Why gas lasers?

[daguin]

Spikes of current, current too high for that particular laser, temperature too high.

Also, I read a post about an argon laser where it was said that if it hasn't been activated for a long time, it was probably unable to be activated again. Why does that happen?

For the first part, I am just going to say that gas lasers are pretty tough compared to diodes. Your question is still too vague. To answer it fully would take more time than I am willing to give. You need to read more and question less

For the second part, when an argon laser works, argon atoms are "driven" into the metal and other components of the housing of the tube by heat and pressure. When a tube sits for a long time, some of the atoms "escape" back out into the gas. If too many escape, the pressure of the gas can rise too high to allow the tube to start. That is why we do "maintenance burns" monthly with our argons. It keeps the atoms inside the housing High pressure tubes can be started with a kick from an oudin coil or a couple of other things, but they are more difficult to get going again after sitting for awhile

Peace,
dave