Synthesis of transition-metal-doped KTiOPO4 and lanthanide doped RbTiOAsO4 isomorphs that absorb visible light

We have substituted aliovalent transition-metal (M = Cr, Fe, Ni, Cu, Co) and lanthanide (Ln = Er) ions that absorb visible light onto the titanium sites of the nonlinear optical materials KTiOPO4 (KTP) and RbTiOAsO4(RTA). The substitution formally creates a charge deficiency on the Ti site. To compensate for this, we have substituted aliovalent counterions on the titanium (Nb), phosphorus (S, Se, Cr, Mo, W, Re), oxygen (F), or potassium (Ca, Sr, Pa, Pb) sites. The resulting new materials expand the KTiOPO4 structure field for partial replacement of one or more ions. The M and Ln ions alter the optical absorption and second harmonic properties of the materials. The ions reduce the second harmonic intensities of the isomorphs (measured at 532 nm) but improve their phase-matching capabilities, allowing fundamental and second harmonic radiation to be phase matched at slightly shorter wavelengths than in the undoped host.