lazer pointers?

Question

why are most uv them red

Answer 1

Most are red because they use Helium and Neon gas. Laser's involve two transitions of electrons within an atom and it is easier to perform this task with He-Ne.

The photons released by the electrons transition are around 650nanometres. It is possible to make Green and even blue pointers but you require two elements where the electrons transitions correspond to a photon release of higher frequency (and thus shorter wavelength) - it tends to be more expensive to do this; therefore most are red.

For green the photon release must be around 550nm and for blue around 430 nm.

Answer 2

Because of Physics. Its easier to make a long wavelength semiconductor laser so red and indeed infra-red were made first. Other colours came along later as the technology improved but they still cost a lot more.