A device and method to provide an optical guide of a pixel to guide incoming light onto a photosensor of the pixel and to improve the optical crosstalk immunity of an image sensor. The optical guide consists of an optically reflecting barrier formed as a trench that mitigates against optical crosstalk. The optical guide is made of an air-filled ring of spaced slots. In another embodiment, the optical guide structure can be filled with a low dielectric material with an index of refraction that is less than the index of refraction of the material used for the surrounding layers.