Nd:YVO4 markings

[shrad]

Hi All,

I'm currently replacing a burnt Nd:YVO4 in a 1W viasho head, but coatings seem less colored than the original... or maybe the decreasing light (end of the day here) doesn't reflect as to see a different coating color in each face

The new crystal obtained from junktronix has a marking, but it's not an arrow, more of a V, and I was wondering if I could take it as the top of the arrow for orientation...

Could someone confirm this?

EDIT:

When shining a white LED at the crystals, one of junktronics ones has exactly the same reflections/transmissions (purple at the pump end, green at the output end) but one has exactly the inverse colours... one should be AR/AR according to junktronix, and I'm wondering why the inverse colors? it's hard to tell...

[dsli_jon]

...but it's not an arrow, more of a V, and I was wondering if I could take it as the top of the arrow for orientation...

Yes, commonly seen on lens-edges / optics where there's no 'room for a stem'... or people were just lazy ..Sometimes you'll see triangles, too.. *Should-be* arrow / V-tip is pointing towards from the pump-side, away-from your SHG x-tal or output-end... AR-coatings can help decipher this.. however..

..one should be AR/AR according to junktronix, and I'm wondering why the inverse colors?

..'Inverse', relative to the 'direction of the V', Is that what you mean? Perhaps it was mis-marked, if it's a 're-firb' - I have seen that before - Re-firbs get ground / re-polished / re-coated on a damaged-end(s), and when they're sent out, they 'goof' the orientation-mark.. putting the x-tal in-place, on *low-power* / seeing the performance, will usually be the 'tell-tale', but... I'd think Kevin should be able to help you sort that... He's usually quite helpful / responsive in that-regard...

Hope that helps...
j

[shrad]

I had a conversation with him where he told me he'd like me to try two of his crystals out, and he know nothing about them except one should be coated AR/HR and the other AR/AR

The strange thing is the colors are inverted whatever the crystal direction... I had no luck with a direct replacement of the one which had exactly the same reflects as the burnt one, so I'm currently trying to rebuild the head with shims under the YVO4 to raise it above the burnt mark...

I'm now trying to find some 64bit drivers for my old webcam as I fear for my eyes ^^

[Bbe]

You can find HT808nm (cold) side by using a green pointer

[shrad]

OK this is nice to know, I'll give this a try

The old crystal died as the coating was too damaged to withstand the power, it started burning again at 2W of pump

The good thing is I traced the current vs power curve and the pump seems quite healthy with a curve from 0.9A for 10mW to 3.7W at 4.7A, which is nice to know... everything is aligned now but the YVO4 so a direct replacement before tweaking should be OK

[Bbe]

The old crystal died as the coating was too damaged to withstand the power

Coating were damaged gradually or instantly? I mean, the laser broke quickly or output power was decreased bit by bit?

[shrad]

Gradually, with overheating and yellow light emission around the pump penetration... when I first opened it for autopsy it delivered 60mW and there was a yellow cone inside the YVO4... at each alignment tryout, the power gradually decreased over several minutes

[dsli_jon]

hey shrad -

...it started burning again at 2W of pump...

kvestion: Did you clean the 'burnt-end', before trying to re-position / re-use? When an end gets burnt, there will almost-always be face-contamination from the coating getting ablated, and if you just continue kicking the crap out of it with IR while still dirty, you're just asking for 'Chapter 2 of the burn-chronicles' to go ahead and commence..

..best-practice, is if/when you suspect a burn, clean very-carefully with a lens-tissue (..see here for some technique-advice: http://www.photonlexicon.com/wiki/in...ptics_Cleaning ..) and *spectroscopic*-grade acetone, if at all possible - you do NOT wanna use alcohol, or any 'store-bought'-grade acetone.. they have additives or can leave a film, and then you heighten the risk of burning it again..

...Also - *very-critical* - do NOT ever use water / get the sides of the x-tal wet, or handle the sides of the xtal with bare-fingers, no matter how 'clean' you think your fingertips are.. best to use a pair of lintless optical-gloves, or, even better, a pair of thin-kerf hemostats, with acetone-cleaned heat-shrink tubing 'socks' on the ends, for a bit of scratch-free 'gription'..

Forgive me if you 'already know all this'.. I simply wished to make the point about cleaning the burnt-face, before trying to use, again, since you didn't mention specifically, that you-had..

Lastly, re: 'the replacement x-tals didn't work'.. Did you try 'flipping the axis'? (front to back..) Again, perhaps the arrow was mis-marked.. Hope this helps..
cheers,
J

[shrad]

I think the initial fake fail was due to alignment of the remaining cavity

Old crystal has been cleaned with medical isopropyl with lens tissue before fry-pumped so it is not an issue with a dirty facet

I have set the old crystal back in the hope of getting it to lase gently with an undamaged part of the YVO4, and the worst case scenario was to get everything aligned quite well before a YVO4 replacement which would involve minor alignment

This is done now, and if the new crystal is OK I might get lasing with only a couple tries, cause the low power conversion was roughly 20% with the old crystal (which is a clue that alignment was set to a good spot)

I still ask myself whether to test the crystals Kevin sent me with a couple lasers, though (I have to setup a small 532, a small 808 and a small 1064 with nice small beams)

[planters]

Old crystal has been cleaned with medical isopropyl with lens tissue before fry-pumped so it is not an issue with a dirty facet

Careful. Medical does not in any way mean pure. As a matter of fact "medical" isopropyl can leave enough residue that it is visible to the naked eye. For optics, use reagent grade acetone or methanol.