DTR's Laser Shop: Diodes-Drivers-Lenses-LEDs & More

[Lazeerer]

It was hard to measure it exactly.

Basically what i was trying to say is at the aperture (Right after the lens) the beam is:

5mm +/- .1mm
by
1mm to possible 1.2mm

If anyone has a method of measuring after the aperture with more accuracy i would love to hear it and i will give it a try to get better numbers.

The issue i was having is the beam is so bright that its hard to tell. (You have to measure at near to full power as with the FAC lens on the diode or frankly most multi mode diodes you can see that the higher currant you go up the more "Modes" open up making the beam larger) So to get Exact numbers the laser must be turned on full.

This is the lens i used:

http://www.thorlabs.com/thorProduct....umber=LA1213-A

I have on order the 100mm FL to see what difference it makes:
http://www.thorlabs.com/thorProduct....umber=LA1207-A

As well as the 1 inch dia version at 75mm:
http://www.thorlabs.com/thorProduct....umber=LA1257-A

In my experience with dealing with FAC diodes from 445nm,635nm and especially the 650nm ones - the 1/2 inch size lenses give the best results.

However i will be trying next to find a lens that is 50mm FL with a Dia size of 8-9mm. Iam thinking that if the beam uses more of the lens area up and not more of just the center that it will help shape the beam better. Weather it will change or not iam not sure but I Noticed a difference using a 1 inch diameter lens to a 1/2 inch dia. lens. The beam looked sharper and the "Dot" was smaller.

They where the exact same lens shape, same Focal length but there size in Dia was the only difference. The 1/2 inch was tighter.

Iam no expert in optics but love to try things out.


The beam is not that bad.

Me and another member about a year ago had a lab put some FAC Lenses "Micro Lens" On the Mitsubishi 638nm 300mW G71 diodes. The Results where Worse then what this diode does.

I still have the diode somewhere in my stock.

I Also Recently DIYed a 445nm diode and added a FAC lens to it. The lab wanted 400$ + a 2 month wait to get it done and i dint want to wait. (The Guy that did us the favor in the lab did it as a side job for the 635nm 300mW G71 diodes because the other member new him. However he no longer works at the lab so full price has to be paid now. which stinks)
http://laserpointerforums.com/f42/i-...diy-81547.html

Though not as pretty looking as the professional labs do it with all the right tools it still performs Perfect.

The Results where also very good.

I did not have a chance to do any extensive testing yet because i just got back from dealing with a close death in the family.

But i will try to keep up with everyone.

Thank You.

[planters]

Thanks for the quick reply.

A good method for estimating the cross section of bright beams at or very near the diode is to use two long FL collimating lenses, say 50mm and 100mm, and collimating the beam with each and then measuring the cross section at each lens. You can then regress this angle based on the distance of each lens from the diode to make the estimate.

Your results are exciting and I would like to see these run cold to allow high (higher) power and blue shift to 640-630nm for the improved brightness. The cost is high for destructive measurements and so this might need to be approached slowly.

[Lazeerer]

Excellent. I just purchased the perfect optical Assembly mount to test the way you explained it. Its setup now with Cylindrical lenses but i can change them out.

Picture of Newport Assembly:


I did a very quick Wavelength test using one of those cheap gratings that you buy for a star effect etc and i shined an LPC-826 660nm diode out it and did the same with this 5W 650 diode just to get a visual how far away it was (Not really measuring) and i can for sure say at ~20C i was at when i did this at ~3W output it was away from the dot of the 660nm LPC-826 laser saying that we are still near the 650nm range. It seemed to barely move going fro 1W-4.5W closer to 660nm.

So cooling it iam certain we can get it into a lower Wavelength. But how much iam not sure because i dont have any way of testing Wavelength due to not having a spectrometer which i plain on ordering later this summer.

Funny enough though i was just showing Jordan my new upgraded recent finished TEC assembly sealed encloser module i made. Its a Dual TEC setup which allows me to hold temp as low -25C to -35C with pretty much any diode i have tried.

Here are a few photos of it but ill have a detailed thread up on it soon with the full setup as this is just the housing part not the main big block heatsink:

I Also Made 3 different diode holders as in this picture in the front. One i made for 3.8mm diodes then 5.6mm and finally 9mm diodes. It has a screw on back that allows me to change diodes out rather then have it pressed in.




This is the outer TEC


Here is the inside setup. I put a resistor for a heater on the glass so that it does not get fogged up and it works Awesome. Second the glass i used your not going to believe. I went looking everywhere to find a glass that had little to no loose in power and had no luck . Most glass i came across coated or not was giving me around a 10mW 15mW loss at 200mW. I dint like that so i got the idea to test the glass that is on the DLP Chips in the C@sio projectors and what do you know there is almost no loss what so ever. Maybe 1-2mW at 200mW. It was a great find but very hard to get a piece large enough off.


Ill do some Temp Testing for power later tonight however as for knowing how much of a Shift to blue we are seeing, its not something iam able to test other then what i did above with the grating but that is far from accurate.

