A device and method for providing an optical guide of a pixel to guide incoming light to/from a photo-conversion device of the pixel to improve the optical crosstalk immunity. The optical guide includes an optically reflecting barrier formed as a trench filled with a material which produces reflection. The trench fill material may have an index of refraction that is less than the index of refraction of the material used for the trench surrounding layers to provide a light reflective structure or the trench fill material may provide a reflection surface.