Sapphire Lasers

The chromium-doped sapphire (ruby) is the first laser at 694.3 nm, and was discovered by Maiman in 1960 at the Hughes Research Laboratory. Chromium gives ruby its red color. The ruby laser at 694.3 nm is due to the R₁ transition from the ²E energy level to the ⁴A₂ ground state.

The titanium-doped sapphire laser was first observed by Moulton at the MIT Lincoln Laboratory in 1982. This represents the first use of Ti³⁺ as a laser-active ion and only the second example of sapphire as a host crystal, the first being the Cr³⁺ ion in the ruby laser. In preliminary experiments, pulsed tunable laser operation was obtained from 718–770 nm. There is no excited-state absorption in the Ti:Al₂O₃ laser. Consequently, the Ti:Al₂O₃ laser is expected to operate over the entire fluorescence region 650–900 nm. Room-temperature continuous-wave (cw) operation of a Ti:Al2O3 laser was first reported at 770 nm with an internal quantum efficiency of 64 ± 10% by Sanchez et al. in 1986.