There is provided an illumination device (100, 150, 200, 300) comprising: a periodic plasmonic antenna array (114), comprising a plurality of individual antenna elements (106) arranged in an antenna array plane, the plasmonic antenna array being configured to support surface lattice resonances at a first wavelength, arising from diffractive coupling of localized surface plasmon resonances in the individual antenna elements; a photon emitter (152) configured to emit photons at the first wavelength, the photon emitter being arranged in close proximity of the plasmonic antenna array such that at least a portion of the emitted photons are emitted by a coupled system comprising said photon emitter and said plasmonic antenna array, wherein the plasmonic antenna array is configured to comprise plasmon resonance modes being out-of plane asymmetric, such that light emitted from the plasmonic antenna array has an anisotropic angle distribution.