Crystal Growth and Characterization of Type III Ytterbium-Doped KGd(PO₃)₄: A New Nonlinear Laser Host

We determined how evolved the P 2 1 crystallization region of ytterbium-doped KGd(PO 3 ) 4 (Yb:KGP) as a function of the ytterbium concentration in the composition region close to that previously determined as the optimum region to grow single crystals of undoped KGP. In this region, the border between the polymorphs KYb x Gd 1 - x (PO 3 ) 4 with long-chain geometry and KYb x Gd 1 - x P 4 O 12 with cyclical geometry varied depending on the ytterbium concentration. Inclusion-free single crystals of Yb:KGP were successfully grown using the top-seeded solution growth technique under conditions similar to those of KGP. Ytterbium doping in KGP was proved to be possible and effective. The effect of the ytterbium doping on structural and optical properties of the KGP host was determined. We found that Yb:KGP decomposed irreversibly at 1130 K. The vibrational structure of both KGP and Yb:KGP was found to be similar to other metaphosphates. The spectroscopic properties of ytterbium in the KGP host were analyzed.