Laser Diode Question

This is a forum to share experiences and ideas about holography.
Colin Kaminski

Laser Diode Question

Post by Colin Kaminski » Tue Sep 07, 2010 1:25 am

Joe Farina wrote:
Colin Kaminski wrote:Reams are very accurate. So, measure the diameter with a caliper and choose a ream that is .003" larger, that should be a slip fit. Mc Master Carr will have one. You will regret a true press fit at .001" over.
Thanks Colin. I checked http://www.mcmaster.com and saw two reamers, part numbers 8803A424 and 8803A426.

I also measured my 445nm diode with a digital caliper (resolution .0005 inch). This particular diode has a base diameter of 5.57mm.

5.57mm = .2193 inch. So if .001 is added to this, you would get .2203, if .003 is added you would get .2223.

The reamers from McMaster are .2205 and .2220. Which would you suggest?
Because I have damaged diodes while pushing them, I would go with .2220. Buy the proper drill bit as well. Check to make sure the can is round by taking a few measurements while rotating the can. Use a good thermal compound. If you are active cooling mount the thermocouple as close to the TEC as possible.

wler

Laser Diode Question

Post by wler » Tue Sep 07, 2010 10:31 am

Well, no need to overdo it, I never had put anything around the diode but always just clamp-pressed it flat on, and I never had any problems (up to 800mA which is the max I ever did). The only slightly subtle thing is that there is a little collar around the neck of the diode, which prevents a flat sit if the hole is not countersunk a little. I'd spend more attention to active temp stabilization instead!

Joe Farina

Laser Diode Question

Post by Joe Farina » Tue Sep 07, 2010 10:56 am

Thanks Colin. I was doing some searching for the selection of drill sizes for reamers, and it seems a bit complicated. Sometimes they factor in the machinability of the metal. For a .2220 inch reamer, I was thinking of using a .2031 drill (13/64).

Thanks Wler for the tips. That's true about the little collar at the juncture of the can and base, Ahmet pointed that out to me earlier. The top piece which presses down on the diode needs to clear that. Regarding the active temperature stabilization, I'm going to let the more knowledgeable people such as Ahmet and yourself worry about that :wink: To me, this is more of something that should be done in connection with ECDL. I want to see what's possible with passive cooling with a good-sized heat-sink. Attached is a photo of the one I'm planning to use.
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wler

Laser Diode Question

Post by wler » Tue Sep 07, 2010 1:14 pm

Well without stabilization you increase the gamble factor by a lot - having seen how sensitive things are, I never would try without. At any rate, you'd need in this case for sure a concurrent monitor such as an interferometer. Also take a sink as large as you can get (that one will do fine) even with temp stabilization, and shield the diode from air drafts as well es possible.

Dutchelm05

Laser Diode Question

Post by Dutchelm05 » Tue Sep 07, 2010 1:28 pm

I got most of my information from these guys.
http://laserpointerforums.com/
Might be cool to have some cross talk from the two groups.
Although Holographers are way cooler and we have better groupies :D :liar: :dance:

Joe Farina

Laser Diode Question

Post by Joe Farina » Tue Sep 07, 2010 1:53 pm

wler wrote:Well without stabilization you increase the gamble factor by a lot - having seen how sensitive things are, I never would try without.
Well, everyone can see the excellent DCG holograms by Dave and Thieu in the gallery section which were made without active stabilization.

Thieu

Laser Diode Question

Post by Thieu » Tue Sep 07, 2010 4:30 pm

Joe Farina wrote:
wler wrote:Well without stabilization you increase the gamble factor by a lot - having seen how sensitive things are, I never would try without.
Well, everyone can see the excellent DCG holograms by Dave and Thieu in the gallery section which were made without active stabilization.
I think you are both right here. Things are really sensitive, and without any means to see the mode structure it's a gamble. But with a spectrograph or a Michelson you pretty much take the gamble factor out. You absolutely need either one, otherwise 90% of your holograms will be breadsliced. I tested what I wrote about the DVD spectrograph myself and can report that indeed it works. One lens and a dvd is all you need. Fuzzy dot = bad, sharp dot = good. It's as simple as that.

Joe, your heatsink is huge! It will be more stable because of the higher thermal mass, but it will also take much longer to reach a steady state. I can't predict which of those will dominate in the final stability. It will be interesting to find out.
Dutchelm05 wrote:Although Holographers are way cooler and we have better groupies :D :liar: :dance:
Wow, we have groupies? :shock: They must be virtual and pseudoscopic then, cause I've never seen them! ;-)

Colin Kaminski

Laser Diode Question

Post by Colin Kaminski » Wed Sep 08, 2010 1:57 am

Joe Farina wrote:Thanks Colin. I was doing some searching for the selection of drill sizes for reamers, and it seems a bit complicated. Sometimes they factor in the machinability of the metal. For a .2220 inch reamer, I was thinking of using a .2031 drill (13/64).

Thanks Wler for the tips. That's true about the little collar at the juncture of the can and base, Ahmet pointed that out to me earlier. The top piece which presses down on the diode needs to clear that. Regarding the active temperature stabilization, I'm going to let the more knowledgeable people such as Ahmet and yourself worry about that :wink: To me, this is more of something that should be done in connection with ECDL. I want to see what's possible with passive cooling with a good-sized heat-sink. Attached is a photo of the one I'm planning to use.
13/64" sounds OK for aluminum. There are two factors that I think about when drilling for a reamer. The first is how soft is the metal. The second is how likely is a chip to gall the hole. Aluminum is fragile as it galls easily. The other thing to think about is how many holes are you thinking about. If you are wanting to ream 1000s of holes you have to be more precise than if you are only reaming 10.

Drill at a slow speed with lots of pressure. Ream at a higher speed and feed. The hole should look polished when you are done. I often ream in steps when confronted with a difficult problem.

Looking at your heat sink, it looks like the base is designed to spread a large heat source into a large area. The thin base will be slow to transfer heat from the diode. It just might not be a problem but if you end up in debug mode remember this.

PS I hope to never build another TEC diode project. If Wler had not bailed me out the project would have been lost.

Joe Farina

Laser Diode Question

Post by Joe Farina » Wed Sep 08, 2010 10:39 am

Thanks Colin.
Colin Kaminski wrote:I hope to never build another TEC diode project.
I had that same feeling in 1999, and it's with me to this day :wink:

Colin Kaminski

Laser Diode Question

Post by Colin Kaminski » Thu Sep 09, 2010 2:09 am

Joe Farina wrote:Thanks Colin.
Colin Kaminski wrote:I hope to never build another TEC diode project.
I had that same feeling in 1999, and it's with me to this day :wink:
If I were to undertake it again I would use a scanning Fabry-Perot interferometer. I would not try without one.

http://redlum.xohp.pagesperso-orange.fr/laser/SFPI.html

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