Enhancement of the erbium concentration in RbTiOPO4 by codoping with niobium

A thorough study of the RbTiOPO4 (RTP) crystallization in its self-flux and WO3-containing fluxes (10, 20, and 30 mol % WO3) has been performed. The c omposition regions and isotherms of crystallization were obtained, and most of the crystallized neighboring phases were identified. Afterward, the pos sibilities of doping and codoping RTP crystals with Er3+ and Nb5+ were stud ied. Adding Nb2O5 substituting TiO2 in the solution increases the distribut ion coefficient of Er3+ but changes the crystal morphology toward thin plat es significantly. This means it is difficult to grow crystals of sufficient quality and size for research and applications. To optimize the crystal gr owth process, the conditions for growing doped and codoped RTP single cryst als with Er3+ and Nb3+ by the top seeded solution growth technique (TSSG) w ere studied. For crystal growth from self-flux, stirring the solution with an immersed platinum turbine significantly increased the efficiency of the crystal growth process. These conditions allow achieving 0.65 x 10(20) atom cm(-3) as an Er3+ dopant concentration in the crystal. The Judd-Ofelt para meters for Er3+ in RTP:Nb determined from the 300 K optical absorption spec tra are Ohm (2) = 5.99 x 10(-20), Ohm (4) = 0.54 x 10(-20), and Ohm (6) = 0 .37 x 10(-20) cm(2). Finally, the second harmonic generation (SHG) efficien cy of RTP:Nb single crystals increased as the concentration of Nb increased up to a 4 atom % of Ti4+ substitution, after which the SHG efficiency decr eased.