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

[steve-o]

Steve-o

I was thinking you might F/U with the seller. His comments suggests he has worked with this assembly and would work with the buyer. The info might be available without the win or may not be available even with it. If it is a one off then it won't be worth engineering around it as no further systems could be built.

Agreed, a one-off wouldn't help us achieve our goal .
I sent him a question anyway asking for a spec-sheet/ manu p/n etc.
I probably won't fool w/ the auction tho after thinking about it because our target is >2W not 0.5-1W.

edit:

I remember at the 1st Selem, a couple of guys brought a 2W 532 CNI to the party. I remember it being very small for that amount of power. I also remember Steve R took out an old-school analog power meter and said something like " 2 watts and change " :]
I would just love to see how that thing is built. No liquid cooling, no fancy stuff .. It can be done.. the technology is here. Seems I remember them saying the pricetag on that thing back then was in excess of 20K // (I might be remembering wrong) ..

[badger1666]

Maybe are new chinese friend linda may be of some help here ,if she has not been scared off
She just may have the needed crystals, or there was another offering crystals recently
I have always fancied having a go at a green but did not know enough to do it
Looks like my chance has come along
Iam in

[mixedgas]

Steve R let his fingers do the walking. Type II KTP hits a wall at around 3 watts from the "green noise" problem. 2 watts to 5 watts is pretty much the same cavity optics moved around for rod lensing and waist size at the KTP. Above 5 watts, resort to Qswitching or expensive optics. Much above 5 watts your starting to look at Z folds. Above 4 watts, pump power gets expensive and intense.

Some place around 4-5 watts they start pumping from both ends with FAPS(tm) or similar in modern systems.

2x2 watts end pumped, combined looks good for the following reasons:
(or 2x3 watts side pumped)

Fiber pumping is a option, not a requirement.
Redundancy, if you loose half a system, your not down.
Simplicity
Ease of making a quality unit.
Off the shelf low cost optics, rod, and diodes.
Easy to make a stable resonantor.
Typically a L fold or linear cavity.
Type I ktp, because you need polarization for combining.
cheap pump diodes.
Make it on a mill, or a standard breadboard, not a CNC.
Consistant beam quality, no mode flopping/hopping.
Your own cooling scheme, ie water.
You can overdrive it for short periods, ie critical shows, with known side effects.

Quality Cavity optics for small DPSS live a long time. From my predecessors notes, one set here of 9 intracavity mirrors has made it 10 years. Cleaned every few weeks.
Rods last a long time if well mounted. So your consumables are KTP and diodes,

If you have a extra 2 grand to spend, extends to 561 nm easily enough.

Buffo, at some point you want to scrap Asian laser failures. Yeah, 1.5 grand is not much for 2 watts, but when you have that fail every N months thing cause your using it day, after day, after day, on the road /at a club, You'd like something built more to US made commercial standards without epoxied optics.

I don't want to hear a thing about reverting to H20. Even the small lasers here at work are on tiny chillers or Water2Air, and its dreamy. They are ultra stable, the coolers are cheap, and water does NOT flow in the lasers. The laser usually sets on a cooled block. The laser head is actually sealed, it bolts to the block. If the block gums up/corrodes, I replace plastic pipe nipples and clean out the cooling grooves with a brush or a milling machine. We're not talking hoses here, just 1/4" ID tygon or teflon tubling from Home Depot. The pumps are quiet, too. Cooling can be 20 feet away and quick disconnects for 1/4 inch are 6$ a side.

With a wet block under it, some of the 532's around here can run for 45 minutes after a cooling crash.

I love to work on the modern lab lasers with standard breadboards as the base. Easier to align, and I can work around a damaged or old optic in many cases. Cooling for solid state to say 8 watts flows through a 3/8" Al breadboard just fine.

Steve

[dsli_jon]

Diagram added to the Wiki, fyi.. http://www.photonlexicon.com/wiki/in...tle=DPSS_Green Thanks, Steve-o!

PS - Yes, indeed, 2+ W of green in a very-compact, TE-only cooled package is certainly achievable... ie: Laser Quantums 'Excel' -

..2.25 - 2.5W in the palm of your hand, and amazing beam-quality.. Too-bad these lil' pups seem to-never die, thus, there's never any 'used / for parts/not-working' on the resale market to snatch-up / dissect / learn, etc..

FWIW, here's an internal of the Excel, someone posted awhile-back..


..Anyhoo, following this great thread with keen-interest..
cheers..
j

[mixedgas]

That does not look hard. In fact the inner machining looks like it was done in a hurry on a hand mill. Only I deburr my work. Some of those burrs are shameful.

Its a baby L-fold.

How many amps do the pump diodes draw?

Steve

[dsli_jon]

..the inner maching looks like it was done in a hurry on a hand mill.

Yeah, not sure if this was a 'demo' / prototype unit, or what the deal was.. iirc, Sir Briggsy posted it (?) ..But I don't believe this was a production unit - ie: the 'open' one does not appear to have the one-piece-base 'mounting tabs', front / back, that the production-units all had.. I think this may have-been a proto or demo, etc.. dunno..

..Anyhoo, gives a peek into an interesting 2-pump scheme / layout.. smart (2 pumps.) and certainly easier to get the green-yield, vs driving 1x pump up the kazoo..
cheers..
j

[planters]

Thanks Jon,

That does give a reality check to this project and yes it doesn't look hard. I really like the double pump scheme with the PBS.

Steve,

I second closed loop water cooling. I started this way and didn't realize how much better everything worked until I tried to "simplify" with air-only cooling.

If you have a extra 2 grand to spend, extends to 561 nm easily enough.

Really?

[badger1666]

Would any of the guru's care to edit the pic of the open laser and name those optics and what they do,
I wana do some learning please

Thanks to who can do it
Ps what does folding do ? Z fold and l fold ?

[steve-o]

Wow those Excels are nice.
http://www.laserquantum.com/products/detail.cfm?id=6
Where are they made? I bet they ain't cheep .. (dare I ask ?)
The dual IR pumps thru the PBS is really a cool idea.
The internals pic is really nice . Thanks Jon !
I'm guessing the vanadate and KTP* are 2 separate xtals in this config? (or *YAG? )
Steve- Good info. Thx. Would you rather use ethylene glycol instead of water in cooling systems? I believe the thermal transfer properties may be better ..

[planters]

I believe the thermal transfer properties may be better ..

No they are worse. But the real impact comes from viscosity and the reduction in flow rate. The glycols and K formate are useful when exceeding the boiling point or freezing point of water. Good old water is a really good medium and at around 20 C it is hard to beat.