Two-photon polymerization, initiated by 2,7-bis[[4-(dimethylamino)-phenyl]methylene]-cycloheptanone and 1,1',2,2'-bis(o-chlorophenyl)-4,4',5,5'-tetraphenyl-bisimidazole, was employed to fabricate refractive index-modulated holographic gratings by the interference of a femtosecond laser pulse at wavelength of 810 nm. The diffraction efficiency of the grating was up to 57% and the refractive index modulation reached 4.3 x 10(-3) after thermal fixation with the film thickness of 40 mum. And dependence of the diffraction efficiency and refractive modulation on laser pulse energy was also investigated. (C) 2003 Elsevier Science B.V. All rights reserved.