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

[planters]

This is good as I am driving dual pumps and if I go to fiber the typical A rating is 7@ approx 7V. Also the raman lasers are a lot less efficient and they will almost certainly require fiber pumps. So, this is probably an inevitable upgrade path. I just need to go there now instead of later.

[planters]

Eureka... I think. The fiber pump arrived from Steve R. and what a difference. The multimode problem seems to be SIGNIFICANTLY less right out of the box. To really test this the pump beam diameter needs to be adjusted from slightly larger to slightly smaller than the mode diameter and I have yet to do this , but wow the single mode beam is even better. It's 2mm out of the output lens and 2mm @ 10M. I will know by this weekend whether to go ahead and order the more powerful pumps. I may have some 10W diodes available for steve-o.

[Soulstorm]

Impressive! Fibre sure seems the way to go, I can't wait to see how it modulates. Sadly, CN modules with remotely similar specs can't modulate for crap.

Can see the attractiveness of ~888nm pumping, less thermal lensing + slightly higher efficiency but good luck finding a source that isn't mega bucks.. perhaps if there is a 'big green 2015' thread, by then, we may be in luck. Regarding the 'improvement greater than 60%' quote; perhaps it's a typo, instead meaning efficiency over 60%.. because from other articles, it seems it is only a little more efficiency and in that ballpark.

Keep up the awesome work planters, mixedgas and everyone else involved.

[planters]

Sadly, CN modules with remotely similar specs can't modulate for crap.

I didn't know that CN modules were available with this kind of beam spec. In all my experience this is the best laser beam I have ever seen including the ions. But, when using the direct diode pump I can understand why. You actually have to align the cavity for each power level because unless you are incredibly fortunate the thermal lensing is not just a low order plain-o positive lens, but rather an asymmetrical, high order, un-aligned blob. This is much less with a Gaussian or bell shaped and focused fiber homogenized spot.

The problem as I see it with the 888 is that aside from the real benefit of the lower quantum defect, the problem of the very low absorption coefficient is that in order to take advantage of the spreading out of the heat effected region you have to produce a very tight and well collimated pump beam to avoid wasting the pump in regions of the crystal that never "see" the mode.

[polishedball]

Video or it didn't happen.
Im on an iPad so hopefully it isn't embedded and just not showing like they do on occasion

[steve-o]

Planters wrote:
I will know by this weekend whether to go ahead and order the more powerful pumps. I may have some 10W diodes available for steve-o.

Thanx Eric but I don't think this skinny little crystal will take more than a watt. It skews the beam/ dot terribly under ~500ms exposure to a watt of 808 . (Tested with multiple focusing lenses) I'm guessing this is the thermal lensing you all are talking about. We're gonna need a bigger boat. Having not much success over here .. :/
Excited about the success that you are having tho, .. can't wait for the next Planters Vid

[planters]

That's OK. If you or any one wants to try these they are available. I am also pretty sure that the CN lasers all use the direct diode approach based on the cost of the fiber coupled modules. Also, the beam when focused is VERRRRY hot and it really is 10 W so they might make interesting cutting/melting or engraving sources depending on the material.

I think I will wait until the set up is complete with both fibers, because I am so close, before I do some videos.

[steve-o]

I'm guessing that they're using discrete components rather than a pre-assembled MCA . Each component would have to have it's own TEC .. 10W is a hellova lot of heat to dissipate .. We're almost treading on OPSL territory now, looks like ..

[planters]

OK, the answer is to focus the pump to slightly smaller than the mode size in the vanadate. This makes sense to me,but I was unsure about the argument that a larger spot tended to produce less of a thermal gradient and less thermal lensing. I don't think this works this way and to me only pumps regions of the crystal that support less axial and higher order modes. I am defiantly going for the more powerful pumps because at 8W unilaterally I still have TEM00.

[dsli_jon]

...I am defiantly going for the more powerful pumps because at 8W unilaterally I still have TEM00.

Hah! I love how every-place (apparently / I *think*) you're meaning to type "definitely" - your 'typo' still works. Just great... 'subliminal-typos', Lol..

As usual, 'brilliant' werk.. ..And yeah, that beam makes even the best sci-grade Laser Quantum beam look like a tritium-octopus' ink-jet..

PS - Got yer email, replying now, thx..
j