[planters]

The published wavelength shift of these AlGaAs diodes is approx. 0.2nm/C around RT and tapers to around 0.15nm/C at VERY LOW temps. You can test this if you trust the 660nm diode or have a lab HeNe and with your grating you note the linear distance on a far field fixed screen. It doesn't matter what the distance is just that as you cool you note the change in this distance compared to the starting point. This change can be compared with the known starting difference between the "650nm" diode and a known reference.

[Lazeerer]

Ok I think i got it.

I have a solid state "Dpss" 660nm laser. SO i will use that.

So what that your explaining me to do is Bring the laser up to 5W "Then" Bring the Temp to 25C for my starting point, "Compare" The Difference to the known 660nm Laser which should be 10nm "Then" Drop the Temp and take note at the final resting place of the 5W diode to as cold as i can get it "Final" Compare that Difference to the Original Difference of the 5W C-,mount diode at 25C to the 660nm SS laser.

So Ex. if it moved half the original distance that would be a 5nm Shift at XXX/C.

Correct.?

Thanks.

[planters]

Exactly!

I would try to get a few (like 3) points to check your self. This way if you make some silly error in a calculation the inconsistency will stand out. Something else I didn't mention is that I have tested a number of these red diodes over a wide temperature range and they all show an increase in EFFICIENCY of approx 1%/C down to at least 50C below ambient. So, I wouldn't be surprised that if you can get the diode to actually reach and hold -20C (this will take one mother of a TEC as in a couple of hundred W) and a good hot side heat sink then you might see 7W output at your previous current setting.

[Lazeerer]

OK will do. Thank You.

Iam using a dual stage like TEC setup,. Its nothing fancy but works very well. Jordan knows Ive been doing testing on diodes with lower temps for some time now.

A Single TEC setup is Not very good in my experience.

It puts to much stress on it. Even if its a 400W or etc...

In my experience using the larger TEC to bring the Block that the laser is sitting on with the secondary tec down to say -20C Then using a lower Voltage rated Tec for fine tuning allows you to get much lower Since now your block is starting in the negatives and its more stable for fine adjustments.

I use a 400W TEC for the Bottom and a 100W IIRC for the Fine turning. I have 2 extra 400W TEC's here that will all fit Within my setup But its not needed. Well I hope not.

These are the 400W TEC's i use for the bottom:
http://www.ebay.com/itm/161018373168...84.m1439.l2649

I dont like those other ones for sale on ebay that are around this size. Even though they have more junctions There stability is terrible. The link above those TEC's are beefy and have thick junctions which allow more stability just maybe not as fast at changing temp. "Which is kinda what i wanted"

I use this for the TEC right under the diode that sits touching the Cold block from the base 400W tec and case.:
http://www.ebay.com/itm/370448062829...84.m1439.l2649

^That is a very nice TEC.

I have been able to Break 2W with the Mitsubishi 500's 73 at 1.95A - 2A at around -25C.(Have not had the chance to upload this video yet)

With the 9mm 445nm diode Ive been able to just break 4W with hand selected diodes. "Binned out"

Iam not sure if you might of noticed but going much lower then around -25C does nothing for power. Well Very little gain. There reach a point where no matter how much "lower" you go it does nothing for gain in power.

However the WL though will continue to drop. I believe that is the only thing that is effective going bellow -25C. Or around there.

I dont have any complete picture of everything but the Module shown above sits on a 35LB Aluminum AMP Heatsink with Fins running across it. I can turn on fans too to help keep the 35LB heatsink from not warming up to much but even after 30 minute the heatsink is not even at 28C. It is very basic but alot of trial and error.

If 7W is reachable then that will be amazing.!

Ill setup tonight for it and hopefully have the video for you guys by the morning.

Got me Excited.

Thanks.

[planters]

Yes, I know what you mean and I am a little surprised that no one else has noticed this yet. We'll see when the headlines print in the morning. I too have reached high powers with the P73

http://www.photonlexicon.com/forums/...?highlight=low

http://www.photonlexicon.com/forums/...?highlight=low

As soon as my new video camera arrives (and I have figured it out), I will do a video of the LN2 operation of these diodes as the module is finished. This will probably be Friday.

I find that the increased efficiency of the reds does continue past -30C and it keeps going, even down to -180C, but at a significantly slower rate. Despite one contributor who mentioned that the V drop increases with lower temperature this only reduces the improvement in the overall electrical to optical efficiency by a small fraction.

I have switched to cryogens for these colder temps because of the diminishing returns as the delta increases with TECs. But, I agree with your methods and there is a cross over point where you need to go to two stage.

There is also a middle ground and I am thinking this is where this might go. The over-clockers use phase change cooling which is basically closed cycle refrigeration for cooling CPUs that can lower the temperature of the processor which generates 100-200W to well below 0 and these systems are turn key and pretty slick ( although a little pricy). A dual PBSed 650nm module operating @ 640nm beam shaped to produce a 5mmx 4mm beam and pumping out 14W into a 0.7x 1.2mrad beam would be...shocking!

[Stiffler]

This is better than porn!!!! lol

[DTR]

This is better than porn!!!! lol

That it is. I just wish I had mine here to play with right now.