Lasers

[Tomisimo]

Don't laugh at my / / signs :D
I wouldn't laugh. In fact I made an tag to use in posts, just for this purpose. If you write [IPA]leizr it will format it for you, like this: leizr

[sosia]

I say it because the "inside" is not really phonetic. :D

[Planet hopper]

I think you guys are treating Spanish as if it were English. In Spanish a latin word is adapted. It would often lose the orthodox latin plural form. Spanish speakers don't respect borrowings as much as English speakers do.

About using rayos it sounds right when you are generalising...Los rayos laser fueron un adelanto...But...El laser fue un adelanto...Possible El rayo laser fue....Unusual but grammatical: Los rayos laseres....Guess it depends on whether you are safe your audience will know what a laser is

Right, I may be looping around, even laseres does not sound 100% common, it's easier to keep the singular, as in Los rayos laser....