<p>An optical tag (200) comprises a chalcogenide glass corner-cube reflector (202) bonded to a silicon MEMS modulator (206) by means of a glass material (214) having a lower softening temperature than that of the reflector. The tag is provided with AR coatings (210, 212). The invention provides a robust, integrated and compact optical tag having a wide field of view and low manufacturing costs.</p>
