An optical device forming an outgoing electromagnetic wave from an incident electromagnetic wave comprises at least one unit cell (UC), comprising: at least two subwavelength optical elements (1, 2), each of them belonging to a different set (MSI, MS2) of subwavelength optical elements, a set of subwavelength optical elements being characterized by a type of optical response to an incident electromagnetic wave; means (21) enabling selective excitation of all subwavelength optical elements belonging to a given set, in response to an electromagnetic wave (20) incident on said unit cell.