Far-infrared lasing in ruby

The feasibility of submillimeter wavelength (870 GHz) lasing in Al
2
O
3
is discussed. The proposed scheme is based on the pumping of the
2\bar{A}
level of ruby via a ruby laser operating on its R
2
line. Lasing is expected on the
2\bar{A} \rightarrow \bar{E}
transition of the split
²
E
level.