trying to repair two Quantum Entertainer

Hi guys,

I got two used Quantum Entertainer Lasers and now I am trying to repair them, because the output is less then 50mW :(

I already checked the pumping Diode, it should be okay and puts out more than 3W.
I also tried to readjust the cavity and the Temperatures for Diode and Yag, now I get 50mW 532nm.
The crystalsand lenses look very well.
What else could I do?
The Yag Temperature was set to 70°C, I reduced it a bit and the power increased, but the lowest Temperature I can set is 65°C.
The Diode Tec Temperature was set to 27°C... I increased it to 37°C

Best regards
Mathias

If you cant verify the pump wavelengths, that is also a issue. Also 3 watts is not much pump. What was the rated ouput power in green?

Steve

I already looked for a maximum when I adjusted the Diode tec.. But I do not known how high i can turn the diode temp? I think it was rated for 600mW

When these things fail, it is almost always, alignment, KTP, or pump diode.

Pump diodes do shift in wavelength with age. Especially ones from a few years ago with impurity migration issues. That is why you need to check the wavelength.

Can we have pics of the cavity?

Good stuff is 10% conversion. Really great stuff is 25% conversion.

Steve

Hi Mat -

Quote:

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Originally Posted by mixedgas

When these things fail, it is almost always, alignment, KTP, or pump diode.

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...aaand when the cavity get's exposed to room-air, :p since these puppies were always hermetically-sealed in a class-super-duper-xyz clean-room by the Mfg..

Mat - couple questions - a) which 'model' of the entertainer did you get - the 'older' Black one - ie:

Attachment 35484..or the 'newer' gold-ano'd ones? ie: Attachment 35485 ...I ask, because the older black-ones, did have a 'seal-integrity issue', around the collimating-lens 'nosecone', and were (apparently) prone to exterior-air 'seepage', and thus = xtal-surface contamination = low-power.. (...and it don't take much to kill the efficiency, when your 'top-end' is only 6-700mW of Green.. :)

b) were these 'opened' by-you, or, did they arrive doing low-power? If-so, you might see if the seller is willing to 'fess-up' / give some sort of 'concession', as an opened-cavity contamination-scenario seems more likely than both of these having 'diode or temp-reg' issues.. then again, I suppose if they both have umpteen-thousand hours on them.. :p

lemme know.. :cool:

PS -

Quote:

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Originally Posted by mixedgas

Can we have pics of the cavity?

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..I think I know 'what you were thinking'... Nice.. :) but, just fyi, these were significantly different / simpler, internally, than the 2W Excels, so.. not sure the beam-waists / optical-spacing / sizes will be of much use, at-least in 'emulating' the 2W Excel-layout scheme.. For that, like I said, if someone could 'afford' to buy that '532 Gem' FS on eBay, for 'sacrificial R&D purposes', that would be a gold-mine of real-world optics data, etc, relative to the 2W quest, over yonder.. .02¢ :)

cheers...
j

Hi,
thank you for your help.
So I would need a spectrometer to measure the wavelegnth..But would it be possible to find the correct wavelength by turning the temp higher.. or lower by shifting wavelenght. What would be the maximum recommended Temperature for the Diode?
first i opened it in a clean room (medical clean room), but the power was already down. So the second time I opened it at home. No changes in output power.
The laser has many working hours on the internal counter... I got them nearly for free, but propably I got more power out of them... the beam is so great :()

I got the second type.. but my ones are not goldern.


Attachment 35490

Attachment 35491

You really need to check the spectrum, power, and mode of the diode to rule out the KTP.

For ND:YAG, its 808 +/- 1 nm. For Vandate, the spectrum can be wider. My guess is you have YAG.

Thanks for the pics.

Steve

Hi Steve,

so I need someone with a spectrometer to find out the wavelength and if it is single or multimode.
Could be difficult to find somebody with a spectrometer at home
I already measured the power.. 3120mW
It is a pitty.. I got NO informations from Quantum.. the only thing they told me, was"well buy a new one" :(

You are welcome :)

Another queston:

What would be the ideal temperature for a YAG crystal? Is 70°C not much to high?

hi Mat -

Quote:

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Originally Posted by matratzki

..first i opened it in a clean room (medical clean room), but the power was already down. ...The laser has many working hours on the internal counter...

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Mk, if the power was already-down, yes, that *may* suggest diode-issues, but are you sure the previous-owner did *not* open it?.. Again, contamination was a 'Mfg.-admitted-killer' for these pups.. and, once 'compromised', not-surprized you would not see much 'worsening', by opening it at your house... just 'food for thought'... However...

