Yb-doped and Yb–Mg codoped LiNbO3 single crystals

Lithium niobate (LiNbO3, LN) is one of the most well known multifunctional materials, due to its excellent piezo-, ferro-, and pyro-electric, electro-optical, photorefractive as well as non-linear optical (NLO) properties. As a consequence, it is extensively applied in fabricating surface acoustic wave filters, electro-optical modulators and NLO components for frequency conversion. LiNbO3 can be doped with rare earth (RE) ions to generate laser emission in the visible to the near-infrared rang. At the same time, the influence of intrinsic Li/Nb defects on optical properties has been studied through an electronic-structure simulation technique, indicating that the defects may lead to a change of the corresponding photorefractive coefficients and self-frequency of up to 30%. Thus research on the effect of the dopants is very important because of the influence of doping on intrinsic defects.

Yb3+:LiNbO3 can be fabricated as an efficient laser crystal, owing to its simple energy level scheme. Much of the interest has been centered on investigations of (i) spectroscopic properties and energy transfer in up-conversion Er:Yb:LiNbO3 lasers, (ii) self-frequency doubling (SFD) in bulk, fiber and periodically poled LiNbO3 (PPLN) structures, and (iii) laser cooling experiments. However, photorefractive damage in Yb3+: LiNbO3 is serious and limits its range of application. Doping with MgO at a concentration of 5 mol% in congruent LN (MgOCLN) effectively reduces the optical damage in laser devices under high intensity illumination. Yb:Mg:LiNbO3 has proved to be an excellent SFD system for all-solid-state lasers. Quasi-phase matching in PPLN structures shows some advantages over single domain crystals. Beyond that, some researchers have focused attention on the occupation sites of the Yb3+ ions in Yb:Mg:LiNbO3 by measuring the electron paramagnetic resonance (EPR) spectrum and the cooperative luminescence. Most recently, Yb3+: Er3+:Mg2+:LiNbO3 has been produced with high optical quality.