the color of the target is more important than the kind of laser your using. As mentioned upthread... very high power IR diodes are very cheap so that's your best burning/$ ratio right there - all you have to do is focus it well. ;)
 

james1095

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I'm trying to decide what my next laser should be. I have green and red, waiting for my arctic. Does IR burn? 808nm vs 1342nm. So many questions in my mind. I'm looking for max burn here!:D. any suggestions?
If you want max burn, you might look at sealed CO2. Yeah it's not gonna be handheld, but holy hell, the thought of an IR diode burning laser is terrifying. The 445nm diodes are scary enough, but at least you can *see* the beam from those. The violet diodes are worse because the lack of apparent brightness can lull you into a false sense of security. IR diodes are almost completely invisible and yet still capable of blinding you. I've avoided building anything with IR lasers for that reason. The only way I would try is built into a cutting table with an interlocked cover.
 

mauijan

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hello, it is said that CO2 laser is more powerful to burn as a shorter wavelength is more readily absorbed by the material to burn.
but a CO2 laser has a wavelength of 10600 nm that is much longer than red, blue or green. am i missing something?
 
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Well CO2 lasers can be had at a much higher power than our diode lasers. A 30W hit is gonna burn no matter what the wavelength is.
 

Wolfman29

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Fret - that's not the case.

A 1W CO2 laser would probably burn better than a 1W 445nm laser. This is because the CO2 main emission wavelength (10.6um) is absorbed FAR better by almost everything than ANY color in the visible spectrum. CO2 lasers really are heat rays - they emit in the mid-IR range.
 
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Thanks for clarifying. I suppose I didn't understand what he was asking.
My point was mainly that 30W of any laser will probably do some serious burning. :crackup:
 
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the way I see it way over simplified, the wavelength that matches the object you want to burn, must be close to the absorption spectra of that object, as that is the wavelength that will cause the atoms to jiggle more, :thinking:
 

james1095

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hello, it is said that CO2 laser is more powerful to burn as a shorter wavelength is more readily absorbed by the material to burn.
but a CO2 laser has a wavelength of 10600 nm that is much longer than red, blue or green. am i missing something?


Blue photons are much more energetic than red photons, but Watt for Watt it's all about absorbion. Any light that is reflected off the target is wasted energy when you are trying to heat the target. Very few things reflect the CO2 wavelength well. This is why it works so well for cutting and engraving, but mirrors and optics have to be made of exotic materials. An aluminized mirror that reflects visible lasers very well will absorb most of the CO2 beam that hits it.
 

mauijan

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ok but lets say a CO2 laser has about 10000nm wavelength as compared to a generic laser diode with wavelength 1000nm (for simplicity). that means with the same power the generic laser is 100 (10 x 10) times less powerful (power per unit area) than the CO2 laser. nonetheless CO2 lasers are still available with more burning power than generic diode lasers?
 
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was I wrong, it has nothing to do with the absorption spectrum of the material, because that data is available for all common matter? It would depend on what you want to burn their is no generic I want to burn ever bit of matter laser. though CO2 lasers are really good and burning some stuff that is clear. In commercial application is it not really the laser doing the cutting but the plasma that is created by the laser?
 

james1095

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The wavelength only matters in relation to absorbtion of the material you wish to heat. A 1W laser at 200nm is putting out exactly the same amount of energy as a 1W laser at 10,000nm. The 10,000nm laser is producing more photons to get to the same output but that's irrelevant in this case. It's no different than comparing two visible wavelengths. A green colored material appears green because it reflects green light. If you try to cut it with a green laser, much of the energy is reflected off the material. A red laser is heavily absorbed by a green surface so it will heat the surface relatively efficiently. Most materials that reflect visible light absorb the deep IR from a CO2 laser very well. There are a few other traits that make CO2 popular for cutting. It is available in very high powers, it can be operated continuous wave, it is electrically very efficient (as lasers go) in that a much larger amount of the electrical energy going in is converted into a useful beam. Also the far IR is much less of an eye hazard at a given power than near IR and visible beams since so few materials reflect it efficiently and your eyes cannot focus it onto the retina. A direct hit can still do some serious damage, but there is nowhere near the hazard of reflected radiation that there is with a visible or near IR beam.
 
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take a common steel a normal co2 laser has 85% of its energy reflected, but a different wavelength laser would say be better for cutting it as long as the absorbed power of that laser is greater than 15% and the W is comparable to the CO2 laser. to overcome this many commercial lasers use pressurised O2 jets to increase temp and remove debris. Or that is my understanding. A NdYag laser seems it would be more suited to steel IMO
 
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SOG

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um... I should read more about CO2 lasers...

About burning, I think... supposedly the more absorbed the energy, the better it's for burning ... because the more it's absorbed, the more energy will be transferred.

So supposedly UV has more energy, but it's not absorbed as well as IR, I think IR should burn better at close range? is that right ?
 
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what do you want to burn? that is the million $ question for what kinda laser to use IMO but yes, the only cheap hi power burning lasers are CO2.
 




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