Crystal Growth of ScBO₃:Cr ³⁺ — A New Near-IR Tunable Laser Crystal

Abstract

Since the discovery of the alexandrite room-temperature tunable laser [1], much effort has been expended in exploring new laser materials and several new room-temperature tunable laser hosts [2] have been discovered. In almost every case Cr³⁺ has been used as the active ion. More recently, there is excitement over the discovery of the Al₂0₃:Ti³⁺ laser [3] because of its broader tuning range, simple energy-level structure and relatively large gain cross-section. But the short lifetime and poor absorption has made Ti³+ difficult to pump. Cr³⁺ doped tunable lasers generally have efficient absorption and adequate lifetime but the optical gain is proportionately lower. Fortunately, through understanding of the physics of Cr-doped tunable lasers, it is possible to manipulate the tunability range by varying the crystal field strength of the host crystal. It is also possible to select crystal hosts with low refractive indices as well as proper site distortions,so that the emission cross-section can be increased to a certain extent without significantly degrading the fluorescence lifetime.