A device, particularly an antenna device, for emitting a beam of optical radiation to irradiate a remote target area. The device includes an optical source (10) having a limited wavelength band, and a hologram pattern (14) positioned in the path of a light beam originating from the source, the pattern being selected to produce a composite beam (20) having a predetermined shape or far field pattern conforming to the target area and/or a predetermined distribution of light intensity in the target area. Where the optical source is a point source, the hologram pattern (10) selectively retards the phase of respective components of the incident wavefront to produce a composite beam having a far field pattern that precludes focusing of the beam into a single small spot. The device has particular application in a telecommunication system wherein a data signal is transmitted through free space by an optical beam, at least one characteristic of the beam being controlled by the hologram pattern in the path of the beam.
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