Improving Red (Maybe ALL) Beams

[drm916]

If the near field is substantially larger than 5mm square, as in "no way fits on the mirror" then as I said that's awful. However, if you're willing to go down the rabbit hole then YOU can build an uncooled, dual P73 diode module, combining with a PBS cube and also beam corrected...and then spatially filtered and this will definitely fit those mirrors and easily exceed 2W.

2w outta just 2 p73s that are uncooled? I would have thought it would have been less.

[resunltd]

Thanks for the reply Planters. That's about what I expected to hear. I just wanted to hear it from someone besides the voice in my head.

I suppose I should have built my own red. Had I seen your videos prior to the purchase, I probably would have gone the DIY route. I've sent a note off to Bridge at Laserwave to see if I have any options with them.

[Sandstorm]

I hope planters meant 4xP73... otherwise I drive my TECed P73s WAY too safe

resunltd, what actual module do you have? I doubt there are any that could not to fit on the bigger mirrors by their specs. If you see two distinct arrays of 6-8 diodes they're poorly PBSed and should not fit into aperture specs...

[planters]

1 watt for each P73 is definitely practical. Look @ DTR's shop evaluation of the diode. The round over begins at about 1.2-1.3A and the peak power occurs at 1.1-1.2A. I have found the same values and about 10% more power when these diodes are well heat sinked. The power output is very sensitive to temperature and so without active cooling, but tight coupling to the heavy base plate the diode remains near ambient. Near room temperature, the power output of these diodes changes at approximately 1%/degree C.

A TECed quad generating anything less than 4-5W seems a waste to me.

resulntd,
I strongly suspect that if you make the measurements I suggested and video or at least image the measurements and they are out of advertized spec then you have some options. It would be interesting if you posted these images here as well. Furthermore, whether you sell, fix or exchange this module, you might want to go the DIY route on just the red in any case. You will end up with a very good beam and longer have to get your lasers as a black box. You will know how they work, be able to repair and upgrade at your discretion and it is a lot of fun.

[drm916]

I hope planters meant 4xP73... otherwise I drive my TECed P73s WAY too safe

resunltd, what actual module do you have? I doubt there are any that could not to fit on the bigger mirrors by their specs. If you see two distinct arrays of 6-8 diodes they're poorly PBSed and should not fit into aperture specs...

I am pretty sure you can drive them up to around 900mw-ish uncooled each.

I need to build myself a few. I have just never really been able to get my hands around what telescopes to use. I got Daves mitsu optics kit. So I am good there. Its just the special filtering optics that confuse me.

[resunltd]

Sandstorm, I have the LWRL638.

I measured the beam size right at the aperture to be about 6 x 6 mm. Measured at 5 meters its about 4 x 10mm with some "wings". The dark band between the two beams is about 0.2mm at the aperture. Measurements of direct output with no other optics.

Even with mirrors large enough to capture the entire beam, it's size dwarfs the 460nm and 520nm projected beams.

[planters]

I checked the Laserwave website and none of their lasers has that big a beam at aperture. It is difficult to actually pull up the spec sheet for the model you listed. Can you provide images of the beam in the near and far field?

[Sandstorm]

^^. I checked their website yesterday and couldn't find a model with beam width too big for galvos at the aperture. so it's out of specs. that leaves you some options, I believe you could get the images of NF and FF beam profile and discuss them with the seller, if you're thinking about sending it back for a replacement... it would be way easier to repair it on your own than sending modules back (in most cases with china, shipping cost too much), but usually chinese models are soaked with epoxy and there aren't many options what you can do inside by yourself

[resunltd]

Even with mirrors large enough to capture the entire beam, it's size dwarfs the 460nm and 520nm projected beams.

So what Laserwave is proposing is that I "upgrade" to their 637nm single mode laser with a claimed 4x4mm beam size. This is $2500 FOB China. No idea what they will give me for returning the 638 I have now. They keep telling me to replace my 506's with scanners with larger mirrors. They are not grasping the fact or ignoring the fact that the red beam is too large for the combining regardless.

[m0f]

Are you sure your 506's have 5mm aperture mirrors on them ? (Actual mirrors should be around 7mm x 12mm to fit a 5mm beam size) It's not uncommon for beam corrected 638nm to be quite a bit larger than the green and somewhat larger than the blue, but for beam show purposes they still combine quite well as long as the divergences are close, and on average they seem to just barely fit the 7mm x 12mm mirrors or maybe just the slightest amount leaking over the edges.

Ways to improve this are to telescope the green in order to expand the beam to the size of the red, leaving slightly out of focus to the same divergence as the red. Or if the divergence of the red is low enough you can telescope the red to match the green instead.

Another way would be to 1:1 telescope the red and then pinhole it to a smaller size, but would be wasting some power in the process.

Edit: Just wanted to add, that it can be quite surprising just how much of a difference there can be in the near field, and still combine well for beam show type purposes. Matching divergence is more important than near field sizes. In a perfect world all beams would match in size, but it's one of the compromises of 638nm. It's great for beam shows, good cheap red power with reasonably low divergence, but the near field size is not perfect by any means. But in comparing to past options of lower cost red (635,650), it's still a huge improvement.