Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

[logsquared]

Yes, I've seen that, but would not moving the diode around have the same effect?

Yes.... but, after the diode is centered if the beam height is off then you need to shim the whole mount to get them to line up. Of course if the tolerances of the mount are bad then your screwed either way.

The truth is aligning more than two diodes is a major PITA when going through one telescope. I built a 6X for someone and ended up telescoping each diode first then knifing them, then PBSing them. More optics. But way easier and probably more stable in the long run.

[planters]

I agree with Dave's simpler approach, but the precision of X/Y screws will probably lead to a little better final performance. What about a small reusable jig built to fit/lock over the top of Dave's diode mount body that extends back over the sides of the retaining plate? Leave a little clearance with this plate and adjust with set screws. To deal with the inability to access the bottom adjustment, just start too high and approach the center from the top down.

[CDBEAM]

OK…Let’s make some assumptions here…

1) The Emitter output axis is completely perpendicular with the back of the LD Can face.
2) The LD Can face back is completely parallel to the receiving face of the optical plane on the collimation lens.
3) The LD Can face back is completely parallel to the main mount back face.
4) The Collimation lens can be adjusted/centralized perfectly to the LD output
5) We live in a perfect world…haha

So…now in both cases…IMHO…if we move/adjust either the diode or the collimation lens…the resultant beam propagation will shift….to a similar degree. If the LD is set at 19mm off the optical main bed…and the collimation lens is centered…OR…the collimation lens is set at 19mm off the optical bed…and the LD is centered…the same outcome results. …a beam that is perpendicular on all axis of rotation to the main mount back face. I cannot agree that either the Diode X-Y adjustment or Collimation Lens X-Y adjustment will deliver a less demanding multi diode beam combining exercise….they will both be an equal PITA.

I really do not care of we end up with an adjustable LD or an adjustable lens…but I remain convinced that X-Y adjustability with screw conveyance is the direction I will follow. If there are other members with knowledge of optical alignment…please…chime in….and I would call into the fray…” Count Von Mount “ !!! HAHA BEAM

[kiyoukan]

I'll chime in on a few points.

Brass Vs Aluminum. Its not so much the thermal transfer but the mechanical properties that make the biggest difference. Aluminum is like a marshmallow. For flat on flat its ok. Anything with high stress like a screw pushing against it or flexure in the metal brass is the clear winner.

Moving lens or moving diode? I think moving diode is the best solution. This should prove true especially for multiple diode combiners. To date I have built a lot of modules with these diodes. The biggest PITA is getting things overlapped or aligned with the high mag. telescopes. I believe that the moving lens is going to change the beam height or exit angle more than the moving diode. The lens is held at the same height at all times with the moving diode mount. So in theory after the diode is centered the beams should all be the same height and exit angle from one mount to the next. With the moving lens this will not be the case.

I certainly see the merits of the moving lens. However, I think it will cause more frustration in alignment than its worth.

my .02$

From what the article that was posted i got 2 main points out of it

Aluminum: Aluminum is a lightweight material, resistant to cold flow or creep, with good stiffness-to-weight ratio. It has a relatively high coefficient of thermal expansion, but it also has a high thermal conductivity, making it a good choice in applications where there will be thermal gradients or where rapid acclimatization to temperature changes is required. Aluminum is fast machining, cost effective, and widely used in component structures.

Brass: Brass is a heavy material, denser than steel, fast machining, but with a less desirable stiffness-to-weight ratio than either aluminum or steel. The thermal expansion of brass is similar to that of aluminum, but its thermal conductivity is nearly a factor of two worse.

So for a flex mount aluminum and brass would work fine, Chad proved that aluminum works with his red flex mounts.
But for heatsinks brass would shorten the life of a diode using passive cooling, for active TE cooled it would not matter. But when using passive cooling into the base plate you need the fasted transfer of cooling. This is the one reason i think the brass mounts for diode's is a non desirable idea.
I kinda like the best idea of using a copper diode holding core with an aluminum heatsink into the base plate.

