"If I recall, it is in the order 0.3nm/C so could be around 642nm @ -35c."
They may have been referencing 660nm, as otherwise the math on that second quote doesn't seem to add-up?
Not sure if the temp-induced shift on a 635 would be the same or not, but if it is, that would result in 617nm at -35C! Break-out some dry ice (-78.5C), and assuming the shift stays the same, you're down around 602-605nm! Even colder, and...
OK, now where did I put that liquid Helium?! :thinking:
Even 617nm is starting to get rather orange, which is what got me thinking about this - I recall seeing someone here selling an experimental orange laser diode, that required extra cooling to reach that color?
But if this same shift continues unabated, you could get all the way to green just by cooling!
(at that shift, even liquid nitrogen would seem to get you into lime green territory!)
I assume either this shift does not stay linear, and/or there is some other practical limitation that is preventing that? But it does make you wonder just how far down you can shift these guys!
Perhaps pullbangdead can shed some light on this?