A diffractive structure (100) has a substantially planar substrate (1). A set of facets (2) is formed in or on said substrate (1), the plane or planes in which the facets (2) lie being arranged at a non-zero angle to the plane of the substrate (1). Each facet (2) has a diffraction grating (5) formed...http://www.google.se/patents/US6043936?utm_source=gb-gplus-sharePatent US6043936 - Diffractive structure on inclined facets
