> It is caused by stimulated emission in the lasing medium, when electrons drop from a higher to lower energy level. In a typical green laser pointer a 1064nm

> It is caused by stimulated emission in the lasing medium, when electrons drop from a higher to lower energy level. In a typical green laser pointer a 1064nm light is produced via ordinary laser mechanisms, then 1064nm light is upconverted in a non-linear medium to 523nm. https://en.wikipedia.org/wiki/Second-harmonic_generation https://en.wikipedia.org/wiki/Second-harmonic_generation Yes, in a medium. You also don't see a lot of conventional computers constructed without semiconductors. :)