A survey of research on KTP and its analogue crystals

This paper reviews the growth and properties of KTIOPO4 (KTP) and its analo gue crystals including its isomorphous crystals and doped crystals. Based o n the calculation of the refractive indices and phase matching of KTP cryst als, it is shown that non-critical phase matching can be achieved theoretic ally. In a 4%Nb-doped KTP crystal, non-critical phase matching was obtained with a pulsed Nd:YAG laser in an efficiency of ca. 4%. Most of the isomorp hous and doped KTP crystals possess similar physical, optical and nonlinear optical properties as those of KTP. RbTiOPO4, KTiOAsO4 and RbTiOAsO4 cryst als have better electrooptical figure of merit and RbTiOPO4 crystals have a fast ion conductor character. Some doped KTP crystals have shown high seco nd harmonic generation efficiencies and damage thresholds. But the homogene ity of KTP analogue crystals is poorer than that of KTP. On the base of dam age threshold tests using a CW Argon laser, it is concluded that the best s econd harmonic generation crystal among. all the KTP analogue crystals is s till KTP itself. Special care must be taken to eliminate impurity centers t o avoid the formation of gray track and photorefractive centers.