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ArcticMyst Security by Avery

Need high power w/ spot diameter of <= 5 microns, close focus OK

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nmz787

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I know there are 14X bluray drives out now, are they higher power laser diodes than the 12X?

Earlier I chatted with Edmund Optics online tech support for about 30 minutes...

they said if the laser is elliptical (think 445nm bar lasers), these "anamorphic prism pairs" may help to correct it to a more spherical shape (they don't sell a mounting package for the 2 prisms though)

Anamorphic Prism Pairs | Edmund Optics

they said to put it through a collimating lens
Blue Laser Collimating Aspheric Lenses | Edmund Optics

then put the collimated beam into a focusing lens
Precision Molded Aspheric Lenses | Edmund Optics



What do y'all think? I only need to etch silicone that's about 100 microns thick, so a close focal length (shallower depth of field) is not a problem. I am thinking 10-25mm focal length would work.

Do you agree with the Edmunds guy that the laser would need to be collimated? If so I need to measure the NA of the laser diode, anyone here done that before and have a HOWTO?
 





Jim

Jim

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It could be focused using only one collimating lens, unscrewed a turn or two. This can give a focal length of 20-30mm, not sure on the spot size though.

Still I dont think a 12x will mark sillicon, perhaps a more powerful infrared laser might tho.
 
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nmz787

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Jim said:
It could be focused using only one collimating lens, unscrewed a turn or two. This can give a focal length of 20-30mm, not sure on the spot size though.

Still I dont think a 12x will mark sillicon, perhaps a more powerful infrared laser might tho.
Click to expand...

Thanks Jim. I need to cut silicone, not silicon... its an elastomer like RTV gaskget sealant, or bathroom caulking. It is clear, and I'd like it to stay clear (rather than mix in charcoal ash to blacken it), but luckily it's also very thin (0.1mm)!

I've heard of the aixiz lens mounts, are there any other common mounts or good DIY solutions floating around here?
 
Jim

Jim

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Haha, should have read that slower.. You are going to have problems marking it if its clear, you need a wavelength that will absorb the laser well. An aixiz holder in a heatsink should do the job fine really.

I'm sure you are going to have to use infrared to make a mark on it though, an 808nm diode may be far enough into the IR spectrum to burn it. How are you going to move the beam? You may need watts to cut it cleanly..
 
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nmz787

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Jim said:
Haha, should have read that slower.. You are going to have problems marking it if its clear, you need a wavelength that will absorb the laser well. An aixiz holder in a heatsink should do the job fine really.
Click to expand...

I don't think I missed anything. I also have a 1W 830nm laser but I don't know if it's single mode, and NIR optics are more expensive than VIS.

I know the material has to absorb to get heated, unfortunately the only spectrum of the material (PDMS) I have cuts off just below 500nm, so the 300-450nm area is unknown.

I'm sure you are going to have to use infrared to make a mark on it though, an 808nm diode may be far enough into the IR spectrum to burn it. How are you going to move the beam? You may need watts to cut it cleanly..
Click to expand...

I don't really want to go into NIR or IR, I've got a good feeling that 750mW @ 405nm and 5 micron spot will have more than enough W/mm^2 to cut this stuff. If not I can use the same setup to expose photoresist and do something called soft-lithography. My focus requirements don't change in this setup.

I'm not planning on moving the optics, rather I'm building an XY table underneath them to move the substrate (thin layer of silicone spin-coated onto teflon or silicon wafers).
 
Jim

Jim

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nmz787 said:
I don't think I missed anything.
Click to expand...

No, I meant I should read slower, theres a big difference between silicon and silicone..

12x at 750mw with an aspheric lens should work, you say the absorption graph stops at 500nm, but which way is the curve heading at this point? It will probably burn at this power density, clear silicone is not that clear really, especially with 405nm. You've said you need to etch it, then cut it? Maybe another forum member could try this out, I don't have a 12x.

Dont forget a fan to keep any vapors from reaching the lens, you could use the same fan to cool the laser too.
 
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nmz787

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I guess I should man up and say that while it is the edge of the graph, it's heading down... this is the only spectrum I've found in 2 years for this compound though, so I'm not entirely convinced this is correct. I've marked right about where 830nm should be.

http://diyhpl.us/~bryan/papers2/PDMS_spectral_response.png

I actually need to get a spectrophotometer for a few reasons, hmm, maybe I'll pick one up this or next week
 
Jim

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The graph goes to below 400, it is not labeled at that point though. And it shows little to no damping for RTV 615, and not much more for the Sylguard.

If you can keep it focused to the smallest spot possible and keep it there, it may do the job due to the extreme power density. The best bet is to do a test and find out, if it doesn't work you still have a cool laser..
 
Meatball

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You shouldn't need such high irrandiances to etch something so thin (and not metallic).

What the edmunds guy described was the process for fixing the bad shape of a laser diode, and it does help increase irradiance. But, with 600mws+ available from a 12X, I think etching will be no problem.

Here's a read for ya,

The aberration correction of a Diode Laser
 
DrSid

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Finally some high grade information on beam correction ! But look at the number of elements ! Expansive .. and there will be power losses. 405nm looks like better idea. For sure worth trying.
 
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grainde

grainde

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Sorry, but what colour is the silicone you are trying to cut. If on the graph you showed optical damping is related to absorbance, then the material although "clear" as you put it is coloured and a 532 nm laser might be a better, although more expensive, option. (Your strongest peak on the graph is at ~540 nm!) As 532 is DPSS you'll also have much better beam characteristics and less issues focussing it to a small dot. :beer:

Edit: BTW have you seen this thread? Maybe of interest to you...: http://laserpointerforums.com/f57/diy-laser-cutter-project-58283.html
 
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Meatball

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DrSid said:
Finally some high grade information on beam correction ! But look at the number of elements ! Expansive .. and there will be power losses. 405nm looks like better idea. For sure worth trying.
Click to expand...

That information goes for all c-plane, side emitting, non-VESCEL laser diodes.

This includes pretty much everything we use here.
 
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nmz787

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Meatball said:
You shouldn't need such high irrandiances to etch something so thin (and not metallic).

What the edmunds guy described was the process for fixing the bad shape of a laser diode, and it does help increase irradiance. But, with 600mws+ available from a 12X, I think etching will be no problem.

Here's a read for ya,

The aberration correction of a Diode Laser
Click to expand...

Thanks, great info to have.

With no experimental tests of 405nm and PDMS (Sylgard 184) I figure I want as high of radiance with best spot for now. I'm also interested in defocusing the target to increase the spot size, so I'll need power to get away with that.
 
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