..What is your definition of "many working hours", on the diodes, like 5000+ ? 10K? Short of that, I'd suspect something else.. 3W certainly sounds-like low-output, although I admit I don't recall what the 'proper-spec' was for these pups.. Wondering if the previous-owners may-have touched diode-pins in the DB-connector, when connecting / disconnecting, etc, or, some other diode-damaging actions.. pretty-sure these units did *not* have any sort of 'lasorb'-type devices, at the time.. I'm guessing by the 'newer alloy-substrate' your models are 'Gen 3', ~2008 > beyond...

Quote:

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Originally Posted by mixedgas

For Vandate, the spectrum can be wider. My guess is you have YAG.

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Quite-certain they used YVO4 vs YAG and LBO vs KTP.. a certain 'gringo' I know has a manual in his NY-archives.. :p ..though, admittedly, that was for units mfg.-before 2005, so.. I suppose they may have 'changed-games', but.. not sure why they would opt to go YAG / KTP for these lil' units..

.02 :)
cheers..
j

Hi,

I am quite sure, that both lasers were not opened before, the seal was okay and not broken.
I did not know that the crystal coating is so sensitiv. so propably it was a bad idea to open it at home whit all the dust an humidity in the air :(...

I do not have the exact number in my mind, but I think there are more than 10000 hours on it (dpss driver)... I also measured the current, it would fit to a 3W Diode.
No there are no Lasorbs inside.. but with those connectors, used to connect head and driver, your are not able to touch the bare pins.
Propably I can measure the wavelenght at my university..

They used two different crystals in both lasers.. the KTP or LBO is the same only one YAG is longer than the other.. and there is a arrow on it, which is pointing to the pumpdiode in one laser and to the ktp in the other one ... a bit confusing

cheers
Mat

Hey Mat -

Quote:

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Originally Posted by matratzki

..both lasers were not opened before, the seal was okay and not broken.....but with those connectors, used to connect head and driver, your are not able to touch the bare pins.

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Unless you connect the head-side before you connect the PSU-side of the two-ended DB-15, iirc.. :p
Attachment 35502 ...that would leave the PSU_side with 'touchable pins'.. Not saying you did, but perhaps the previous owner may possibly-have.. just a thought..

However..

Quote:

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Originally Posted by matratzki

.I think there where more than 10000 hours on it (dpss driver)...

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..that's a fair-amount of mileage on the diodes, I suppose they might be 'tired', but even at 10% SHG, you should be getting more than 50mW.. perhaps this is a 'combination' of contamination / temp-reg, and tired-pumps..

Quote:

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Originally Posted by matratzki

They used two different crystals in both lasers.. the KTP or LBO is the same only one YAG is longer than the other.. and there is a arrow on it, which is showing to the pumpdiode in one laser and to the ktp in the other one ... a bit confusing

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Can you take a pic of the 'RIGHT' duh.. (diode-side) mount, there, looking 'into' it, more? Looks like, starting from the 'rear', you've got a TEC for the pump, the pump-plate, and an XY-adjustable plate, with ?? in-it.. Also, wondering if that's a Vanadate / LBO 'combo-sandwich' on the TEC in the center (?) Need moar pix.. :)

cheers..
j

Hi,
the order beginning from the right : TEC, Diode, back cavity mirror (adjustable),Crystal, LBO or KTP, lense, IR Filter
both Quantums are at home in my "laboratory" ;).. at the weekend I can take mooaar pictures ^^

Cheers
Mat

Hey Mat -

Quote:

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Originally Posted by matratzki

.. at the weekend I can take mooaar pictures..

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Cool.. I'm betting ya've got a Vanadate / KTP 'sandwich', then.. I was thinking LBO, cause it's rather 'long' for a KTP, and I have emails stating they-use LBO vs KTP, but.. I guess, re-reading them, they might have been talking about the Elites.. so, I suppose the Entertainers could-be YVO4 + KTP, but.. in any-case, I do-also think 70˚C sounds high.. I know the 'trip-out' thermals for the case was only 45˚C, but not sure how 'far away' they have the thermistor for that, so... ??? That's where the 'P'Fesser' comes-in.. (mixedgas / Steve..) :p

..look-forward to more pix..
cheers..
j

My best guess.

YAG/VANDATE, a little above specified operating room temp, ie 5-10 'C to actually cooled. KTP, very Hot. LBO very warm.

They can, of course, order the crystals for other cooling/heating schemes. The classic one is what I describe above.

