The Big Green Thread (I'm gonna regret posting this in the morning)

[steve-o]

Hmm. Wouldn't have figured that. Thought there would be some superior chemical for thermal transfer and low viscosity invented out there somewhere ..
Anyway, here's a 10 watter that fits in the palm o' ur hand ..

http://acuphase.com/?page_id=39

Here's my take on the L fold path.. probably dead wrong.. I'm unfamiliar with z and L folds, yes, gurus, please enlighten us

[mixedgas]

Buffo, I would NOT suggest submerging a standard cavity design in Flourinert. That simply was for Steve-o to try with his MCA assembly. Yes, you need to cool the fluid, either way. For a one off bonded assembly about to be overdriven, he has two choices. Butt it up against a thin sapphire or diamond plate for heatsinking, or submerge it. No one has tried either at home yet. The trick is coupling the MCA to the disk without crushing it, yet allowing for expansion.
The idea is the small/moderately thin disk conducts the heat to a copper slab.

Sapphire is cheap and has great thermal conductivity as a thin disk. Commercial units can and do go the sapphire/copper route. Diamond is coming on-line for similar purposes. Small diamond disks are not that expensive today.

Other units use undoped YVO4 diffusion bonded to the doped Nd:yVO4 for similar heat and damage reduction purposes. Adding the undoped YV04 adds some ways to get other wavelengths. This is, however, out of the scope of this post.

For some reason linux on the download machine hosed the DVD of pics/pdfs I was going to add to this thread.
I'm at home and can't read the DVD.

Side pumped got abandoned for symmetry reasons in small lasers.

What is not so obvious about the design Jon posted pics of, is the diameter and lengths of the pump waists from the diodes and the diameter and lenth of the beam waist in the KTP or LBO in the photo. That is what is critical, picking the matching to the rods and crystals to the cavity. I dont want a fat, high divergence beam.

From a European source that makes and stocks crystals, with a 1 day availability:

A stock 55 mm length, small diameter Nd:YAG rod is about 400$ AR coated, from the source the Hungarians use. That is the cost of good side pumping, going to thin rod.

Good European hydrothermal KTP is 95 to 140$ coated for a small length, and goes up about 22$ a millimeter. Going to LBO is twice that price. BBO IS 3X more expensive. The longer the KTP is, the better the 1064-->532 conversion, to a point.

If you want the square Nd:YAG or YVO4 its cheaper, but not perhaps better, from the Asians.


Steve

[LaNeK779]

I do remember bridge from laserwave posting very recently that he had a number of ktp crystals for sale really cheap (like 15usd or so for a crystal or 3x3x5mm)
these were crystals they used for their green dpss, but now they use lbo, so the ktp is surplus. So, this could be an easy source of ktp with the right coatings.

I do remember about a little software suite called SNLO that provided some help with cavity calculations, if one was to know what he was doing, but i can't remember where i got the link from... (I wouldn't be surprised if i had to thank a PL member for this though)

[steve-o]

Well, I can't find a DPM or MCA that outputs more than a couple hundred mw anyway, so I'm presuming this won't be the approach for the 2W design.

oops- posting at the same time as you Lanek .. :]

[mixedgas]

At the power levels we're suggesting, MCAs are not capable of handling the power.

Only hydrothermal KTP need apply, or LBO.

As far as SNLO, I have it, but it only models the cut angles. The manufacturer determines those, we just buy them.

Steve

[steve-o]

Why is this so friggin complicated. Certain overseas Asian nations can pump out 2W green dpss lasers all day long if they wanted .. aargh ..

[dsli_jon]

Heya Sir -

Wow those Excels are nice. Where are they made? I bet they ain't cheep .....I'm guessing the vanadate and KTP* are 2 separate xtals in this config? (or *YAG? ).

Yes, they are pretty-bullet proof.. and, actually, kinda 'sad', cuz, in our experience, once you sell them, you almost never 'hear-back' from the Client (..last ones-sold were in ~2005, iirc, and went to an install in Mexico.. have not *yet* been to Mexico for any 'complaints' / issues.. (dangit! jk, but they are make in Cheshire, UK, and the 2.5W models are, uh, 'north of $10K', so, ..yeah, not 'cheap'... But, with LQs, you 'spend the $$, once'...

RE: the xtals, no, there's only one LBO and one Vanadate - that's what they use, not KTP, for the SHG to green.. better 'yield' / stability, at these lower-powers, iirc..

RE: your 'diagram', I think you're close, but not-quite.. I'm a bit 'confused' by what appears to be the LBO-xtal on a 'heater' or TEC, there, because it's at such a 'wild-angle' relative to the (apparent) resonator-mirs.. I know that, at least with the Laserscope KTPs, the xtal is-often at-such a 'radical angle' relative to the path of the IR, but.. not-sure if these little pups follow-suit..

Too-bad we don't have any 'recent lotto-winners, with R&D cash to burn' - http://www.ebay.com/itm/Laser-quantu...-/110765643149 and http://www.ebay.com/itm/Laser-Quantu...-/360446227317 - Pretty-sure both of those heads are 'layed-out' very-similarly to the Excel, internally.. certainly, the 'Torus' will have more 'bells n whistles', inside, to keep it mode-locked, etc, for it's Lab-grade purposes.. But optical-path / optics-used, and size, etc, are all gonna be very-similar, if-not identical, to an Excel.... Anybody got an 'extra' $1800. floatin-around for some R+D??? - yeah, I know - 'pipe dream', right?

Anyhoo, keep at it, I'm sure you guys will nail somethin..
j

[Linda]

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[dsli_jon]

*facepalm* oi vey...

[planters]

Something I can't figure out in the Jon pics. The two IR diodes seem to be passing through very different optics prior to the PBS. I could understand a wave plate, but the top diode is passing through a highly curved lens while the beam from the right is not.

What is not so obvious about the design Jon posted pics of, is the diameter and lengths of the pump waists from the diodes and the diameter and lenth of the beam waist in the KTP or LBO in the photo. That is what is critical, picking the matching to the rods and crystals to the cavity. I dont want a fat, high divergence beam.

You are spot on here. The drivers, cooling,mounting etc are relatively easy, but these are the important numbers along with the OC R%. We need a design that works .It doesn't matter if it isn't quite right, but if it gives the relative proportions for these #s then a test laser starting from this point will likely succeed with fewer iterations.

A stock 55 mm length, small diameter Nd:YAG rod is about 400$ AR coated, from the source the Hungarians use. That is the cost of good side pumping, going to thin rod.

Question. That SEEMS like a long rod. You think that is ballpark for 2W? You say side pumping here, but you suggest above there are maybe symmetry reasons to stay away from side pumping?
Another question. Do you know a target for doping % for a typical diode pumped 2W