Near field optical microscopy has been used to evidence the existence of damage channeling in femtosecond micro-structured Nd:SBN crystals. The self-channeling of fs pulses produced a well-defined modi. cation channel with rectangular cross-section, characterized by a different surface reactivity, which sharply finishes with an optical breakdown structure. From the analysis of confocal micro-luminescence images, we have found that these permanent micro-structural modi. cations are accompanied by a large density of defects that act as luminescence inhibiting centers. (C) 2008 Elsevier B.V. All rights reserved.