Raman and FT-IR spectroscopic characterisation of flux grown KTiOPO4 and KRbTiOPO4 non-linear optical crystals

Single crystals of KTiOPO4 (KTP) and K0.5Rb0.5TiOPO4 (KRbTP) have been grown using the slow fooling flux method. Laser Raman and FT-IR spectra were recorded on these crystals in the frequency range 20-4000 cm(-1). The observed Raman infrared bands are assigned to vibrations of the PO4 tetrahedra, TiO6 octahedra, combination and overtone bands of PO4 groups, OH- ion modes and external modes. The vibrational assignments of PO4 and TiO6 vibrations have been approximated in terms of T-d and O-h, symmetry species, respectively. Changes observed in the Raman and FT-IR spectra of KRbTiOPO4 crystals are discussed due to the presence of Rb ion. The vibrational data indicate that the tungsten (W6+) impurity is incorporated into the tungsten based flux grown KTP crystal at Ti4+ sites. Further,it has been observed that the presence of OH- defects is dependent on the growth conditions, i.e. type of flux used and the presence of impurity.