If you have two heads and two drivers you can backcheck this.

I assume you have the factory cables and the thermisters are thus hooked up?



Steve

Quote:

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Originally Posted by mixedgas

I assume you have the factory cables and the thermisters are thus hooked up?

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Very-good point.. We still have one of the OEM DB-15s for these kickin around in NY, but I don't remember if they were 'cross-over' / custom-wired, or, just 'DB-15, straight'.. most-likely, were, but.. certainly worth a double-check, Mat... :cool:

j

Hi,
so I checked both heads and drivers.. all thermistors are hooked up and the the temperature changes when I turn the temperature trimmer.
Yesterday I adjusted the second head and this one has a actual outputpower of 70mW and a better beam than before (after adjusting the cavity). At both heads the Temp of the laser crystal is set to 74°C..
I also cecked the crystals of one laser with a microskop... all coatings look perfect.
So here are more pictures..

Mathias

Attachment 35580
Attachment 35581
Attachment 35582
Attachment 35583
Attachment 35584
Attachment 35585
Attachment 35586

I can't believe how crappy all of the machining is in those things.

Chad

Kinda rough.. but neat from a hobbyist's perspective :p How much power are those supposed to be putting out ?

They should put out 600mW ;/

Hmm, maybe tune into the big green thread over yonder to learn how to rebuild them .. or, maybe even hot-rod them a little ;] (there's some big brains over there a-working) you can see the smoke comin' out of that thread .. ~ whew .. ~

Quote:

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Originally Posted by chad

I can't believe how crappy all of the machining is in those things.

Chad

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Wait till you see the $9000 one in the other thread. They look like a million bucks on the outside. But inside, ahhh beginners level manual Bridgeport...

Check and see if the pump diodes have changed wavelength from metal migration.

Then disable a diode TEC for just a few seconds. Make sure you re-enable it quickly. Does power go up or down?

Got access to Liquid Nitrogen? You just need a tiny bit of cold, dry, N2 vapor streaming under the diode, over the TEC. Does power go up or down?
Dont crack the TECs, they do not like temperature shock.

You want anything cold away from the optics, least it cause condensation. I would not use component cooler spray for this trial, unless it is on the aluminum case when sealed.


Steve

I work with LN2 almost everyday . Unfortunately, it's in fairly large chambers and not confinable to a small area.. If I can help, let me know ..

Quote:

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Originally Posted by chad

I can't believe how crappy all of the machining is in those things.

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Yeah, I gotta say, I'm flabbergasted.. I mean, based-on how these things have always performed / are tough-as-nails.. but these look like they gave a fork and butterknife to a 6 yr old! :rolleyes: I really-do wonder if these two might-be 'early-gen' or even in-house 'engineering-samples'.. ..curious Mat - what are the 'serial #s? Might tell us something..

..The 'bottom line' is those things do-produce an amazing beam, like 0.25 mRad, and just last and last and last, just like the Excels and Elites, at least, in our experience...*still* have one of these lil' pups down in El Sal, still doing ~800mw, (as-of last Dec, granted..) but the head was sold in ~2003 (!) so.. And one in Spain (iirc..) still going-strong, afaik.. And a few-Clients with the 2.5W Excels, on-Tours, and they testify they're just (still) bulletproof.. And even the little Entertainers always did really-good power for us..

Attachment 35597 (...and, yes, this was 'IR-filtered'..) :p

I guess it all gives 'encouragement' to the '2 Watt project-thread', looking at the materials / fab, in-here.. don't see much of anything 'not-doable', and much-better, given the right optics / specs / temps, etc..

Mat - did you verify that the TECs are actually *working*? Does-appear like the one, at-least, looks 'kinda baked', ya? http://www.photonlexicon.com/forums/...0&d=1352723588 Just a thought..

Another silly-question - have you actually tried to 'tune' the back-plate to peak the sweet-spot? Yeah, it ought-to be 'perma-locked', but.. what have you got to lose, besides 50-70mW? :p I-do also think the optical-cleanliness has a lot to do-with these things outputting to-max (or not..).. Again, the only time we've seen 'drops' in power like this, (over about 6 units..) was with the old black-head's seal-integrity-issues.. Nothing like this with the 'gold' heads / your-Gen... (???)

.02
j

Hi, so next week my exams are over and I get some time again to spend on my quantum baby.
So now I am going to buy two new Pumpdiodes to test them with the Laser.
Does anybody of you know if a Pumpdiode of a Quantum entertainer head uses a FAC lense???