Abstract

Tm³⁺ ions in crystals offer optical transitions in the blue region which have been successfully lased at 483 and 455 nm using upconversion pumping schemes. Current pump schemes use either two sources (e.g. 780 nm and 645 nm^1–4) for Tm³⁺ singly doped crystals or one source at ~ 960 nm⁵ for Tm³⁺ and Yb³⁺ codoped crystals. Ytterbium sensitized Tm³⁺ upconversion lasers have the advantages of using single pump source and having higher pump efficiency over the single-active-ion upconversion lasers. However, they suffer from energy back transfer from Tm³⁺ ions to Yb³⁺ sensitizers which depletes the populations not only of the blue emitting levels but also of the intermediate levels and makes it very difficult to achieve lasing ⁶. We propose in this paper a new pumping mechanism for upconversion blue lasing in Yb³⁺, Tm³⁺ codoped crystals which is based on this back energy transfer process and uses only one pump source at ~ 780 nm.

© 1995 Optical Society of America