Withdrawal of Chinese Physics Letters 26 (2009) 114209

This paper has been retracted because Fig. 2 is copied from an earlier paper, "Interband photorefractive effect in β-BBO crystal due to multiphoton excitation by intense ultrashort optical pulses" by Shixiang Xu et al., which appeared in Optics Express 15 (2007) 10576, and its Figs. 3 and 4 also present similar data as in Figs. 3 and 4 of the same Optics Express paper though they are measured at a different pumping power. See Also: Original Article, XU Shi-Xiang et al., A Sensitive Scheme to Observe Weak Photo-Refraction Effects in Some Nonlinear Optical Crystals Pumped by Ultrashort Optical Pulses, Chin. Phys. Lett. 26 (2009) 114209