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Single mode, or...?

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GrahamRounce

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Hi - For burning (or rather heating, in actual fact, say 1-2W) lasers, I've been searching for single mode types, for ease of focussing, as I thought. But unfortunately they don't seem to be that thick on the ground. Is this a bit pointless? Can multi-mode types be used almost as easily? (How?)
Thank-you again,
 





Grix

Grix

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There are pretty much no single mode diodes at powers that high. Only exception might be 405nm, the BDR-209 can reach 1W in some cases.

Most multimode diodes can achieve a quite small point too, especially if you use correction optics. I'd say if you don't require focus point accuracy of more than 1-2 mm, then multimode is good enough.
 
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GrahamRounce

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Sorry, but I should have said I'm hoping for 0.1mm.
As I understand it, single mode gives a circular beam, and multi-mode an oval one. Is the multi-mode oval the same proportions for every diode? I'm happy to use a corrective lens, but it will be a pain to have to match and check availability etc of a different lens for each possible device?
Thank-you! (Eventually I hope to know all this!)
 
S

steve001

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GrahamRounce said:
Sorry, but I should have said I'm hoping for 0.1mm.
As I understand it, single mode gives a circular beam, and multi-mode an oval one. Is the multi-mode oval the same proportions for every diode? I'm happy to use a corrective lens, but it will be a pain to have to match and check availability etc of a different lens for each possible device?
Thank-you! (Eventually I hope to know all this!)
Click to expand...

Modes refers to how many beams are created by a laser. TEM00 means one beam. Even if it is oval in shape it's still TEM00. A link to multi mode photos https://en.wikipedia.org/wiki/File:Hermite-gaussian.png
 
Cyparagon

Cyparagon

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Can you be more specific, please? What is your intended application?
 
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GrahamRounce

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Ok. I want to be able to write in quite high resolution, say 10-20 dots per mm, onto heat sensitive paper.
I realise that the white shiny surface is a problem, but, as I noted in another thread, the power used to write to a dvd is about 50mW, which I thought was surprisingly low, especially as the disc surface is probably not less reflective than the paper.
Thanks,
 
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WizardG

WizardG

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GrahamRounce said:
Ok. I want to be able to write in quite high resolution, say 10-20 dots per mm, onto heat sensitive paper.
I realise that the white shiny surface is a problem, but, as I noted in another thread, the power used to write to a dvd is about 50mW, which I thought was surprisingly low, especially as the disc surface is probably not less reflective than the paper.
Thanks,
Click to expand...

OK, will the laser be handheld or will it be aimed by some type of plotter or something. A well focused BDR-209 will simply burn through the paper (even white paper) very very quickly making hand held use a bit tricky.

If you intend to do 'light painting' on thermal paper with a hand held laser you might want to commission a custom build by one of the forum members using the '209 diode but with the addition of a power adjustment knob so it would be easier to control. At max power it would be great for laser scrimshaw!
 
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GrahamRounce

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Hi, and thanks. No, it would definitely not be hand-held! I think I'll have enough trouble with the focus however carefully I make (or re-use) an X-Y plotter arrangement, and vacuum-suck the paper flat? I haven't started investigating it properly yet, but I'm thinking it would be great to get the auto-focus in the sled of a dvd burner to work!
Thanks,
 
L

lazeristasUVISIR

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GrahamRounce said:
Ok. I want to be able to write in quite high resolution, say 10-20 dots per mm, onto heat sensitive paper.
I realise that the white shiny surface is a problem, but, as I noted in another thread, the power used to write to a dvd is about 50mW, which I thought was surprisingly low, especially as the disc surface is probably not less reflective than the paper.
Thanks,
Click to expand...

Do you really need a visible laser for you application? Can you investigate where your paper is sensitive? Is there a laser diode operating close by?

With too much power and a dirt on the paper you might start a fire :can:
 
G

GrahamRounce

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Thanks, yes, I hadn't really thought of using an IR laser because of being nervous about the invisible beam. I think I'd rather stick with a visible one for that reason, and the relative ease of focussing.
I did do a little googling about thermal paper, but turned up nothing on the ideal wavelength for writing onto it
As I keep saying, the power level for writing to a dvd is very modest considering the reflectivity of the disc, and the lasers are mostly visible red. If anyone has any experience of making the auto-focus on the sled work, please write!
 
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