Periodically poled lithium niobate (PPLN) is investigated by micro-Raman spectrum and luminescence in a confocale microscopy configuration. It is observed that there exists a different in fluorescence strength between reversed domain and non reversed domain. And the Raman result shows that a Raman forbidden line occurs in the interface between the two domains. Results suggests a new non-destructive method to image polarisation gratings and provide important information about the mechanism involved in the polarisation reversal process.