Can anyone explain to a layperson what produces the actual "glow" in thin air?
The best I can do on my own is that the laser beam(s?) is(are?) focused on a point and briefly converts some of the air at that point into plasma, which glows? (on its own? because of the laser?) How hot does that get?
I was thinking the same thing. Wikipedia tells us that a flame is visible at 525 °C (977 °F). (I don't know if this is relevant as they talk about a 'plasma' and not a flame.) This might sound too hot to be safe but it only has to be that temperature for a very short time so presumably the energy density doesn't have to be very high.
The best I can do on my own is that the laser beam(s?) is(are?) focused on a point and briefly converts some of the air at that point into plasma, which glows? (on its own? because of the laser?) How hot does that get?