Exactly what Stalker said.
He did cryo tests on a 445, a 638, and a 658.
The 445 dropped a couple nm before it stopped working. The 658 dropped to maybe around 650. The 638 went all the way down to -191C doing fine, at 608nm. He took two of the P73's, combined and cooled them. 2W @ 608nm.
The smaller 520nm diodes have also been cooled. Resulting in 1-2nm difference (changed from current to current) relative to the same current at room temp. These tests were either done at 0C, or -20C. Not sure, but TECed nonetheless.
As far as the 10nm being a big difference. It all depends. 650 vs 660 is not going to be nearly as different as 510 vs 520, or 594 vs 604. It all depends on where you are in the spectrum. Some colors have a wider swath of the spectrum. I.E. the orange spectrum vs the green.
However, in this case, there is a huge difference between even 514 and 523. I have seen this difference with my own eyes. I've seen 514.5 argon, I've built a ~514nm pen, and I've built a few between 518 - 523. These are noticeable differences, especially to a trained eye.
It's just a matter of what you want. Visibility, and just the most green possible? Or the lowest wavelength possible? You can't have both, is what I'm driving at here. Even a TEC won't get you 516-518nm when driving the thing at 2-2.5A. That is, unless this diode is different from all the others. We'll have to wait and see.
