Single crystal paraelectric K0.99Li0.01Ta0.60Nb0.40O3 is grown with a room-temperature Curie temperature (T-c). The parameters of the Sellmeier dispersion equation were determined. A large quadratic electro-optic (QEO) effect was observed. The QEO coefficient R-11 reaches as high as 2.48 x 10(-15) m(2) V-2 around Tc. The induced refractive index change under an electric field of 500 V/mm is 40 times bigger than that of commonly used LiNbO3. The large QEO coefficient makes single crystal K0.99Li0.01Ta0.60Nb0.40O3 a promising candidate in optical devices. (C) 2012 Elsevier B. V. All rights reserved.