Yb³⁺ is the most promising ion that can be used in a non-Nd³⁺ laser in the near-IR spectral range of 1030 nm,the Yb³⁺ ion has several advantages compared with Nd³⁺ due to its very simple energy level scheme, consisting of only two levels. This makes it possible to avoid upconversion, excited state absorption, and concentration quenching within a large concentration domain.Since the advance in commercialized laser diode sources allowed excitation of Yb³⁺ in the near-IR, several oxides and fluorides have been thoroughly investigated.

Researchers at Key Laboratory of High Power Laser Materials——Shanghai Institute of Optics and Fines Mechanics (SIOM/China) successfully prepared

Yb-doped Yb:PbF₂ crystals. It was found that Na⁺ ions act as the charge compensators to enhance the Yb³⁺ near-IR emissions (~0.1µm), broaden the emission bands, lengthen the fluorescence lifetime, and simultaneously suppress the upconversion emission. Na³⁺ ions also effectively suppress the formation of Yb²⁺ ions, preventing the fluorescence quenching of the Yb³⁺ emission.[ LASER PHYSICS LETTERS ,10(4),045803]

Na-codoped and only Yb-doped Yb:PbF₂ crystals were successfully grown using the vertical Bridgman method. The influence of the ions codoped with Na⁺ on the distribution coefficients has been studied. Enhanced  emission and simultaneously suppressed upconversion emission was observed for Yb:PbF₂ crystals codoped with 2 mol% NaF. A time-resolved spectroscopy study showed that the ions codoped with Na⁺ lengthen the fluorescence lifetime by 6%. Absorption spectra were also studied and showed that the ions codoped with Na⁺ can effectively suppress the formation of Yb²⁺ ions.