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# Burning power equivalency in lasers

#### Outermostline

##### New member
Hi guys,

I've been looking all around and I couldn't find any info on the burning capabilities of different wavelengths/colors of laser light.:undecided:
In other words, say you have a 405nm diode which is 50mW, and that laser is just barely able to light a match. So you could assume that (hypothetically) it would take 50mW of a 405nm diode to light that match. How would diodes of other wavelengths compare to it? Like, what wattage would you need to light a match if the diode were a 532nm or 450nm or 635nm or an 808nm?

I've heard that when it comes to burning power, a 405nm is the most effective and an 808nm is the least effective. Is this true? How would the other wavelengths compare in power?

I'm sure there's no chart or table that exists which shows the exact equivalency I've described, so this is mostly each person's own estimation.

Thanks.

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#### ARG

##### New member
It depends on the material being engraved. Some materials absorb certain wavelengths better than others.

405nm diodes are also single mode and can be focused into a smaller area for a larger power density than a multi-mode diode of the same power.

#### Outermostline

##### New member
It depends on the material being engraved. Some materials absorb certain wavelengths better than others.

405nm diodes are also single mode and can be focused into a smaller area for a larger power density than a multi-mode diode of the same power.
That kind of makes sense. But aren't most other diodes also single mode, as in they only have one given wavelength, or is there something special about 405nm diodes?

#### ARG

##### New member
Single mode means something else. Having a single wavelength is coherent light, which all lasers have.

#### Outermostline

##### New member
Oh, OK. Sorry, I'm new to lasers. So you're saying if someone had to pick between 5 different diodes all with different wavelengths but the same wattage, in order to build a laser which they would use strictly for burning, there wouldn't be any one that stands out as a "better" laser for burning.
Thanks for the clarification.

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#### ARG

##### New member
If they all have the same wattage the single mode diodes would be best. Desired wavelength depends on what material is being engraved.

#### Outermostline

##### New member
If they all have the same wattage the single mode diodes would be best. Desired wavelength depends on what material is being engraved.
So are all 405nm diodes single mode? Is there any way you can tell a diode is single mode? I looked up "single mode laser diode" and nothing useful came up.

*edit: I read the Wikipedia article about laser diodes and theory of operation, I think I understand what you were saying a little better now.

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