Mapping Domain Walls of PPLN by Dark Field Polarized Raman Spectrometry

In attempt to increase contrast and resolution to image domain walls of PPLN we modified our Raman spectrometer in a 'dark field' configuration. This set-up collects non-paraxial Raman scattering from sample. We observe effectivelly different characteristic of scattered light. Domain walls present Raman shift and intensity variations. Question are raised concerning the origin of this variation between photrefractive effect, strain effects and collection of oblique modes.