[planters]

Diode/lens centration is much more demanding and important than beam pointing which is easy to compensate for with knife edge mirrors over the small angles applicable here. Find the easiest and most effective
method and deal with the beam in a separate step.

Just did a back of the envelope calculation of thermal transfer across Dave's mount and with the brass I got 3W/C. If that's even close, then with 6W of input and no laser output a delta of 2c is not very significant and the material choice should be based on availability and ease of manufacture.

I think working through these issues is interesting and having several competing approaches in an operational form is valuable. I'm just thinking about the bottleneck that the Flexmod P3 caused when it was essentially the only game in town and it was unavailable for such a long time.

[steve-o]

We're gonna break 1000 posts on this thread. I wonder if that's a record here ..
I've been working in electronics all my life and have never seen brass used as a heat transfer mechanism. It's good for door-knobs. Argon lasers use copper heatsinks to extract the extreme amount of heat they produce. Semiconductor heatsinks are aluminum. Engineers since the 1950s have known this.. We need to learn from the pros, imho.

[logsquared]

From what the article that was posted i got 2 main points out of it


So for a flex mount aluminum and brass would work fine, Chad proved that aluminum works with his red flex mounts.
But for heatsinks brass would shorten the life of a diode using passive cooling, for active TE cooled it would not matter. But when using passive cooling into the base plate you need the fasted transfer of cooling. This is the one reason i think the brass mounts for diode's is a non desirable idea.
I kinda like the best idea of using a copper diode holding core with an aluminum heatsink into the base plate.

I probably missed a few things as I haven't read all the latest posts.

I don't think using Al for a diode mount will cause any problems because everything is "flat on flat". In fact Andy makes his with Al and they must work or he wouldn't use Al. But as Planters pointed out, and the real world test I did somewhere back in this post showed, the thermal conductivity of brass is adequate for a diode mount.

I haven't used Chad's mounts so I can't speak to them. However, I have made a lot of different flex mounts from Al. I could not get the stability I needed. Making the exact same mount with the same tools on the same machines with the same hardware from brass solved the problems. If you don't believe me that's fine. But... take a look at any high-end, high stability aluminum kinematic x/y mount and you will see they use a hardened seat (hardened steel, sapphire, etc) of some kind where the adjusters meet the body. This is because Al's mechanical properties make it perform poorly under stress (also for reduction of friction but that's not a concern for us).

I am just trying to help from experience I have gained building lots of different mounts over the past few years. You can make your mounts from swiss cheese if you want (although I wouldn't recommend it)

[steve-o]

Flex-mounts and diode mounts--what are we talking here? Apples and oranges?? I'm talking about the thermal conductivity of metals for a laser diode mount which the LD produces heat. For optics such as mirrors and dichros I'm sure flex-mounts made from brass is fine. Probably the best choice.. dunno. not a metalerologist .. dammit Jim ..

[Stoney3K]

Flex-mounts and diode mounts--what are we talking here? Apples and oranges?? I'm talking about the thermal conductivity of metals for a laser diode mount which the LD produces heat. For optics such as mirrors and dichros I'm sure flex-mounts made from brass is fine. Probably the best choice.. dunno. not a metalerologist .. dammit Jim ..

What's the motivation for using brass anyway? The way I see it, Aluminium has a lot better properties across the board, and is just as easy to machine with common house-hold tools.

The only reason I can think of is brass being cheaper, but that would only make a very marginal difference.

[steve-o]

Brass is cheaper? I bought a solid brass plate for a door and it was more expensive than the aluminum one.. I guess it might depend where you live.. Well, anyway back on topic (sort-of) .. I guess the people who like the moving diode mount will build those and the ones who like the other will .. etc ..etc .. same with brass/alum .. I might just try to find a mount that's centered where I don't have to move anything around
Anyway.. now that we've got the LD figured out and the optics, what now..? Back over to the GB thread to see what's going on there i guess ..
damn, this waiting around is getting old.. I'm ready to do something .. gotta build ..gotta build .. gotta build ..